Come spring, excited gardeners drive to nurseries, load up their cars and go home to plant. That’s tradition. But fall planting also ranks high as a time to put plants in the ground.
Nurseries may not be as jam packed with plants in fall, but as more people push to plant in autumn, garden stores are bringing in more stock at the end of summer.
“For trees, shrubs and perennials fall is a great time to plant,” said Weston Miller, Oregon State University Extension Service horticulturist. “If you plant mid-September through mid-November, the soil is warm and gives plants a long time to establish. And once rains start, people don’t have to water them as much as plants installed in spring.”
Preparing the soil
Assuming that it’s an average winter and not getting really cold really early, that establishment period is important because plants concentrate on root development in fall and that’s what you want, Miller said. But before planting, it’s necessary to prepare the soil.
“The trick as always is to prepare the soil well in advance,” Miller said. “That means clearing away annual weeds and dealing with difficult-to-control perennial weeds like bindweed and quack grass.”
Dig weeds out by the root. If your soil is dry, pre-water to make it easier to remove them.
For perennial weeds, consider using an herbicide, which Miller said is the most effective way to deal with persistent weeds. September is an effective time to apply it when weeds are still visible and sending sugars to their root systems; the herbicide effectively travels down with them.
“Weeds are a total bummer in the landscape,” Miller said. “If you don’t deal with them upfront, they will be an ongoing problem. Judicious use of an herbicide in a planned way creates long-term outcomes. If you don’t want to use an herbicide, you’ll need to remove as many roots as possible.”
Next, it’s time to add compost. Miller recommends topping the soil with compost and digging it in as deeply as possible. For terribly compacted soil, you may want to rent a mini-excavator or hire a professional. By hand, dig in 3-4 inches of compost 6-8 inches deep. With an excavator, mix in 8 inches of compost down to 2 feet.
For more information on compost, see How to Use Compost in Gardens and Landscapes, co-authored by Miller. Before digging, be sure to call 811 to get permission from utilities. For in-ground irrigation systems, be sure to locate pipes.
Installing the plants
“Now comes the fun part of buying plants and installing them,” Miller said. “While the selection may be a little less than spring, there’s plenty to choose from. If a plant has been sitting in a pot all season, it may be rootbound. If so, tease out the roots or score them, making sure the roots grow into this beautiful soil you’ve created.”
When planting, think in the long term. Woody plants often get bigger than you expect, so space them for their mature size. That doesn’t mean you can’t plant fast-growing, temporary plants until larger shrubs fill in. If you want to save money, follow spacing guidelines. Also, before buying a plant, do some research so you put them in the right place where sun exposure and overall soil conditions are right. Miller recommends Sunset Western Garden Book for finding the right plant for the right place.
After planting, water immediately and thoroughly, Miller said. If the soil is bone dry, pre-water before adding compost. Soak the soil, wait a couple of days and dig the compost in. If the soil is still dry, dig the planting hole, fill it with water, let it drain, fill it again and plant while the water is still there. That way wet roots go into wet soil. To wet the roots of a plant in a container, put it in a 5-gallon bucket with water and wait until it quits bubbling.
Once planted, water every week or twice if it’s hot before the rains start. After that, plants should be fine unless there’s an extended dry period. Then it wouldn’t hurt to add water. Mulch around plants to keep weeds down and conserve soil moisture. Miller recommends wood chips. Bark dust is OK, but not as good for fostering soil health. Check out Mulching Woody Ornamentals with Organic Material for more information.
If you’ve prepared your soil, a flush of weeds will show up and need to be scraped out before mulching. Keep mulch 6 inches away from woody plants so you don’t smother them. For herbaceous perennials, it doesn’t hurt to put a flag where you planted them so you don’t lose track when they die back in winter. Write the name of the plant on the flag.
Remove tags from trees, shrubs and woody perennials and store then in a binder or something similar. Tags cinched around branches can be a problem over time as the limb grows. If you want to keep a label on a plant, us zinc labels, write the name on them and twist on loosely so the plant has room to expand without being constricted. After your plant installation is complete, make a map showing where plants are located.
“Moving into spring, the key will be weed control,” Miller said. “Know what to expect when plants start to grow. Let woody plants emerge and wait and see if there are any dead areas before pruning.”
At the beginning of summer, it’s important to water even if you’ve chosen native or drought-tolerant plants. Miller suggests installing soaker hoses, hose-attached drip systems or drip systems with emitters. There’s expense upfront, but in the long run it saves water, which is good for the planet and for your wallet.
“With climate change that results in drier, hotter weather, you can’t assume a plant will survive,” Miller said. “They will do better with water. I haven’t watered my native flowering current and it’s looking pretty torched.”
The chances of survival in the era of climate change are heightened by selecting native plants or plants from Mediterranean zones like South Africa, Australia, South America or any of the Mediterranean countries. For native plant lists, refer to the Extension guide Gardening with Oregon Native Plants West of the Cascades. Miller also recommends Metro’s Native Plants for Willamette Valley Yards.
About OSU Extension: The Oregon State University Extension Service shares research-based knowledge with people and communities in Oregon’s 36 counties and the Confederated Tribes of Warm Springs. OSU Extension addresses issues that matter to urban and rural Oregonians. OSU Extension’s partnerships and programs contribute to a healthy, prosperous and sustainable future for Oregon.