Dealing with Invasives in the Winter

Fall and winter are good times to use herbicides to control invasives.  At this time it is easier to spot many invasive species because they often hold onto their leaves longer than native species and there is less likelihood of harming native species with any mis-directed herbicide.  However not all invasive species can be treated effectively during this period.  At their January meeting, Blue Ridge Prism, an organization based in Virginia to address the threat of invasive species and to restore native habitats, the topic was about which plants could be treated over the winter months. A recording of that meeting can be found at this link:  January Meeting.  For each species mentioned here there are links to Blue Ridge Prism's  Fact sheets .  These provide lots of information each species including how to identify them and others species that may look similar.

One of the most obvious targets for winter actions are invasive vines growing up trees.  These include  English ivy, Hedera helix, and winter creeper, Euonymus fortunii.  At a minimum, these vines should be cut at the base of the tree and again a few inches to a foot or so up to create a gap.  If possible the lower stump of the vine should be treated with a 50% dilution of a recommended herbicide (e.g., 20% solution of glyphosate) to kill the roots.  This is referred to as the cut stump treatment.  The remaining vines in the tree should be left in place to slowly die.  Attempting removal can damage the tree and/or injure folks on the ground with falling debris.  Be observant when cutting the vines, wintercreeper vines especially are good at hiding in the furrows of the bark of trees. [photo of EI in tree]

This tree has surrendered tp English Ivy.  The added weight
 can cause limbs to break, particularly with
accumulated snow and ice in winter.

These trees have winter creeper euonymus climbing up.  Winter creeper
sends out longer branches than English ivy.  These branches will bear
flowers resulting in the spread of this invasive species. 
Note that both of these vines have been 'deer pruned',
 but doesn't keep them from climbing.

For plants growing along the ground, these evergreen vines can also be treated with foliar sprays in winter, though not with 100% success.  Digging when the ground is soft and moist is quite effective at any time of year.

While not expressly discussed, Japanese honeysuckle, Lonicera japonica, vines cane also be treated in late fall and winter by either cut stump or foliar spray, if leaves are present.

Winter foliar spraying of  Vinca (V. minor and major) was reported to be effective, though personally I have not seen satisfying results.  For small infestations hand pulling is very effective.  I find that using a rake to lift most of the stems followed by using a trowel to get out the rooted plants is pretty effective.  Many folks recommend cutting, mowing or weed whacking first, then, later, hitting the regrowth with a foliar herbicide.  In doing this one must be very careful about killing non-target plants.  (These herbicide treatments are likely to be during a time while desirable plants are actively growing as well.)

There is not much else growing around this patch of Vinca minor
(Periwinkle) in January so careful foliar spraying shouldn't damage other plants.

I do have several areas where vinca has escaped the beds and is moving into forested areas.  Later in February I will try an experiment with foliar spraying alone compared with string trimming + raking followed by a spray with glyphosate.  There are some natives in this area, such as white avens, so I don't want to wait too long before I get started on this.

Fall and winter are good times to treat garlic mustard, Allairia petiolata.  The leafy rosettes of overwintering plants are easy to spot treat with the appropriate herbicide when other plants are still dormant.  Treatments can be done when temperatures are above 40°F.  I've done treatments in November and February-March. In my opinion the treatments later in winter were more effective because the leaf litter had broken down more making the garlic mustard leaves easier to target.  See this link to an earlier blog post about my efforts to eliminate garlic mustard.

Here's some garlic mustard in November,  In a mild winter
 these leaves will remain active all season.  Around March
 they will begin a growth spurt and put up a flowering stalk.

Gill-over-the-ground or creeping Charlie, Glechoma hederacea, can be treated with foliar sprays in early winter before a hard frost, but these would be more effective in early fall while plants are moving nutrients to their roots.  By January  most of the leaves have fallen off so there is no good target for a foliar spray.  Multiple treatments will likely be necessary.  The advantage of winter spraying, again, is that there are few non-target species actively growing at that time.

For Autumn olive, Elaeagnus umbellata, Nandina, Nandina domestica, and Bradford pear, Pyrus calleryana (fall to early winter), cut stump, hack and spray or basal bark treatments are effective. Autumn olive and Nandina can be treated effectively through the fall and winter. Treatment is not so effective in early spring when sap is flowing upwards.  Bradford pear should be treated earlier, while sap is still flowing downwards to the roots.  Smaller plants can be cut close to the ground and immediately treated with a concentrated herbicide on the stump.  Larger specimens can be treated using basal bark treatments (herbicide in an oil carrier) or hack and squirt.

These autumn olive bushes are in full bloom with their sweetly scented
 flowers seen here in early May.  I eliminated both of these with the
cut stump method using glyphosate.

