Choosing Best Plants For a Dry Summer
Gardening - A drought tolerant label may not be enough to guarantee survival
by Steve Whysall
May 21, 2004
The hot, dry days of summer are coming, so now's the time to think about what plants you have growing in those blistering hot, full-sun, fast draining locations.
The plants you have there right now may be considered drought tolerant, but that may not be enough to get them through an extended hot spell from July to September.
Last week, I made major changes to a hot spot in my garden. I tore out all the hardy geraniums (G. macrorrhizum) along with some euphorbia and lamb's ear.
All these plants are considered drought tolerant, but last year in the 90-degree, full-sun exposure of the August heat wave, the geranium scorched badly, went limp and looked miserable. I decided then to not put up with that again this summer.
Geranium macrorrhizum, by the way, is a first-class plant. It is evergreen in coastal gardens, has wonderful magenta-pink flowers in mid-spring and the leaves also have a lovely, pungent musky scent when touched.
This plant has the ability to thrive in pretty much any location, except for a total west or south exposure.
In its place, I have planted a wonderful selection of ornamental grasses. I am hoping these will quickly bulk up to give me a striking grass-scape that will thrive in the heat of summer. It produces lovely soft white-and-tan flower spikes that will move around gracefully with even the smallest hint of a breeze.
Another strategy is to practise what has become known as water-wise gardening. This involves using mulch to reduce water loss through evaporation and choosing plants that, while not totally drought-tolerant, can survive on very little water and require little maintenance.
But the planting principle used throughout the sunny areas of the garden remains the same: use material that requires little watering and is able to tolerate long spells of heat.
Photo Caption: Judith Cowan getting ready to plant a Garry oak in the waterwise garden at City Farmer. It is a boulevard garden half a city block long, and Cowan favours mostly native plants such as Rosa woodsii.
You can see a good example of a water-wise garden at the City Farmer garden at 2150 Maple St. in Vancouver. Started by Ross Waddell in 1995, this is now being redeveloped by Judith Cowan because some of the areas have become a little more shady.
It is a boulevard garden, half a city block long, and contains mostly native plants such as nodding onion (Allium cernuum) and red flowering currant (Ribes sanguineum).
One part of the site, alongside railway tracks, still needs to be developed. Cowan is starting to work on this and is looking for volunteers to help with the planting.
Here's my recommended list of 10 top drought-tolerant plants. Remember, soil and drainage conditions can make a big difference, and the range of plant material available will expand if the area is shady during some part of the day, especially in late afternoon.
Grey foliage plants: It is a safe bet when looking for drought tolerant plants to pick ones with grey foliage, usually a sign that they can take the heat and need little water. Pick of the litter are the artemisias, notably 'Valerie Finnis', and 'Silver Mound ' and 'Silver Brocade'; lamb's ears (Stachys byzantina), especially Silver Carpet and Giant Lamb's-Ears (a.k.a 'Helene von Stein'); cotton lavender (Santolina chamaecyparissus) and annual specimens such as the curry plant (Helichrysum italicum).
Daylilies (Hemerocallis): 'Stella de Oro' is still the best pick, being shorter and longer flowering than most, with golden-yellow, trumpet-shaped blooms. But daylily whiz Pam Erikson, of Erikson's Daylilies in Langley, says many of the reds from cold climates, such as 'Chicago Brave' and 'Chicago Apache', are "incredibly tolerant of major droughts".
Spirea: 'Goldflame' is outstanding, with bronze leaves that turn golden-yellow as they mature followed by rosy red flowers from June to fall. It is a firstrate shrub for a small garden, being compact, and grows only three to four feet (90 cm to 1.2 m.) Other top cultivars, mostly classified as a form of S. japonica, include 'Magic Carpet', which has foliage of gold, lime green and red hues and produces plenty of pinkish-purple flowers in mid-summer; 'Anthony Waterer' with rosypink flowers from July to September; 'Little Princess' with mint green foliage and rose-pink flowers.
Other top performers you'll come across include 'Fire Light', 'Neon Flash', 'Shibori' (a.k.a 'Shirobana') and 'Goldmound'. They all grow three to four feet (90 cm to 1.2 m).
