Monday, September 24, 2018

Japanese Stiltgrass Sitrep


For the past 5 years, since moving to rural central Maryland, I have been trying to figure out how to eliminate Japanese stiltgrass, Mircostegium vimineum, from my property.  This has been the subject of multiple blogs over the years and, unfortunately, will be so for a few more years.  Here's a link to my previous post on stiltgrass.

This area in the woodlands took about 30 min to clear by hand
and filled about half of the basket.  Rosy sedge is growing well underneath.
In shady woodland areas pulling stiltgrass out by hand, or string trimming and removal of the cut grass, seems to be pretty effective.  Removing the grass in late summer, prevents a new crop of seed from being produced.  The shady conditions seems to limit germination and flowering of the stiltgrass so that the sheer  volume is more manageable.  Annual pulling has reduced the amount of stiltgrass significantly.  As the stiltgrass has been going down I am seeing more native species, like Virginia jumpseed, Polygonum virginianum.

In part to full sun areas pulling the grass alone has not been as successful.  In some beds, with lots of competition the amount of stiltgrass has been reduced significantly.  In more meadow-like settings I have not seen great results, despite removing large quantities of stiltgrass each year in mid-summer.  One possibility here is that there is enough seed produced in the cleistogamous flowers trapped at ground level by the undergrowth to regenerate the seed bank. 

Getting stiltgrass out of the lawn is a more recent area of focus. There are two methods that have been effective for me.  One is to use a garden torch to burn the stiltgrass to the ground in late summer-early fall.  This eliminates the cleistogamous seeds in the lower stems and, in late summer, it is too late in the year for new plants to mature.  The burned areas are immediately ready for reseeding and most perennial grasses present will regrow from the roots, as long as you don't overdo it with the torch.

Another method that I tried last year that has proven very effective in the lawn is to use a pre-emergent herbicide in early spring.  Most products that work on crabgrass should work on stiltgrass.  See this earlier post for more details.  I used a product containing 'Dimension' (Dithiopyr) and had areas that were free of stiltgrass through the entire season.  To battle stiltgrass, these herbicides should be applied a couple of weeks earlier than you would for crabgrass.  When the forsythia are in early to mid-bloom should be about right. 

In the treated area I applied 'Dimension' pre-emergent herbicide the 3rd week of March. 
Now, at the end of summer, it is relatively free of Japanese stiltgrass.  In the untreated areas you can see
the brownish color of stiltgrass as it is beginning to die at the end of the season.

One problem with pre-emergents is that they are pretty much non-selective and will inhibit the growth and/or development of most seeds in the soil.  (Dithiopyr also inhibits the growth of new roots, not so good for really young plants.)  They are not appropriate to use at the time of reseeding or on lawns that are not well established.  For this reason I am reseeding/over seeding as early as possible this fall so that the new turf can get established before I treat again next spring.  In 2018, I applied Dimension at the end of March, this year I will wait until early-April (mid-to-late in the Forsythia bloom) to give the new lawn some extra time to grow.

This is an area where I raked out the stiltgrass and thatch to prepare for overseeding.
Most of this debris came from the 'untreated' area.
This year I am overseeding most areas with a sun-shade blend containing tall fescue, red fescue and perennial blue grass.  I have also put down the 'No Mow' blend of red and creeping fescues in areas of open shade where there is less competition from other turf grasses.  I'm located on the southern edge of the 'cool season' grass zone.  If I were a few hundred miles further south where warm season grasses dominate, I would be trying the native buffalo grass/blue gamma grass mixtures.  Raking out stiltgrass from the lawn alone has not proven effective.  While it removes a large mass of stiltgrass, it likely leaves enough seed behind to continue the infestation.  Raking is still necessary if you are going to reseed, in order to provide access to the soil for the newly applied grass seed.


You can see how poor this unmown area looks after the stiltgrass has been pulled out. 
This area has since been overseeded with 'No Mow' fescue.  If the fescue germinates
well this fall, I will probably treat  this area with a pre-emergent come springtime.
One suggestion that I read about was to leave stiltgrass alone until late summer, then mow it down short.  The idea is that by not mowing throughout the summer, fewer cleistogamous seeds are produced and the late timing of this mowing does not give the plants an opportunity to produce new flowers.  I have had a hard time getting this to work for me.  If you leave the stiltgrass to grow for too long, all of the shorter vegetation is starved of sunlight.  I tried this technique in one area, and we will see how quickly the perennial grasses bounce back.




