I am still musing over the renovation of my front garden. As I consider the myriad of plants that are hardy in our climate I have decided that I need to determine my goals and priorities for this garden. I know I want it to be attractive and nourishing for pollinators, especially butterflies, so I will need a variety of nectar producing plants, that will provide blooms throughout the growing season, especially in mid to late summer and fall. It has also been found that flowers of similar colors grouped together are more attractive to butterflies – and people! Observation also indicates that flowers regularly visited by butterflies include butterfly weed, coneflowers, lilacs and asters. I have butterfly weed, lilacs and a number of coneflowers thorough out the landscape so I am considering adding some asters to provide late summer and fall bloom.
Asters are hardy and sun loving, can grow from two to four feet high and three feet wide, and bloom late enough and long enough to provide food for pollinators into the fall. Several varieties of asters do well in Minnesota.
- New England Asters prefer full sun and well-drained soil. They can get quite tall and leggy if they are not pinched back in the early growing season. They can be cut back until July 4; they even benefit from shearing off up to 1/3 of the plant in June. This will create a bushier plant with more flowers when it blooms in September. A popular cultivar is Purple Dome which can be covered in deep purple flowers when it blooms. An added feature is that they are attractive to butterflies but rabbits don’t like them!
- Smooth Aster is native to prairies and meadows of the Midwest and is hardy to zone 4. They have a rustic look and grow two to three feet high and do well in dry sites. They have smooth blue/green leaves (thus the name), and produce light pink to blue to purple flowers beginning in August and through October and even November.
- Native Asters have shallow blooms providing landing pads and easy access for pollinators. They produce numerous blooms which allow pollinators to hang out for longer feeding, thus conserving their energy. Most native asters produce blooms in the pink to blue to purple range. The following species are hardy to zone 3.
- Sky Blue Aster likes a hot dry and sunny site and does well in well drained sandy, rocky, clay or loamy soil. It is a bit more airy and open than some other asters.
- Heart-leaved Aster prefers medium moist soils and as the name implies has heart shaped leaves. It grows two to three feet tall and one to two feet wide.
- Calico Aster actually thrives in deep to part shade. (This is not for my front garden but I might consider this for other areas of my landscape.) With ample moisture the plant can grow to three by three feet. The flowers are white with a yellow center that goes to pink as the nectar is depleted.
- Aromatic Aster is tough, slow spreading and shrub-like. It prefers full sun and well-drained soil and tolerates drought but can grow to two feet tall and three feet wide with adequate moisture. The flowers range from magenta to violet blue.
- Big Leaf Aster is also not for my purposes because it prefers a shady to part shade site, but if you are looking for a low, almost groundcover and flowering plant this might be it. As the name implies, it has oversized leaves. It rarely gets over one foot tall and blooms in late summer with white flowers on tall spikes.
Asters are not without their problems. They are susceptible to fungal diseases, such as yellow asters, powdery mildew and botrytis. To avoid these infections leave plenty of air around your plants — don’t crowd them. Water at ground level to keep the leaves dry. Lastly clean up all leaf and plant debris in the fall, because fungi can over winter in the soil. With good garden practices you and the pollinators can enjoy your asters for many years.