Let's get ready to plant cool-season annuals

Published on Wednesday, 20 September 2017 16:57 - Written by GREG GRANT, Texas A&M AgriLife Extension Service

Beautiful flowers are one of the gardener’s rewards for planning and hard work. Flower beds and borders provide color against the predominant green of a typical landscape as they supply accent and contrast, making a landscape lively and interesting.

Flowers also complement most of the features established by conventional landscaping materials, such as trees, shrubs and garden art, while also providing a source of homegrown cut flowers.

Let’s cover a few terms so we can all be landscape color artists. The first one is “herbaceous,” which simply means “not woody.” The herbaceous plants we use in the landscape are further divided into annuals and perennials.

Annual flowers live only one growing season. True botanical annuals grow, flower, produce seed and die during the same year. Horticultural annuals die during the same year because of changes in temperature (hot or freezing temperatures). Therefore, annuals must be set out or seeded every year or multiple times per year, all depending on the seasonal and their associated temperatures.

Annuals are versatile, sturdy, relatively inexpensive and often easy to grow. They provide instant color, can beautify containers, baskets and window boxes, and are great for filling in gaps between perennials or adding pockets of color in front of shrubs or groundcovers.

Just as it’s time to plant cool-season vegetables in the fall garden, it’s also time to plant cool-season annuals in the landscape. The annuals we plant now must be able to thrive on cool nights and tolerate a frost (our first frost is generally around Nov. 15). Examples of cool-season annuals that can be planted as transplants in the fall include dianthus, floral mums, ornamental cabbage and kale, pansies, petunias, snapdragons, sweet alyssum and violas. Those that should be directed seeded now are bluebonnets, larkspur and poppies.

As with vegetable gardening, growing and maintaining annual flowers requires proper site selection, soil preparation and adherence to sound cultural practices.

The next thing to consider is site selection. Unfortunately, most cool-season annuals prefer a full day’s sun. The more sun, the more flowers and color. All annual bedding plants also prefer excellent drainage and high fertility. Before planting annuals, I typically sprinkle a 3:1:2 type lawn fertilizer such as 15-5-10 (a premium fertilizer with a slow release nitrogen source is even better), fluff up the bed with a tiller or spade, then top dress with compost or potting soil. I do the same thing with container plants except I use a slow-release fertilizer such as Osmocote in the pots to make sure the roots don’t get burned, and I use a high-quality potting soil instead of cheaper compost. Although it’s not always feasible with landscape color, I make sure and add a half-strength water-soluble fertilizer like Miracle-Grow to newly planted containers.

Many beginning gardeners fret about the approaching fall and winter, thinking that garden color will soon be coming to an end. But that’s certainly not the case. Fall in Texas is literally a second spring. In addition to a number of fall-blooming perennials starting to flower, it’s time to switch gears into cool-season annuals, that like us, are glad summer is over and autumn is knocking at the door..

Greg Grant is the Smith County horticulturist for the Texas A&M AgriLife Extension Service. You can follow him on Facebook at “Greg Grant Gardens,” read his “Greg’s Ramblings” blog at arborgate.com or read his “In Greg’s Garden” in each issue of Texas Gardener magazine (texasgardener.com). For more information on local educational programming, go to smith.agrilife.org.