Get gritty: A drier palette and gravel gardens

I don’t know about you, but when I read the phrase “Northwest Garden style,” I take it to mean a predominately shade-loving palette of maples, hydrangeas, and ferns. Think moist woodland.

That is not to discount all the sunny gardens full of Mediterranean and summer-dry plants from South Africa and New Zealand, it’s just a generalization that stuck somehow, along with rain, coffee, and grunge.

However, the Northwest garden-style plant palette is ready for a makeover.

As summer weather is getting increasingly hot, many Seattle gardeners are reimagining their gardens to use less water and handle the heat. The scorching summers we’ve had recently — and their attendant water bills — are enough to make you think twice before planting another hydrangea (its name comes from the Greek for “water vessel”). Even spring, which used to be a time you could count on for cool, wet planting weather, has been rife with dry spells and heat waves, so even if you wanted to establish a hydrangea, you’ll need to keep the hose handy.

If you are looking to make your garden more drought-tolerant or xeric, start from the ground up. When looking for successful plants for the PNW, “summer-dry” is a more useful term than drought-tolerant because we are typically summer-dry and winter-drenched. Many drought-adapted plants will melt away in winter rains, so it’s important to find ones that can tolerate being wet in winter and dry in summer.

Fast-draining soil is a crucial factor for these plants. I’m sure you’ve seen certain plants thrive in rocky hillsides, rubble, cracked driveways, and gravel, or grit as the Brits say. It’s a matter of choosing the right ones for your conditions.

GET GRITTY

The British have gone a long way to pioneer beautiful examples of gravel gardening, famously starting with designer Beth Chatto, who turned her driveway into a renowned destination. Despite being one of the driest areas in England, receiving an average of 20 inches of rain annually, it is never watered. You can read about it at bethchatto.co.uk or in “Drought-Resistant Planting: Lessons from Beth Chatto’s Gravel Garden,” her book from 2016.

She broke up her compacted soil, laid gravel paths, filled beds with compost, spent mushroom compost, and bonfire waste and mulched with more gravel. Plants were selected from regions that had mild winters and could withstand desiccating wind and summer drought. Before planting, plants are dunked in water until their rootballs stop releasing air bubbles — a sign the root ball is fully saturated. With new plantings, gardeners avoid overly rich soil which encourages lush growth vulnerable to summer heat spells.

One issue with gravel planting is that the sparse fill allows plenty of pockets for seeds to germinate, so regular hand weeding, especially during the first years, is important. You can also exploit this tendency by planting plants you enjoy that self-sow, whether Verbena bonarensis, Eschscholzia californica (California poppy), or Bellis perennis, (English daisy). 

Gardening in gravel and concrete offers the chance to recycle when renovating, keeping that waste out of the landfills while creating habitat for flora and fauna.

More recently, landscape architecture professor James Hitchmough and designer Tom-Stuart Smith, among others, dumped tons of concrete waste rubble in humps and hummocks to create homes for 900 species of low-water, low-fertility plants in the Knepp Castle Estate’s “rewilded” Walled Garden: knepp.co.uk/rewilding/.

WATER AN ISSUE

Here in Seattle, reader Sally Cole wrote in to say she has converted her backyard to gravel and her parking strip to a rockery and is delighted with the results. She feels that “In view of the high costs and scarcity of resources, it is important that we conserve water.”

When it was time to remove her “leaky” 16-by-32 swimming pool two years ago, she left the surrounding concrete pathway intact but replaced the former pool area with fill soil topped with three inches of pea gravel and some large boulders.  A patio table and chairs are decorated with flowering pots. It’s still early days, but she says, “… It is really quite beautiful.”

Unlike full gravel gardens, Cole does not plant in the gravel — she is using it as an easy-care breathable hardscape for her backyard. 

“We are very happy with this design,” she continues, “because we do not have to water, mow or fertilize. Additionally, we discovered that fleas and slugs do not like the  gravel. Our project conserves water, reduces the water expense, lessens the need for chemicals and, most importantly, frees up our time.”

She envisions the city could come to recommend or incentivize such gardens if water becomes harder to find.

A garden is made up of countless choices. As we move into hotter summers, you might want to ask yourself, like Sally Cole, how much water you want to spare for your garden. If you’re not ready for a full gravel garden, you can streamline your effort and water use by dividing your garden into zones. If you can’t break up with your hydrangeas, dahlias, or tomatoes, cluster them together in a high-water zone and try to incorporate more low-water zones going forward.