Drought-resistant Plants

Credit: John Glover

A dozen ways to beat the heat, plus the secret to keeping drought lovers alive through the long, wet winter

Recent summers in this province have been particularly dry – last summer felt as if we were in southern California! Now, more than ever, gardeners want drought-tolerant plants, but in B.C., particularly on the coast, these plants must not only be able to withstand drought but also tolerate autumn and winter deluges of rain. It is a fact that water is a precious commodity and should not be wasted on lawns and high-maintenance plant beds and borders. Fortunately, a wide range of lovely drought-tolerant plants is available to us, and by gradually changing our gardens over to such choices, we will lessen the heartache of loss while providing a pleasing and colourful landscape throughout the summer. Full sun and well-drained soil is absolutely necessary for all of them, well-drained soil being the key to their survival during those winter rains. Allium cernuum, our native nodding onion, is indigenous to many areas of North America, particularly drier prairies and B.C. interior sub-alpine meadows. On hikes into the backcountry it is always a joy to find a clump or two of these wild onions – adding a few leaves to your sandwich can really spice things up.

In the wild this is a rather low-growing bulbous perennial with strap-like leaves. During summer stiff stems 30 to 60 cm (1 to 2 ft.) in height with sharply curving tips bear pendant umbels of 20 to 40 bell-shaped pink flowers. In a cultivated garden situation, the taller stems are the norm. It must be stressed that these nodding onions need really well-drained soil. You can see a large patch at the entrance to the Native Garden at UBC Botanical Garden where, for more than 10 years now, every summer their massed flowers look like a pink mist for six weeks. After they have finished blooming, the attractive seed heads remain all summer long. In the right conditions they seed themselves about, not to the point where they become weedy, but just enough to maintain the quality of their planting area. They are very hardy, to zone 4. While I do not have a garden of my own, if I did I would interplant my nodding onions with Artemisia alba ‘Canascens,’ a clump-forming semi-evergreen perennial with intricately formed silver leaves. The pink haze of the nodding onions combines with the laciness of the artemisia to conjure up a very pleasing and relaxing effect. While artemisia’s flowers are brownish and not terribly attractive, its lovely foliage forms a rather nice clump with an overall height of about 20 cm (4 in.). Hardy to zone 4 and up, this one prefers a dry, sunny and well-drained spot. It seems quite deer-resistant, too. For those wanting to make a stronger statement, Artemisia absinthium offers the same exquisite foliage in a 75-cm (30-in.) version. Silver foliage is usually a dead giveaway that a plant is from a dry region of the globe and therefore ideal for drought-prone garden spots. This next one, Hieracium lanatum, may be more difficult to find and is a little less hardy – to zone 5 and up. It is native to southern Europe. This is a clump-forming perennial with attractive, lance-shaped, grey-green and white-margined leaves up to 10 cm (4 in.) in length. They are densely clothed with long white hairs, which give them their distinctive colour. Each leaf is somewhat cupped, making it even more intriguing. In summer, wiry branching stems up to 45 cm (1 1⁄2 ft.) long bear loose panicles of deep-yellow flower heads. Some people want only the silver effect of the foliage and remove the flower stems as they appear, but in the right location and grown in large clumps, the flowers can really brighten up a border. Poor but well-drained soil is the key to success with this one. Silver-foliaged Thymus pseudolanuginosus, fondly known as woolly thyme, is a mat-forming sub-shrub native to Europe and hardy to zone 4. Its tiny oval leaves are covered with minuscule silver hairs that give the plant its common name. In midsummer whorls of very small pink flowers are produced. In Europe, woolly thyme has long been used to fill in the cracks of flagstone paths or cover dry-stone walls. In fact, at Sissinghurst in Britain and at Ravenhill Herb Farm on Vancouver Island, there are attractive stone benches planted with woolly thyme to form cushions on the seat; as one sits the aroma of the thyme is released into the air. I find this little plant to be great all season in the dry interior, the Gulf Islands and in arid spots in the garden, however on the soggy coast it has been known to turn black in the winter. Don’t be discouraged, though – it does bounce back in the early spring. In dry areas, it can even serve as an alternative to a small grass lawn if it doesn’t get too much foot traffic, as thyme will stand up to some, but not constant foot traffic. It is great for boulevard planting, and if interplanted with strong foliage plants such as Yucca glauca or Yucca filamentosa ‘Golden Sword,’ it can create a very pleasing textured planting.

