Cool Season Annuals Are Cool

Warm season annuals are now passé. Cool season annuls, such as these violas, are in.

Now that it is time for cool season annuals, it is difficult to remove warm season annuals if they are still blooming and healthy. that is probably why so many of us prefer mixed plantings, where cool season annuals can be added as needed to replace warm season annuals as they deteriorate. Some warm season annuals that are actually perennials, like wax begonia and busy Lizzie (impatiens), can be cut back and overplanted with cool season annuals, so that some might regenerate next spring as the cool season annuals finish. Petunias may be looking overgrown and tired, but are at least easier to remove without guilt.

Pansies and smaller but closely related violas are probably the two most popular of cool season annuals. They work something like petunias, but for autumn and winter. They are commonly grown in uniform beds, but work just as well in mixed plantings. There are not many colors that can not be found in pansies, although only a few of the more popular varieties can be found at any particular nursery. Some are ‘solid’ colors. The most familiar varieties have those funny ‘faces’ that pansies are known for.

The various primroses require a bit more effort because deteriorating flowers need to be removed. They can also be a problem for the few who are allergic to them (like poison oak). Like the warm season annuals that can survive as perennials through winter, some primroses, particularly English primrose, can survive through summer as perennials. English primrose displays bright cartoon shades of almost any color. Fairy primrose are more commonly pastel shades.

Stock has an intense and distinctively rich fragrance. Taller types are excellent cut flowers, but are not so practical for uniform beds. Even shorter types are probably best in mixed plantings, or in borders with lower flowers in front. The single or double flowers can be white, pink, purple and almost red.

Ornamental cabbage and kale are grown for bold rosettes of colorful pink, white or pink and white foliage. The shades of pink range from soft light pink to rich purplish pink and almost red bright pink. Cabbage provides more color. Kale has more variety of foliar texture. Ironically, both look rather weedy, and should be removed as they begin to bloom in spring.

Chrysanthemum are strikingly colorful cool season flowers, but rarely bloom as uniformly as they do when first planted. Because they bloom so profusely, they need to be groomed frequently. If they get what they want, they can perform for several years, blooming all sorts of shades of yellow, orange, red, pink, purple and white. Chrysanthemum also displays a broad range of flower structures and sizes, from minute to jumbo.

Sweet William, Iceland poppy, calendula and alyssum are also in season. Yellow or orange calendula, with single or double flowers, is best through autumn, but may mildew by winter. Alyssum is white or subdued shades of pink or purple, and is actually good throughout the year, and can self sow indefinitely.

Late Summer Merges Closer To Autumn

Late summer flowers are still blooming.

It always seems that by the time the garden gets as productive as it can, it is already time to get ready for the next season. Pretty soon, cool season annuals will be arriving in nurseries to replace warm season annuals that had been so colorful all summer. If seeds are to be collected from summer flowers for next year, this would be a good time to do it.

Seed for certain cool season vegetables like broccoli, cauliflower, cabbage and kale, can be sown in flats or cell packs now to have seedlings ready to put out into the garden as warm season vegetables finish in autumn. If there is space available in the garden, turnips, turnip greens and beets can be sown directly. Carrots should probably wait a few weeks or so to get sown directly.

Although corn of a single variety sown in a single phase tends to ripen at the same time, different varieties planted in different phases can extend the season significantly. Those that continue to produce until autumn are greedy for nutrients and water. Squash and tomatoes likewise appreciate a bit of fertilizer and regular watering, even as the weather starts to fluctuate this late in summer. However, fertilizer does not need to be applied in the last month of expected production.

Zucchini should be harvested when they get about six inches long, not only because they are best when immature, but also because the plants are more productive if regularly deprived of their fruit. If plants have the choice, they prefer to concentrate resources into fewer large fruit instead of more small fruit. The problem is that the larger fruit is tough and lacks flavor.

Hubbard, butternut, acorn and other winter squash get the opposite treatment. Each vine should produce only a few fruits. Those that produce smaller fruits can sustain more than those that produce larger fruits. Yet, excessive fruit exhausts resources, which compromises fruit quality. The fruit that will continue to grow and ripen through autumn should already be somewhat developed. The smallest of excessive fruit, or underdeveloped fruit should be removed.

Coleus

Coleus works both inside and out.

Without bloom, the richly vibrant foliar colors of coleus, Coleus scutellarioides, rival floral color of other warm season annuals. Striking foliar patterns are as exquisite as any floral display. Growth is efficient through the warmth of spring. Foliage might last until autumn. Late in its season, spikes of tiny blue flowers can be trimmed off to promote more foliage. 

With bright ambient sunlight, coleus is more perennial as a houseplant. However, it may get persistent with pesky bloom as it matures. Some who grow it prefer to let bloom, and then prune it back afterward. Recovery from such pruning can be slow. Vegetative stems, without bloom, root easily as cuttings even in water. New cuttings can replace old plants. 

Coleus foliage is intricately variegated with countless combinations of green, chartreuse, yellow, orange, red, burgundy, pink, white and brown. Variegation can be symmetrical or random. Leaf margins may be deeply lobed or just serrate. Modern cultivars might be no better than old fashioned sorts. Mature plants can get as tall and broad as about two feet. Some stay lower.

Cockscomb

Plumose cockscomb blooms with pinata colors.

The flowers of the two different specie known as cockscomb do not seem to be as closely related as they are. Celosia cristata exhibits two or three inch wide, weirdly stunted and crested blooms that resemble the combs of roosters, although the most popular varieties are so densely furrowed that they look more like fuzzy little brains. Celosia plumosa, as the name implies, has plumose flowers that look more like three or four inch long pampas grass flowers than like anything associated with chickens. What they have in common is their very bright red, orange, yellow, pink or white blooms. Foliage can be bright green to rich bronze.

