If you want to be an environmentally friendly rose grower, you can avoid the most common diseases of PDX roses by finding varieties that resist mildew and fungi, and by planting your rose bushes in sunny spots.
But that might not be enough prevention when the weather is as wet has it has been in Portland lately. A friend emailed recently to say:
…I have two red roses that are the long-stem kind, but one of them hasn’t started blooming yet and the blooms on the other one look deformed.
As a serial gardener (4 PDX gardens, all with different growing conditions), I volunteered some advice.
Is Mildew/Fungus to Blame?
If there are leaves with black spots or yellowish blotches areas on them or if you see dryish leaves with patches of whitish dust on them, that’s fungus/mold/mildew from too much moisture.
Peninsula Park Rose Garden (by Ren Thompson)
I’ve never tried the homestyle, organic remedies (which Google will help you find–e.g., spray the leaves with diluted milk), so I can’t vouch for them. But they’re certainly worth a try.
If you must resort to a chemical remedy, try to keep its impact local to the plant itself. Buy the tiniest bottle of spray-on mildewcide/fungicide that you can, because you won’t use much per year.
I prefer this to sprinkling fungicide around the plant’s roots. This “systemic” treatment is taken up by the roots, making it work for a long time. But it also wipes out all the “good” fungi in the surrounding soil ecosystem–not a good idea, in my opinion.
Hungry Aphids
The other affliction that I’ve seen deform rosebuds like that is aphids. So look for those suckers (literally, that’s what they do to the plant). They like tender new leaves and the flower buds.
Aphids line up along the bud or new leaf, spilling onto the stem below. If they’ve been eating well they get really fat and orangish in color. If you’re patient, you can buy ladybugs at the garden center and let them loose to eat the aphids.
Or you can wipe away the aphids with your gloved fingertips and smash them into oblivion. Then rinse the buds & leaf tips with water or spritz them with water that has a little dish soap in it. Stores sell “insecticidal soap” for this, but regular dishwashing detergent (like Dawn, etc.) is handy and effective.
I use the smash-then-soap method several times before resorting, very rarely, to chemical warfare. Again, I keep the treatment as local as possible, and use a homemade insecticide.
The recipe: Soak a small piece of a cigar (with a tobacco leaf wrapper, not artificial) in ½ cup or less of water overnight. In the morning, strain the brown liquid into a small spray bottle and lightly spritz the new growth at branch tips.
***Store leftovers where kids and pets can’t reach.***
The tobacco juice is a neurotoxin that stays around on the new growth long enough to keep a new bunch of aphids away. It’s nasty stuff and should be handled with care. (Wear gloves. Don’t put the wet tobacco in your compost pile. Wash hands carefully after using. Keep it away from children and pets.)
And enjoy your beautiful roses!