Ornamental grasses: Warm - and - cool - season grasses are both shallow rooted and able to thrive in full sun. Best of the miscanthus are 'Adagio', 'Rotsilber' and 'Gracillimus'. Most reliable of the pennisetums are 'Hameln' and 'Moudry'. But also check out varieties of molinia, sesleria, calamagrostis panicum and deschampsia. It would be a mistake not to testdrive some of these in hot spots in your garden this summer.
Potentilla: The plants for gardeners who want the impossible: something that flowers perpetually, requires no maintenance, has no pest or disease problems and grows less than three feet (90 cm) high. 'Goldfinger' is a striking yellow, producing larger warm-yellow flowers over a compact mound of foliage. Two other excellent yellows are 'Goldstar' and 'Yellow Gem'. 'Abbotswood' is the best of the whites, but 'Snowbird' (double white) and Mckay's White (creamy-white) are popular rivals. Best of the reds is 'Red Robin', which has fiery, brick-red flowers that hold colour in full sun instead of turning orange, as some red- and pink-flowering types have a tendency to do. Other star hybrids include 'Pink Beauty' (pink), 'Princess' (light pink fading to white), 'Tangerine' (orange-yellow), 'Red Ace' (orange-red) and 'Royal Flush' (rosy-pink.)
Yarrow (Achillea millefolium): This grows two to three feet tall (60 to 90 cm) and thrives in the warmest, driest sites. 'Moonshine' and 'Paprika' are highly recommended but you will find even more appealing cultivars in a wide range of colours from subtle pastel shades of apple blossom and lilac to bright red.
Stonecrop (sedum): These perennials never fail to thrive in hot spots. Look for 'Autumn Joy' or 'Brilliant', both of which have thick, green succulent-like leaves and pink or dark red flower heads in late summer. Some kindred cultivars have bronze red or purple foliage. Look for 'Atropurpureum', 'Matrona', 'Morchen', 'Vera Jameson', 'Bertram Anderson' or 'Ruby Glow'. For the sunny rockery or fast-draining slope, try Sedum spathulifolium, which grows only four inches (10 cm) high and has tiny rosette-shaped silver-grey leaves and bright yellow flowers. Sedum spurium, also known as 'dragon's blood', grows a little taller, about six inches (15 cm), and has pink, red or white flowers.
Spurges (Euphorbia): Wonderful foliage plants, often with great flowers, these are an excellent choice for a protected, welldrained site. Look for E. myrsinites (donkey-tail spurge); E. amygdaloides 'Purpurea' and 'Robbiae' (wood spurge); E. dulcis 'Chameleon' ; E. 'Excalibur', delightful foliage, and all the various cultivars of Euphorbia characias, especially wulfenii and Humpty Dumpty.ΚΚΚΚΚ Κ Tickseed (Coreopsis): Best of the bunch is still the threadleaf coreopsis 'Moonbeam', which gives you delicate lacy green foliage and masses of dainty yellow flowers all summer. 'Zagreb' comes a close second, but there are some exciting new cultivars such as 'Limerock Ruby' (maroonred flowers), 'Creme Brulee' (yellow flowers), and 'Sweet Dreams' (white with red centre) that are all very heat tolerant.
Overlooked favourites: How can I leave out of this list such popular favourites as Nepeta 'Dropmore Blue' for its fragrance and blue flowers, especially around rose beds; Crocosmia 'Lucifer' for its dramatic foliage and fiery red flowers in July; and all the varieties of lavender, especially 'Hidcote', 'Munstead ' and Spanish lavender (L. stoechas). Other stalwarts not to overlook include sages, especially the plain foliage types such as Salvia officinalis 'Purpurascens' , 'Tricolor' and 'Icterina', all of which are unapologetic sun-lovers.
For more suggestions, check out the Heritage Perennials website at www.perennials.com and the City Farmer website (www.cityfarmer.org/boulevardplants.html) where you will find an excellent list of drought-tolerant plants for city boulevards compiled by volunteer master gardeners from VanDusen Botanical Garden for the Prince Edward Street Waterwise Blooming Boulevard Project.
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