Combine the actual temperature with the heat index and outdoor chores, including gardening, became downright dangerous with heat advisories leading many weather forecasts. Dan Gill, as a part of his presentation on botany to the new MG Class of 2015, talked about USDA Zones for heat and cold, saying that for many years most Louisiana gardeners primarily paid attention to the cold hardiness zones. Dan pointed out that as gardeners become more educated about weather patterns and how heat impacts plants in the landscape, more attention is being paid to USDA heat zones. He also emphasized that as gardeners we need to focus our attention to the growing conditions plants need to perform, and less on where we want to put plants or what we want them to do. We must not forget that plants have been genetically programmed to require growing conditions and perform like their ancestors. For example, we cannot expect a plant that requires shady growing conditions to survive in full afternoon or western sun. The stress from heat directly impacts plant performances and when compounded by drought conditions, plants can be injured or killed. During the month of July, and so far into August, I’ve seen more trees and shrubs suffering from die back, defoliation, and death than I’ve seen in several years. It appears to me a lot of the damage began in the spring with above average rainfall resulting in saturated soils, depriving roots of oxygen, and making roots more susceptible to root rot. Instead of plants being able to recover, they were then exposed to drought conditions and above-average day time temperatures, leading to further stress and decline. Most gardeners are looking forward to fall gardening with the hopes that cooler temperatures and timely rainfall will result in more pleasant working conditions and better plant performances.
On my visits to address the various landscape issues with plants, I’m noticing that many of the plant beds have settled and mulches have decayed and thinned over the summer. Topping the beds with bed builder and adding additional mulch should be included in the list of fall gardening chores. Replenish mulch layers with fresh material to maintain approximately a 2-3 inch thickness in beds. Ideally many people will mulch with what they can get their hands on for free such as leaves or pine straw. If you prefer the look of purchased mulch, put down an inch or two of leaves or pine straw, then top it off with an inch of your favorite purchased mulch. This can save money and still give you the look you desire.
Pecan trees tend to be alternate bearers, that is producing a heavy crop every other year. Pecan trees have relatively brittle wood, having branches that can sometimes break without warning. Pecan trees that are loaded with a heavy crop are prone to limb breakage especially during rain and thunderstorms with gusty winds. Although it is disheartening to see a large branch fall from a pecan tree, there is not much that can be done. It’s important to water pecan trees slowly and deeply during this month if it is dry. This will help the nuts finish filling out and also minimize nut drop.
The hurricane season will be kicking into high gear this month. This is the time of the year where you should be evaluating the overall health of shade trees, and prune if needed or remove dead or broken branches. Additionally, if there are dead trees or partially dead trees in the home landscape that threaten a structure, they should be removed.
Chinch bugs can remain active in lawns at this time of year. Look for dead, tan, straw colored areas in the lawn, particularly those areas located in dry sunny areas next to concrete driveways or sidewalks. Generally these areas will get noticeably bigger and these sucking insects move into healthier greener grass which enlarges the area. These areas can be treated with Talstar, Bifenthrin, or Orthene (acephate). It’s very important that label directions on pesticides are read and followed carefully.
From now on don’t apply any fertilizer containing nitrogen to home lawns. Fertilizing lawns with nitrogen containing fertilizer this late in the year can lead to lush green growth that can increase the problems with a fungus disease called brown patch or large patch. Additionally, nitrogen can slow the grass from going dormant leading to winter injury or winter kill. If you choose to winterize your lawn, the only nutrient applied should be potash. Any winterizing fertilizer containing moderate to high nitrogen should be avoided.
No pruning should be done on spring flowering shrubs such as gardenias, hydrangeas, sasanquas, and azaleas because they’ve already formed their flower buds and pruning now will reduce the quantity of future blooms.
If you have areas of Virginia Buttonweed in your lawn, as we move into the fall and it approaches maturity, pull as much of it as you can being sure to remove as much of the plant containing seeds as you can. Place all the old plants that you pull up in a garbage bad and discard. This will help to reduce the numbers of seeds that will germinate in your lawn next spring.
Evaluate caladiums - when the plants begin to look less attractive, and two thirds of the leaves have fallen over, it time to dig the tubers. Caladiums may return next year if left in the ground, but it’s more reliable to dig them and store them indoors over the winter months. Dig the tubers carefully to minimize bruising leaving the foliage attached. Spread them out in a well ventilated area to dry. When the foliage is dry and brown, remove foliage and store tubers in paper or net bags indoors.
Happy Gardening!! Gerald P. Roberts
Horticulturist/Master Gardener Program Coordinator
LSU AgCenter 1010 Lafayette Street, Suite 325 Lafayette, LA 70501 GRoberts@agcenter.lsu.edu Office (337) 291-7090 Fax (337) 291-7099