Have you ever wondered where the plants you buy in local garden centers come from? While there are thousands of sources, this week's column focuses on those for one plant — the pansy.

One major producer is Olson's Greenhouse in southern Utah County. Between its locations in Santaquin and Salem, it has more than 1 million square feet of greenhouse growing area. That translates to almost 25 acres.

Chad Olson, vice president of production and growing, is a fourth-generation member of the business. His great grandfather, Ray Olson, started it in the 1940s, and his grandfather, Jack, who still works in the business, carries it on. His father, Bart, one brother, and three brothers-in-law are also active in the business.

Olson's grows pansies. Chad Olson estimates that the company's recent crop included some 50,000 flats, which would mean they grow more than 1.8 million pansies for sale throughout much of the western United States. "We ship down as far south as Cedar City and as far north as Kalispell, Mont. Our marketing area is Utah, Idaho, Nevada, Wyoming and western Colorado," he says.

While pansies are tough and perform well in our area, their greatest enemy is heat. They are cool-season plants that do well in the spring and fall, but they suffer in the summer.

Olson explains how they produce these cool-season plants in the heat of the summer. "We sow the seeds in plug trays (small trays used for germinating the seeds) and then put them in the germination chamber for two or three days. The chamber has a very high humidity because we mist in there constantly.

"Next, we move them into the greenhouse and keep misting them for another two to three weeks. We then transplant them into the finishing flats and grow them on in cool greenhouses."

Temperature control is critical. If the pansies get too warm, they stretch out and do not perform as well in the garden, where they will likely die rather quickly.

"We use growth regulators to keep the pansies from stretching out and becoming too large," Olson explains. "We have to be careful because if you use too much, it stops the plants from growing. You also have to use the right fertilizer, so we do not fertilize the plugs much. When we fertilize, we use a very low parts-per-million (fertilizer concentration) until they are in the finish containers.

"The hardest part is keeping our greenhouse building cool enough. We try to keep the temperature between 75 and 78 degrees in the summer, although that can be hard. If we have pansies in the spring, we try to keep the temperatures much cooler — at 55-60 degrees F — but that is impossible in the summer," he explains.

Because of the temperature requirements, it is difficult for gardeners to start their own pansies because they cannot keep them cool in the summer heat. But they are one of the best flowers to plant in the fall for a spring garden.

Olson strongly recommends that gardeners along the Wasatch front plant their pansies in the autumn. "Fall is the best time to plant pansies. You can have color in the fall. They are biennials so they come back in the spring . . . you get twice the benefit."

It's important to avoid planting pansies too early, when it's too hot, but you should plant them early enough to get a root system established before winter. "We recommend (gardeners) look at the weather as the planting time changes from year to year. Wait until the summer annuals start to decline and then pull them out."

Pansies grow best with soil temperatures between 45 and 65 degrees F. Pansies planted when soils are too cold are stunted, with pale green leaves, little growth and little or no flowering. Cold-stressed root systems are less efficient in taking up nutrients. During very cold weather, when soil temperatures fall to near freezing, plant roots shut down.

Soil temperatures lag behind air temperatures, so planting can continue even after air the temperature drops.

The modern pansy, Viola x wittrockiana, likely came from Viola tricolor, a native of central Europe. The Greeks in the 4th century B.C. used them as medicinal herbs, and they were used in gardens throughout the Middle Ages.

By 1850, many pansy strains were sold in Europe. These soon made their way to the North American market. By 1900, pansies were popular throughout North America, and today there are more than 300 cultivars of pansies.

Intensive plant breeding programs have created one of the most amazing arrays of color available from any flower. Rich and vibrant, they range from white to rich gold, orange, purple, red, rose, maroon, orange and violet, with many shades in between. Some varieties are almost black, and others are almost pure white.

You can choose solid colors, called 'clear' faced pansies, while others have a darker, contrasting center. These are often called 'faced' pansies. Look also for two-tones and all sorts of color blends and pastels.

Flower size is another important variable. Some have small, petite blossoms, while others produce flowers up to 4 inches in diameter. Some varieties have petals with crinkled or ruffled edges.

Olson has two favorite types of pansies that he recommends for our area. "There are many different types of pansies, including many novelty varieties. Our favorite series for those who want large flowers and plants with lots of flowers include the "Majestic Giant II" and the "Delta" series. They come in many colors and are dependable growers.

"Plant them from late August into October, depending on where you live. I seldom hear of any disease or insect problems, and they are one of the best plants for our fall and spring gardens," he says.

Larry A. Sagers is the USU Extension horticulturist at Thanksgiving Point.