In climates with four distinct seasons, common sense would suggest that most planting should be done in spring, at the beginning of the warm season. However, fall has some advantages as a time to plant, and some plants are biologically designed to be planted before cold winter winds blow in Pennsylvania.
Below is a look at plants to consider planting in autumn, including benefits and cautions.
Trees, Shrubs, and Hardy Perennials
Container-grown plants in this category can be planted from early to mid-fall. You should plant early enough in fall for the root system to establish itself in the new soil (plan on at least six weeks before first frost). Before winter sets in you should check weekly and water if dry. A thick layer of mulch will keep them from heaving out of the ground during periods of freezing and thawing.
A huge advantage to planting woody plants and perennials in fall is that they are often on sale at nurseries. You should make sure they are not pot bound from growing in a container all summer, however. Pot-bound plants may appear dry, because the water has no area to soak in, and may have roots growing out of the bottom of the container. For any container-grown plant, loosen the roots before planting. In the case of trees and shrubs, you should cut an X in the bottom of the root ball and several shallow slits on the sides of the roots to allow them to spread out into the backfilled soil.
Most of the turf grass grown in Pennsylvania lawns is “cool season,” including Kentucky bluegrass (Poa pratensis), perennial ryegrass (Loliam perenne), and fine fescues (Festuca spp.) Because these grasses grow best in cool weather, late summer to early fall is an ideal time to plant a new lawn, patch bare areas, or overseed an existing lawn. Grass seed must receive regular irrigation, especially until it begins to germinate. This is more likely to happen naturally in fall rather than in spring, when the new grass must withstand hot summer days. When purchasing, you may find grass seed embedded in what looks like dryer lint.
The premise is that this will hold water when the seed is planted and watered. Though this may seem like a good idea, the best practice for getting grass seed to sprout is by making sure it has good contact with the soil. This can be done by loosening the top of soil before planting or raking the seed in. Newly planted seed may be mulched with a light layer of straw.
You don’t have to be a farmer to grow a cover crop. If you have a garden area where you grow warm-season vegetables or annuals that you normally leave fallow in winter, you can improve the soil during the winter season by growing a grain or legume.
Benefits of cover crops
- Retain nutrients in the soil and, in the case of legumes, fix nitrogen in the soil
- Help keep soil from eroding
- Alleviate compaction
- Add organic material to the soil when turned under in the spring
Cover crops that can be planted in fall and their primary advantages
- Alfalfa, crimson clover, hairy vetch: Legumes; fix nitrogen in the soil; alfalfa’s deep roots break up the soil
- Barley, oats, winter rye, winter wheat: Add organic material; improve soil structure
- Cover crops can be planted between the last of your warm season vegetables to give them a head start before the weather cools. If you have waited until the end of September (or even early October) to plant a cover crop, winter rye is probably the best choice.
Bulbs such as hyacinths, narcissus, and tulips are programmed to grow foliage and bloom after an extended cold period. They should be planted when the weather is cool in the fall and before the first hard frost. Most people are familiar with this time table for planting the best-known spring-blooming bulbs. You might want to also consider planting some of the lesser known, but subtlety beautiful spring-blooming bulbs. Fritillaria have nodding, bell-shaped flowers available in various colors (my favorite is the checkered variety F. meleagris). Galanthus are commonly known as snowdrops, which perfectly describes these small, white flowers. Scilla, sometimes called wood squill, sport clusters of small star-like flowers and can be found in shades of purple, white, and pink.
Fall planting is definitely for the patient gardener. The reward in spring will be well worth it!