While some invasive species can be treated throughout the winter months, usually when temperatures are above 40°F, some require treatment in a more specific time period.  Mid-fall to early winter is a time in which sap is flowing from the upper parts down to the roots.  Herbicide treatments at this time will carry the active ingredients to where they will have the greatest effect.  As mentioned above Bradford pear and gill-over-the-ground should be treated earlier.  Tree-of-heaven and Asiatic bittersweet are also in this group.  

Tree-of-heaven, Ailanthus altissima, is best treated in early fall when the sap is following down to the roots using basal bark or hack and squirt methods.  Cutting the this tree down is not an effective means of control.  The response to being cut down is for it to put out many root sprouts, so even treating the stump with herbicide is not going to be effective. 

Italian arum, Arum italicum, does not have an effective approved herbicide so digging is currently the only effective means of removal.

Lesser Celandine, Ficaria verna, is a major problem in moist areas, particularly along streams.  These can look like violets when not in bloom.  Digging small infestations can be done all year but care must be taken to remove all the roots, tubers, and bulbils, as well as seeds, if present, to avoid recurrence or spreading of this species.  There is a very narrow window of opportunity (about 2 weeks) for effective foliar treatment with glyphosate.  This is in the March-April time frame shortly after the plants have started to bloom, but before full bloom is achieved.  In wetland areas so you need to use a herbicide approved for those places (e.g., Rodeo®). 

This photo of lesser celandine was taken in mid-April toward
the end of the herbicide application window. 
When not in bloom the leaves do look similar to many violets

Some General Comments

Make sure you can positively identify the target species.  Especially with shrubs.  You could always tag the plant of interest with florescent tape in the winter and come back to it when it's leafed out or in flower to do a positive ID.

If you don't wish to use herbicide treatment, winter is a good time for pull up plants at times when the ground is thawed and moist and plants can be easily removed.  Just be careful not to disperse any seeds associated with the plant that you are removing.

For most plants a form of glyphosate will work.  Check the links for specific guidelines for each species.  In general, I prefer glyphosate as it is not translocated in the soil to other plants and that which reaches the soil is broken down quickly by soil bacteria.  In all cases follow the herbicide label instructions.

Just to throw in my own two cents, I wanted to add two things.  First while there is nothing you can do with Japanese stiltgrass  in winter, early spring (when forsythisas are blooming) is when you can put down preemergent herbicides to help eliminate this from lawns and areas where you are not encouraging growth from seeds.  Check this post for details.

Second, winter is also a good time to treat Japanese barberry using a cut stump treatment.  It can be spotted by the few remaining red berries along the stems.  There is a native barberry but it's quite uncommon.  It differs from Japanese barberry in that it has spines in groups of three along it stem, rather than the singular spines on Japanese barberry.

Wild berries

In my neck of the woods in the Mid-Atlantic we have three common species of wild berries that can be good eating.  These are wild blackberry (several similar species, mine is Allegheny blackberry, (Rubus allegheniensis), black raspberry (Rubus occidentalis), and Northern dewberry (R. flagellaris).

Wild blackberries bloom for a couple of weeks here in early May. 
They are very fragrant and quite attractive to bees.

Wild blackberries are the most noticeable of these three species of brambles.  The two most widespread species in the upland areas around here are Allegheny and Pennsylvania (R. pensilvanicus) blackberries.  The upright growing canes are typically 5-10 feet long.  Each individual cane only lives for 2 years.  These are continually replaced by new ones growing up from a rhizome 6-12" deep underground.

The thorns along the petioles are hooked and will grab onto any
clothing as you are pulling away.

The glandular hairs on the peduncle are indicative of Allegheny blackberry. 
Pennsylvania blackberry lacks glands in this area.

Blackberries ripen over several weeks around early July. 
Fully black colored berries that detach easily have the best flavor.

The square canes of Allegheny blackberry are armed straight spines.  The leaf veins and petioles have curved prickles.  These allow one to reach into the thicket relatively easily but much harder to withdraw your arm without getting snagged.  The 2-3 inch fragrant white flowers bloom in early May.  This is about the same time as multiflora rose.  Left on its own these canes will produce large quantities of small, seedy and very tart berries.  By cutting the cans back to about 6' tall and each of the side branches by half (down to as few as 4-6 buds) fruit size and sweetness is greatly improved.  These berries are still seedy, by the increase in fruit size makes it less noticeable.  I have also noticed that these cut canes provide habitat for small insects, although I don't know if these are beneficial or not.  The clusters of berries ripen over an extended period  from late June through July.  The best test for ripeness is if the berry comes off without pulling.  If you need to tug on the fruit, it's not ready. Berries that I don't eat right away are rinsed briefly, to remove ants, dried, then put into the freezer.  The berries do have a tendency to ferment if not picked.  These fermented berries do not taste as good as perfectly ripe fruit.

