Pruning to keep gardens in line

There are few things sadder for a gardener than a plant that falls short of its potential. Sometimes it’s because it was put in the wrong spot. Other times, it’s because of neglect. And sometimes it’s a double whammy of poor placement and just letting it run wild.

There are two plants common in Whidbey Island gardens that are prime examples of squandered potential. Chances are you or someone you know has one or both of these in their landscape. They’re Lithodora diffusa and Erica.

Lithodora diffusa is a low growing perennial groundcover in the Boraginaceae family. It has bright blue flowers, loves plenty of sunshine and is a great addition to a rock garden. The fact that it spreads is probably one of the main reasons for its popularity.

But if you’re expecting a carpet of green foliage dotted with blue flowers to drape gracefully over rocks and across your beds for years to come, don’t be surprised if over time the end result bears little resemblance to the mound of flowers you brought home from the nursery long ago.

This plant has a tendency to sprawl unproductively like an unemployed teenager if not kept in check. If you never prune it, the foliage at the center of the plant will die back and the only vibrant green will be at the outer edges on the new growth. The number of flowers it will produce will also drastically be reduced.  I’ve seen far too many mats of drab green four to five feet wide and with only one or two flowers

Make a decision in the first year to cut the new growth back by half after the flowers are finished blooming. It will take longer for your plant to spread, but it will also ensure you actually have flowers every year.

The other plant that I often notice neglected is Erica. You probably know it as heather, or you think you know it Actually, Erica is the genus of the Ericaceae family that contains heaths, or what we often mistakenly call heather. An example is Erica x darleyensis Kramer’s red, which has been flying off nursery shelves this spring.  Calluna vulgaris is the correct name for heather, an entirely different plant, which is taller and blooms later in the summer.

The problem I encounter most often with heaths is they’re planted too close to taller plants, often trees. As the little trees grow, the shade the heaths are thrown into deepens. The result is that instead of forming a low mound, they become totally one sided and splayed as they crawl farther out into the sunshine.

The other problem is they don’t always get the pruning they need to maintain a mound shape and encourage more flowers.

Give them a light haircut right after they’re done blooming and stay in the green part of the plant. This will keep them from getting too woody and spindly.

It’s difficult to rehabilitate Lithodora and Erica when they run amok, so commit to a bit of pruning every year. This will keep them where you want them: in your flower beds and out of your compost pile.


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