Not only does it start to bloom late in summer, but as the name implies, four o’clock, Mirabilis jalapa, blooms late in the afternoon to attract nocturnal moths for pollination overnight. By morning, the white, yellow, variable pink or rarely pastel orange flowers are closed, and their yummy fragrance is gone. Individual flowers often display irregular stripes or blotches of alternate colors, and can be divided into zones that are shaped like slices out of a pizza. Plants get nearly three feet high, but then die to the ground with the first frost. They regenerate from big tuberous roots as winter ends, and can seed profusely.
A flower that is so prominent in American culture should have a more appealing name than black-eyed Susan. Even the Latin name, Rudbeckia hirta, sounds bad. Is Becky really so rude? Did she hirt Susan? Well, black-eyed Susan is good enough to be the state flower of Maryland, and is one of the most popular of flowers for prairie style gardens of the Midwest. After all, it naturally grows wild in every state east of Colorado. Here in the West, it is a light-duty perennial that is more often grown as an annual. As a cut flower, it can last more than a week.
In the wild, the three inch wide flowers of black-eyed Susan are rich yellow with dark brown centers, and can stand as high as three feet. The typically smaller but more abundant flowers of modern varieties can be orange, red or brownish orange, on more compact stems. Gloriosa daisies are fancier cultivars, with larger flowers that are often fluffier (double) or patterned with a second color. Individual plants do not get much wider than a foot, with most of their rather raspy foliage close to the ground. All black-eyed Susans bloom late in summer or early in autumn.
Are warm season annuals really the most colorful flowers for summer? Perhaps. They have their limits though. They are also very demanding. They need to be watered very regularly, and should probably be fertilized too. Many need to be deadheaded frequently. After all that, they are only temporary, and will get replaced with cool season annuals in autumn. Perennials are more practical.
Lily-of-the-Nile is likely the most common and most familiar of blooming summer perennials. It is a shame that it blooms only once. Bloom is usually in time for the Fourth of July, and lasts a good long time, but is already fading. Deadheading as the blue or white color is eventually exhausted will not promote subsequent bloom, but will keep the evergreen foliage looking tidy until next year.
Daylily might be the second most popular of summer perennials. Some of the older types bloom only once like lily-of-the-Nile, but various cultivars bloom at various times to prolong the season if a few are grown together in the same garden. The most popular modern cultivars probably bloomed earlier, and will bloom again, perhaps with little time in between. The color range is extensive.
Penstemon are not committed to their natural schedule of blooming in late spring and again in autumn. A good pruning at the end of winter eliminates tired old foliage, and enhances and delays bloom until summer, without compromising the later autumn bloom. Like daylily, a few different varieties of penstemon in the same garden prolong bloom, which can be white, pink, red or purple.
Salvias are a big group of summer perennials that really should be more popular than they are. Some are native. Others are from other chaparral climates. Naturally, they are right at home here. Many bloom about now, and some will bloom again in autumn if deadheaded or pruned back. What they lack in flashy color, they compensate for in resiliency and reliability. They really are tough.
This is by no means a complete list of summer perennials. It does not even include the perennial daisies such as coneflower, black-eyed Susan and gaillardia.