Care for Astilbe Plants

Astilbe, also known as false spirea, is a perennial flowering plant native to North America and parts of Asia. The plant is hardy to zone 4 and produces attractive fern-like foliage and large plumes of dense, tiny flowers in colors of pink, white or violet. Astilbe plants can reach up to 6 feet in height, depending on variety, with flower stalks reaching up to 2 feet in length. They are easy to grow and make a wonderful addition to shady flower beds and border gardens.

Planting

Plant astilbe in early spring after all danger of frost has passed. Choose an area of the garden that receives light shade for the best results. Astilbe plants will grow in full sun if constant moisture is provided, but they thrive in partial shade. The planting site should also have rich, well-drained soil. Although astilbe likes moisture, good drainage is necessary for the health of the plant. Avoid heavy, clay soils. Work 2 to 3 inches of peat moss or organic compost into the soil at planting to increase fertility and drainage. Space plants 12 to 24 inches apart to allow room for growth.

Watering and Mulching

Water astilbe plants thoroughly after planting to compact the soil. Continue watering once or twice per week as necessary to keep the soil consistently moist, but not soggy. Reduce watering on weeks that receive natural rainfall. Consistent moisture is required to prevent the leaves from browning. Astilbe will drop its leaves if water is not provided during hot weather.

Apply a 1- to 2-inch layer of mulch to the soil surrounding astilbe plants just after planting and watering. Mulching will help conserve moisture, which is vital for the health of astilbe. Use shredded bark mulch or hay for the best results. Replenish the mulch anytime it begins to visibly deteriorate.

Fertilizing and Pruning

Feed astilbe plants twice per year in mid-spring and summer with an all-purpose slow-release fertilizer. A fertilizer with an NPK ratio of 3-1-2 or 5-10-5 is recommended. Refer to the manufacturer's instructions for proper application rate. Water plants thoroughly before and after fertilizing to prevent nitrogen burn and to evenly distribute nutrients throughout the soil.

Remove dead leaves as necessary, and cut back astilbe plants to soil level if they dry out and turn brown during the summer. This will encourage the plant to grow healthy foliage when ideal conditions return. In some cases, the plants will remain dormant until the following spring after being severely pruned. Do not remove spent blooms, as they are considered ornamental throughout the fall and winter months. Deadhead only if you don't wish astilbe to self-seed, as the process does not encourage more blooms.

References

• Horticulture and Home Pest News: Astilbe
• Cornell University Flower Growing Guides: Astilbe
• Astilbe Production and Consumer Care