Alyssum is a fast-growing plant that responds well to regular shearing back and deadheading. Most gardeners grow Alyssum as an annual that will last for only one season, although this plant is a reliable perennial in USDA zones 9-11. These warmer zones can support Alyssum growth through the winter months. In the cooler zones of 6-8, Alyssum germinates in the spring and self-seeds heavily.
When to Prune Alyssum
Alyssum needs deadheading through the summer months and shearing back done once or twice during the primary growing season. Deadheading will extend flowering and delay seed ripening. Alyssum can ripen seed at a fast rate all season long, and deadheading will help to curb excessive self-seeding. The shearing back rejuvenates overly leggy growth and allows the plants to rest during hot periods. In the hottest growing zones, shearing back will be necessary again in the fall to keep plants looking tidy.
Why Prune Alyssum
Alyssum in hanging baskets may require more shearing than those growing in the garden or other containers. Depending on the desired look, hanging baskets should be snipped back every 2 or 3 weeks. Cutting back stems to the first set of leaves will force the stem to branch and push out dense growth. If the Alyssum is intended to be the spiller in a hanging basket, purchase a suitable cultivar.
Some types develop a mounding shape and look leggy as a container spiller. Alyssum ‘Snow Princess’ and ‘Blushing Princess’ are two trailing cultivars that will spread up to 4 feet and look beautiful in hanging baskets.
How to Prune Alyssum
Step 1 - Deadhead weekly
Carefully cut the spent bloom stems back to the first set of leaves. This helps to keep Alyssum from setting seed early.
Step 2 - Shearing back of the whole plant
Cut the top growth back by half to encourage a new flush of fresh growth and flowers.
Step 3 - Some cultivars of Alyssum have a trailing shape
Mounding types of Alyssum will only spread 16-20 inches. Trailing Alyssum will spread to 3-4 feet.
Alyssum Pruning Tips
- Deadhead Alyssum regularly to encourage longer blooming
- Shear back the top growth to rejuvenate the plant
- Hanging baskets need light pruning regularly to promote vigorous growth
- Trim all of the plants at the same time if Alyssum is mixed with other annuals
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