Question: What is the correct way to prune a Physocarpus ‘Summer Wine’? It seems like no matter what method I use, I get a lot of new, strictly upright shoots, which are extremely vigorous.
Answer: I love this plant, and we've had it here at the experiment station long enough to understand its habits. It does send up vigorous shoots, but they will eventually mound over until the plant has the approximate form of a forsythia—wider than tall, with a spreading, somewhat weeping habit.
Simply leave it alone, and it will soon grow into its natural, graceful form. If it is too large for the spot, (and it will be at least six feet wide, and nearly that tall), consider moving it. If you can't and want to manage it, yet keep it graceful, remove the limbs that are “too big” by reaching in and pruning them within the shrub, where you do not see the pruning cut. Always cut just above a bud (leaf), and you can actually control the direction of the new limb growing from that stub. You do this by choosing to cut above a bud that is “aimed the right direction.”
It's too late to prune this summer—itwould force out new growth that would be damaged by frost. Besides, the bloom buds are already set, so you would be cutting off next spring's flowers. Wait until just after bloom next spring (though the red seed heads are also pretty, darn it!) if you simply must prune, but I hope you won't!
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