“Planting them in early fall gives their roots several weeks to get established before the first frost,” said Julie Janoski, Plant Clinic manager at The Morton Arboretum in Lisle. In September and early October, the air will cool off, but the soil will still be warm enough for roots to grow.
“Growing roots is the most important task for a new plant,” Janoski said.
You can plant any species of tree or shrub in early fall as long as it was grown in a container. Most plants sold in garden centers are container-grown. Fall planting may be more risky for trees or shrubs that are sold with their roots wrapped in burlap, as they were grown in a field and dug up for sale.
“Those plants lost the majority of their root system when they were dug out of the ground,” Janoski said. “They will have a better chance to recover if they’re planted in spring and have the entire season to grow.”
This is especially important for some kinds of trees, such as many oaks, maples, hawthorns and magnolias. Consult the Plant Clinic for advice before planting a balled-and-burlapped tree in autumn.
You can also get help from the Plant Clinic to select a tree or shrub that will be appropriate for your site. “It’s important to think carefully about hardiness, sun or shade conditions, and mature size,” Janoski said. “A tree or shrub is a long-term investment, and it shouldn’t be an impulse purchase.”
Trees and shrubs are often on sale in late summer, just in time for fall planting. But be careful about sale shopping, said Sharon Yiesla, the Arboretum’s plant knowledge specialist. A plant is no bargain if it’s not healthy enough to survive.
“Plants that have been around the garden center since spring will be picked over, and the ones that are left may not be the best,” she said. “Examine a sale plant very carefully and buy it only if it’s sound and healthy.”
Even if you’re an expert gardener, don’t plan on being able to nurse a damaged plant back to health in autumn, when it only has a few weeks to grow roots before frost.
When you get your plant home, give it a good start by planting it properly. The hole should be wide, so new roots can grow outward, and relatively shallow, so you don’t plant the tree or shrub too deep. When the tree is in place and the hole is refilled, the root flare — the place where the trunk widens out into roots — should sit right at the level of the surrounding soil, or a little bit higher.
You’ll need to water the tree thoroughly when you plant it, and water it again every week or so until the ground freezes. In fact, a new tree or shrub will need supplemental watering all through its first two or three years after planting.
Spread a layer of mulch to insulate and protect the plant’s roots and keep the soil from drying out. The mulch should be an even layer, not a pile. Ideally, it should be spread in a circle several feet across around a newly planted tree or shrub, 3 to 4 inches deep. Be sure not to pile mulch up against the tree’s bark or the shrub’s stems; piled mulch against the bark can encourage decay or shelter gnawing animals.
New trees usually do not need to be staked for support. “If you have firmed the soil around the roots, the tree should be secure,” Janoski said.
PREVIOUS ARTICLE