Wednesday, September 19, 2018

New Sloping Path

One area in my lawn has a steep grade, about 28%.  That is a rise of 4.5' over a 16' run.  The lawn tractor could make the climb, but usually left some tracks, particularly if the ground was moist.  Also when walking through that area it was a real chore.  This is a prime area to replace the turf with a lower maintenance planting and to put in some steps to make navigation easier.

When doing a project that involves both planting and hardscape (elements like steps, walls and patios) it is best to put in the hardscape first.  The positioning of plants has greater flexibility and there is usually less heavy lifting than when positions stones.

Overall Plan for this sloping site.  The 9 steps are shown as rectangles,
though in reality they are irregularly shaped.  The highest elevation is at the top,
sloping down about 4.5 feet to the lowest step.  Scale 1" = 3'.
The first step in putting in steps on a hill is to determine the slope of the hill and then position the steps.  Having a consistent rise and step length makes the steps easier to navigate.  The overall rise here was 54".  For a 6" rise/step, that calls for 9 total steps.  At this time you can also move the shrubs around, while they are still in pots, to determine how you would like to position them.

Here, after the steps were installed, you can see the level lines that were used to determine the overall slope
and to guide the installation so that the change in elevation from step to step was about the same.
(In the background you can see the tamper that is used to compact the soil and paver base.)

I try to use a sustainable approach to landscaping whenever possible.  In this case that means using stepping stone materials that were on site, left over from an earlier dry laid stone wall project.  These stones give a naturalistic appearance.  Also by using the same materials the two projects become visually and materially united.  One down side of using irregular stones as steps is that each step needs to be engineered individually to set it on a solid foundation.  Rectangular steps installed in a straight line require less customization.

For steps that get a lot of use a crushed stone base of 6 or more inches is recommended.  Since these steps are only for occasional use, I cut back a bit on the amount of base.  The riser for each step is supported by 2-3 inches of compacted paver base separated from the soil by a layer of landscape fabric over the compacted native soil.  Behind this reinforced riser is compacted fill.  Supporting the riser with a firm base gives the step a firm feel underfoot.  It's much more comfortable to step onto a firm, well seated step than one that wobbles even a little.

Here's a view underneath one of the steps showing the compacted paver base
underneath the the riser and the landscape fabric that is being used to hold the dirt
behind the dry-laid riser.  For some of the steps that were difficult to stabilize I used
construction adhesive to secure the step to the riser.

The standard formula for garden steps is that the tread length be about 26" minus 2 times the step height. 

Tread Length" ≈ 26" - (2 x step height")
So for a 6" step height the tread length should be approximately 14".  The formula is based on a comfortable stride length for the average person.  Had I put he steps in a straight row down the slope it would have been close to this formula.  Instead I spread the steps over a longer, curving course.  I thought that the slightly longer course would have made for an easier, more gentle climb, but instead the longer distance between steps makes the trip feel less certain, especially when going downhill.

However, the way I chose to do it created a more naturalistic look and used materials that were already on hand.  Also by following the existing slope I minimized the changes to the existing grading.  Looking back, if these steps were to be used on a regular basis or in a more formal setting I would have built a deeper foundation, used more regularly shaped stones and followed the formula more closely.

This is the area after scalping the grass with a string trimmer. 
I also used a garden torch (circled) along the edges to burn the areas that had
Japanese stiltgrass in an attempt to kill any new seeds/seedlings. 
Once the steps were in it was time to eliminate the existing grass and weeds.  (This could have been done before installing the steps, but I felt it was less disruptive to the stability of the slope to wait until the steps were in place.)  There were several options for getting rid of the existing turf and weeds:  dig it out, spray it with a broad spectrum herbicide, or cover/smother with cardboard and mulch.  Digging is a lot of work and could destabilize the slope.  Herbicide would be easy and would be less disruptive to the soil surface, leaving roots intact to hold the soil.  I opted for the cardboard smothering/mulching method.  It leaves the soil intact, is non-toxic, and there are limited debris to deal with.

I used thick cardboard from moving boxes to cover the unwanted grass.
After mowing/scalping the existing grass, I covered the slope with cardboard and pinned it in place with landscape staples.  After moistening the cardboard to make is more flexible to conform to the soil surface I covered it with 2" of wood chips.  Most of the lawn will die due to lack of light in a few weeks, but planting can be done sooner by cutting holes through the cardboard, removing all the exiting grass from around the area and inserting the new plant.  The re-exposed soil should be well mulched or recovered with scraps of cardboard to keep the old grass from growing through.

