Dilemmas are common in gardening. Should summer vegetables that are still producing be removed so that winter vegetables can get started on time? What about replacing summer annuals that are still blooming with winter annuals, and then replacing winter annuals with summer annuals half a year later? Should tender perennials be regarded as annuals, or get a second chance?
Right now, some perennials are looking tired. Many will be going dormant for winter. Many do not get much down time, and will start to develop new growth faster than old growth deteriorates. Not many make their intentions obvious. Deciding how to work with them can be confusing at times. It might take a few years and a few mistakes to get familiar with the habits and lifestyles of some.
If cut back too early, hardy zonal geraniums will not regenerate much until the weather gets warmer at the end of winter. In the interim, they are more likely to be killed by frost without the protection provided by old growth However, some varieties start to grow in winter. If not cut back soon enough, new growth mingles with old, so that they are difficult to separate when they do get cut back.
It is best to observe what hardy geraniums are up to before deciding on when to prune. If they start to develop vigorous new growth down near the ground, the old growth should probably be cut down as far as the new growth. It is likely better to take a chance that they might be damaged by frost. Those that do not start to grow right away can enjoy the insulation of old foliage for a while.
Thoroughly deciduous perennials, like deciduous daylilies, dahlias and some ferns, can be groomed of their deteriorated old growth without risk that they will start to regenerate new growth prematurely. However, cutting back some specie of salvia might actually stimulate development of exposed and frost sensitive new growth. Perennials that get damaged by frost later In winter should not be groomed of damaged growth right away. The damaged material provides a bit of insulation for lower growth, particularly if new growth was stimulated by the damage.
That is a term that we do not hear much. There are not many plants that it applies to. Cyclamen is one of the more familiar plants that is summer deciduous. It is from a climate with reasonably mild winters and unpleasantly dry and warm summers. Just like most deciduous plants are dormant through winter to avoid the unpleasantries of the weather, cyclamen defoliates as the weather gets warm in early summer to avoid the expected heat and aridity. It somehow knows how to stay dormant until the weather starts to get cooler in autumn, and is ready to regenerate new foliage and bloom as the rain starts. The active growing season is through autumn, winter and into spring. It is all a matter of taking advantage of the weather while it can, and avoiding the discomforts of severe weather when necessary.

