I had clematis in these barrels and continually had to spray for powdery mildew. Finally I moved the clems to the ground (they needed more root space anyway). I would like to re-use these barrels and the dirt.
What can I rinse through the dirt and what can I clean the inside of the barrels with that will kill the powdery mildew?
For general year-end disinfecting of plastic or ceramic pots, I've heard people suggest blasting off the dirt, cleaning with soap & water, THEN soaking in 10% Clorox for ten minutes. That's just what I've heard, but it makes sense to me to FIRST emove 99.9% of everything with soap & water, THEN disinfect.
Why they don't use 0.2% hydrogen peroxide I don't know, but I don't hear that reccomended.
For disinfecting wood - that sounds harder. Clean it really well, then soak it, then expose it to sun and rain? If you do soak or spray with Clorox, I guess you'll find out if it hurts the finish or weakens the wood surface.
Thanks Rick. After doing some research I think it is clematis wilt rather than mildew. But I need to clean the containers anyway. I think you are right about the 0.2% hydrogen peroxide. It should work just as well and not harm the wood. I guess I'll power wash them and then rub the inside down with HP and leave them in the sun for a couple days.
Is there something I can drain through the soil to kill this stuff or do I just have to toss the dirt?
I want to plant some more clematis in these barrels.
Sun might help. Power-washing is bound to help, peroxide can't hurt and might help - but nothing gets rid of every spore.
Maybe (I'm just guessing here) a coat of water-resistant paint on the inside? That's just a WAG and may be a bad idea. You would lose the benefit of wood "breathing" air into the soil.
I've never grow in wood plants, but maybe someone in the "Container" forum knows a potent cleaning method that won't hurt wood..
For re-using the soil, here are a variety of fungicides, some designed to be "soaks" that you pour through soil - but would they happen to affect whatever that infestation happened to be?
If you do wind up using that soil for something else in some other pot, one inexpensive way to expand any soil mix that you use is to add 50% screened pine bark. You can make it faster or slower draning by using coarser or finer pine bark. Even the best, cleanest, least-powdery pine bark mulch is cheaper than any potting mix - like $4-8 per 2 cubic feet.
I would think it's a good idea, anyway, to rotate the plant you grow in any given soil. Like rotating crops in the field or garden.