As short lived annuals, cockscombs blooms only for about two months from the middle of summer to autumn. As cut flowers, they can last a week or two. However, because those popularly grown as summer annuals are mostly less than a foot tall, the flower stems are rather short.

Summer Annuals Are Grateful For Deadheading

Blooming through summer is serious work.

So many of the pretty warm season annuals planted last spring are now at their best. Sweet alyssum, lobelia, verbena, moss rose and busy Lizzy never stop blooming, and only get more colorful as they grow through the season until they get replaced by cool season annuals in autumn. (It is unfortunate that busy Lizzy, which had been a standard warm season annual for so many years has become less available due to disease.) However, French marigold, petunia, floss flower, cosmos, statice, pincushion flower (scabbiosa) and zinnia need a bit of attention to perform as well that long.

These few warm season annuals can get tired of blooming if not ‘deadheaded’ (groomed of deteriorating flowers). Deadheading not only keeps plants looking a bit neater, but also prevents the diversion of resources needed for continued bloom into the generation of seed. As far as these blooming plants are concerned, seeding for the next generation is their priority anyway. As long as they are not allowed to set seed, they will continue to try, by producing more flowers to replace those that fade and get removed without setting seed.

Cosmos, statice and pincushion flower can continue to perform adequately without deadheading. The main advantage of deadheading these annuals is the removal of fading flowers. (There probably will not be much left for cosmos.) Many people actually prefer to leave fading cosmos flowers to disperse their seed for the following year.

Petunia is perhaps one of the more demanding of warm season annuals. It often needs to be clipped back in the middle of the season, right when it is expected to bloom the most. The best way to avoid serious pruning at one time it to keep plants snipped back lightly but continually as they grow, so that they can not develop the awkwardly long and weirdly jointed stems that eventually stop blooming. Short stems that stay close to the roots are the healthiest and most productive.

The various types of cockscomb are odd warm season annuals that become available halfway through summer, just in time to add color if some of the annuals planted earlier in spring are not performing adequately, or are finishing early. Of course, all of the other warm season annuals will still be available in nurseries until it is time for cool season annuals next autumn.

Petunia

Petunias are quintessential warm season annuals.

There are too many varieties of petunia to be familiar with nowadays. The species name is Petunia X hybrida because almost all are hybrids of two primary species, as well as a few others to complicate the situation. The color range of the bloom of these hybrids now lacks only a few colors. (GMO orange petunias are only beginning to become available.) 

Besides an impressively extensive color range, bloom can be spotted, speckled, striped, blotched, haloed or variegated by too many means to list. Flowers can be rather small or as wide as four inches. Some are surprisingly fragrant. Some have frilled double flowers. Stems of cascading types may sprawl wider than three feet while only a few inches high. 

Petunias are warm season annuals that perform from spring until frost. They can survive as perennials for a few years if cut low for winter. Cool season annuals can obscure and shelter them until they resume grown in spring. They prefer rich soil, systematic watering and sunny exposure. Although mostly sterile, some appreciate occasional deadheading. Trimming during summer may promote fluffier growth for lanky stems.

Nasturtium

Nasturtium bloom is sensitive to aridity.

Whether feral or planted intentionally, nasturtium, Trapaeolum majus (which is actually a hybrid with two other species) is a delightful flower that just about everyone appreciates. Its eagerness to self sow and possibly naturalize in riparian situations attest to how easy it is to grow. Seed for many varieties is readily available. Feral plants provide feral seed.

Bloom of domestic nasturtium can be various shades, tints and hues of yellow, orange or red. Flowers can be striped or blotched with colors of the same range. Some are double. The palest yellow is almost creamy white. The darkest red is almost brown. Feral plants, after a few generations, generally revert to blooming with simple bright orange or yellow.

Plants are more or less annual, but can replace themselves almost as readily as they die out. Those that perform through spring and summer succumb to cooling autumn weather, as their (feral) seedlings begin to replace them for autumn and winter. Those that perform through winter may succumb to frost where winters get cool, but also self sow feral seed for next spring.

Moss Rose

Moss rose can bloom until frost.

The recent unseasonably warm weather was no problem for any remaining moss rose, Portulaca grandiflora. They usually start to look rather tired as the weather gets cooler this time of year, and eventually succumb to the first frost. Where allowed to do so, they can regenerate next year from seed. I like to collect their seed during the summer or autumn so that I can sow them after the last frost of the following winter. Through spring and summer, I find that additional plants are easy to grow from cuttings.

The inch wide flowers are white, pink, red, orange or yellow, with only a few ruffled petals. Modern varieties that have rufflier ‘double’ flowers and richer colors still seem to be less popular than the more delicate traditional types. The cylindrical and succulent leaves are only about an inch long. The small plants can get more than six inches deep where they are happy or crowded. Moss rose likes good exposure and decent soil, but does not need the rich soil that most other annuals demand. Nor does it necessarily need such regular watering.

Angelonia

This annual can actually be perennial.

Angelonia is one of those warm season annuals that can actually survive through winter as a pernnial to bloom again next spring. It may even want to continue to bloom untill frost. The flowers can be blue, purple, red, pink or white, and look something like small snapdragon flowers. Most have spots or stripes of an alternate color or two in their throats. Some modern varieties have fragrant flowers. Plants can get a foot or two tall, and almost as wide. In sheltered spots, angelonia can be cut back as soon as it starts to look tired in autumn. Exposed plants might be happier if cut back significantly later, as winter ends. Old growth may be unsightly for a while, but can protect interior stems and roots from frost. Besides, pruning stimulates new growth that will be more susceptible to subsequent frost.

October Brings Cool Season Annuals

Warm season annuals are now passe.

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.