The cardboard was covered with about 2" of woodchips that were left by our
arborist this spring. I started planting about 10 days after spreading the chips. 
For the areas between the steps I dug out the grass by hand since it was hard to get small pieces of cardboard to stay in place and there will be a lot of gaps where the grass can peek out and get re-established.

Now it's time to plant...

The plants I chose for this area are all low maintenance natives that are from the mid-Atlantic area, mostly ones that grow nearby.  I chose plants that area fairly low-growing to minimize the amount of pruning needed to keep the pathway open, both physically and visually.  The selection of plants will have something in bloom from early spring through fall.  You can see the plant list in the drawing at the beginning of this post.

The Grow-Low sumac are at the foreground in this photo, with the Red Sprite holly at the back.
First to go in are the woody shrubs. I put in three Grow-Low aromatic sumac, Rhus aromatica 'Grow-Low' and one of the shorter female cultivars of winterberry holly, Ilex verticillata 'Red Sprite'.  I chose this sumac because it grows under a almost any condition, it only grows to about 3' tall and is a good choice for stabilizing slopes.  In addition it has a nice bright orange fall color and tends to be resistant to deer browse.  The female Red Sprite winterberry holly has a proper male mate in the nearby Jim Dandy.  I also transplanted in some extra black and brown-eyed Susans, Rudbeckia sp., to fill in around some of the newly planted shrubs.

As for flowering perennials, located 1-2 feet from the path, I chose foxglove beardtongue, Penstemon digitalis, short-toothed mountain mint, Pycnanthemum muticum, black cohosh, Actaea racemosa, and aromatic aster, Symphyotrichum oblongifolium. As the grass components I also put in some bottlebrush grass, Elymus hystrix, and wavy hairgrass, Deschampsia flexuosa.  I really like the looks of the bottlebrush grass and it is a species that commonly grows on the woodland edges in this area. Finally around the stepping stones and outer edges I put in the shortest species, two cultivars of moss phlox, Phlox subulata, and Pennsylvania sedge, Carex pensylvanica.

This is the completed installation.  I finished this in mid-July - later than is optimal for planting around here (mid-Jume would have been better).  I added in some old landscape timbers that were taken out from an earlier project to from the upper and lower edge of this garden.  Reusing materials on-site is part of being sustainable (and cheap).
As we are approaching fall the deer have come through and ate back the Penstemon and stripped most of the leaves and berries off of the holly.  I'm surprised about the holly, but our deer usually eat up most new plants no matter what they are, then leave them alone the following year.  Also the cohosh died back early, it may be getting too much sun, we'll see if it comes back next spring.






Friday, June 29, 2018

New Plants for 2018

One of my big plans for this year was to replace the non-native, invasive leatherleaf grape holly, Mahonia bealii, with some native shrubs.  Features of the grape holly that I wanted to preserve were flowers and berries for wildlife and some evergreen qualities that help define that space in the winter.  I decided to use inkberry hollies, Ilex glabra, to carry most of the load.  Also in this space I put a 'Snow Queen' oakleaf hydrangea, Hydrangea quercifolia 'Snow Queen' to continue a screening effect started with two older oakleaf hydrangeas nearby.  A few cinnamon ferns, Osmunda cinnomonea, completed the composition.

Shrubs from left to right are Jim Dandy winterberry holly, Nigra inkberry and Shamrock inkberry. 
Also new are the bright green cinnamon ferns toward the front.  The background is dominated
by a Carolina allspice, Calycanthus floridus.

