What are the pros? Edible flowers, strong growth
What are the cons? prickly
I popped a few of these into some gaps in a raised bed and they quickly grew to 2 feet high and 18" or so across, flowering prolifically for several months. The flowers and young leaves do indeed have a mild, cucumber-like taste, although the leaves were too prickly for me to enjoy eating them. It's a very pretty plant and it produced biomass quickly, which I chopped and dropped into the bed. The earthworms and other critters seem to like it as it's rapidly been decomposed under a light layer of wood mulch. I plan to grow it again for its edible flowers and green manure.
Be aware that it readily re-seeds itself. I planted it in late winter in a warm climate, took it out in late spring, and have seen many little borage plants popping up in the bed since then.
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