This overwintered cane shows evidence
of an insect resident.

Wild blackberry has smooth red stems in winter
armed with stiff red spines. Older branches
are square with indentions on each face.   

An additional benefit of these upright brambles is that they can act as a fence between tree saplings and browsing deer.  As an example, I have a white oak planted in the middle of a blackberry patch that has, so far, not been damaged by deer browse or rubbing.

Black raspberries, Rubus occidentalis, showed up here on their own about five years ago.  They became more obvious as I was reducing the amount of invasive wineberry (R. phoenicolasius) plants.  These are easily distinguished from wild black berries in that they have round canes, instead of square, with a white blush on them and the spines are straight rather than curved.  these have white flowers in mid-May with fruits ripening by mid-June.  The fruits are initially bright red, but turn nearly black when ripe.  They have have a unique sweet-tart taste, different from red raspberries.  The blue Jolly Rancher candies capture their flavor quite well.   Another way to tell blackberries and raspberries apart is how the fruit comes off the plant.  Raspberries leave a conical core, or rasp, on the plants while blackberries come off completely.  That's why picked raspberries seem to have a hollow core.  Where I live, black raspberry season is pretty short, maybe 10-14 days. Black raspberries are more shade tolerant than blackberries, but they are also more attractive to deer, particularly the foliage in early spring.  Where branch tips contact the soil new roots will form resulting in a thicket of arching canes.

These flowers, in mid-May are just opening and will
expand to about an inch across.  They are not as showy
as on the blackberry.

Black raspberries are borne in neat little clusters.  Normally the
center berry ripens first, followed by the surrounding fruits. To the right
in this image is a primocane, a first year stem with larger leaves.

In winter black raspberry has red canes with somewhat smaller thorns
 than a blackberry. It is distinguished by the white bloom on the older branches 

The earliest blooming of my wild berries is Northern dewberry, with flowers appearing by the end of April.  Unlike the other two berries dewberry stems are very lax and they tend to run along the ground, or over and through other plants.  The canes are typically 2-4 mm wide, often red in color and the spines are very narrow.  They don't twine, so they won't scale a tree.  Like the black raspberry, new plants can form where branch tips contact the soil.  Unlike the other two species, the number of berries in a cluster is smaller (2-5) and often single.  While wild blackberries can have 7 or more berries in a single cluster and black raspberry typically has 5 berries (3-7).  Like the other wild berries these are essentially black when ripe.  Based on the few that I have eaten, they are not as tart as blackberries, but are generally pleasant.  Since plants are  trailing on the ground or hidden in shrubs, I haven't harvested near as many of these as I have blackberries or black raspberries.  These berries end up being eaten mostly by the wildlife.

These flowering branches of Northern dewberry grow
up from the horizontally growing floricane.

These unripe berries grow in smaller bunches than the other brambles. 
Note the difference in leaf shape and texture between the dewberry
 (middle foreground) and poison ivy (upper right).  As of June 18th
these berries are about as far along as the blackberries, i.e. still green.

All these berries share a similar life cycle.  In the first year a cane sprouts from the ground and grows to some length, depending on species.  This cane, called the primocane only has leaves and does not flower or bear fruit.  The following season this cane matures and sends out more lateral branches that flower and bear fruit.  These are referred to as floricanes.  After fruiting, the cane dies, but additional canes are sent up from the perennial rhizome. As an aside, while flame weeding one spring, I found that the primocanes are sensitive to fire, but this did not have a long term effect on the life of the plant.

For reference here's an image of the invasive wineberry, Rubus phoenicolasius.  It's intermediate in size between our blackberries and black raspberries and it has a tendency to form dense thickets especially where the branch tips root on contact with soil.  

Wineberries turn bright red when ripe.  They can be distinguished from
 our native berries by the color of the fruit, the broadly ovate leaves
and the densely bristled stems.

Plant fertility as a factor in landscape design

When designing a landscape a lot of effort is put into plant selection.  Getting the right forms, colors and shapes, proper placement and repetition to establish rhythm and flow throughout the design are critical to its success.  Maintenance issues are often a secondary consideration. If the goal is to also support wildlife, use of native species and fruit and seed production is also of high importance.  An aspect of landscape plant selection that has a lasting effect on both maintenance and performance of the design is plant fertility.  That is the ability of the plants to reproduce.

