You’ve pulled your garden through a ridiculously late spring followed by an oddly dry start to summer.
You’re out savouring the aromas, enjoying the colours, and what do you see? The bee-balm’s leaves have gone pasty grey, the roses look like they have a case of black measles, and the apple tree has been set on fire. Does it never end?
With disease, it doesn’t. Fortunately, the horticultural wizards are equally persistent. If a plant has succumbed to disease, or if you’re simply tired of trying to out-manoeuvre a disease and are going to replace the plant, there’s no need to go without a plant you adore. There are cultivars that have been specifically bred for their disease resistance.
That pasty grey is classic powdery mildew. It’s a fungus and can quickly cover most of the foliage in a grey powder. Roses, bee-balm and phlox are especially susceptible. Roses add a classic elegance to any yard, phlox are a flower garden cornerstone, and bee-balm plants are just plain fun. No yard need do without these plants. ‘Prairie Joy’ and ‘Winnipeg Parks’ Roses have good powdery mildew resistance. If it’s phlox you need, try ‘David’ or ‘Spinner’. ‘Grand Marshal’ and ‘Grand Parade’ are good choices for bee-balm.
You know you love a plant when it’s susceptible not just to one, but to two diseases, yet you want to grow it anyway. Roses are also prey to black spot. This is a fungus, and shows up as small black spots with discoloured green spots. Ugly. Cultivars with good black spot resistance include the many of both the parkland series (‘Prairie Joy’, ‘Winnipeg Parks’) and the explorer series (‘John Cabot’, ‘John Davis’).
The apples, ornamental crabapples, and mountain ash are susceptible to fireblight. Aptly named, infected plants look very much they’ve been torched. These trees are a significant part of our prairie landscape with their magnificent springtime flowers and fruit. There is no substitute for home-grown apples. And there is no substitute for the ornamental flowers, summertime leaf colour, and wintertime effect provided by the ornamentals.
Mountain Ash, with its flamboyant red fall colour, is incomparable. ‘Kerr’ applecrab is an old-time favourite apple with excellent fireblight resistance, and very good flavour. ‘Emerald Spire’ and ‘Selkirk’ rosyblooms are new disease-resistant introductions of ornamental crabapples. ‘Oakleaf’ mountain ash is the best disease-resistant choice for mountain ash.
Carla Keast has a master’s degree in landscape architecture and is a Winnipeg-based freelance landscape designer. She can be reached at firstname.lastname@example.org.