To help you learn how to grow great roses without poisonous pesticides Metro Natural Gardening Expert Carl Grimm shared the latest natural tips and tricks.
Plant pest- and disease-resistant varieties
Choosing the right variety is the single most important thing for avoiding common rose disease problems. There are several roses native to the Willamette Valley that offer delicate pink blossoms in spring and beautiful hips in fall for attracting wonderful wildlife to your yard. Native Nootka- and Bald hip roses are good choices for a hedgerow, thicket or large space as they spread by rhizomes. Portland Rose Festival's official rose for 2013, "Pop the Cork" is a disease-resistant hybrid tea rose, as is fragrant "Sugar moon." "Altissimo" is an amazing tough and gorgeous climber. Other great performers include "Knockout," "Drift," and "Flower Carpet." For more ideas, search online for Oregon State University disease-resistant roses pnwhandbooks.org/plantdisease/cultivar-susceptibility-tables/rose-cultivar-resistance or check out the Gold Award Garden in the International Rose Test Gardens.
Give good sun and ventilation
Roses need at least six hours of direct sun to be healthy. They also need good air flow to reduce common fungal disease. Plant them with plenty of space so they are not crowded by plants nearby and use mulch underneath, not groundcovers. Prune heavily in early spring, and as the season progresses cut out the center stems so the foliage is not too dense.
Ensure rich, organic soil
Royal Rosarian Dave Etchepare says steer manure is the secret ingredient for many award-winning rose gardeners in our region. He also says "don't step on your soil too much!" Compaction causes problems for plant roots. For a dependable fertilizer, the Portland Rose Society sells an organic blend for applying a few times throughout the season. Alfalfa meal is also a great organic fertilizer, especially when combined with a trace mineral source like Azomite, Cascade Minerals or Excelerite. With any fertilizer, do not apply more than the label says - as too much can exacerbate pest problems, especially aphids.
Use least-toxic pest control methods
If aphids or other pest insects do come in large numbers - squish them with your fingers or blast them off with plane old water. Insecticidal soap can be used if you have a huge problem, but remember a few pests are good as they keep the pest-eating insects and birds around your garden for preventing future problems. Diseases are trickier, but if you've provided good soil, sun and air and still have a big problem, try Neem oil, Jojoba oil, or potassium bicarbonate, all low-toxicity fungicides. Always follow label instructions to the "T." It's smart, and it's the law.
Got more nontoxic gardening questions?
Give Metro a call at 503-234-3000, and we'll connect you to an OSU Extension Service Master Gardener in your county. You can also visit us online at oregonmetro.gov/garden.