Deadheading Annuals & Perennials
Plants will go to seed once their blooms are finished. That's nature. If left alone a flowering plant would bloom, that bloom would then be fertilized and set seed. In this reproductive cycle the plant expends all its energy and nutrients to set seed instead of producing more flowers. But a trick called “deadheading” will stop the plant from setting seed too soon. Remove the faded flowers from the plant by pinching off the flower head. Now the plant will spend its energy producing more flowers instead of seed! Deadheading will not only encourage many more flowers it will create a longer blooming period.
Another tip to increase plant growth is to pinch the central growing tip of the plant. This will produce side shoots further down the stem, creating a bushier plant that will produce more flowers throughout the season.
Whether you’re deadheading your annuals or cutting them back, make sure to fertilize them to complete the job. Annuals are very heavy feeders and will respond amazingly well to standard water-soluble fertilizers. Simply connect a hose-end sprayer to your hose and use Jacks (20-20-20) or a Miracle-Gro type product.
Deadheading / Cutting Back Perennials
This idea is a simple one and fairly familiar: by trimming off the faded flowers, many perennials can be coaxed into producing more buds and flowers, rather than wasting their energy forming seeds. For certain plants (peonies, for instance), although no amount of deadheading will trick them into repeat bloom, plants look so much better after deadheading that it becomes part of the regular list of summer chores.
Cutting Back Hard
With just a few exceptions, the vast majority of late spring and early summer-blooming perennials will deteriorate in appearance after flowering, and can look hideous later in the summer. The mounding types of perennials like Cranesbill Geraniums and Silver Mound Artemisia are just two examples of plants that are notorious for looking terrible by July. With these types of perennials a hard shearing back will encourage a new round of fresh, healthy, compact foliage to be produced, causing the plants to actually be an attractive addition to the landscape during the heat of summer and not the tired looking perennial with a large dead hole in the center of the plant.
This hard pruning technique is recommended for most mounding perennials including: Alchemilla, Coreopsis, Dicentra, Nepeta, Saliva, and Tradescantia, just to name a few.
Pinching for Height Control
Pinching of fall-blooming Garden Mums (Chrysanthemum) is a familiar technique for most perennial gardeners. The same basic concept works for these late summer and fall bloomers: Aconitum, Aster, Eupatorium, Helenium, Monarda, Summer Phlox (Phlox paniculata), Autumn Stonecrop (Sedum) and many, many others.
After cutting back your perennials or when they have completed their bloom cycle, be sure to feed them with a water-soluble fertilizer. Simply connect a hose-end sprayer to your hose and use Jacks (20-20-20) or a Miracle-Gro type product.