To create some size variation in the evergreen I got a variety of inkberry cultivars.  'Shamrock' being the shortest (3-4') is in the front and behind it are a 'Densa' (8-10') on one side and 'Nigra' (4-6') on the other.  All three of these are listed as female plants.  To get berries a male plant is needed.  Unfortunately I was not able to get hold of a male plant (such as the 'Chamzin' cultivar).  I saw somewhere that any male holly that blooms at the same time is capable of fertilizing a female, so I put in a 'Jim Dandy' winterberry holly, Ilex verticillata 'Jim Dandy' nearby.  This bloomed at about the same time as the three inkberries. 
Since I was watch the flowers rather closely I noticed that while both 'Densa' and 'Nigra' had exclusively female flowers, 'Shamrock' appeared to have both male and female flowers.  I could find no mention of 'Shamrock' bearing both types of flowers.
Also on the holly front I added a 'Southern Gentleman' winterberry near a well established female.  A few years ago I but in an early blooming 'Jim Dandy' as a pollination partner, but berry production did not improve much.  The 'Jim Dandy' is usually finishing up blooming just as the established female is starting to bloom.  This new 'Southern Gentleman' here has started blooming about 2 weeks later than 'Jim Dandy', hopefully in better synch with the female.  Maybe this year we will get a bush full of red berries. 

Here's the slope prior to planting.  The winterberry is at the top left and
the lower growing aromatic sumac cultivars are on either side of the steps.
 In another area of the yard is a slope almost too steep to mow (about 30% grade).  This year I've decided to put in some steps and plant the slope with native shrubs, perennials and grasses so that it can be left alone.  New plants for this area include 'Grow-low' aromatic sumac, Rhus aromatica 'Grow-low', 'Red Sprite' winterberry holly, Ilex verticillata 'Red Sprite', and fireweed, Chamerion angustifolium.  The 'Red Sprite' is a female clone and was put in as a partner for the 'Jim Dandy' that I planted a few years back. 

Tried to grow fireweed from seed last year, but no luck. 
This year I got some as seedlings.
Here are two red oaks that I will be planting in the woods.
These saplings are about 4 years old.
In the woods around our house a number of older trees are dying.  Some of this may just be natural, some may be the work of the emerald ash borer.  I've also been identifying and killing as many tree of heaven, Ailanthus altissima, as I can.  To fill the open spaces I've been planting oak saplings.  This year I am putting in the more shade tolerant oak  species, red and black oaks, Quercus rubra and Q. velutina.  [P] 

We are also seeing a number of our white pines, Pinus strobus, in our wind break coming apart.  These were planted 40-50 years ago and are probably not in their ideal habitat.  To fill in the gaps in this row of evergreens I've planted some seedling of Canadian hemlock, Tsuga canadensis.  I've spaced these out widely so that any future attack by wooly adelgid will be slowed, since the plants won't be in contact with one another.  I've marked the location of each with a pink flag, otherwise these little plants would disappear into the undergrowth.
 
I also got a bunch of bare root wild ginger, Asarum canadense, in early spring.  I would like to use them as aground cover along with some Heuchera and violets.  So far most of these are surviving, but they do need some help by removing some of the competitive plants.  My previous attempt did not go so well as the plants were overwhelmed with vinca  and the leaves of an English walnut. 

Most of the American plums, Prunus americana, that were planted last fall survived winter.  One died rather suddenly this spring when all the leaves wilted.  There was a lot of insect activity near the roots, or it could have been too much shade from a neighboring box elder.


I've always loved the look of blue cohosh, Caulophyllum thalictroides, blanketing a shady hillside.  I've been reluctant to plant it in the past because I haven't seen it growing nearby, even though I seems like the right conditions.  This year I broke down and bought a couple of plants to put in on a shady, moist hillside.  This is an area where I have been removing garlic mustard and Japanese stiltgrass, so it's time to get some more plants in there to take their place. 


Post bloom, this Itea tends to blend in with the surrounding foliage.
A few years back I planted a small Virginia sweetspire, Itea viginica, possibly 'Henry's Garnet' under a tulip tree.  It has never got too tall.  Possibly due to the shade and possibly due to deer browse.  Despite its lack of size, this year it managed a couple of blooms.  Encouraged by this, this year I added a larger specimen to a sunnier location.  'Little Henry', a cultivar growing to about 3', was my choice.  It has a compact habit and large flowers.  While the flower display on this one this spring was impressive, now at the beginning of summer it's hard to recognize.  It should have good fall color, though.








Wednesday, May 16, 2018

Stiltgrass progress - May 2018


It would be nice if the growth of Japanese stiltgrass, Microstegium vimineum, would wait until we were done dealing with garlic mustard for just a little while, but I have seen signs of it germinating here (Central Maryland) in early May.  So now is a good time to take a look at how some of the steps I've been taking to get rid of this invasive grass are doing.
A snapshot of one of the lawn areas.  In the foreground is
Zoysia grass, still in the process of greening up. 
This grass grows thickly and excludes many weeds.  Further
on are areas where Japanese stiltgrass has infested the lawn.