Drought-resistant plants, cont’d

Moving on to more showy plants, Crocosmia ‘Lucifer’ jumps to the forefront as a superb drought-tolerant candidate. Stunning for both its foliage and flowers, this bold perennial has mid-green lance-shaped, pleated leaves up to 1 m (3 ft.) in length. The bright-red, upward-facing flowers are borne in slightly arching, sparsely branched spikes. Hummingbirds adore crocosmia, and placed in a sunny spot near a patio it can give you much pleasure during the summer months. It should also be noted the strong growth often requires no staking, although it’s a good strategy to plant it behind other perennials on which it can lean if it gets a little top-heavy. Hardy to zone 6. Lychnis chalcedonica (Maltese cross) is another stunning red-flowered perennial. It comes to us from northern Europe and Russia, making it hardy to zone 4. Its stiff, hairy, 1-metre (3 ft.) long stems grow from a basal clump of mid-green leaves that clasp the stems with heart-shaped bases, while summer’s scarlet flowers are each shaped like a Maltese cross. If you are planning a red border, place this close to Crocosmia ‘Lucifer’ for a real showstopper.

Thymus pseudolanginosus (Woolly Thyme)
Artemisia absinthium ‘Lambrook Giant’

While on the topic, I must mention another well-known old-fashioned member of the family. Lychnis coronaria (rose campion) is hardy to zone 4, a tremendous self-seeder and very drought tolerant. Friends who garden up the coast on Thormanby Island, which gets crispy-dry in the summer months, have this seeded about among the rocks where it thrives and appears to be deer proof! The silver-grey basal leaves are 18 cm (7 in.) in length. In late summer stems up to 80 cm (30 in.) long bear magenta flowers. Pure white forms are also available. Penstemon heterophyllus comes to us from California and is hardy to zone 7. A drought-tolerant, evergreen sub-shrub, its bluish-green leaves are 2 to 5 cm (1 to 2 in.) in length. In summer it blooms heavily with racemes of funnel-shaped pinkish-blue flowers with blue or lilac lobes. It grows to a height of 30 cm (12 in.) and forms clumps 50 cm (20 in.) across. Due to the delicate colour of the flowers, the entire plant seems to glow in early-morning and evening light, making it a must for warmer areas. A rather aggressive perennial that is absolutely drought tolerant is Phygelius x rectus ‘African Queen,’ an upright suckering shrub with dark-green leaves. During summer showy panicles up to 30 cm (12 in.) in length bear 6-cm (2 1⁄2-in.) pale-red flowers with orange/red lobes and yellow mouths – naturally very popular with the hummingbirds. As the cultivar name suggests, it is of South African origin, so is unfortunately limited to zone 8. A lot of people throw up their hands in horror when I praise this plant. As I mentioned above, it is a bit rambunctious and will spread in the right conditions. But it happily thrives where other plants would perish and is invaluable for sunny dry banks, even near salt breezes. My last recommendation is a real beauty: Salvia sclarea (clary sage), native from Europe to Central Asia, is hardy to zone 5. It is very fussy about having a hot, sunny, well-drained spot in the garden. An erect biennial or sometimes short-lived perennial, it has many-branched hairy stems and wrinkled, mid-green leaves that are notched and 23 cm (9 in.) long. From late spring through summer the plant produces many-flowered terminal panicles or racemes of cream and lilac to pink or blue flowers, with prominent lilac bracts. It is a very showy plant and well worth a prominent position in a drought-tolerant border. The overall height is 1 m (3 ft.). Having included this wonderful salvia, it must be said that all the different forms of Salvia officinalis, the edible sage we use in cooking, make excellent candidates for a waterwise border. To top it all off, you’ll enjoy its gorgeous blue-purple flowers, and the bees find these blossoms irresistible! David Tarrant of the UBC Botanical Garden is a well-known gardening expert, author, and host of Spring, currently on HGTV.