Flowering plants have a variety of strategies for sexual reproduction.  Some species have perfect flowers, that is there are both male and female parts within the same flower.  Others have separate male and female flowers on the same plant, but in different locations.  These are referred to as monecious plants.  If the male and female flowers are borne on separate plants then they are referred to as being dioecious.  There are also shades of gray between these.  You can read more about the different flower types in this article from the Master Gardeners of Northern Virginia.

There is a strong bias for plants to encourage cross fertilization.  It improves the adaptability of species to evolve and cope with change.  Plants, even those with perfect flowers, have a variety of means to encourage cross fertilization:  In some, there are genetic mechanisms where pollen is unable to grow through the pistil and reach the ovary if they has the same genetic makeup.  In some there are physical barriers that keep pollen within a flower from reaching the pistil and there are timing mechanisms the pistils of a given plant are not receptive to pollen at the time that that plant is releasing its pollen.  In many species of oak, female flowers are concentrated near the top of the tree, while the males are lower down.  As the pollen is released it is carried by the wind where, hopefully, an updraft will carry it to the top of neighboring trees.

Even when self pollination is a viable option, seed production is generally higher when cross-pollination has occurred.  Pawpaw (Asimina triloba) and maypops (Passiflora incarnata) are two examples of North American fruits that benefit from this.

When considering plant fertility are two extreme ends of the spectrum.  For formal gardens and situations where consistency of appearance are of primary concern, minimizing plant fertility to minimize unplanned reproduction  is the goal.  If the plants are not producing fruits or viable seed then there won't be as many randomly placed plants popping up that need to be weeded out and there will be fewer fruits falling from the trees that require clean up.  

This semi-formal designed planting has a clearly defined placement of plants.

Conversely in landscapes intended to benefit wildlife with a less rigid, more naturalistic appearance, maximizing the ability of plants to produce fruits and seeds and to reproduce improves its function.  The composition of such a garden will change over time as more successful plants displace the weaker ones.

This parking lot island utilizes primarily native species adapted to dry conditions and
tolerant of summer heat.  Aside from the juniper and the chokeberry cultivars in the
back, all the perennials are wild type.  The installation here is 2 years old so
reseeding has not affected the appearance.

I live in a very naturalistic environment so for nearly every native species I plant I will make an effort to ensure that fertile seeds are produced.  The main reason for this is to support wildlife with natural sources of food.  However, there are a few cases where I will limit fertility such as using a non-native species or a North American species that is not a regional native or on those occasions where the properties of the cultivar are critical to the function of the design, particularly where size is concerned.  I these instances I would choose to use only a single cultivar (or gender).  

To the left, a freely reproducing/reseeding native garden bed.

In the photo above, the bed to the left consists of primarily native species and has been allowed to reseed naturally.  Over the course of 12 years, the dominant perennials have waxed and waned.  At first it was dominated by asters, mostly by Short's aster (Symphyotrichum shortii), then Phlox paniculata, then pale-leaved sunflower (Helianthus strumosus), and now there appears to be a return to aster dominance.  The 'October Skies' aromatic aster is the only one of that species in the bed and has remained in place for about 10 years with only two extra seedlings produced.

How to manage fertility...

Reproductive fertility in the landscape can be minimized by using single cultivars of a given species, using only one gender of dioecious species (often just males), choosing sterile cultivars or flowering plants with reduced numbers of fertile parts (double flowers), and having only a single individual of a species.

If you want to maximize fruit and seed production you should plant genetically diverse individuals (use seed grown plants, multiple wild type or a mixture of cultivars within a species), have both male and female partners of dioecious species, avoid cultivars with sterile flowers, plant mixed individuals of a species in proximity to increase cross pollination.

Back in the 1930's E. M. East of Harvard Univ. was compiling a list of plant genera, organized by family, and their propensity to self-pollinate (self compatibility).  Though not completed by the time of his death, this listing does give some clues about the ability of plants within a genus to self-pollinate.  Some notable genera that have multiple instances of self-incompatibility are: Trifoliums, perennial species of Festuca, and North American of Prunus (plums).  Species of Hamamelis, Fothergilla, Berberis and Spiraea are largely self-fertile.   

Examples of self-incompatible plants include many Asteraceae species.  Also apples, some cherries, and many grasses, e.g. Miscanthus, do not self-pollinate effectively.  Even though many of these have perfect flowers, that is their flowers have both male and female parts, there are genetic mechanisms (both mechanical and biological) in place that prevent or discourage self-pollination.  

Examples...

Examples of dioecious plants that you may want to use in your landscape are trees  fringetree,  persimmons, sassafras, tupelo, and willows, and shrubs such as bayberry, hollies, junipers, spicebush, and sumacs. In many cases male flowering plants produce showier flowers, with their larger pollen laden stamens.  Examples of these are spicebush, willows and fringetree.

