September signals the time when plant growth is centered on root development. It is an excellent time to transplant plants in your garden as well as plant new perennials. This month is also great for many plant divisions as was mentioned in the last article. These last few months of the growing season are very productive and it certainly is a busy time for gardeners.
A commonly asked question in the fall is what to cut down and when to do it. Our first killing frost of the season is usually around October 10th. Many annuals will then need to be cleaned out of the garden beds. As I work in the garden over the next month I will begin to cut down many of the flowers that have completed their summer bloom, such as bee balm, coneflower, black eyed Susan, phlox, and heliopsis. Many times a plant has new basal growth and pruning should be done to that point. Cleaning out plant debris in the fall helps with disease control as well as helping to eliminate hiding places for garden pests. It is also a good time to take care of weeds that may have taken hold in the last month.
Not every plant needs to be cut back though. Iberis, or candytuft, is a spring flowering evergreen plant that should not be cut to the ground in the fall. This plant will stay green well into the winter season and will only require some minimal trimming in the spring. When in doubt about cutting a plant back, it is best to wait until spring. There are many other plants that do not require a fall pruning provided that recommended summer maintenance has been completed. An example of this would be removal of the flower stalks and yellowing leaves on a daylily clump at the end of its flowering period. If this has already been done, there really is no need to do any other fall pruning to the plant.
Roses should not be pruned or cut back in the fall. This would stimulate cane growth when the plant should instead be getting ready for winter dormancy. Some roses require additional winter protection. Rose collars can be used in late fall. Shredded leaves or compost can be used around the base of the plant. Rose cones are not recommended as there can be quite a temperature fluctuation in the cone over the course of the winter months, which can be detrimental to the health of the plant.
You may decide to leave some plants in your garden for the winter interest they bring to the landscape. They also may be a winter seed source for birds.
The Green County U.W. Extension offers excellent assistance with your gardening questions. Inquiries about the Master Gardening class can also be answered by calling 328-9440. Your garden is created from a palette of ideas full of gardening knowledge and creativity. Every gardener helps make this world a bit greener and brighter.
Nina Binkley, U.W. Extension Master Gardener Volunteer