Deadheading, which simply means removing spent flowers, can prolong bloom, promote a second flush of flowers, discourage disease and improve a plant’s appearance. Nipping off dead flowers (or the spikes/plumes of ornamental grasses) prevents seed formation, which is good for reining in vigorous self-seeders, such as lady’s mantle (Alchemilla mollis) and northern sea oats (Chasmanthium latifolium). However, if you want to collect seed for next year or if the seedheads are particularly decorative, deadhead only partially or not at all.
Technique 1: Deadheading by shearing
Many annuals and perennials will take the rather drastic treatment of shearing. Good candidates are low-growing rock garden plants, such as aubretia; fine-textured plants, such as thread-leaved coreopsis and trailing lobelia; plants that send out long-flowering shoots, such as hardy geraniums; and vigorous growers, such as snow-in-summer. Using clean, sharp garden or grass shears, clip away all the spent blossoms and any leggy, untidy growth. Shearing also refreshes annuals, such as petunias and nasturtiums, that tend to get straggly.
Plants to deadhead by shearing
- Aubretia (Aubrieta cvs.)
- Basket-of-gold (Aurinia saxatilis and cvs.)
- Snow-in-summer (Cerastium tomentosum)
- Thread-leaved coreopsis (Coreopsis verticillata cvs.)
- Hardy geraniums (Geranium spp. and cvs.)
- Candytuft (Iberis sempervirens cvs.)
- Sweet alyssum (Lobularia maritima cvs.)
- Rock soapwort (Saponaria ocymoides and cvs.)
- Spike speedwell (Veronica spicata cvs.)