Q: I have a blue potato bush (solanum rantonnetii) that I purchased in September. It is trained like a tree. Has a bare trunk (staked) and was trimmed to a round shape on the top. I transplanted it and that encouraged a flush of new growth. It is not a round shape any more. It has long branches going everywhere! I would like to prune it back to a fairly round shape and I am not sure when or how I should do this. It has lovely flowers and I would hate to ruin it.
I live in El Cajon, CA and our winters get down to about 35 degrees. No snow. Should I wait until Feb or March to prune it? How should I prune it? I found you on the Fiskars web site and enjoyed your video on pruning. I am not sure what category my plant falls into. Sounds like I follow a branch back until I see a branch off and clip there, keeping a round shape in mind?
Thank you for your time.
Cheryl
A: This plant is hardy down to 25 to 30 degrees Fahrenheit and the growth usually slows down considerably once cold weather hits. It may come back in the spring if even colder weather cuts it down in the winter, although that should not be a problem in your part of California.
The blue potato bush is notorious for sending out suckers which need to be pruned back if you want to keep the tree shape. If left unpruned it can grow to a bush of twelve feet or higher and perhaps just as wide. Prune the wayward branches back in spring and whenever needed to keep it tidy in throughout the summer and fall. Pruning does stimulate growth and blooms. It is a very forgiving plant and you probably cannot ruin it, even with severe pruning. Grow it in full sun for best blooms. Keep it staked for additional support if the top of the plant becomes too heavy.
Good luck, Cheryl.
Best regards,
Joe
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