This is what a shady, unmanaged area looks like.  The arrows are
pointing to areas with a high density of stiltgrass seedlings. 
Also present are plantain, dandelions and violets.
In areas where I have not been actively managing Japanese stiltgrass I am seeing dense patches of seedlings, mostly in the gaps between clumps of grass and other lawn plants.  This area has been overseeded with a 'no-mow' fescue, but otherwise gets no special treatment.
Vigorous raking does seem to have reduced the number of stiltgrass seedlings in this early period of germination.  This practice will be continued here to see if the lawn can grow back together to exclude future invasions.  This method takes a lot of work, especially if I were to expand beyond the 100 sf test area.  Left alone even these few seedlings would expand to fill in the gaps in the lawn and produce a significant crop of seeds.

In this area I have been vigorously raking the lawn in mid-
 to late-summer for the past 2 years to remove established stilgrass plants
to try to reduce the number of seed produced.  The arrows (3) point
 to small clusters of stiltgrass.

In the areas treated with the pre-emergent herbicide, Dithiopyr ('Dimension'), I've noticed little to no seedlings of stiltgrass, or other plants for that matter.  Reflecting back on the timing, I should have waited until mid-April to apply this material so as to let some of the cool season grasses get started.  But it's hard to predict when a warm snap will come along and mess everything up. 

I
This area was treated with a pre-emergent herbicide, dithiopyr ('Dimension') at the
end of March.  I was not able to spot any stiltgrass seedlings in this area. 
Other plants here are clover, Indian strawberry, and purple lamium.
One of the most dramatic results was where I used a lawn torch to burn off all the surface vegetation in late summer last year when the stiltgrass was in flower.  A few perennial grass plants bounced back after a week, but it was necessary to reseed the area to provide cover for the soil.  As I mentioned awhile back burning seem to be most effective in the fall prior to the seed ripening/dispersal.  Burning also eliminates the cleistogamous seeds found low on the stem.  Burning after seed is dispersed is too late and spring burning just opens the group to germination from the existing seed bank (see this report from the Forest Service.)  The burned area seems completely free of stiltgass, as well as some other weeds while the contol area is dense with stiltgrass seedlings.

 
Here is a comparison of an area that I burned with a yard torch in late summer
last year (right side) with an control patch where nothing was done. 
The burned are was overseeded with a tall fescue blend, nothing for the control. 
Arrows indicate dense patches of stiltgrass seedlings.
  
While it is too early to be certain, it appears that there is progress being made against stiltgrass in my lawn.  The pre-emergent seems to be working at this early date.  The downside is that it also affects desirable seedlings.  As indicated on the label, it is best used on established lawns.  There is a possibility that stiltgrass will reemerge in mid-summer after the pre-emergent breaks down (about 3 months after application).  Burning seems to be an effective non-chemical approach.  It looks bad for a little while, but there are not residual effects to worry about.  Since stiltgrass seed can remain viable for 5 years in the soil I will need to stay with this for some time to come.


Wednesday, April 25, 2018

Preping the Garden

Last year's garden did not do so well.  On reflection there are a number of reasons, some of which are in my control.  Others, not so much.  To do well all plants need sunlight, nutrients and water.  And in my location, protection from pests.  In my mind I was providing all those, but in practice I was coming up short.

Here's the garden half-way through: last year's growth raked out, garden mowed low,
3 beds weeded with scuffle-hoe and rake.  Note the log pile just beyond fence,
all that remains of the big box elder, Acer negundo.

I have been adding compost, shredded leaves and a little organic fertilizer in the past. Last spring I sent samples for a soil test and learned that levels of most nutrients were too high: phosphorus, potassium, calcium and magnesium.  On the positive side, there was an increase in the organic content and cation exchange capacity (a measure of fertility). So this year I will only add an organic nitrogen fertilizer to the soil.  Of the organic choices that had minimal phosphorus and potassium I considered soybean meal and feather meal, both with about 7% nitrogen.  I opted for the soybean meal because I could by it from the feed store for about 25 cents a pound.  One warning with the soybean meal that I read was that it could inhibit the germination of small seeds.  So I'm not using that in the beds where I am planting lettuce, collards, chard or arugula.  I'm hoping that the beans, peas, spinach and others will be OK.  I got all the fertilizer down now (mid-April) and that should give it some time to be digested by the soil biota and have food ready for the bulk or the planting in mid-May.

