As temperatures rise in early May, cool-season bedding plants that have put on such a wonderful display the past few months begin to fade. Even now, you should be noticing the gradual, but inevitable, decline of these plants in your flower gardens. But don't despair; the floral display can continue through the heat of summer by replanting beds with warm-season bedding plants.
Whether in flower beds, containers, hanging baskets or window boxes, bedding plants can quickly and economically help create the colorful landscape that so many gardeners crave. Through careful selection, a gardener can grow bedding plants of just about any color or color combination they can imagine, during any time of the year and on plants that range in height from a few inches to several feet.
Cool and warm
Bedding plants are classified into two groups, based on the temperatures they prefer. Cool-season bedding plants (such as pansies, dianthus, snapdragons, stock and calendulas) do best in the cold to mild temperatures of October through early May.
Warm-season bedding plants (such as torenia, begonia, marigolds and zinnias) grow and flower best in the warm to hot months of April to October. Because they are sensitive to freeze damage, they are planted after the danger of frost is over.
Now is the time to plant warm-season bedding plants into new beds in your landscape, or as you remove cool-season annuals from existing beds.
True annuals are an important group of bedding plants that we use to add color to the landscape. These short-lived plants grow from seed, bloom and die within one growing season. Few true annuals have the stamina to last all the way through our exceptionally long, April-to-October summer growing season.
These 'annuals' last longer
Tender perennials, such as impatiens, periwinkles, blue daze, pentas and begonias, are often grouped with the true annuals. This is because, in most parts of the United States, they only last one season before dying in winter's freezes.
However, these plants do not die after a period of blooming, as do the true annuals. If not for winter freezes, these plants would live and bloom for several years -- and in Louisiana they often do, when winters are mild.
Tender perennials grown as annuals have more stamina in the garden than true annuals. While true annuals may play out before summer's end, tender perennials bloom from late spring until cold weather arrives in November.
Consider growing conditions
Choose annuals well-suited to the growing conditions where they will be planted. Light is especially important.
For beds that receive at least six to eight hours of sun, choose sun-loving bedding plants.
In beds that receive about two to four hours of morning sun, choose bedding plants that prefer shady conditions.
Even annuals that like part shade to shady locations, however, will generally not perform as well in full shade where they receive no direct sun during the day. Caladiums, planted from tubers or growing plants, are one of the best choices for color in full shade.
Before you go to the nursery, look at the size of the area to be planted, and try to estimate how many plants you will need to buy. On average, bedding plants are spaced about 8 inches apart, but check the tag of the plants you purchase.
Beds will look skimpy when first planted, but plants that are spaced properly should grow to fill the bed. Keep a record of how many plants are used in a bed from one season to the next to make this process simpler.
Bed preparation is key
Prepare beds carefully before putting in the summer bedding plants. A common mistake is to remove faded plants, halfheartedly turn the soil and then plant the new plants.
It takes a lot out of the soil in our flower beds to produce vigorous plants and abundant flowers, and we must give back to the soil if we expect each new planting of bedding plants to do their best.
First, remove any weeds or other unwanted plants from the bed. Next, turn the soil to a depth of about 8 inches. Spread a 2- to 4-inch layer of compost, rotted leaves, aged manure, composted finely ground pine bark or peat moss over the bed, and then evenly sprinkle a light application of an all-purpose fertilizer.
Thoroughly blend the organic matter and fertilizer into the bed, rake smooth, and you're ready to plant.
Make sure you plant the transplants into the bed no deeper than they were growing in their original container, and space them properly. Bedding plants generally look best, and the beds will fill in better, when the rows are staggered.
Lay out the first row of plants, spaced properly. The second row is laid behind the first row at the appropriate spacing from it, but the plants are placed between the plants of the first row so that they form triangles with those plants.
Once the bed is planted, mulch and thoroughly water the plants. I like to use a hose-end fertilizer applicator, and water with a fertilizer solution to get the plants off to a good start.
Newly planted bedding plants do not have well-established root systems, and should be watered thoroughly every few days, or as needed, if the weather is dry the first few weeks after planting.
Beds of beautiful flowers are not low-maintenance. As you decide where to plant beds -- and how large and how many -- keep in mind that they will need regular care through the summer.
WARM-SEASON BEDDING PLANTS
For sun to part-sun: Abelmoschus, alternanthera, amaranthus, angelonia*, baby's breath euphorbia, balsam, blue daze*, celosia, cleome, coleus*, coreopsis, cosmos (cosmos sulphureus), Dahlberg daisy, dusty miller*, gaillardia, gomphrena, lantana*, marigold, melampodium, narrow-leaf zinnia, ornamental pepper*, ornamental sweet potato*, periwinkle*, pentas*, portulaca, purslane*, rudbeckia, salvia*, scaevola*, sunflower, tithonia, torenia, perennial verbena*, zinnia.
For part-shade to shade: Balsam, begonia*, browallia*, caladium (perennial tuber), cleome, coleus*, impatiens*, pentas*, salvia*, torenia.
Plants marked * are tender perennials.
DAN GILL'S MAILBOX
Last year, I noticed the yellowing and brown spotting of some of the leaves on my Sunny Knock Out roses. I thought our extreme temperatures and stress were the culprits. But, again this year, the same thing is happening. Can you diagnose and suggest what to use? For some reason I thought Knock Out roses were virtually disease-free.
Also, a few of my day lilies are showing rust spots on the foliage. Should I dig them and discard?
The yellow leaves are likely the result of black spot disease. Knock Out roses, in general, are quite resistant (not immune) to black spot disease. During wet weather conditions, however, even resistant plants can be attacked to some degree. That's what's happening now to your Sunny Knock Out roses. Still, there is no need to spray. The rose will get over this disease on its own without your intervention and will look better eventually.
Blame the wet spring for the bad outbreak of day lily rust this year as well. Day lily rust was first reported in the Southeastern United States in 2000 and has spread rapidly to many states, including Louisiana. The disease causes the foliage to yellow and brown. Turning an infected leaf over, you will see orange, raised spots. The rusty orange spores will rub off on your finger.
Susceptibility of day lily cultivars to this disease varies: Some are very susceptible, and others seem fairly resistant. Gardeners may choose to eliminate the cultivars that show the worst symptoms and retain those that don't seem to be bothered as much by the disease.
Should a gardener decide to treat the disease, the infected plant should be cut within an inch of the ground, and it and all the plants around it should be sprayed regularly with a fungicide. Recommended fungicides include mancozeb (Dithane, Fore), chlorothalonil (Daconil), azoxystrobin (Heritage), propiconizol (Banner Maxx) and triadimefon. Application may need to be repeated as often as every seven to 14 days; follow product label instructions.
As most of us will not want to cut our day lilies back just as they are blooming, or to spray constantly, it is likely that the solution to this problem will be to eliminate highly susceptible varieties and use existing cultivars that are resistant to the disease, as well as to develop new, resistant cultivars. More information on day lily rust can be found at www.daylilies.org/ahs_dictionary/daylily_rust.html.
We have a few citrus trees, and one of the orange trees has leaves that are beginning to turn yellow. It is loaded with fruit. Is there anything you can tell us to do, with just this little information? Thanks.
Ed and Jeanie Guynes
It might be because of all of this rain we are having. Wet soils make the roots unhappy, and that leads to the symptoms you are seeing in the foliage and canopy of the tree. There is nothing you can do for this. Trees usually recover, unless root rot sets in.
Dan Gill is extension horticulturist with the LSU AgCenter.
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