Answer: This shrub (Physocarpus opulifolius) tends to be a bit unkempt and scraggly looking in its natural growth habit. You you may want to prune it for shape early each spring by removing some of the oldest branches by cutting them off at the base. (This will probably not be bnecessary for a newly purchased plant.) This annual pruing regime will tify the plant a bit and also keep encouraging new growth from the base. An alternative method is to simply cut the entire plant off short near the base in late winter or early spring. This more extreme treatment would be done as needed, probably just once every few years. I think the operative word in the advice you received is "could" rather than it being a "must". In any case, prune in very early spring as needed.
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