Gazette Gardener: Growing plants under a maple tree easier said than done
“What plants can you grow under a maple tree?”
“When can you transplant daffodils?”
These were two questions asked of me lately.
The co-worker who asked about planting under a maple tree also wanted plants that were very easy to grow and required little maintenance.
Planting under a mature maple tree is a challenge. Anything trying to grow under the dense foliage of a maple must be able to survive in little light, compete with unrelenting demands for water and nutrients by the surface roots of the maple tree, and live in small pockets of dry soil.
Given the harshness of these restrictions, a gardener who truly desires low maintenance might be better served by mulching. It’s neat, tidy and — if edged — looks finished.
However, if you want to try to grow under a maple tree, then I would suggest addressing the problem from a number of different angles.
First, trim up the lower branches to let more light under the tree.
Next, add a few inches of loam over the roots and install soaker hoses on a timer or an irrigation system to provide reliable water. This is key.
These steps will improve the growing conditions for the plants you install. Just know that the maple will also appreciate your efforts and extend its surface roots into the fresh topsoil. This may choke out whatever you plant.
There are solutions. Some gardeners dig holes in the fresh soil and line the hole with layers of landscape material. Then they place the shade-loving plant in the hole. From what I’ve heard, this works for several seasons, but the maple trees roots will work their way past this barrier in time.
Another option may be to plant your shade-loving flowers in containers and place the containers under the tree.
The tough get going
If you want to plant directly into the new loam, the following plants are tough enough to compete.
My first choice would be Geranium macrorrhizum, aka bigroot geranium. This plant is a workhorse in the garden from spring to fall. It spreads quickly and has petite white to deep magenta flowers early in the season. It tolerates drought because it has thick rhizomes and — unlike other geraniums — it doesn’t need to be cut back after flowering. In fact, by not removing the flowering stems, some self-seeding will occur, which is a real plus for filling in the area under a tree.
These geraniums grow about a foot tall with a spread of about two feet. As an added bonus, come the cool temperatures of fall, the foliage turns an attractive reddish bronze.
If I were doing all this preparation for a new garden, I would also add bulbs to extend bloom time. Choose daffodils, scilla or snowdrops or all three for a pleasing color combination that will lift your spirits early in season.
For a ground cover, sweet woodruff is a good choice. It spreads vigorously and blooms in May with small white flowers growing above star-like whorls of leaves.
It likes moist conditions, and given enough water will fill in quickly. A planting done three years ago under a Japanese maple in my yard has more than tripled in size. If you notice the woodruff is waning during the hot days of summer, water more frequently.
Sweet woodruff is used as an ingredient in May wine, but it has other uses as well. It is a natural insect repellent. Pet owners tell me they dry it as a flea repellent. Crafters like it as an ingredient in potpourri.
Daffodils have been putting on a lovely show this spring. But what if yours didn’t bloom? It may be time to divide your clumps and replant them elsewhere in the garden. A co-worker, who is also a fine gardener, asked when the best time was to divide and transplant bulbs. Experts agree that you can dig and divide in early summer once the foliage withers. This signals that the bulbs are dormant.
As you dig, you will discover that you have bulbs of various sizes. Try not to damage any bulbs as you work. The largest bulbs will bloom best, so plant them where you want the most show. But replant all the bulbs, as even the small ones will continue to grow and eventually bloom.
As you work, replant the bulbs at the same depth as they were growing and leave about six inches between each bulb.