As the name implies, ‘annuals’ need to be replaced ‘annually’. What is worse is that they do not even function for an entire year, but only for a specific season. Cool season annuals mostly work from autumn to spring. Warm season annuals mostly work from spring to autumn. Calendula is a popular cool season annual that may not last even that long, since it can mildew half way through winter.
Now that it is time for cool season annuals, it can be unpleasant to remove warm season annuals that are still performing well. In mixed plantings, new annuals can be phased in through autumn as older annuals deteriorate. Busy Lizzie (impatiens), wax begonia and other warm season annuals that are actually perennials can get cut back and overplanted with cool season annuals. The cool season annuals that temporarily overwhelm them can provide shelter from frost. As the cool season annuals finish next spring, the warm season ‘annuals’ can regenerate
However, not all cool season annuals need to finish next spring. Sweet William, cyclamen, chrysanthemum and the various primroses are popular cool season annals that are actually perennials. When the time comes, they can be overplanted with warm season annuals, so that they can regenerate the following autumn. In cool spots, sweet William and some primroses can actually perform all year. (Some people are allergic to primroses like poison oak.)
Alyssum and nasturtium really are annuals, but can function both as warm season and cool season annuals. They sow their own seeds so that new plants can reliably replace old plants without being noticed. The old plants only need to be pulled as they deteriorate. Alyssum is white, or pastel hues of pink or purple. Nasturtium is just the opposite, with bright hues of yellow, orange and red, with only a few pastel options.
Pansies and smaller violas are the two most popular of cool season annuals, since they function like petunias for cool weather. They lack few colors. Most have two or three colors. Ornamental cabbage and kale produce big and bold rosettes of pink, white or pink and white foliage. Kale has weirdly distinctive foliar texture. White, lavender, pink, purple and rose stock is the most fragrant of cool season annuals, and taller varieties are great for cutting. Iceland poppy has delicately nodding flowers on wiry stems. They can be pastel hues of white, pink, yellow, orange or soft red.
Tony Tomeo 
My biggest problem is removing plants that are still blooming, then it becomes too late to find the cool weather plants.
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We get the new plants first, and then plug them as the old ones get removed.
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Interesting. The whole concept of warm season and cool season plants, to have several growing seasons in the same year is relatively new to me. Where I grew up we had snow 8 months out of the year. I assume all the plants we had in the summer would be considered cool season plants here.
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You may have grown some of the same warm season annuals that other grow, but not the cool season annuals. That is common where winters are cold. Climates with cold winters do not necessarily have cool summers. The days are longer in summer farther north than they are farther south.
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We had carrots, potatoes, lettuce, different types of kitchen herbs, rhubarb, strawberries, red and white currants, and gooseberries. We tried apples, but we didn’t get enough sun.
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Well, carrots and lettuce really would be cool season annuals (vegetables) for us, which might have been warm season annuals for you, as you mentioned earlier. Potatoes might be grown in the same season here as there, although they likely finish early here. This is not the best place for potatoes. Now that you mention it, some of the kitchen herbs that grow in summer there just might be cool season herbs here, since many happen to produce better in autumn and spring than through the arid (minimal humidity) summer. The others are perennial, so are subject to the same seasons both here and there.
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I thought so, I grew up in the mountains in Sweden. Some summers it didn’t get warm enough to wear a t-shirt all summer (even though that was rare.)
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Gads! I work with guys who always wear shorts. It gets my attention if it gets cool enough for them to wear pants.
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That’s funny!
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That’s California.
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Yes 🙂
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One of the most-used winter landscape plants here in the pansy. Then, there are the snapdragons, and also the decorative cabbage and kale. I’d never seen them used in large municipal plantings until I moved here, but they really are lovely.
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Snapdragons are an odd one. In some places, they do well through mild winters. Where winter is too cool, they might do well through mild summers. In our region, they can do both, although they are very susceptible to rust.
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