As far as sunlight goes, I thought that I had good exposure.  That may have been the case 5 years ago, but the trees have been growing taller and eventually cutting a couple of hours of direct sun from the garden area.  While I hate to remove trees, there was a big box elder just south of the garden that appeared to be causing most of the trouble.  Since box elders are pretty common here, it was only with a little difficulty to say good-bye to that tree.

We usually have good rain here and I have a soaker hose to put in place for supplemental water.  So for moisture, I should be in good shape.

The last problem is the critters.  Every time I think I have a solution, they seem to adapt, or another problem crops up.  The double fencing seems to keep the deer at bay and the buried chicken wire slows the ground hog down; however I think it can still climb over the chicken wire when it really wants to.  Last year many seedlings were getting eaten and I'm not sure who to blame.  This year I have a motion activated trail camera to use so I can get a clue as to what is getting into the garden.  I am also expecting that the thicker layers of wood chip mulch will make it more obvious where any burrowing is taking place.

Other garden preparations:
I cut back the long tips of the wild blackberries growing on the outer fence. 
This improves fruit quality and gives more space to move around.

I've allowed wild blackberries to grow along the outer fence of the garden.  This re-enforces that area against deer.  I've read that by pruning the side branches to 4-8 leaf buds the fruit quality is improved.  I've been doing that for a couple of years now and it seems to be true.  The 'managed' wild blackberries have larger, sweeter fruits than the unmanaged plants nearby.



Rather than cutting to the ground I left 1-2' of the hollow
Monarda stems as potential bee nesting habitat.

Another plant growing along the fence line is wild bergamot, Monarda fistulosa.  These grow up about 4' and are very attractive to bees in early to mid-summer.  The hollow stems can provide nesting sites for small bees, like mason and leaf-cutter bees.  Since these bees build their nests in summer and develop there through the fall and winter, these stems need to be left intact for over a year.  When I did the garden clean-up I cut most of these stems to leave 1-2' intact.  These old stems will disappear into the new growth by the end of spring.  I just need to remember to leave them alone for the next year. 

As a result of a lot of tree work done here this spring, I have a large supply of wood chips.  This year was therefore the year to replenish the garden paths with fresh chips.  Many folks don't like to use fresh chips in the garden because they take up nitrogen from the soil as they decompose.  Since I want to suppress growth on the paths and garden perimeter, these fresh chips are just the thing to use.  (This loss of nitrogen from the soil only occurs where the mulch touches the soil and does not significantly affect the root zone unless the wood mulch is dug into the soil.)

The gardens all ready for plants:  freshly weeded, fertilized and mulched. 
I ran out of mulch for the last two beds...we'll call this an experiment. 
The remaining greenery are mostly native perennials like
beebalm and coneflowers to attract pollinators.
One new thing I am trying this year is to put down a wheat straw mulch over the bare soil.  This should help with moisture retention and reduce the number of weeds, or at least those from new seeds being blown into the garden.  I am expecting that wheat straw is much lower in weed seeds than is regular hay.

Now it's (past) time to plant those peas!!!



Monday, March 26, 2018

The Forsythia are in bloom, now it's time to...


The blooming of Forsythia is a signal to begin a number of outdoor tasks.  It signals a good time to apply preemergent herbicides for control of summer annual weeds.  I'm giving this a go this year as another tool to get rid of Japanese stiltgrass, Mircostegium vimineum, from my property.  I've been making progress in the woods where I have been pulling it out in July and August as it is getting tall.  Getting it out of the lawn is another matter.  


It's the end of March, and although the Forsythia started blooming
at first in January, I think they are doing it for real now.
There, repeated mowings keep it short and actually induce early seed formation in the lower stems.  I have been raking/combing it out of the lawn in a few areas but that does not seem very effective.  It seems that while I remove a lot of the weed, any remaining stiltgrass just expands to fill in the gaps.  So while I prefer to avoid the used of synthetics, I've tried going it alone for a couple of years and now I need some help.  

