Why plant in September and October? Warm soils in the fall will encourage root growth of plants and typical rainfall in our area reduces the amount of watering that gardeners need to apply - and - the weather is so much cooler to work in the garden. Because of better root development in the fall, when spring arrives, the plants have a much better start as compared to plants planted in the spring. Then when the hot dry weather of summer hits, the fall planted plant will be well established and therefore, can withstand the tough summer environment. When planting perennials in the fall, earlier is better. Don't wait till late October, the plants will not have enough time to take root into the soil, and hence, they will heave out of the ground, because of our freezing and thawing periods that are typical during our winters. Shrubs and trees are not as likely to heave.
Container grown plants as well as balled and burlapped plants do well when planted during the fall season. If planting a container grown plant, be sure you break up the root system before placing it in the hole. This will encourage the roots to grow into the existing soil. A balled and burlapped plant can be planted well into the late fall until the ground freezes. These plants move best when they are going dormant, because the roots are disturbed when digging. Just be sure to roll back the burlap from the top of the ball, and cut all string from the ball, especially around the trunk.
Whether planting a container or balled and burlapped plant, be sure you don't plant it too deep, the top of the soil ball should be level with the existing grade. Be sure to water the plant well after planting.
This is an exciting time of year. There is so much color from leaves and berries that you can really appreciate living in this area, where there are four seasons, each treating us with beautiful color of different kinds. Enjoy your garden, whether old or new, and always continue to learn about nature's wonders!