Deciduous trees will eventually begin to defoliate.

Even without significant cool weather, the garden knows that it is now autumn. Most of the late summer blooming flowers are finishing their last bloom phases. Leaves of some of the deciduous trees, shrubs and vines are changing color, and some are already falling. Perennials that are dormant through winter are starting to deteriorate.

One of the several difficulties of living in a climate with so few difficulties is that autumn and winter weather is so very mild. Just as so many warm season annuals and vegetables want to continue to perform when it is time for them to relinquish their space to cool season annuals and vegetables, many other plants that should go dormant in autumn really want to stay awake as long as they can. Some semi-deciduous perennials even start to regenerate new growth before they shed their old growth.

Where winters are cooler, such plants generally shed the growth that developed in the previous year; in other words, they die back. They then stay dormant through the coolest part of winter, to break dormancy and regenerate late in winter or early in spring.

Beard tongue (Penstemon) can really look bad as the last flower spikes deteriorate, and the foliage gets spotty and grungy. It will be tempting to cut them back early. If possible, it is better to prune off only the deteriorating flower spikes, but wait until later in winter for major pruning. Premature pruning stimulates premature development of new growth that does not mature as well or as fast through winter as it would in spring. Such growth can be discolored, sparse and less vigorous until it gets obscured by later growth.

Marguerite daisy, ginger, canna, some salvias, most begonias, the various pelargoniums and all sorts of other perennials will likewise seem to be rather tired this time of year and through winter, but do not necessarily need to be pruned back just yet. Simply plucking or shearing off deteriorating flowers should be enough for now. Ginger and canna should not need to be pruned back until the foliage deteriorates enough to be almost unsightly. Begonias and pelargoniums, particularly common zonal geraniums, will be better insulated from potential frost damage through winter, and may not produce so much sensitive new growth if not pruned early.

6 thoughts on “Plants Know What Time It Is

    1. Mild climates can be boring. They certainly have advantages, but autumn is not one of them. I had always been satisfied with autumn here, but still have not experienced autumn in a normal climate.

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      1. I know I have been here too long when I actually think the trees have autumn colors. Our trees “turn” about December and the leaves are mostly brown. I’m from the northeast where the sugar maples grow.

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      2. Sugar maples color even here, but they are very rare, and do not hold their foliage well after it colors. Sweetgums are more common. Californians think that they are maples. They turn color even in Los Angeles.

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  1. There are a lot of plant, including wildflowers, that look very raggy this time of the year. As day length decreases, it triggers leaves of some trees to fall without an “F” (frost). Other plant do weird things like growing new leaves when it starts to get cool. Well, this is Missouri, and we definitely have seasonal changes, which is different from year to year. You never know how the winter will be…

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    1. Many plants that are accustomed to cooler autumn and winter weather get confused here. I would expect less of that where autumn weather is actually cool, such as Missouri.
      Some of our perennials start to go dormant, but then start to grow early because the weather is warm enough for them to do so. I am supposed to bring some cannas with me on a trip up north, but they started growing, and are actually growing quite nicely now! I will bring them anyway, but do not know what they will think when they get frosted. I know that they will be fine in spring, but they might be confused.

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