This season I have found myself practicing what I think of as Subtractive Gardening. By this I mean that most of the work in the garden and landscape consists not of adding plantings or beds but the diligent, often ruthless, care and tending of what already exists. This did not necessarily happen by design, however it is certainly turning out to be a worthwhile process.

Especially if you have added a major landscape project in recent seasons — such as a patio, water feature, new foundation plantings or perennial beds, subtractive gardening can be the key to your new landscape’s success.

What do we mean by Subtractive Gardening? With our warm El Nino winter and early hot dry weather and lack of rain, the usual seasonal sequence of gardening has gotten a little mixed up. Seeds planted in the garden and meant for transfer to beds were subject to a lengthy delay caused by a lack of rain to support the transplants. They grew bigger and bigger in the seedbed, waiting for their place in the sun. Perennials and shrubs that performed well last season turned out to be too susceptible to heat and wind and needed to be rearranged or moved to different areas to thrive.

Instead of visits to the Nursery Center to choose an interesting or unusual new plant or variety, this year’s labor has consisted of weeding, weeding and more weeding. “Keeper” plants as well as villains such as crabgrass need to be kept at bay and prevented from taking over areas they were not meant to occupy.

Perennials such as Artemesia and Primrose are lovely and tough, however, their tendency to spread requires strict maintenance or they can choke out other desirable plants. Both of these varieties spread by sending out runners underground. Pull up the new shoots when they get out of bounds and trim back to just a foot or so when growth gets leggy.

Mint of all types, including Catnip, is a common invader and requires constant attention. I pull up mint on every trip into the garden, and when it begins to develop flower buds, I get out the trimmers and cut it back Two types of mint grow by the water feature and the scent is lovely but vigilance is the key!

Balsam is a sturdy and beautiful Victorian flower that can withstand very harsh weather. Unfortunately, it reseeds itself with a vengeance and must be contained to a limited area or completely eliminated. It likes to hide among other plants and not reveal itself until it has become quite large with a thick stalk. It’s easy to pull out and I’ve actually managed to avoid feeling guilty about it. I gave my non-gardening neighbor some Balsam starts to plant in a previously untended bed. This way I can avoid the problems of Balsam while still enjoying its unique beauty. The extra benefit is that she will never have to plant anything in that area again!

Celosia is another culprit that is grown as an annual from seed. It’s tall, brightly colored cone-shaped flowers are very nice in perennial beds as backdrops and in cut flower arrangements. A neighbor gave me some seed last year and, not realizing at the time its amazing power of regeneration, I planted them in the seedbed. Then they started coming up on their own everywhere in the garden and beds. The seeds are tiny and each flower makes lots of seed. A good solution for Celosia — plant it in containers. It stands up well to heat and creates a different look when mixed with zinnia, marigolds, geraniums and the usual container plants. This year I am going to cut down the flowers BEFORE they go to seed or it will be next year’s Balsam (see above).

As for Crabgrass, the simplest solution takes place in the spring when the lawn is being treated with a pre-emergent to prevent its coming up in the first place. Any beds, garden or planting areas should be treated as well. A small hand held spreader will do the trick in tight spots and will make your entire landscape crabgrass-free, not just the lawn. If this didn’t happen in your landscape this year, be diligent about pulling out what comes up. It usually looks worse than it actually is since it sends out many long blades from each root. Once you start rooting around in the crabgrass patch, you will find there are actually fewer plants than it seems. A small trowel will easily dig out the roots that are too tough to pull. Plant or mulch weeded areas to prevent its return.

Mulch is an important aspect of subtractive gardening. After finally eliminating the crabgrass, weeds and too-vigorous perennials from the beds, mulch the area heavily to prevent regrowth. Even if you’re not planting anything in that area, the mulch provides moisture retention and good looks. There is no law of gardening that says every square inch of the garden needs to be filled with plants. Experiment with blank areas to provide a rest to the eye viewing the garden and a rest for the gardener as well.

Fertilize plantings regularly to maximize the blooming season, but avoid over fertilizing of container plants. Over fertilizing can cause weak stems and excessive leaf growth which makes plants in our area susceptible to wind damage. If the pot or the soil surface is chalky, over fertilization is probably the cause.

Practicing a season of Subtractive Gardening from time to time will keep the maintained look of the landscape and better acquaint you with the qualities (both good and bad) of the plants you have. We have found it very satisfying to make this a season of Subtractive Gardening with the added benefit of maximizing the performance of the remaining plants.

Robin Milliken is a Landscape Specialist and Master Gardener
The Master Gardener appears monthly in The Olathe Daily News.
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