Radio program directors and garden-section newspaper editors teach a guy to say what he means as succinctly as possible, and then to move on. Sometimes I feel like the answers I give to gardeners' plant questions could sometimes come across as uncaring, but I've found that if I give encouragement to unwinnable situations, it merely prolongs the pain, angst and expense. So, I've learned to be both quick and honest. Here are some of the most frustrating of gardening dilemmas, along with my suggested alternatives.
The situation: Shade tree has yellowed leaves with dark green veins, most prominently at the ends of its branches. Leaves may even be turning light yellow/creamy white with brown spots. Most commonly afflicted: sweet gum, slash and loblolly pines, and pin and water oaks, but there are others.
The explanation: This is iron deficiency, and the real reason we see it here is because iron in the ground becomes insoluble in really alkaline soils. Insoluble iron won't dissolve in water, so it can't enter the plants through their roots. Sure, you can add big doses of iron for a temporary solution, but the tree will grow a little more, so the next time the chlorosis appears (usually just a month or two later), it will be worse.
The solution: You'll never outrun this nutrient shortage, so your best bet is to cut your losses (and your old shade tree), and plant a new type of tree that doesn't need so much iron. Your local independent retail nursery will have the best advice. Fall is a great time for planting.
The situation: Redtip photinias are becoming discolored. Worse yet, their leaves are yellowed, then white and burned. And it all began with harmless-looking maroon spots on the leaves.
The explanation: This is Entomosporium fungal leaf spot, and it has become epidemic all across America. It does eventually kill the entire plant. Indian hawthorns are now being affected as well. Old-fashioned Chinese photinia does not appear to be susceptible.
The solution: As your old redtips die, do not replace them with new redtips. They, too, will succumb. Instead, switch to another unrelated shrub that grows to the desired height. Nellie R. Stevens holly makes an outstanding tall screen, since that's the way that redtips are most commonly used. Again, a Texas Certified Nursery Professional can give you accurate advice. There is no effective fungicidal treatment, organic or inorganic. Redtip photinias are ticking time bombs. As long as this disease continues unchecked, you should choose alternatives.
The situation: Shrubs, most commonly crape myrtles, have outgrown their spaces -- they've become too tall or too wide.
The explanation: Gardeners then want to "cut the plants back," so that they will stay within bounds.
The solution: What people forget is that height and width are driven by genetics. Pruning isn't going to change those genetics, so if a plant was once too big for its surroundings, it's going to grow too big again. You need to replace it with a shorter or more compact plant. In the case of crape myrtles, there is a variety for every need. They grow to mature heights ranging from 2 to 32 feet. Choose a replacement accordingly.
The situation: Bald areas are developing beneath shade trees. Grass used to thrive there, and other parts of the yard look just fine.
The explanation: This is insufficient lighting -- it's just too shady way up beneath big trees (that have grown larger with each passing year). It's not nutrient shortages, and it's not competition from trees' roots. St. Augustine is our most shade-tolerant turf grass, but even it must have four hours of direct sunlight per day to hold its own, and six hours or more if you expect it to grow vigorously. It grows best in full sun.
The solution: Remove one or two low-hanging branches from your shade trees. That might be enough for early and late sunlight to reach the grass. Or, switch to a shade-tolerant groundcover such as mondo grass ("monkey grass"), liriope, purple wintercreeper euonymus or Asian jasmine. Throwing your money at more St. Augustine sod is definitely not a part of the solution, nor are the "miracle" grasses with the incredible claims of shade tolerance. If St. Augustine won't grow there, the other grasses won't, either.
Neil Sperry publishes Gardens magazine and hosts Texas Gardening 8-11 a.m. Sundays on WBAP AM/FM. Reach him during those hours at 800-288-9227 or 214-787-1820.