We’ve written a lot in this series about plants for shade, such as foamflower, giant fleece flower and martagon lilies. But what if your garden is in blazing sun and you want it to look dramatic in the late summer and fall. We have one word for you: Asters.
While not problem-free, asters bloom late enough in the season–and long enough into fall–to be considered one of the great plants for northern gardens. There are several types that do well in Minnesota.
New England aster (Symphyotrichum novae-angliae) grows best in full sun and well-drained soil, though its cultivars can tolerate somewhat wet soils. It can get leggy, but pinching it back a few times earlier in the summer (you can shear one-third off the top of the plant in June, for instance) leads to bushier plants and more blooms. Generally, it’s recommended that you stop pinching by July 4. Many northern gardeners grow the variety ‘Purple Dome’, which is covered with deep purple flowers for several weeks in early fall. For a September garden, this is a star — bushy, colorful, dramatic. Butterflies like this variety, but rabbits don’t — two more reasons to consider it for a sunny spot.
Smooth aster (Symphyotrichum laeve) has a more rustic look but is a good choice for those wishing to grow native plants. A native of the prairies and meadows of the Midwest, smooth blue aster does well in dry sites. Its light blue-pink-purple flowers appear in August and often will still be present in late October or even November.
One problem with asters is their tendency toward fungal diseases, especially powdery mildew and botrytis. To avoid fungal diseases in all plants, be sure that plants have plenty of air around them, clean up leaf and plant debris in the fall (that’s where the fungi overwinter) and water plants at ground level rather than from above.
Consult with your local nursery or garden center for the best aster choices for your garden.