Many of the common preemergent herbicides used for crab grass control have been found to be effective on stiltgrass when applied prior to seed germination.  Preemergents that have been shown to be effective include Dithiopyr ('Dimension'), Pendamethalin ('Pendulum'), Prodiamine ('Halts') and Trifluralin ('Preen Weed Preventer').  One of the challenges is finding a preemergent that does not come with added fertilizer.  In my case I do fertilization in the fall, since I am growing mostly cool season grasses, particularly fine fescues, Festuca rubra cultivars.  Fine fescues have low fertilizer demand and I see no good reason to apply fertilizer at a time when weeds are about to take off. The product I found contained only Dithopyr, no excess fertilizer.



Hairy Cress is a winter annual weed that has been taking over here.  Last year I mowed
it early before much of it started producing seed.  This year I'm hoping
 to get some added help from the preemergent herbicide.

As an added bonus this may help control the hairy bittercress, Cardamine hirsuta, that is growing in the lawn.  This weed is a winter annual, sprouting in fall and again in early spring.  While it dies back by mid-spring, this creates gaps in the turf that provides space for the stiltgrass to fill in. 

Dithopyr works by interfering with development of new roots, after seeds have germinated.  Perhaps I should have waited a little longer to put this down in order to allow the existing grasses to get further along, but I didn't want to forget. We'll see how all this works out later in the summer when I can compare treated and non-treat areas for amount of stiltgrass.  Check out this earlier post for some things I tried last fall. 


Sunday, January 28, 2018

Replacements for Nandina and other learnings

Recently I wrote an article for Houzz on plants to use instead of Nandina domestica, aka Heavenly Bamboo or Sacred Bamboo.  This overused Asian species is adaptable to a wide range of growing conditions in USDA zones 7-9 and has reached invasive status in the Southeastern US.  In Maryland it is listed as a Tier 2 invasive plant meaning that, while it can still be sold in Maryland, it must be accompanied by signage stating that this is problematic species. 



In addition to its invasive characteristics, the bright red berries so prominent in winter are actually quite toxic to over-wintering birds.  The cedar waxwing is particularly susceptible due to their feeding behavior.  Blue Jays and Mocking birds are examples of other species that are at risk from this shrub.

You can read more about the toxicity of Nandina berries to birds in this post from Audubon Arkansas. You can mitigate this problem somewhat by planting more plants that bear fruit late in the season, particularly native species; but, you should not consider Nandinas as wildlife-friendly plants. If you want to use Nandinas for aesthetic purposes consider cultivars that do not produce berries such as 'Nana', 'Nana Purpurea', 'Atropurpurea Nana', or 'Gulf Stream.' These non-bearing cultivars are also less likely to spread outside the garden.

One of the species that I recommended in this article is Oregon Grape, Mahonia aquifolium, and other members of the genus.  This broadleaf evergreen shrub is native to the Pacific Northwest, but is also found growing wild in some eastern states, most likely as a garden escapee.  I thought I had some growing in my backyard, too.  While researching this species I discovered that what I had was, in fact, Mahonia bealei, Leatherleaf Mahonia.  This species, originally from western China, is listed as invasive in many of the same states as Nandina.   



Here are two Leathrleaf Mahonia growing in a clump in late January. 
This species of shrub typically grows 4-10' in height,
compared to 3-6' for the Northwest native Oregon grape.
The bright yellow flowers of Leatherleaf Mahonia bloom in late winter to early spring
on clusters of terminal racemes.  This species can be distinguished from Oregon Grape,
M. aquifolium, by the number of leaflets, 9-15 vs. 5-9, for Oregon grape. 
Also the leaf color of leatherleaf mahonia is a dull bluish green compared to
the shinier dark green leaves of Oregon grape.

Learning that what I thought was Oregon Grape was actually a non-native species with invasive tendencies, I've decided to replace it with species native to this area.  Even before this revelation I was considering replacing it with a more appropriate East Coast species.  I would like to have an evergreen shrub that likes moist soils and open shade.  Looking at my list of Nandina replacements for inspiration, I think I will go with Inkberry Holly, Ilex glabra, as the replacement. As with most hollies I will need both a male and a female plant to get berries for the birds.  Fortunately there are both male and female cultivars available in the nursery trade so I will be able to start an inkberry family without too much trouble.  As the male I will go with 'Nordic', a fairly compact species.  There are more choices for the female.  I would like them to grow to about 6 feet, so I have a choice of 'Compacta', 'Densa' or 'Nigra'.

This inkberry is part of a new parking lot planting at a local library
that features mostly native species.  It does well in part to full sunlight. 
My site may be on the shady side, but that may encourage
a more open form that I would like for my particular application.