The female fringetree, has a moderate f lowering display and will bear black berries
in early fall.  Male plants tend to be showier with somewhat larger and denser flowers.

Here are close ups of female and male spicebush flowers.  Female flowers have
a single style attached to the central ovary while the male flowers have up to
9 anthers loaded with pollen packed into each flower. 

The white catkins on these male pussywillows, Salix discolor, compete well with
forsythia in early spring.  Also, unlike forsythia flowers, the willow flowers are very
popular with the native bees.

Unfortunately, other than some ash trees and hollies, finding gender information from the retail nursery trade is pretty difficult.  This is understandable for seed grown wild type plants since the genders are not easily determined until the plant has matured, many years after the plants have sprouted.  For cultivars, plants reproduced asexually, the gender of the parent should be determinable and that information could easily be passed along.  Also be aware that any cultivars are generically identical to each other.  Planting 5 pots of 'October Skies' aromatic aster is the same as planting one as far as their genes are concerned.

The female flowers of this winterberry holly are dominated
 by the central ovary  surrounded by non-functional stamen. 

Male flowers have 4-6 stamen tipped with yellow pollen. 
Male flowers are usually in tight clusters.

One notable species of the Asteraceae family is Jerusalem artichoke (Helianthus tuberosus) also known as sunchokes, , native to the Northeast and Midwest.  In the wild these plants are aggressive spreaders, however single cultivars, readily available from mail order nurseries do not readily self pollinate, so spreading by seed is not a concern.  

Viburnums are another example. To get berries you need at least two individuals of the same species.  If you are shopping at retail nurseries that would mean buying two different cultivars.  If you have access to seed grown wild type plants then any two will do you. Or you could do a wild type and any cultivar, if you wish. For more on this check out my viburnum blog post from a few years back.

One situation that gets repeated time and again is the use of Ginkgo trees, Ginkgo biloba, as street trees.  These ancient trees, native to Asia, are tolerant of many stressful conditions making them a good choice as an urban street tree.  The caveat is that the fruit of the female trees has a large amount of butyric acid in them which smells of rancid butter or, to me, dog poop.  The fruit is a little less than an inch long and have a rather slimy coating.  Altogether stepping on one, on a beautiful fall day, can ruin an otherwise delightful experience.  For this reason, many towns that have planted a mixture of ginkgo have opted to remove their female ginkgo trees.  You can read more in this story from CBS News.  

'Gro-low' Aromatic sumac is a horizontally spreading shrub.  This female cultivar
 is wind pollinated in spring before the leaves come out.

Another example of the importance of knowing the genders of the plants used in your landscape is the Gro-Low cultivar of aromatic sumac, Rhus aromatica 'Gro-Low'.  Gro-low aromatic sumacs are all females.  The design intent with this cultivar is as a ground cover/soil stabilizer that maintains a height of 3' or less.  Planting males nearby could result in seedlings that do not have the same growth characteristics of the mother plant.  The result would be an irregular planting with a scattering of taller (6 or more feet) plants.  (I don't know of a low growing male cultivar.  But even then there is no assurance that the offspring will share that shorter stature.)  The flip side is that without a male present for pollination no berries will be produced to help feed the birds.

A case of what was thought of as a safe introduction of a self-sterile exotic is the Bradford pear, Pyrus calleryana 'Bradford'.  Initially this single cultivar was not able to fertilize itself and it largely stayed put.   After a few years, the poor characteristics, particularly the weak branches, became evident and new 'improved' cultivars of Pyrus calleryana were introduced.  These new introductions were able to cross pollinate with the large existing population Bradfords leading to an explosion of in viable seedlings and a serious invasive species.  A similar situation is brewing with Chinese silver grass, Miscanthus sinensis.

If allergies are an issue, use more female plants to reduce the amount of pollen produced for wind-pollinated species, particularly Junipers, and ash, maple and Oak trees.  Also reducing the amount of lawn grass, as well as other grasses, which are 100% wind pollinated, will reduce the amount of pollen in the air.  For more on this see The Allergy-Fighting Garden, by Thomas Leo Ogren. 

To read more about managing fertility in your landscape check out chapter 3 of  Designing Gardens with Flora of the American East by Carolyn Summers.

Groundcovers, do they need to be green all the time?

As I think about the landscapes that I have idealized from an early age, they are green and full of life all year long.  But I grew up in an area that did not have four seasons and at a time when droughts and water management were not something that we worried about.  So the expectation of having some sort of green ground cover 365 days a year was not difficult to achieve.  Now after living in the Northern half of the US for 40 some years I have come to realize that having four seasons means that there is a good chunk of time when the plants in the landscape take a break and rest. 

