Gardeners get excited about planting in spring, but fall is actually a better time to plant trees and shrubs, according to Homegrown NH Host Emma Erler, lead horticulturist at Kirkwood Gardens.
Benefits of fall planting
Cooler fall temperatures mean there is less transpiration, that’s water loss through plant leaves, and fall tends to be a period of higher precipitation.
Plentiful water means less environmental stress on plants and allows for more root development. When air temperature drops below that of the soil, shoots aboveground cease to grow but roots will continue to develop until the soil dips below 40 degrees.
Plants that are transferred in the fall have time to develop stronger roots to withstand late snowfalls in spring and a hot, dry summer.
However, the chance of failure increases the later in the season you wait to plant. Aim to give plants at least six weeks of mild weather for root growth before freezing temperatures arrive. Erler says early October is a good deadline for the Granite State.
Best trees and shrubs for fall planting
Deciduous shrubs and trees, those that lose their leaves, are more suitable for fall planting than evergreens, says Erler. Apples, crabapples, lindens, maples, hawthorns, honey locust, elm, lilac, witchhazel and forsythia are all good candidates for fall planting.
“I've had mixed success with fall planting of evergreens, like arborvitae or rhododendron,” Erler says. “Because they keep their leaves or needles all winter, and lose water through their leaves in winter, they're going to continue losing water all season long.
And if their root system doesn't have time to establish in the fall, these plants are going to have a lot of damage come spring, or they may not survive at all.”
Erler recommends waiting until spring to plant magnolia, tuliptree, oak and ginkgo as well.
Fall plant care
Make sure to choose healthy plants if you’re at a nursery and tempted by bargains. Erler says the benefits of fall planting cannot resurrect unhealthy plants. She looks for plants with good structure— with no dead or broken branches— and that are disease free.
“Mulching is going to be really important,” says Erler. “One of the things that can happen when you plant things late is that freezing and thawing can end up uprooting plants that don't have an established root system.”
Erler recommends laying a few inches of bark or wood mulch around the root zone of the plant (not up against the trunk or stem) to help moderate the soil temperature and prevent the plant from being heaved out by freezing soil.
The most important consideration, Erler says, is to water thoroughly and consistently, at least an inch of water a week, until freezing weather.
See you in the garden!
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Homegrown New Hampshire is a collaboration between Squam Lakes Natural Science Center and NHPR.
