Vigorous plants such as impatiens may be getting leggy now. Trim them back this month to get another bloom before winter.
Late August to early September is the time to prune twice-blooming roses to have better blooms in fall.
Hedges should be pruned by the end of September.
Vigorous plants such as impatiens may be getting leggy now. Trim them back this month to get another bloom before winter.
Pruning and fertilizing are two important activities in properly caring for landscapes. Both are carried out throughout the summer, but late in the season, we need to think more carefully about whether it is still appropriate to prune or fertilize.
Fertilizer applications to hardy shrubs, lawns and ground covers should be finished up this month. However, I'm not saying you should fertilize now.
If you fertilized your lawn, shrubs and ground cover plantings earlier this year and they look healthy and have grown well, there is little indication that fertilizer is needed.
If, on the other hand, you haven’t fertilized your lawn since spring, or if there are some plantings of shrubs, ground covers or flowerbeds that you feel would benefit from fertilization to boost their growth and vigor, now is the time to do it — not later.
WHY NOT FERTILIZE LATER?: As we move into the fall, it is important for hardy plants in the landscape, such as trees, shrubs, ground covers, lawns and vines, to slow their growth and prepare for the coming cold.
Late applications of fertilizer, especially those with nitrogen, may stimulate growth and prevent the plant from properly going dormant. This can increase the possibility of cold damage even to plants that would normally be hardy.
Because fall temperatures in Louisiana are generally warm to mild and do not give plants a strong signal to go dormant, late fertilization is especially discouraged in the Deep South.
THE RIGHT MIX: Typically, choose general-purpose granular fertilizers that have an analysis with a higher first number, lower middle number and third number in between the first two (ratios like 3:1:2 or 4:1:2). Examples would be analyses like 15-5-10 or 16-4-8.
The exact numbers are not as important as their ratio to one another. Follow label directions carefully.
You may still fertilize summer bedding plants to encourage vigorous growth and flowers. And you certainly will want to add fertilizer during bed preparation before planting cool-season bedding plants in October and November.
This also applies to vegetable gardens. Vegetables in active growth may still be fertilized, and fertilizer should be incorporated into the soil when preparing beds for planting vegetables now through the fall.
Late August to early September is the time to prune twice-blooming roses to have better blooms in fall.
Now is the time to prune hedges, many types of shrubs and overgrown tropicals, and cut back some summer bedding plants. It is time to stop pruning spring-flowering trees and shrubs.
Fall-, winter- and spring-flowering trees and shrubs should not be pruned extensively now. Generally, this includes any type of tree or shrub that blooms from November through April and includes sasanquas, camellias, azaleas, spiraeas, Indian hawthorns, cherries, redbud and Japanese magnolias. Gardenias and hydrangeas also should not be pruned.
All these plants have already set their flower buds. Extensively pruning or cutting back these plants from now onward generally will diminish, or eliminate, their flower display. It is all right to selectively remove specific shoots or branches to shape these plants without affecting the overall flowering of the remaining growth. Just don’t get carried away.
BY LATE SEPTEMBER: Hedges, such as ligustrum, boxwood, loropetalum and viburnum, should be pruned by the end of September. Later pruning would stimulate new growth during warm fall temperatures. This growth would not have time to harden off before winter, increasing the chance of freeze damage. In last week’s column, I reminded you now is time to cut back repeat-flowering roses.
Our long growing season allows for the abundant growth of tropicals and tender perennials used as summer bedding plants in our gardens. In many cases, they look somewhat overgrown now, but they will continue to grow and bloom until fall.
Hedges should be pruned by the end of September.
WHAT TO TRIM NOW: August is an excellent time to trim some plants back so they will be shapelier, fuller and not so tall for the fall blooming period.
Tropical plants that have gotten too large, such as hibiscus, tibouchina, brugmansia and night-blooming jasmine, can be trimmed now. The farther back you cut them, the longer it will take for them to come back into bloom. Tropicals may be pruned anytime during the summer, and it is better to trim lightly occasionally than severely after they get way overgrown.
When cut back this month, shrubby tropicals will resprout and grow quickly. If you wait until October, finally decide they are too large and cut them back then, the cooler weather will not encourage rapid recovery. The plants likely will not come back into bloom before winter.
Shoots of cannas and gingers that have already bloomed may be cut to the ground to keep the clumps looking tidy and make room for fresh new shoots.
Popular bedding plants that benefit from trimming this month include periwinkle, salvia, lantana, Mexican heather, blue daze, pentas, scaevola, purslane, begonia, ruellia, impatiens and ornamental peppers.
HOW MUCH IS ENOUGH?: How far back you prune them depends on how overgrown you think your plants are. Generally, plants are cut back about one-third to one-half their height, but I have cut many of the plants listed above back farther with good results. After pruning, you may apply a fertilizer to encourage vigorous new growth.
I must admit this takes some determination and a strong will. Your plants will likely be blooming when you cut them back and certainly will not look their best immediately after the procedure.
In many instances, though, it is well worth the down time. If some of these plants look overgrown now, think of how they will look by October.
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Dan Gill is a retired consumer horticulture specialist with the LSU AgCenter. He hosts the “Garden Show” on WWL-AM Saturdays at 9 a.m. Email gardening questions to gnogardening@agcenter.lsu.edu.
“When your garden is finished, I hope that it will be more beautiful than you anticipated, require less care than you expected and have cost only a little more than you had planned.”
Thomas D. Church, garden writer
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