Most books recommend transplanting primula after they bloom. I usually try to avoid this, as by the time most of my allionii and marginatas have finished flowering and have begun to set seed (May), the weather is getting a bit too warm and the danger of root rot increases. I usually transplant in late September when the night temperatures fall below 50 degrees.
This week I am breaking with my tradition. I am repotting many of my marginatas and allionii. I have also broken down a couple of troughs and removed the plants. One trough was originally set up in 2009 and the marginatas and allionii had outgrown it. The plants were very healthy and produced more offsets than I can really handle.
I am becoming more of a trough convert. Troughs seem to keep the soil more stable in terms of temperature and moisture. Also, Allionii and other alpine primula seem to like company, so it looks like there are more troughs in my future.
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