I have a client whose Clematis I just renovated. The client called to say the ends of the cut stems were frothing! What could be causing this?
My best guess (and it is only a guess, since I am basing it solely on your description) is that it could be slime flux. According to the Royal Horticultural Society, “pruned stems may fail to reshoot and ooze a sticky substance–this is known as slime flux.” To confirm this theory, ask the client if the frothy ooze was pinkish orange in hue, and if it had an unpleasant odor. Here is more about this problem from the Daily Telegraph’s garden advice column by Helen Yemm excerpted below:
“This is not so much a disease as a condition that affects some trees and shrubs in spring. Bacteria enter the plant through cracks in the stem – which may well be caused by a combination of adverse weather conditions – and then attack the sap as the plant springs into action early in the year.
Slime flux is often fatal but it depends where the damage is. Everything above the oozing wound will certainly die and should be cut down. However, the plant may well shoot out from below and recover.
Slime flux will not spread to other plants as diseases do, nor will it contaminate the soil like clematis wilt. However, its occurrence would indicate that, for some reason, the general growing conditions in that part of the garden have become unsuitable. If you do lose your clematis, then perhaps it would be a better idea to plant a new one in a less exposed spot.”