Great Gardens Begin in the Fall
September and October are GREAT months for planting...
for the following reasons:
1. The soil is soft, workable and still warm - perfect for encouraging root growth.
2. Air temperature is cooling and the days are becoming shorter. On the fall equinox, September 22, there are equal periods of day and night. Plants are not subject to long hours of searing sun and therefore lose less water through their foliage.
3. Even when above-ground activity seems to have halted, root systems are still very active underground. As the ground gradually cools, roots continue to absorb moisture until the soil temperatures reach about 40°. With this in mind, even though temperatures are cooler, continue to water plants until a hard frost.
4. Fall's shorter days also mean that less light is available for photosynthesis. Deciduous trees and plants go into seasonal slumber.
5. Since many insects go dormant for the winter, plants suffer less from insect damage.
All of this means less stress on plants; fall plantings can settle into their new sites with relative ease.
If you choose to plant in the fall, these are a few things to remember:
1. Check always to make sure plant is not pot-bound before you plant into your prepared spot. If it is pot-bound, take a sharp knife and make three or four vertical cuts into side of the root ball to encourage new growth. You can also loosen the roots by hand if the plant is loosely pot bound.
2. Avoid using nitrogen rich fertilizer (manure, fish emulsion, blood meal, cottonseed meal) when planting in fall, as the nitrogen will encourage tender new growth that is susceptible to cold damage. If you want to fertilize, use a phosphorus rich fertilizer such as Rock Phosphate or Roots 2, as this will stimulate an abundance of healthy root growth.
3. Always make sure the variety you are planting is winter hardy in your hardiness zone (Zone 6 or lower for coastal Connecticut).
Source: Organic Gardening