Thursday, July 11, 2013

Diagnosis: Scorch

Another inch and a quarter of rain yesterday. Unbelievable. It is only in the high 70s today, very darkly overcast, so I went out to weed and start moving things around in the Drive By Garden, which needs a total redesign.

But the mosquitoes were awful and the humidity was so high that it just wasn't doable. I did manage to cut back the floppy Huskers Red penstemons in the Birch Garden, and do a little weeding. Not much.

I don't think the alpine willows (Salix yezoalpina) on the east side of the house have bacterial scorch. The brown edges do not have the ring of discoloration at the edges. But they do have a scorch problem, and my diagnosis is that heat and sun are the problems.

The whole patch looks terrible, with new leaves all deformed and banded in brown.

When these groundcover willows scorched in last summer's dry stretch, I put it down to drought. But this year that simply can't be.

We've had so much rain! Three and a half inches just in the first ten days of July. Over 12 inches of rain in June, record breaking downpours.

The older leaves look great, and I think when the temperatures were cooler with all that rain, they did well. But then we got very high temperatures for a while, and it is the new leaves that seem to be affected.

These are alpine plants and they want cool temperatures and perhaps more shade than they are in. They get what amounts to full sun -- even though they are on the east side of the house and in deep shade during the height of the afternoon, they are in a full seven hours of direct sunlight from dawn to 1 p.m.

So even with all the rain, I really think the bright summer sun and temperatures in the 90s are browning the leaves. It's not a water problem. They surely are as wet as can be this year. Maybe too much, even. As alpine plants they can take dry conditions, but I do think they need cooler weather.

So, what to do?  They are not diseased, they are spreading well. But they look awful in the height of summer.

  • Should I leave them and just don't look?
  • Or take them out and replace with vinca or pachysandra? Those are easy, overused but reliable groundcovers that will do what the willows are doing for coverage.

What to do, what to do.