Vinca minor is a widely used and invasive groundcover, originally from
central and southern Europe, that is often used where an evergreen carpet is desired.   

English ivy forms a dense evergreen cover that spreads by both
 runners and seeds.  It is particularly damaging when it is allowed to climb trees.

This brings up a question, does all the ground need to be covered all the time?  Yes, for protection from erosion, extreme temperature fluctuations and evaporation coverage is beneficial.  Groundcovers, both living and dead, also provide wildlife habitat.  There has been increasing awareness of the importance of  providing habitat for overwintering insects as they are critical sources of food for birds and other predators.

Alleghany spurge, Pachysandra procumbens, native to the mountains
of the Southeast, acts as a more naturalistic groundcover.

Does it need to be green all the time? No, not really.  But there is a desire among many for a lush green ground covering year around.  This desire is' might I say, for primarily aesthetic reasons.  To get this year-round green in temperate climates many folks are drawn to non-native species like Japanese pachysandra, English ivy, Vinca minor , yellow archangel (Lamiastrum galeobdolon), wintercreeper euonymus, mondo grass and lilyturf.  Most of these species are invasive in many parts of North America.

Here's my listing of the importance of having a ground cover, roughly in order of importance:

Minimize Erosion by holding soil against the forces of rain and wind;
Water management, by improving water infiltration and reducing evaporation;
Soil Health, by avoiding compaction, maintaining good aeration, moderation temperature and moisture extremes.  All these help maintain a healthy soil microbiota;
Maintain ecology by providing places for native insects to overwinter, less disturbance provides better survival rates for overwintering insects and nesting sites;
Weed management, its harder for seeds to geminate on shaded soil, in competition with established plants or where roots cannot take hold; and,
Aesthetics, create a visually pleasing composition.

As I alluded to above, the ground cover does not need to be green and growing year round.  In fact, depending on the climate and the environment the most appropriate ground cover may not be green at all.

In the majority of cases the material covering the ground will be some sort of plant material.  Having a actively growing root network under the soil to stabilize it and keep it biologically active is the ultimate goal. Where climate and conditions allow having a living mulch is an ideal solution for protecting the ground. The plants making up this living mulch need not be green though all four seasons.  They just need to continue to to hold the soil in place.  Green and actively growing on top is nice but not a year-round necessity.

The following are descriptions of how natural groundcovers function in three habitats that are similar to what you might encounter in a residential setting: Woodlands, Grasslands, and Deserts.

Mayapples, Podophyllum peltatum, provide a dense cover throughout
the spring as the forest canopy leafs out.  They hold the soil
with a wide spreading network of rhizomes.

Spring beauties are another spring ephemeral that are found on forest edges.

Woodlands: In Eastern deciduous forests the ground is covered year around by a layer of decomposing fallen leaves, natural compost.  Similarly, in coniferous forest there is a slowly decomposing layer of fallen needles.   Depending on the amount of light there is an understory of perennials and shrubs adapted to those conditions.  Where there are gaps in the canopy and accessible soil, new plants can get a start.  Depending on the composition of the seed bank these may be native or non-native species.  In a well balanced system the amount of undergrowth will be determined by the available resources.  Because of the way the available light changes through the year the nature of the ground cover plants also changes through the seasons.  In springtime the ground may be covered with ephemeral species like mayapples and Dutchman's breeches.  By summer these disappear and the ground plane is less densely covered with shade tolerant species like ferns and sedges and understory trees and shrubs.  Fall and winter feature the return of fall leaves which slowly decompose to replenish the soil with nutrients as well as serve as habitat for overwintering creatures.

Grasslands: In grasslands the winter ground cover consists of dead leaves and stalks from the past growing season and a network of crowns of the overwintering plants.  A healthy layer of this plant debris serves to protect the soil and fill the necessary roles of a ground cover.  The root networks of perennial grasses and forbs help to hold the soil.  Standing stalks of tall grasses and perennials form important habitat for some overwintering birds and insects.  Where the ground has been cleared by natural (fire) or unnatural (cutting and raking) processes, space is opened up for new plants to grow, both desirable and unwanted, depending on the seeds that are present.

Little bluestem, Schizachyrium scoparium, is a common
component of many eastern grasslands and dry meadows. 
Even after it dies back in winter it maintains its visual appeal.

Arid lands: In desert environments growth is limited by the availability of resources, particularly water.  Here you typically see plants growing much further apart because they are limited by the amount of available moisture. Root systems of perennial species tend to be much larger in order to access sufficient moisture for growth and survival.  Particularly in hot deserts most of the organic material that falls to the ground gets burned up and does not contribute to build organic material in the soil for the long term.  In these environments a natural ground cover would be inorganic in nature, rocks, stone and sand. While plants may not stabilize the soil on the surface, many have very wide spreading shallow roots systems adapted to harvest rainfall before it evaporates.   These wide systems can help to stabilize the soil, leading to less erosion.  Trying to maintain a green ground cover in a desert environment can be very resource demanding and not at all sustainable.

