It's that time of year again, when Daylight Savings Time trades an hour of weekend sleep for lengthier spring and summer evenings. It's an excellent time to plant the flowers nicknamed "four o'clocks" and watch them open up on a sunny afternoon.

These flowers, in the genus mirabilis, can be grown as perennials in warmer climates but are usually grown as annuals in climates with cold winters. The gardening organization Pacific Bulb Society says there are about 60 different species in the genus, but mirabilis jalapa is one of the most popular due to its brilliant colors.

Mirabilis flowers have been cultivated for many years. William C. Welch, writing for the Texas AgriLife Extension Service at Texas A&M University, says the flowers were grown by the Aztecs and later introduced to Europe by Spanish conquistadors. The Department of Agriculture says mirabilis is now found in many parts of the United States, including much of the South, West Coast, and Northeast.

Most species of mirabilis grow about two to three feet tall. The Utah State University Extension says some varieties include bushy foliage of oval or heart-shaped flowers. Mirabilis plants usually get their nutrients through a woody taproot, and some form tubers.

The flowers themselves are funnel-shaped and come in a variety of colors, including magenta, red, yellow, pink, and white. The flowers grow close together, usually arriving in clusters of two to four.

The seed company Burpee says mirabilis are often referred to as four o'clocks because the flowers will open up around that time. However, they may open earlier on cloudy days or as late as 8 p.m. The flowers have a sweet scent and can attract creatures such as hummingbirds and moths.

Four o'clocks aren't too picky when it comes to soil. The Cornell University College of Agriculture & Life Sciences says well-drained soil is essential. However, the flowers can also tolerate dry soil.

The plant is similarly hardy when it comes to sunlight. It will grow well in full sun, but can also do well in partial shade.

Seeds can be started indoors about four to six weeks before the last frost date. The Missouri Botanical Garden says you can also directly sow seedlings or tubers outside once the risk of frost has passed.

The plant requires relatively little maintenance other than keeping the soil moist. Scott D. Appell, editor of the 2003 book "Annuals for Every Garden," says four o'clocks are good for either urban or rural gardens since they are resistant to both air pollution and grazing deer.

The flowers will self-seed, so out-of-control seedlings can sometimes spread to other parts of the garden. However, this problem generally occurs in warmer climates and is not an issue in areas with chilly winters.

The Utah State University Extension says four o'clocks will die back to their roots at the end of the growing season. At this point, the tubers can be dug up and stored for the winter. The Missouri Botanical Garden says these roots should be stored in a dry basement or a garage where frost does not occur. Plants grown from these established roots will usually flower better than the previous season.