They are really just smaller versions of the larger perennial dahlias that are grown for their big bold flowers and flashy colors. Technically, annual dahlias produce smaller versions of the same perennial roots that can survive through winter to regenerate the following spring. Yet to most of us, it is easier to purchase new plants in spring than to grow new plants from stored roots.
Relative to larger dahlias, everything about annual dahlias is subdued. The flowers are neither as big, nor as variable. They can bloom any color except blue or green, but are usually simple shades of red, orange, yellow, pink or white. Their main advantage is that they do not get much more than a foot tall, so they fit into more situations and do not need to be staked.
Bloom starts rather late in spring and continues until about now. Some varieties have bronzed foliage. Fertilizer promotes bloom and healthy foliar color; but too much nitrogen can inhibit bloom. Dahlias can be happy in pots, but only with good drainage and regular watering.
Their pastel hues and blends of pink, lavender, near red and white are so perfect for the middle of spring when cosmos, Cosmos bipinnatus, begin to bloom. They are just as perfect as bloom continues right through summer and almost to autumn, when the tall and airy plants finally begin to wear themselves out. If they continue through autumn, they eventually succumb to frost in winter.
Good old fashioned busy Lizzie is hard to find nowadays, if it can be found at all. The nasty mildew that kills it so quickly might not be prevalent everywhere, but happens to be a serious problem where most of the bedding plant farms are located. Now, the formerly uncommon New Guinea impatiens, Impatiens X hawkeri, which is somehow resistant to the mildew, is becoming popular.
In only a few years, busy Lizzie, Impatiens walleriana, went from being one of the most popular warm season annuals to being unavailable in nurseries. It is now making a slight comeback. Most of those planted during their planting season last spring are now so profuse with bloom that their rich foliage is mostly obscured. Although they can be perennial, almost all get replaced in autumn.
Why would anyone want to grow annual gazania when perennial gazania that is popularly grown as ground cover lasts for several years? Well, as long as the weather stays warm, annual gazania blooms with an impressive abundance of bigger and more brightly colored flowers. Perennial gazania blooms less profusely and only in midsummer, with simpler and somewhat smaller flowers.
This is one of those warm season annuals that we do not hear much about. Verbena looks something like lantana, but rather than maturing into a nice shallow ground cover or low mounding shrub with a bit of staying power, verbena lasts only until frost next autumn. The blooms are a bit larger. The leaves are a bit greener. They stay lower than a foot, and get only a few inches wider than tall.
They are short term annuals in spring or autumn. Where winters are cold, they may last from spring through autumn. Where summers are hot, they may last from autumn through spring. So what are snapdragon, Antirrhinum majus, here? They can be either or both, depending on where and when they get planted. For most of us, they are a cool season annuals that finish before summer.
Just before the weather gets warm enough for real marigolds, and after the weather starts to get too cool and rainy for them, pot marigold, Calendula officinalis, is at its best. It can bloom at any time of year, depending on when it gets planted, but prefers cool and humid spring and autumn weather. It is not so keen on frost in winter, or the arid warmth of summer that real marigolds enjoy.
Tony Tomeo 