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.

Wednesday, January 10, 2018

Using Bare Root Plants

Over the 5 years or so that I've been here in Pleasant Valley (Zone 6b) I've been augmenting our grounds with more native species.  In order to get some of the species I wanted I've been getting more bare root plants than in the past.  What I like about them is that you can find many species that are not available in containers and that they are much less expensive, averaging about 1/3 the cost of the same plant in a container.  This lower cost is due in part to the lower costs of shipping, only the plant without the soil, and to lower production costs at the supplier.  The down side is that these plants are only available when they are dormant and that they need to be planted while it is still pretty chilly out, either in late fall or very early spring. So right now (January) is a great time to get in an order, in time for early spring planting.

I've had mixed success with these bare root plants.  Reasons for failure include not planting them in the right place, competition from existing plantings, deer browsing and some poor technique.   I won't go into the steps of planting bare root plants, they often come with detailed care and planting instructions.  You can also find instructions on the web. 

Here are some things I've learned from my experiences:

Get plants in the ground quickly.  If possible get them in the ground within a day or two of when they arrive.  While you can keep them in cool storage for a time as long as the roots stay moist, or you can heel them in, by laying them in a shallow hole and covering the roots with moist soil.  I seem to be having better results with plants that I put in place quickly.  It is important to get plants in the ground while they are still dormant.  This way roots can get in good contact with the soil before the buds open and put a greater stress on the plant.  I have planted bare root stock in both late fall and early spring.

This Canaan fir has been in the ground for about 2.5 years. 
It started at about 6 inches.  The chicken wire and steel posts help
protect it from male deer who will rub off the branches
as they clean their antlers.
Get good soil contact with the roots.  When planting in the garden make sure that soil is well packed around the roots and spread the roots out in the hole as you layer in the soil.  What I have been doing lately is carefully spreading out the roots as I have been adding in the soil.  After about half of the hole is filled I fill the hole with water and let it settle.  This removes air pockets and improves soil contact with the roots.  I continue to fill in around the plant with soil, continuing to spread out the roots, followed by another through watering. 

Plants in pots need time to develop a good root system.  For bare root plants that I haven't had time to plant, I've potted up with container mix, watered them well and left them in a cool protected location.  Only about half of the plants survive until the weather warms up.  Not a particularly good record.  The survival rate of these potted up plants after transplanting has not been great either.  What I believe to be happening is that the roots have not had a chance to develop while in the pot and there is too much damage done to these weak roots when they are transplanted into the garden.  I've had better success with plants that I've allowed to grow in the pot for a full season before going out in the yard.

Protect plants from critters and competition.  I've lost a number of young plants to deer browse, so now I put a little chicken wire cage around most of my new plants.  I've also lost a number that have been shaded out by surrounding vegetation.  When planting in mid-fall or early spring it is not obvious how much crowding there will be come June and July.  I need to remember that these are still little plants and they are easily over-shadowed by larger established vegetation.  Like any new plant, bare root plants need extra water while they are getting established.  I also tie a fluorescent pink ribbon around each new plant so that I can locate them more easily when clearing out the competition.

Close examination of this Juneberry shows that the leaf buds
are still plump and healthy looking.  A good sign
that it will survive the winter.  The pink ribbon helps me keep
track of these new additions in the landscape.

Here are some of the species I've worked with:
Here is the Twinleaf in bloom.  This is one of the first bare root plants
I put in.  It's now 4 years old.

Perennials:  Celendine poppy (Stylophorum diphyllum), Christmas fern (Polystichum acrostichoides), Merrybells (Uvularia sessilifolia), Twin leaf (Jeffersonia diphylla),and Jack in the Pulpit (Arisaema triphyllum) have performed quite well.   Mayapple (Podophylum peltatum) and  Large-flowered bellwort (Uvularia grandifolium) are in dryish soils and have been struggling.  The wild ginger (Asarum canadense) was planted in a very challenging location, under an English walnut and surrounded by vinca, and has faded away. Alleghany pachysandra (Pachysandra procumbens) was planted in November in a dry shady location, so we'll see how that works.

Shrubs:  Black chokeberry (Aronia melanocarpa),  Gray dogwood (Cornus racemosa),  American hazelnut (Corylus americana), Witchhazel (Hamamelis virginiana), Spicebush (Lindera benzoin),  Chokecherry (Prunus virginiana),  Smooth sumac (Rhus glabra), Red elderberry (Sambucus pubens),  and Meadowsweet (Spiraea alba v. latifolia).  The meadowsweet and hazelnuts have been the most successful at getting established.  Smooth sumac has suffered from both deer browse and being over shadowed by other aggressive plants.  The red elderberries and witchhazel which did not make it were in very shady spots.  The chokecherries were potted up when they got here and only 2 of the 6 survived.  Those 2 were planted out 3 months later.  Soon we'll see how they made it through their first winter.   

This American hazelnut has been in the ground
for about a year now.  In the inset you can see the swollen leaf bud
that indicates that this branch is still alive.

Trees:   Canaan fir (Abies balsamea v. phanerolepis),  Concolor fir (Abies concolor),  Juneberry (Amelanchier canadensis),  Redbud (Cercis canadensis), Red cedar (Juniperus virginiana), Tupelo (Nyssa sylvatica),  Virginia pine (Pinus virginiana), American plum (Prunus americana), and  Douglas fir (Pseudotsuga menziesii) .   The best performers of this group are the tupelo and the Douglas and Canaan firs.  Ones that have not worked out here are the Virginia pine (wrong soil type here), Redbud (location had too much shade from competition), Red cedar  and  the Concolor fir (uncertain).  The American plum was just planted this fall, so the jury is out, but they look OK so far.