How to Grow Series
Astilbe is a wonderful shade loving perennial with fern-like foliage and feathery plumes for flowers. Hardy in zones 3-9, astilbe prefer loamy, compost rich soils that drain well, but that are consistently moist. They range in size from 1-4 feet tall to 1-3 feet wide depending on variety and are not bothered by too many pests or diseases.
Astilbe pair nicely with hostas as they provide a different type of foliage and a bright burst of color from their blooms. Blooms can range from just a few inches tall to more than a foot tall, so they can certainly add a dramatic touch to any garden. Common bloom colors are red, white, pink, and lavender, all having rich green foliage.
Though astilbe thrive in shade gardens, they will bloom better when they receive a couple of hours of morning sun. Astilbe generally bloom in late spring and early summer. If you ever find that your astilbe have stopped blooming, they may not be getting enough sun or they could be getting crowded out by other plants or might need dividing. They also benefit from a fertilizer that is high in phosphorus. If flower buds dry up before they bloom, it is likely they are not getting enough water.
Astilbe are difficult to start from seed, so buying small plants to transplant to your garden is ideal. When planting astilbe, make sure the crown of the plant stays just above the soil line so that the crown does not rot. Dormant astilbe roots can also be purchased and planted in the garden. Simply fan out the roots in a shallow planting hole about an inch below the surface of the soil with any new growth facing upwards.
Divide the plants every 4-5 years to keep them healthy. Divide in early spring or late summer and water them well until you see new growth. Don’t be surprised if newly divided astilbe do not bloom next year. Dividing in early spring will help ensure that they will bloom the following spring. Always add compost to the soil when planting and top dress at least once a year to help replenish the soil. Astilbe can be fertilized in late summer when they are setting buds for the next year, but in my experience, if you have good compost rich soil and they are watered well, they don’t need a lot of fertilizer.