I live with my Mom, who needs help with IADLs now that she is pushing 90. We are in upstate New York. My parents had a plain green yard, to which I have just this year started adding plants. Mom has given me carte blanche to do whatever I like in the yards, front and back. The problem is heavy clay, acidic soil, and dappled shade. So the front yard will wait until I'm better at gardening here. [I had great gardens when I lived in Lexington, KY, but we’re talking different microclimate and very different soils.]
If possible, I’d like to crowd as many plants as possible into the back garden, to do our little part to help combat climate change. Although we always hear about trees absorbing carbon, all plants absorb some carbon, and diversity of plantings is important for plant health and for wildlife habitat. Also, we enjoy our aminal habitat, and colourful flowers like the above that are pleasing to the eye. Ideally, we’d have a colourful palette of flowers and/or leaves in every season, and minimal lawn monoculture.
Local daily wildlife currently include a variety of birds, squirrels (or skwirls as I like to call them) and (as long as we aren’t outdoors) bunnies! We also have a variety of evening/nighttime wildlife that I can’t even begin to photograph, including skunks, possums, raccoons, and groundhogs.
My “blank canvas” is a yard surrounded by very old trees. Preservation of old trees is preferred for climate change reasons, since they store the most carbon; and they certainly give us privacy, so their health is Job One. However, they are underplanted (not on purpose) with small invasive trees, so if possible I’d like to take those out and add woody bushes. The good trees include pines to either side and oaks in the back.
I looked up more information for use in improving the garden, so thought I’d share the results with all of you. If I had my way, the garden would look sort of like this!
So, I had questions and maybe you do too:
Is it OK to plant under trees? According to the American Horticultural Society (AHS), it’s OK with these precautions: First, be careful of damaging roots. It’s not that you can’t damage any, I have taken out a few bits near the surface that I could pull out by hand, which were quite a bit away from the trunks; but it shouldn’t be substantial or the tree could suffer. Use more care near the “drip line,” the part covered by the tree’s crown. The closer to the trunk, the more respectful to be of the tree’s roots. If you don’t have your big trees planted yet, see the link for a list of “tough trees” that are more tolerant of disturbed roots. Also, “Older trees are generally less tolerant of disturbance than are younger trees, so if you have a choice, consider creating a new bed under a younger tree.”
Alternative to digging under trees? Build up a planting area and then plant shallow-rooted plants such as bulbs and violas. Too thick a layer can starve roots of oxygen, nutrients and water, so care still needs to be taken but may work better than damaging roots. They suggest “adding no more than two to four inches of planting medium to the base of any tree at one time. Make sure to use a light blend of soil—or, better yet, compost—and organic mulch such as wood chips, shredded bark, or pine needles.” Don’t let them touch the trunk, though, as it could encourage fungi that harm the tree. Also, be aware that trees may not like a lot of water: “Trees such as birches, alders, bald cypresses, sweetgums, and some maples will thrive in moist soils, but most others do not.”
Can the right bushes and flowers survive under trees? As long as they’re shade loving, they should be OK. But there are actually trees that will kill your underplantings (same source)!
A few tree species are allelopathic—they produce chemicals that can kill or inhibit the growth of other plants growing underneath or nearby. The best known examples of this are walnuts (Juglans spp.), which produce juglone, a chemical toxic to a wide range of plants including azaleas, blueberries, and tomatoes. Other trees known to have allelopathic tendencies are sugar maple (Acer saccharum), black locust (Robinia pseudoacacia), some eucalyptus (Eucalyptus spp.), and sassafras (Sassafras albidum). Establishing new plants under these trees may be more difficult than under others.
What to plant under trees?: Plants for dry shade, per AHS. The denser the tree canopy and thirstier the trees, the drier the soil beneath. For the least disturbance, “In general, shallow-rooted herbaceous perennials, bulbs, and groundcovers are best suited to sharing soil space with existing tree roots because they need less growing medium and will not require the digging of large holes around the tree.” Perennials are preferred to annuals to limit repeat digging:
Asarum canadense (wild ginger) Carex pensylvanica (Pennsylvania sedge) Chrysogonum virginianum (green and gold) Convallaria majalis (lily of the valley) Dennstaedtia punctilobula (hay-scented fern) Epimedium spp. (barrenworts) Eurybia divaricata, syn. Aster divaricatus (white wood aster) Hakonechloa macra (Hakone grass) Helleborus foetidus (stinking hellebore) Liriope spp. (lilyturfs) Ophiopogon spp. (Mondo grasses) Polypodium virginianum (rock fern) Polystichum acrostichoides (Christmas fern) Sanguinaria canadensis (bloodroot) Symphyotrichum cordifolium, syn. Aster cordifolius (blue wood aster)
What about smaller trees and shrubs underneath trees?
