The Tidy Garden
The perennial garden in early summer is a pleasing display of lush foliage and plants touting their first flush of blooms. But as the peak season fades the garden takes on a more tired, untidy look with spent flowers and foliage that has become floppy and messy. A few techniques involving some simple cuts can bring your perennials back to looking their best.
One proactive technique that although isn’t widely used, will manipulate a plant by promoting better growth habits. Some plants tend to grow too tall or too leggy. For example, after a period of time the large heavy flower heads on Sedum Autumn Joy will cause the plant to flop over right at the time of the season when it should be its showiest. The staking and tying up of its stalks is unsightly and would be unnecessary with a little early pruning. Cutting the plant back by a third to a half by early summer will promote it to be sturdier, shorter and have more, but smaller blooms. The pruning should be done by July 4th to give the plant enough time to set flower buds. Ideally the cuts should be made just above a leaf node but if this involves a larger number of plants hedge shears can be used. The new plant growth will look most natural if the cut is done along a curve. Additional perennials that this technique would work on include monarda (bee balm), aster, tall garden phlox, perovskia (Russian sage), veronica, shasta daisy, dianthus deltoides and helenium (sneezeweed).
Removing spent flower stalks or deadheading isn’t important only to help the plant look better. Perennials will expend their energy producing seed instead of putting it back into sending out a second flush of flowers if the spent flower stalks are left untouched. Deadheading will also help strengthen the plant itself by redirecting its energy. Some perennials are notorious for unwanted spreading by reseeding. The development of new seedlings can be halted by spent flower stalk removal before seeds are produced.
Knowing your perennial and how to best prune it so to not damage future blooms, but to maximize more bloom potential is essential. Salvia has two pruning options. Either cutting off the spent flower spike back to just above where the second set of blooms are to achieve a continuous bloom or cutting the flower stalk to the basal foliage to encourage a nice slate summer bloom. Gaillardia (blanket flower) and Coreopsis grandiflora can be kept blooming almost all summer by pinching off individual flowers back a few inches below the seedhead. The wilted blooms on a reblooming daylily flower stalk can be removed and once the whole stalk is spent it can be cut to the ground. Achillea (yarrow) benefits from cutting the spent flower stalk down to the ground to get another good late flowering. The Echinacea varieties that rebloom can be deadheaded by just removing the spent blooms throughout the summer, leaving the last blooms of the season for the birds to feed off. Threadleaf coreopsis and catmint prefer to be sheared back hard after the flowers fade leaving a few inches of growth. Applying a liquid fertilizer at this time will enhance the rate of growth and light rebloom.
To get a more continuous blooming time without the pause you get when you wait to deadhead after the main flower stalk is spent involves another type of pruning technique. Before the plant sets its flower buds selectively prune a third to half of the stems by a few inches and before a node. The cut stems will bloom later than the ones unpruned. This works well on perennials that bloom in summer or later such as tall garden phlox, helenium and asters.
There are those plants that are graced with seed heads of unique interest after their blooms are spent. Baptisia, Siberian iris ‘Caesar’s Brother’and Lilium martagon are examples of perennials that aren’t rebloomers and deadheading them would remove the potential later structure they can add to a garden. The flower stalks on astilbe stay upright and tidy and the plant may fit a setting better if they are left intact. Personal preference comes into play when working with hosta and Stachys ‘Helene von Stein’ (lamb’s ear). Deadheading the spent flower stalk will help strengthen the plant although if the tall flower spikes seem make the hosta or stachys look too wild and unkept they can be removed as soon as they emerge, not ever letting them develop.
It’s rewarding how a little pruning can tidy up a garden and increase the blooms. Get the most out of your plants all season long by incorporating the right pruning technique for each individual perennial.