It seems that as quick as it arrives as quick it starts to go. I garden in a very definite four season climate with very hot summers and relatively mild winters for Canadian standards. No matter how hot the days still are the evenings come late August start to cool off quickly, and there is a smell to air that changes are upon us. I try to hang on to summer as long as possible and ignore the back to school and pre fall sales with all their propaganda. I am a believer of living the season at hand, not prematurely moving on to the next before it even arrives. Gardening in fall will arrive soon enough all by itself.
I still have to be realistic though and accept that we are moving towards the last quarter of the year. The garden is still beautiful although a few things are waning and there are garden chores to be done. By doing them now I know I will reduce the work load for fall garden cleanup.
Very important is that you continue to water your garden, especially the trees and shrubs. This is probably the kindest thing you can do for them as we approach winter. Keep controlling your weeds, most like the cooler temperatures and can get away on you at this time. Many survive just fine under the snow and will be back to greet you first thing in the spring. If you have any perennials that need dividing do it now. Leave it for later and you risk their chances for winter survival. They will need about 6 weeks to develop a strong enough root system to carry them through the cold months ahead. Otherwise cut down those that are finished blooming to about 3 inches from the ground and remove the debris. Exceptions are tender perennials and mums, these can wait until spring. Those perennials that are still blooming de-head the spent blooms to encourage a few last flowers and to tidy them up. They can be cut back later when you do your fall chores. If you have a hedge give it once last trim for the year.
Any annuals that have lost their charm should be removed from the beds. Those in containers may be tidied up as they will continue to perform if they have been well fertilized and watered through the season. Now is not the time to fertilize, except perhaps the lawn. Encouraging new growth now will only weaken your plants going into winter. There are fall fertilizers for lawn that may be applied now if needed.
Check your flower beds and any areas low on mulch should be topped up. Again this will help protect them from the cold. This is especially important for any tender plants you are trying to hold over. If you enjoy a vegetable garden keep harvesting. If your area is prone to early frost protect your plants during the nights with straw or sacks. It takes very little and you will be rewarded by extending your fresh vegetable season by a few weeks. Make sure to harvest everything ripe, even the green tomatoes, before the killing frosts arrive.
Gardening in the fall will be a busy time and by investing a bit of energy now you will not be overwhelmed when the season changes. There will be enough to do at that time when it arrives.