Ferguson: It’s time to plant cool-season flowers
Published 10:51 am Friday, October 21, 2022
Many of the warm-season flowering plants in our area had their late-season glory cut short by this year’s early frosts and, in some places, freezes. Unless they were protected, the season is over for many of our warm-season annuals like zinnias, pentas, and coleuses.
That doesn’t mean that we’re without color in the landscape till next spring. Evergreen plants are still going strong, sasanquas will be blooming soon, citrus is hanging on the trees, and many of our hollies have red berries.
We also have time to plant cool-season flowering plants.
Petunias are classic cool-season annuals. To maximize cool-season color, plant them between September and early November. The period between early February and mid-March provides another planting window. Planting at that time can help extend the flowering period of heat-tolerant varieties into the summer.
One such heat-tolerant variety is Supertunia Vista Bubblegum, which was chosen as a Louisiana Super Plant several years ago. Individual plants of this vigorous, pink-flowered variety can reach 16 to 24 inches tall and three feet wide.
Another group of traditional cool-season flowers includes the pansy and its close relative, the viola or Johnny-jump-up. Compared to pansies, violas produce an abundance of smaller flowers. The Sorbet series of violas, which includes members with a wide variety of flower colors, joined Louisiana Super Plant ranks in 2012. Plants in this series grow to approximately six inches tall and 12 inches wide. It’s advised that violas and pansies be planted between late October and early December.
Perhaps one of the most striking cool-season flowers is the foxglove. Those in the Camelot series were chosen as Super Plants for 2010. These can be planted between November and February, before they’re in bloom, for beautiful spring flowers.
Other cool-season Super Plant selections have included the Jolt and Amazon dianthus series, the Swan columbine series, Diamonds Blue delphinium, and one that you can snack on, Redbor kale. Besides these Super Plant selections, some other cool-season flowering plants include alyssum, calendula, snap-dragon, and stock.
Choose a well-drained site for bedding plants. Tilling the soil to several inches deep and incorporating two to four inches of an organic material such as compost or aged pine bark is advised. If drainage is questionable, form a raised bed. A couple of inches of mulch help will suppress weed growth and retain soil moisture.
Fertilizer can be incorporated into the soil or broadcast on the surface at a rate of 0.1 pound of actual nitrogen per 100 square feet. The first number in the fertilizer analysis is the percentage of nitrogen in the fertilizer. Examples of fertilizer quantities that would give you 0.1 pound of nitrogen include 0.7 pound 15-9-12, 0.8 pound 13-13-13, or 1.0 pound 10-10-10. Slow-release fertilizers are considered a better option for this purpose than readily soluble ones, though either can be used.
Many flowering bedding plants perform best when planted in full sun, though some tolerate partial shade.
Let me know if you have questions.
Dr. Mary Helen Ferguson is an extension agent with the LSU AgCenter, with horticulture responsibilities in Washington and Tangipahoa parishes. Contact Ferguson at firstname.lastname@example.org or 985-277-1850 (Hammond) or 985-839-7855 (Franklinton).