Many landscape architects and garden designers treat garden design as if it were the same as selecting paint colours or fabric swatches for an interior. The ultimate extreme of this is the show garden approach producing a perfect garden frozen in time but impossible to sustain in the long term. Failure to understand the importance of maintenance techniques in shaping the very look of a garden is a major flaw of many modern gardens.
This is particularly true of herbaceous perennial and cottage gardens. A house may look a bit shabby if it goes unpainted for decades but not painting it or using a roller instead of a brush does not fundamentally change the structure and design of a house – in the garden neglect or inappropriate maintenance changes everything.
Ultimately, garden design lies in the gardeners’ techniques for keeping plant vigour, making sure plants keep to their allocated lot, flowers bloom for extended periods, and plants are timed to flower in desired combinations. The techniques for achieving these ends are simple; the timing and correct application take a lifetime to master. For the perennial garden these primary tasks are deadheading, cutting back and dividing.
Deadheading is one of the simplest, yet most powerful, tools for manipulating flowering plants. We do this for several reasons. Plants simply look fresher when dead blooms are removed. Once dead, the heads of Euphorbia can make the healthiest plant look parched. Removing browned heads visually returns the plant to vigour. Some plants, if left to run to seed, would over take our gardens and beyond.
The privilege of growing bronze fennel or Agapanthus comes with the responsibility of removing seed heads before they mature. Deadheading also protects stands of desired varieties from being overrun by their offspring that may not be true to type.
At Heronswood we pay particular attention to our stands of Echium and Hellebore varieties. If you want to experiment you will be amazed at the variety of forms that may appear – just be prepared for your display to eventually devolve into a collection of nondescript blooms.
The prime reason for deadheading is to extend flowering by delaying seed formation and directing energy back into flower production.
Deadheading techniques vary. The easiest and most meditative method is to pinch the blooms off by hand. With some plants you need to be careful not to get too gung-ho about removing the whole flower spike.
Flowers, like bearded iris and many cannas, flower progressively along a single spike, check for new flower buds before you cut the whole thing off. The flowering period of Dahlias is extended by deadheading but you really need to recognize the difference between the spent flower head and the round newly formed buds. In contrast, Delphiniums benefit from severe deadheading; cutting old stems to the base will encourage a new flush of blooms later in the season.
Repeat flowering roses can be given a summer pruning if you simply “deadhead” by picking flowers for the vase cutting back to about 5 shoots. Some plants flower so profusely that shears are the best line of attack. This is true for annuals, preventing the likes of that Naughty Marietta marigold from becoming wayward and running amuck. In my more brutal moments I have deadheaded Pink Evening Primrose and Catmint with a brush-cutter.
This brings me to another important reason for deadheading, controlling the time of flowering. At Heronswood we ruthlessly remove the flowers of Evening Primrose and Catmint that line our drive just when they are hitting their stride in spring.
The reason being, by limiting spring flowering we achieve a more spectacular display in summer when we welcome the majority of our visitors. You don't need to deadhead all your ornamentals as many drop their spent flowers. There are also specific cases where you don’t deadhead. Leave the flowers on Rugosa roses to produce their beautiful hips. Likewise, plants like Honesty and Love-in-Mist are grown as much for their spectacular seed heads as their flowers.
While deadheading is mostly about manipulating flowering and seed formation the cutting back of perennial foliage is all about controlling plant form and vigour. At the most basic it is the foliage equivalent of deadheading removing yellowing leaves. This not only makes the plant tidier it also removes potential homes for pests and diseases and allows for better airflow and light penetration. Many plants direct their energy to their tips while lower buds remain dormant, tip pruning or pinching out the tip buds of a plant helps promote bushiness and prevent plants from becoming leggy.
Hedging or shearing fulfills a similar role. We lightly shear our Artemisia to keep it compact without being too formal. Cutting back of herbaceous perennials in late spring, or the ‘Chelsea chop’ as they call it in the UK, keeps plants compact and can promote a second flowering in late summer.
Salvia nemerosa varieties and Delphiniums get a chop after our late spring festival. Be aware that in Australia's summer drought, extra watering may be needed for the plant to bounce back from this treatment!
The ultimate cut comes in the dormant period when the big chop of true herbaceous perennials occurs. It is partially a matter of taste when to chop. Some find seed heads and browning foliage beautiful and seasonally appropriate and leave them until late winter; others see untidy dead twigs that may harbour disease and cut them back as soon as possible. I leave it to you to decide who you are.