Shrubs with larger root balls are also problematic. “There is no good way to incorporate a lot of large plants close under a tree without doing long-term damage to the tree,” says Nina Bassuk, a horticulture professor at Cornell University and program leader for its Urban Horticulture Institute. Your best bet is to select the smallest possible ones and plant them in phases over several growing seasons.
If you are planting a bed of mixed shrubs and perennials, consider placing perennials closest to the tree trunk, then gradually integrating shrubs as you get further away from the tree’s major roots.
How to best nurture all the plants after planting?
Once you’ve planted underneath trees, you will have multiple root systems competing for water and nutrients. Be sure to water your new planting regularly for a couple of months until the plants are well established. Then gradually reduce the frequency of waterings but soak the entire planting area thoroughly each time you water.
Deep watering encourages root systems to grow deeper, making plants more drought tolerant and reducing surface rooting that can interfere with your garden. Letting the soil dry between irrigations allows for natural shrinking and swelling that will help improve soil structure.
Watering the lower trunk near the root collar can lead to fungal problems so aim sprinklers or irrigation nozzles away...
Established trees generally don’t need much supplemental fertilizer, but with new roots to feed, you may want to add a balanced slow-release fertilizer (10-10-10 is fine) or compost tea at the time you install your new plants. Once the new plants get established, apply fertilizer a couple of times a growing season or amend the bed annually with compost or other organic matter.
So I decided that, because of the age of my trees, and disturbing the invasive trees will likely disturb the roots of the old trees, I will get an opinion from a certified arborist before I disturb things further!
Similarly: www.gardeningknowhow.com/… and www.thespruce.com/… and www.finegardening.com/… (this one includes some possible shrubs). This one also includes shrubs, www.countryliving.com/…
Which plants are best to grow for climate change? Different sites have different opinions! But if starting fresh, probably best to plan a variety of fast-growing trees. And if you do cut some down, use the wood for lumber! That will sequester carbon, where if they decay then carbon is released, www.mprnews.org/… Broad leaves are best, and planting season for trees is in fall, early probably better, www.glendale-services.co.uk/… Large leaves, wide crowns, native, fast growing, long lifespan, www.americanarborists.net/… Another reason to talk to a local certified arborist: To know what grows here. “Wood is good,” so any trees and woody shrubs would be better than other plants, although all plants sequester some carbon. Grasses may be better for carbon in a drought www.earth.com/…
And finally: Note that it is important to keep the plants growing, rather than digging them up or cutting them down, when they would release carbon during decay. So if possible, the garden should be maintained beyond one lifetime. Useful plants, such as fruit trees and bushes, might be considered more valuable, so less likely to be cut down by new owners. Same with ornamentals. Very interesting discussion with multiple knowledgeable opinions, www.researchgate.net/… So I may decide to plant fewer plants, concentrating on low-maintenance natives, in hopes that the garden will have a very long life.
And Now Some notes having nothing to do with Preventing climate Change
Rhododendrons: This autumn has been very mild to warm. For the first time anyone in the family can recall, our oak tree leaves are turning red instead of yellow! And Dad did plant a few rhododendrons in the backyard that have done extraordinarily well, as did a rhododendron I planted this past Spring (grown from about 1 foot at planting to about 3 feet now). And they are all budding again! They have never done that before. Will they have time/energy/light to bloom a second time? Is climate change doing this? Inquiring minds would like to know!
Wildflower identification: I didn’t mow the back lawn this year, to see what we already have. We have lots of wild violets and clover. It’s quite the purple carpet in Spring, to which I’ve now added naturalised bulbs of short irises and crocuses! The tall grasses are particularly adored by the bunnies, whose “noshing at the salad bar” has kept them reasonably short. Then there are these. They all bloomed in late summer/early fall and are still going strong. I’d like to keep them, but I’d also like to name them. I don’t know what they are. Do you?
And finally, these showed up in front of the house, growing right through where Dad had laid weed-suppressing membrane overlaid with about 6 inches of brick chips! So I thought I’d see what they’d do around the base of a pine by the driveway. We’d earlier tried various grasses under that pine, including some “guaranteed to grow under pines,” and last Spring I tried geraniums. Nothing grew. These, though, do seem to have established! Yay! They seem delicate, one of these easily fits in the palm of my hand.
If you made it this far, thank you for reading! I hope you find some of this information useful. Please feel free to add more information in the comments!
Update 1120 AM: I have to go make lunch and keep Mom company. See y’all back here sometime probably late this afternoon! Thank you all, please discuss amongst yourselves and I’ll catch up on my reading when I return.