By Susan Martin for Proven Winners
Photographs courtesy of Proven Winners
Being a skeptic, I wondered when I saw slogans like "Fall Is for Planting" posted boldly on banners at nurseries in fall: Is this really a good time to plant? Or is this just a marketing initiative meant to motivate people like me to buy more plants? To find the answer, I sought out the origins of the campaign. To my surprise, I learned that it was launched nearly 50 years ago by the American Nursery and Landscape Association (now AmericanHort), a group of professional nurserymen and landscapers aiming to educate the public.
Further research led me to Dr. Steven Still, Executive Director Emeritus of the Perennial Plant Association, to learn of his philosophy on fall planting. "In most cases, with the exception of warm season grasses, fall is an excellent time to plant perennials. The cooler weather and warm soil helps perennials settle in nicely before winter. It's also a good time to transplant or divide perennials. Everyone plants in spring, but fall is an even better time to plant," said Still. This is a practice he preached in his decades as a professor of landscape horticulture at Ohio State University.
It turns out there is some science behind the "Fall Is for Planting" idea. A plant's roots grow most vigorously when the air temperature is relatively cooler than the soil temperature. Warm soil in fall keeps root development going while a plant's top growth slows. The roots continue to expand until the soil temperature falls below about 50°F.
In addition to vigorous root growth, there are more key benefits to planting perennials, shrubs and trees in fall. Spring and summer flowering plants tend to produce more flowers when planted the fall prior. That's because the plants have more time to become established and reemerge larger the following spring. Larger plants bear more flowers.
Another benefit to fall planting is that garden pests tend not to be as active in the cooler months. Less stress from insects means that plants can spend more energy on root development rather than fighting off attackers.
An obvious benefit to fall planting is that many nurseries discount their plants at the end of the season. Bargains can certainly be found. However, take care to avoid any plants with obvious signs of disease or with whole branches or sections that are dead. You don't want to introduce any pests or diseases into your garden from discounted plants—fighting them will cost much more than what you saved in the long run.
Is your garden lacking in fall color? Red Rover® silky dogwood (Cornus) will spice things up! Fall is an excellent time to plant shrubs that will light up your garden with their brilliant fall color every year.
Fall Planting Tips
The best time to plant perennials in fall is six weeks before the first frost. That date can vary from year to year, but you can look up the average frost date for your zip code using this tool from the National Gardening Association. The best time to plant shrubs and trees in fall is six weeks before the ground freezes. If you miss those planting windows, plant them anyway. They will be safer with their roots below ground than if you leave them in their nursery pots over the winter.
If you haven't chosen or prepared the perfect place yet, you can "heel in" hardy plants anywhere there is open ground. Maybe that's a spot where you've removed a bunch of annuals or along a fence line. In spring, pop them back out and into their new permanent space in your garden.
One tip I've learned over the years in my own garden is to plant before the leaves begin to fall. You'll be surprised how hard it is to find that spot you've earmarked for a new perennial or shrub once it is covered in a layer of fallen leaves. If necessary, blow or rake the leaves out of the bed to get your bearings back before planting.
Zone 3 hardy hydrangeas like Incrediball® can be safely planted in fall. Remember to keep any fall planted shrubs watered well until the ground freezes.
Keeping newly planted perennials, shrubs and trees watered until the ground freezes is critically important. Remember, their roots are continuing to grow long into fall and they need moisture to develop. Thankfully, soaking fall rains help sustain our plants' roots. But if your sprinklers are shut off before the growing season ends and it is relatively dry, you'll need to hand water any newly planted perennials, shrubs or trees at least once per week.
Mulch anything you plant in fall with shredded leaves or bark. The mulch will help to keep the ground warmer longer, giving the plants' roots more time to get established before winter. It will also conserve moisture, which is critical to healthy root development.
Butterfly bush is zone 5 hardy but is best planted in spring in most zones.
Which Ornamental Plants You Should NOT Plant in Fall?
While many kinds of plants benefit from fall planting, there are a few that are better off planted in spring. They include:
Warm season grasses and sedges do most of their growing during the warmest months of the year and then bloom in fall. Avoid planting, dividing or transplanting them in fall. You'll enjoy their winter interest while you wait for spring planting time to arrive.
Evergreen shrubs and trees can be planted safely until early fall, but after that it is best to wait until spring. That's because their persistent foliage is subject to drying winter winds and sun. Once the foliage dries out, the plant can't replace it because the ground is frozen. It's better to plant evergreens when there is plenty of moisture available.
Borderline hardy plants need plenty of time to establish a strong root system before winter arrives. Be sure to plant them early enough in spring to allow sufficient rooting in before the heat of summer arrives. An example is zone 5 hardy butterfly bush (Buddleia). If you garden in zone 5, which is the coldest climate in which it can survive, plant it in spring rather than in the fall.
It's not just a marketing campaign—fall really is for planting. Follow these tips and you'll be glad you did when your healthy plants reemerge next spring. Happy planting!