During the asters rapid growth period at the end of summer, you will need to water them at least once a week so they don't dry out. Also be sure to leave enough room between the plants so that they get enough air circulation. Asters don't have many pests, but they will sometimes fall victim to a powdery mildew if water stays on the leaves or if they go without water for too long of a period, especially when they're crowded.
At the end of fall, you can cut your asters to the ground after the blooms have faded. You can also leave some stalks to provide seeds for the birds, but if you do be aware that some of them will reseed.
Do not be surprised if that small tight mound of purple flowers you bought last fall is a gangly, open plant this year. Asters that are grown in nurseries are usually sprayed with a growth regulator to keep the plants short and stocky so they won't outgrow your
containers if you use them. If you plant them in your flower garden, they will not be that compact next year. However, even though you probably will not resort to growth regulators, you can pinch your aster plants to keep them more compact. Simply pinch out the tip of each stem, this will force them to branch out on the sides more easily. You'll need to start at the end of spring and pinch them every couple of weeks in order to get really bushy plants. Cutting back asters may delay flowers by about a week or two, but you can use this to your advantage because it will extend their bloom time.
If you pinch the asters at the front of your
flower garden but not those at the back, the un-pinched asters in the back will grow taller and bloom earlier. When they are finished, cut them back and the shorter plants that you pinched in the front will bloom and cover the old stems of the tall ones in the back of the
flower garden.
Are you just getting started with asters? Try tidy, compact New York asters, these will form perfect mounds and will have a good range of flower colors. You can try the 'Peter III' type, it is excellent in containers, but in the garden it will spread so you'll have a healthy clump of flowers in just a few years. You can also enjoy watching the bees and butterflies with this aster. The Frikarts' aster is another good specimen. It has a tendency to get a little floppy, but the violet-blue flowers bloom the longest of any of the perennial asters until the first frost. New England asters, such as the 'Purple Dome', are some of the showiest flowers. They bloom later than most of the other asters due to their cold-hardiness. Even as a beginning gardener you will find that asters are beautiful
fall flowers.
