The arrival of fall does not mean an end to your landscaping season. Warm soil and cooler, wetter weather creates perfect planting conditions for certain plants.
Spring Flowering Bulbs
Create a fabulous spring display by planting spring blooming bulbs in autumn. But don’t wait too long, your bulbs need time to root before the ground freezes. A bulb only stores the flower bud along with food to get it started. In order to grow, it needs to establish its’ roots and many then need endure a cold winter. If the soil does not get cold in your region, you may need to refrigerate your bulbs for at least 6 weeks before planting.
The perfect time to plant bulbs is when the soil temperature drops to 60 degrees. That temperature is usually reached when the overnight air temperatures have fallen to about 40 or 50 degrees. This should give your bulbs about six weeks to establish roots before the ground freezes. Although it is always difficult to predict the weather, this usually occurs in early September in zones 1 and 2; mid September in zone 3; late September to early October in zones 4 and 5; mid October in zone 6; early November in zones 7 and 8; and early to mid December in zone 10.
If you plant too late, your bulbs may not flower well in the spring. Heavily mulching your bulbs may keep the soil warm long enough to develop good roots.
Annuals and Perennials
It may seem silly to plant annuals at the end of the growing season, but if you drop into your garden center mid season, you will see that they are available at bargain prices! As soon as the heat of summer has passed is a great time to plant. If you buy the leggy and more ragged looking plants in July or August, snip them back and nurse them along until the weather cools down. Or temporarily pot them into an unused container to nurse them in a sheltered spot. A little care will go a long way with a neglected plant. Stop in again in late August and you may find young healthy plants that were not ready for the spring season at good prices.
Look for annuals to perk up your gardens right away, as well as late blooming perennials. Aster, coneflower, coreopsis, gaillardia and rudbeckia are all good late bloomers. Mums, marigolds, flowering cabbage and ornamental kale add classic fall color and interest to the garden. And the more frost resistant they are, the longer you can enjoy them. Ornamental cabbage, pansy, primrose, cornflower and violets are very hardy and can hold up through overnight hard frosts. Annual phlox, annual candytuft, Coreopsis, Rudbeckia, Dianthus, annual geranium, marigold, sweet pea and snapdragon will withstand a light frost. Aster, scabiosa, alyssum, petunia, and alyssum may survive a light frost.
Shrubs and Trees
Fall can be a good time to plant shrubs and trees. The roots of shrubs and trees are naturally growing agressively in autumn, aided by warm soil and cooler, wetter weather. Establishing roots before winter will be essential for newly planted shrubs and trees. The roots become important quickly to take in water to prepare for winter dormancy. So you need to make sure you plant early enough for that to happen.
A few points to keep in mind regarding planting shrubs or trees in autumn:
Allow about six weeks for roots to establish before the ground freezes.
Allow at about eight weeks for evergreens to establish roots and soak in plenty of water to sustain the needles through winter.
WATER, WATER, WATER. Water trees and shrubs thoroughly and deeply each week for the first 3 or 4 weeks. Start to back off after that so the plant can start it’s natural dormancy process. Water evergreens right up until the ground freezes. Evergreens will continue to supply the needles with water until the roots are frozen.
If you do plant a bit too late, mulch heavily to keep the soil warm longer. The roots will continue to grow until the ground freezes.
Do NOT plant marginally hardy trees or shrubs in autumn. Although many will adapt to survive winter, it will adapt slowly. Marginally hardy trees and shrubs should be planted in spring. It will have all season to establish itself and grow strong, and then should be protected at least the first winter.
Container grown plants will establish fairly quickly because they have not had their roots disturbed. Balled and burlapped or transplanted shrubs and trees will go through the stress of their roots being cut shortly before the stress of the transplant. A little more time to establish will be helpful.
Planting shrubs and trees in cold climates should be completed no later than mid October. Zones 4 and north should complete planting by the middle to end of September, zones 5 and 6 by the middle of October, but a warm fall can prolong the planting season. Container grown plants (trees, shrubs and perennials) should have just enough time to establish a some roots before the soil freezes. The best time to plant, fall or spring, is debated by gardeners. Each has their own preference. In my experience, fall is a perfect time to plant evergreens. It is generally cool and wet, which gets them off to a good start. Watering right up until the ground freezes is critical to get them through the first winter. However, I always complete evergreen planting in the first week or two of September in zone 4, end of September in zone 5. I believe they need the extra time to establish roots, which ensures that water can be taken in well. Winter is stressful to a plant, but not as stressful as a hot dry summer. Spring planted evergreens seems to struggle to stay alive through summer. With that said, proper care is everything. My first choice to plant shrubs and trees is VERY early spring, as soon as the ground begins to warm. Next would be September in zone 4. But I have been known to plant in the height of summer heat and drought. Water, water, water, and more water. I haven’t lost anything to summer heat yet, but I have lost a young evergreen to desiccation when I planted a bit late, although other factors contributed to the problem.