Deteriorating Clematis

Asked July 9, 2019, 5:12 AM EDT

A Polish Spirit clematis near our entryway grew for 20 years vigorously up a brick wall to the roof eave, about 10-12 feet. The last few years it gradually lost that vigor, and this year consists barely of a few spindly vines a couple of feet long. Last winter I pruned it back, uprooted it, amended the soil, and replanted it. This spring it’s still weak. I suspected perhaps a large pod of gladioli encroaching in the flower bed might be affecting the clematis and 3 weeks ago I thinned them out to a foot or 18” from it. But a vine or two wilted and the plant still refuses to snap out of it. Though I’ve had wilt issues with other clematis on the property regularly, this is the first incident where the Polish Spirit suffered wilt; and thanks I guess to Daconil none of the others display wilt so far this season. Is there hope of saving our entryway clematis?

Clackamas County Oregon

5 Responses

Thank you for your question. Without a photo or a chance to examine the plant, the best guess is the disease described in this handbook: If you could bring photos of the plant, and some leaf and stem samples to the CC Extension office any weekday between 9-noon, and 1-4, Master Gardeners can examine them. The address is 200 Warner-Milne Road, Oregon City. Thanks!

I don’t get up to Red Soils too often anymore, but need to hit Wilco before long. I will try to remember to put the sheet of photos I took in the car, and drop by to check in with a MGardener then. The Clematis has just plain stalled this summer; it’s few runners are 2ft long and devoid of stem circumference and vigor. It used to climb up a custom trellis I built over a 4 ft wide brick wall, 12 ft to the roof fascia and beyond, then bloom profusely.

one new question, I know one can’t use cedar products around certain plants due to antagonistic oils (like cedar chips can kill blueberries), but can I get away with using 1/2” strips leftover from a cedar fence repair as garden stakes for tomatoes, gladiolus,rudebeckias, etc.?

I know the MGs at CC office can help!

As for cedar, it is not harmful (allelopathic) to blueberries. In fact, because it acidifies the soil, it actually helps blueberries, rhododendrons and azaleas, all of which need more acidic soil. But even cedar loses its ability to do that after 15 months or so. (I think you may be thinking of walnut, whose harmful chemical is juglone.) So, you can safely use cedar strips for stakes of all these plants.

Good luck!

Hmmm. 40 some years ago I’d read or been told to never put cedar bark dust/chips on my Dad’s 25 blueberries on our old farm; just Douglas fir barkdust. A neighbor impressed by Dad’s success planted a big patch of blueberries of his own. One year he replenished his mulch, and within a month or so most of his berries had died. I asked him what he’d used and he said cedar, at which point I reminded him that wasn’t advisable.

my memory is dim and details may not be necessarily precise, but I’ve never used cedar since except forclematic trellises.

Well, I’ve read about 30 articles on blueberries and cedar, and only one indicated that it may ‘harm young plants,” with no science to back up. The following more recent article purports to dispel that rumor (about 3/4 through the article: And, I have had 4 blueberry bushes directly under a deodar cedar for all of their lives and, if I remember to prune, I have more berries than I can eat.