I read (here I think) about a simple treatment for these aphids: spraying with a soap solution. However, I've forgotten what dilution I should use.
So here's two questions:
1: What dilution of a soap solution should I use?
2: What can I do to prevent this annual infestation of aphids?
I have 13 helleborus hybridus, each a different variety, all but three from Plant Delights. They, alone, are in a raised flower bed (approximately 40' x 3') on the entire side next to my house; since they range from 6" to 2' wide, they are in a staggered line with about 2-3' between each plant. The bed is mulched with about 1" of coarsely shredded pine wood.
I THOUGHT that this, my first summer in my new house out in the country, plus other changes (old: city, leaf mulch, crowded hellebores sharing a bed with other plants) that I would no longer have this aphid problem!