The ocotillo and purple-tinged prickly pear cactus each have shallow
wide-spreading roots to scavenge water thus limiting what else can grow nearby.

If green in winter is really what you need there are several native species here in the Mid-Atlantic that fit the bill.  Native (near)evergreens include, wintergreen (Gaultheria procumbens), green and gold (Chrysogonum virginianum), heuchera, tiarella, Alleghany spurge (Pachysandra procumbens), golden groundsel (Packera aurea), evergreen ferns (Christmas and intermediate wood ferns) and some sedges, like creeping sedge (Carex laxiculmis) are good for partly shaded locations.  For sunnier sites moss phlox (Phlox subulata), wild strawberry (Fragaria virginiana), common and creeping junipers, barren strawberry (Geum ternatum), as well as some grass-like plants like prickly bog sedge (Carex howei).  On most sites these plants will still be green through most of the winter, but they generally will not be lush with fresh foliage

Golden groundsel in winter.  The interconnected leaf rosettes
are held close to the soil.

In spring golden groundsel puts on fresh growth and sends up flowers.  

Botanical History of Northern Loudoun County (VA)

For the past few months I have been preparing a talk for the Lovettsville Historical Society in Loudoun County, Virginia.  This talk focuses on the importance of native plants to the functioning of the ecosystem, how native plant populations have changed overtime, and their relationships with humans.  It also looks at important species for the indigenous peoples in the Northern Piedmont of Virginia and many of the native species that are hiding in plain sight.

Here's a link to the video Zoom presentation.  It does run a bit more than an hour.  There were just so many plants that I I wanted to talk about!

While doing the preparation for this presentation I did learn many new things.  Here are just a few of the things I learned:

• The new digital Flora of Virginia is a fantastic app for your smart phone.  Not only is there information on all the plants found in Virginia there is a ton of background information on the history of the land from its geology to forest use.
  
  
• I based my talk on the ecoregions and physiographic regions contained in Loudoun County.  These are defined by the climate and the soils present in the area.  While the soils in northern Loudoun County tend to be acidic there are a number of locations with calcium-rich soils.  These sites have a greater diversity of plants.  Some of the rich-soil sites are in the Blue Ridge ecozone where you would normally expect to find thin, acidic soils.
  
  
  

  

  From Sweet Run State Park you can find several different forest types.

  
  
• Sweet Run State Park has just opened in the northwestern corner of Loudoun County.  Here there is hiking access to a variety of forest types from dry oak forests, some calcareous oak forests and riparian woodlands in the  northern part of the Blue Ridge Ecoregion.
  
  
• To identify the vegetation types at specific locations in the county I used the interactive maps on Landfire.  Landfire is cooperative venture of the Dept. of the Interior and the Forest Service to map out vegetation coverage across the US as a means of better controlling wildfires.  This allows identification of forest types down to less than one acre resolution.  You can then look at an attached document that gives details about what constitutes each vegetation type.  It was a little clunky going between the maps and the descriptions, but there was a ton of information buried there.
  
  
• I also learned a lot more about the Pawpaw tree (Asimina triloba).  For example it is the largest tree fruit native to North America and that there is evidence for its presence on what is now North America from the Miocene period, 23-5 million years ago.
  
  

  

  These pawpaw fruits are not quite ripe.

  
  
• During the discussion afterward it was mentioned that researchers at MSU have isolated a gene from resistant elm trees that may impart resistance to the Emerald Ash borer.  A crop of potentially resistant trees is being grown.  This brings great hope for returning this significant tree to our forests.

Spring Finds 2023

 

A weakened garlic mustard.  Arrows pointing out insects on
the stem and leaf and a weakened flower stalk.

While out evaluating the effectiveness of winter spraying and pulling up garlic mustard this spring I noticed aphids on the plants that I had not noticed before.  These might be the garlic mustard aphid, Lipaphis alliariae.  These are native to Europe but have been showing up in the US of late.  I first noticed these dark colored aphids on plants that had been sprayed with glyphosate.  As I became aware of them I found scattered populations on the untreated garlic mustard as well.  Plants that were heavily infested with aphids were not coming into bloom.  Fortunately this species is host specific, meaning it only feeds on a single host plant, in this case garlic mustard. If you see them you can report the sighting on iNaturalist or EDDMaps, a web-based app for reporting and tracking invasive species.  

