This morning I went into my semp garden for my usual fix of sunshine-on-the-sempervivums. I looked down upon my Jovibarba 'Blaze' and decided the situation had gone on long enough. There were three individual plants that had come with an order from Young's. One was a largish rosette looking quite spry. Another was a a smaller rosette divided in two, also looking quite happy. I could feel that both of them were quite firmly rooted. Between them, however, was a third plant with three rosettes dividing it. It was obviously struggling. The leaves were small and leathery, and there were multiple dried, brown leaves around the perimeter. It seemed to actually be shrinking slightly from week to week. It also did not feel solidly anchored. Pulling it from the ground revealed the obvious, lack of root development. But why? Then I noticed small white creature moving quickly around the old dead root stump. Then another. I immediately recognized them as the dreaded Garden Symphylan, an agricultural pest that wreaks havoc along the west coast of North America and is impervious to any controls available to the home gardener. I believe this is the biggest reason the farmers around me fumigate their soil on a regular basis.
Anyway, this is the second plant I've found with these symptoms although previously I had not suspected Symphylans. But it does make perfect sense. In both cases I found a few brand new tap roots although there had been time for extensive root growth. Those roots I believe would be soon discovered and attacked. The Symphylan loves to eat tender new root tips. As the semp desperately tries to grow new roots to establish itself, those roots are nibbled right back. The semp keeps trying and trying, losing vigor with each lost root. The plant ends up looking very much like a plant that has been left on a table top, unable to root.
Symphylans are a regular pest in my vegetable garden, especially with squashes. I hadn't thought Symphylans to be a Sempervivum pest but I now know otherwise. My garden is particularly vulnerable since it is at least slightly moist throughout the year. The Symphylan requires moist surroundings and soil that dries out completely from time to time will limit their numbers. In no case have I found plague-like numbers, just nuisance levels.
The good news is that I don't think that semps with healthy root systems are much affected. However, rootless transplants may have trouble establishing new roots if Symphylans happen to find them. Going forward I don't think I have much to worry about except an occasional victim. Although I will take some special care for any rootless specimens received from Europe.
