What plants to grow under Chinese elms

(Question)

Hi,
I live in North York, and I am currently trying to plan the plants to be planted along a new 15m lattice fence. I would very much appreciate if you could give me some advices.
The fence is facing south, but lies along a row of Chinese elms, which are old and high (about 10-20 cm behind them). The trees make the soil pretty dry and create dappled shade beneath them. There is also a big magnolia and a big cedar in front of the fence (about 6-7m in front), which also increase the shade. I was initially planning to plant only ornamental plants and climbers, but while searching for them I came across many web sites urging to plant native plants only. Now, I am thinking to plant some ornamental and some native shrubs and climbers. Later I may add some native ground covers, grasses, sages and flowers.
Regarding the climbers, which I would plant right next to the lattice fence, i.e., right next to the Chinese elms, I was thinking to plant:
1. Climbing hydrangea (Hydrangea anomala ssp. Petiolaris)(2 of them)
2. Schizophragma hyd. ‘Rose Sensation’
3. Clematis virginiana (native plant) – if I manage to find where to buy it, or Clematis ‘Comtesse de Bouchaud’
4. Lonicera sempervirens ‘Major Wheeler’
5. Lonicera periclymenum ‘Scentsation’
I did not want very aggressive vines nor Virginia creeper, since I have the latter one in three places in the garden already. I would appreciate your opinion about these plants – whether they can grow well in the environment which I described to you. If you would have any other suggestion for a climber for shade and dry soil (or a different variant of the above plants), especially if it would be a native one, that would be great.
Regarding ornamental plants, I would plant them about 1- 1.5 m in front of the climbers. I am currently thinking to plant the following plants:
1. Picea pungens ‘Glauca Slenderina
2. Aralia cordata ‘Sun King’
3. Acer palmatum ‘Crimson Queen’
4. Hydrangea paniculata ‘Vanilla Strawbery’
5. Thuja occidentalis ‘Jantar’ (3 of them)
6. Hosta “Humpback Whale’
In the corners of the garden (at the two edges of the fence) and orthogonally to the fence I will plants some native shrubs, such as serviceberry, elderberry, winterberry, nannyberry, etc.
Please, let me know what do you think if these plants can grow successfully under the Chinese elms and in dappled shade. I am particularly worried about Picea pungens ‘Glauca Slenderina. Do you have any other suggestions which you think would be better.
Thank you very much for your help. I would really appreciate it.

(Answer)

One of the best things about winter is making plans for the next season in our gardens ! It sounds like you have been doing a lot of research on plants that will be suitable for your dry ‘dappled shade’ garden beneath your Chinese elms. It is important to have a good idea of how many hours of sunlight various parts of your garden get. Definitions of ‘shade’ vary, but it sounds like this part of your garden is ‘part shade’ to ‘shade’. (I have included a link below with information about light definitions that you might find helpful.) The light conditions for plants are often described as a range, for example ‘Full Sun to Part Shade’. Something to keep in mind is that the first condition listed is the plants preferred location. So in this case the plant will grow best in full sun but tolerate some shade.

https://extension.psu.edu/planting-in-sun-or-shade

So with all of this in mind, for your first list (climbers) I think Hydrangea anomala subsp. petiolaris (Part Shade – Shade) and possibly Lonicera periclymenum ‘Scentsation’ (conflicting information whether Full Sun – Part Shade or Part Shade – Full Sun) would thrive best. The other plants you have listed are all Full Sun – Part Shade, so they will probably grow reasonably well in your garden but with less flowering than if they were situated in Full Sun.

For your second list, I share your concern about planting Picea pungens ‘Glauca Slendarina’ in your garden, since spruces typically grow best in Full Sun. I think Aralia cordata ‘Sun King’ (Part Shade) and Hosta ‘Humpback Whale’ (Part Shade – Shade) could both do well in your garden. The other plants on your list are Full Sun – Part Shade, so while they may grow reasonably well, the conditions aren’t ideal for them to thrive.

Here are a few websites that provide suggestions for plants that will do well in shade :

https://extension.psu.edu/shade-tolerant-trees-shrubs-and-groundcovers

https://hgic.clemson.edu/factsheet/plants-for-shade/

https://extension.umn.edu/planting-and-growing-guides/gardening-shade

https://www.rhs.org.uk/advice/profile?PID=934

The soil in your garden is also a very important consideration when choosing your plants. In addition to being dry under the Chinese elms, I’m guessing based on where you live that it might well be clay, and could be compacted after years of growth of your trees. Many of the plants on your lists require organically rich, moist, well-drained soil, so if your soil is clay (or even sand) soil amendment with compost or well-composted animal manure before planting and then every year afterwards is going to be really important for a successful garden. The roots from the Chinese elms will continue to take a lot of moisture from the soil, so it might be a good idea to look for plants that are drought tolerant. It will also be important to provide additional watering as needed and to mulch around the plants to retain moisture.

Another thing to keep in mind when planning is the height and width of your chosen plants at maturity, so when you plant it might look sparse at first but will fill in over time. There needs to be enough room for good air circulation between the plants to prevent disease, and enough room between the plants and the fence to accommodate their eventual width without crowding (I am thinking of H. anomala subsp. petiolaris as an example of a plant that should not be planted right next to the fence).

You have mentioned native plants, and this would be an excellent opportunity to choose these as much as possible for your new garden. There is a great non-profit organization called LEAF that has a backyard tree planting program that offers native trees and shrubs to homeowners in the City of Toronto at a subsidized cost. They will help you choose the right plants for the conditions in your garden. Their website lists the trees and shrubs that they have available. Here is a link :

https://www.yourleaf.org/

Below is a website with LOTS of information about native plants, including native plants by region, where to get them and plant catalogues.

http://frontyardrestoration.com/index.html

Good luck with your new garden !

January 15, 2021