Close up of aphids on a garlic mustard leaf.  Coloration and
markings are consistent with the garlic mustard aphid.

The aphids on this garlic mustard are
interfering with blooming.

The area to the left of the line was sprayed with glyphosate in late February. 
The effects of spraying didn't show up until the weather began to warm in April. 
This photo was taken about 2 month after spraying.

As I mentioned in my last blog post one of my to dos was to spray a number of invasive plants with glyphosate before the native species broke dormancy.  I was a little late in getting this done so I had to be very careful not to spray the emerging native plants.  It took a long time to see any effect of the treatments. It became clear where I had sprayed after the weather got a little warmer and the Japanese honeysuckle started greening up.  The sprayed areas were definitely browner.  However, there is new growth of Virginia creeper, ash seedlings and grasses.  The box elders that were covered with honeysuckle took some damage, but they are now beginning to leaf out.  The targeted spraying technique that I have been using limits damage of non-target species and reduces the amount of pesticide applied but it also allows a lot of target plants to be missed.  As practiced, it is one of several tools I use to control invasives.  Pulling, cutting and replacing are all important components in my battle. While not 100% effective using my technique, it did set back the early growth of Japanese Honeysuckle and garlic mustard and multiflora rose.  This spraying has little effect on Oriental bittersweet, which does not put out foliage until much later. The cut stump method seems to be more efficient for shrubs and climbing vines (less overspray).  I will try to do the spraying in November this year after most of the native have died back.  There are studies that indicate that glyphosate treatments for garlic mustard at that time are more effective than in the spring.

Rattlesnake, or common grape fern, has a distinctive triangular shape

While putting out tick tubes a week ago (this is nearly a month later than I had planned) I came across a fern I had not seen before.  It has distinctly triangular appearance, quite unlike the Christmas and wood ferns that are pretty common here.  A photo sent to the ‘Seek’ app on my phone identified it as rattlesnake fern, Botrychium virginianum.  This is one of the grape ferns, named for the clusters of sporangia on the fertile frond that may look like a cluster of grapes.  The fern that I spotted lacked a fertile frond.

A Christmas fern (left) and an unusual form (right)

The pinnae of this fern are distinctly toothed, many with spiny edges.

Another unusual fern I spotted was in a clump of Christmas ferns, Polystichum acrostichoides.  Usually the margins of the pinnae (leaflets) are nearly smooth.  On this fern the margins of the pinnae were distinctly toothed, many were spine-tipped.  The pinules do have the enlarged lobe at the base, common to Christmas ferns.  So this probably is a variant of the regular Christmas fern.

The blue-green foliage of these twinleaf plants forms an effective ground cover.

I have been working on finding native replacements for vinca in a dry shady location for quite a while.  One plant that continues to impress me is twinleaf, Jeffersonia diphylla.  While its native habitat is rich moist woods, it seems to have found a home in the dry shade of this driveway planting bed.  After taking a year or two to settle in it has been doubling its spread each year for the past 3 or 4 years.  The flowers last for only a few days in early spring but the interesting foliage persists until fall. 

The branching habit of this violet sets it apart from most of the others
growing here. The large, toothed stipules indicate that this is pale violet.

Springtime is when most of the violets come into bloom.  By far the most common here are, appropriately, common blue violet, Viola papilionacea.  So when I saw a white violet in the woods I stopped to examine it.  Besides the white color, what distinguished this violet was its branching flower stalk.  Most violets only have basal leaves.  Checking in my Newcomb’s guide led me to ID this as pale violet, Viola striata.  Canada violet, another similar white violet has yellow coloration in the throat of the flower and lacks significant stipules.

Some of the flowers in my early May lawn.  Most noticeable
 are the Philadelphia fleabane (native) and the bulbous buttercup (not).

 No mow May?  I still haven’t mowed yet this year.  I have been allowing the fleabane and other natives time and space to flower and go to seed.  However, this also allows bulbous buttercup to do the same.  There are several aspects of looking at the ‘No Mow May’ trend.  It is valuable if your lawn contains early blooming plants that benefit insects/pollinators.  Natives like fleabanes, selfheal, spring beauties and violets, can benefit the local insect population.  If your lawn is a near monoculture of turf grasses skipping the mowing in early season will save on gas, but do very little to help the pollinator population.

 

Saw lots of salamanders in the pool this spring.

After opening the swimming pool this past month I found about a dozen salamanders hanging out in the cold water, about 58°F.  Normally salamanders are tricky to get out, but these were relatively sluggish and were easily caught in the basket skimmer.  These were most likely red-backed salamanders, Plethodon cinereus.  At this size these were probably a year of two old, old enough to be looking for a mate.