September should be a time of much to do in the garden. You will still have some success preventing spring lawn weeds by using a pre-emergent herbicide, if you are not over seeding.
At the first hurricane rains, we can begin to seed the lawn or repair patches. Success, however, will depend upon your commitment to keep daily water on the seeded area throughout the germination process, a few times a week after germination, and taper gradually to once a week.
If the seed starts to germinate and then dries out, the tender shoot will die. Light watering is sufficient at first, but as the grass begins to grow, the length of watering should be increased until the soil is wet 3”-4” deep. You can quickly train yourself to judge the timing by the resistance you get when probing with a screwdriver or other sharp object.
A common mistake leading to failure of newly sown lawns is seeding too heavily. I encourage people to use the lower number in the recommended seeding rate range. A thin lawn takes patience, but will reward you in at least two ways.
A lawn that is seeded too heavily will look great at first, but about 3-4 months into the process it will start to “tiller”, which means the clumps fill out. A thickly seeded lawn will literally choke itself out and you have to start all over again, except you have lost the window of opportunity during the prime seeding season.
Secondly, a crowded lawn is prone to brown patch and other fungal diseases. Once established in the lawn, these fungi are extremely difficult to eradicate. In fact, you may never totally get rid of them. A healthy lawn will establish enough to tolerate some annual fungal damage and mostly recover from the crown, when weather cools.
Start the first of three fall lawn fertilizer applications. Let the weather guide you. If it is dry you will likely start fertilizing in late Sept., Oct., and Nov; otherwise earlier in the month.
Begin to move or divide perennials, especially those that prefer a fall move, like peonies. In clay, you should plant peony “eyes” (like eyes on a potato) 1”-1½” deep. Lighter soils allow a depth of up to 2”, but plants will fail to flower if planted too deeply.
Evaluate your garden’s color scheme. Many of us have great color in the spring or early summer, but do you have any color now? Granted, your beds will not look sterling after the wear and tear of the heat, but you should still see some color.
Here are some ideas for late summer and fall blooming perennials to round out your planting scheme: Agastache, Alliums, Anemones, Asters, Black-eyed Susans, Boltonia, Bugbane, Chrysanthemums, Coreopsis and Gaillardia if deadheaded, Fall Crocus, Goldenrod, Ironweed, Joe-Pye-Weed, Malva, Monkshood, Obedient Plant, Ornamental Grasses, Russian Sage, Salvia, Scabiosa, Sea Holly, Sedum, Sneezeweed, Stoke’s Asters, Sunflowers, and Toad Lilies.
If foliage is looking a little ratty on your perennials, cut them back. Some may have time to bloom again. Decide how far to cut back based on the individual plant. If most of the foliage looks OK, a light pruning may suffice and stimulate more flowers.
Some plants falter if you remove too much foliage during these stressful times. On the other hand, if most of the foliage is dead, you have nothing to lose to cut it to the ground.
For plants that have most leaves somewhat affected, but are still largely green, I suggest two cuts. First, cut back by 1/3-1/2. Cut the remaining old foliage off when new basal growth gets several inches tall. Do not fall fertilize perennials or shrubs until they go dormant in late October.
Enjoy this fall gardening season!