Planting for Drought Tolerance

Planting for Drought Tolerance

We don’t hear the term “xeriscaping” used quite as often in our corner of the Pacific Northwest as one might further south, but setting out to create a landscape that uses less water and that will stand up better to periods of drought is still a worthwhile gardening pursuit here in Portland. After all, much of our state is still caught in a multi-year period of drought, and our changing climate is trending both drier and hotter. If you're looking ahead and wanting to plant for these conditions — or you just want to spend a bit less time watering your garden — we’ve put together a few tips to help you plan a resilient, water-wise garden, plus a collection of drought tolerant plants curated just for you.

Here's a few things to keep in mind:

1: "Drought tolerant" doesn’t mean zero water.

Most plants will need some amount of supplemental water to perform — and look — their best during the heat of the summer. This is especially true for new plants just getting established in your garden: Until they have had time to send roots outward and downward to reach water and nutrients in the soil, new garden additions don't have the same ability to support themselves as plants that have been growing in the landscape long-term.

2: Water to establish.

Most perennials will take a year or so to establish, while slower-growing woody plants may take two years or more. In this time, it is important to provide these plants with the water they need to effectively transition to life outside of a nursery pot. This is why planting in the fall or spring is ideal, as there is generally sufficient precipitation falling from the sky to help you with the task of irrigation, but when these rains dry up, you should plan to give your plants plenty of supplemental water in their first summer in the ground. Additionally, when you water, water deeply. This not only allows you to go longer between waterings, but also ensures that your plants can make efficient use of the water you're giving them by encouraging them to develop deep, healthy root systems. A drip irrigation system or soaker hose can help with this task, and for trees, a watering bag is another great choice.

3: Plant like with like.

If you plant moisture-loving plants right next to ones that prefer their feet never to be soggy, at least one of the two will always be unhappy — and very likely both! That's why it's always a good idea to group plants with similar cultural needs close together in the garden. (Here's where efficiency-minded gardeners can plan ahead: Why not locate the plants that need the most frequent water and attention close to your water source and place your water-wise bed further away?)

4: Know your site and pick plants accordingly.

Although we may think of rich, moist soils as the ideal for our gardens, many drought tolerant plants actually prefer sharp drainage and poor soils, and giving them too much "love" can end poorly. Our climate's winter precipitation can be a challenge for many drought tolerant plants adapted to life in consistently arid regions, and such plants are better candidates for planting on sloped sites or at the top of walls than in low-lying areas that may become soggy in the winter. Additionally, consider whether your garden is shady or sunny; these are very different worlds when it comes to planting for drought tolerance! A few perennials that do well in dry shade include Lamium, Epimedium, Hostas, Pachysandra, and Autumn Fern. For shrubs in these conditions, Japanese Aucuba, Fragrant Sweetbox and Japanese Aralia are good bets.

5: Seek out native plants.

Not all native plants are created equal (a native bog plant likely won't offer much in the way of drought tolerance!), but they are a great place to start when looking to create an all-around resilient garden. After all, the plants best adapted to our unique conditions here in the Pacific Northwest are the ones that have been growing here since time immemorial! While our climate is changing, we aren't losing our wet winters anytime soon, and nothing will change our clay soils that hold water in the winter and bake and harden in the summer.

6: When trying to figure out a plant's drought tolerance, look at its structure.

It's always good to do a quick Google search to confirm your gardening instincts, but plants have a few tried-and-true evolutionary solutions to deal with the problem of low-water conditions that we can learn to recognize. Effectively, their strategies boil down to water acquisition, retention, and conservation. While it may not prove particularly helpful when looking at a plant in a nursery pot, it makes sense that plants with deep tap roots are more resilient in the face of drought conditions because they can access water further down in the soil. Some plants have also evolved to store water in tuberous root structures or in succulent or leathery leaves, whereas others have focused on reducing transpiration — the evaporation of water from leaves — by growing smaller leaves. Still others have developed tiny, hair-like structures that reflect light and trap water, which give certain plants like lavender or dusty miller their lightly fuzzy, silvery foliage.

With a little careful planning, gardeners in our region can create a water-wise garden full of drought-tolerant plants that are not only beautiful, but highly resilient. We carry many great options here at Cornell Farm, and our team is always happy to help you pick out plants for any garden design.