Photinia scorching caused by organic-matter paucity
July 15, 2012 - 1:02 am
Here are some questions I handled this past week.
Question: Why are the leaf tips on my red-leaf photinia turning black and scorching? The rest of each leaf is OK.
Answer: It’s a lack of organic matter in the soil. Organic matter is what frees iron in our alkaline soils to nourish your plants. Add iron chelates such as EDDHA, which will green up your plants. It will take time to correct the problem. Early each spring before new growth emerges, apply this special iron. Make sure the plant is getting ample water. A lack of water is causing the scorching.
Q: What are those bugs that look like overgrown roaches on our palo verde tree?
A: They are palo verde beetles. They resemble a 3- to 4-inch long roach with long antennae. The adults lay eggs in the soil where they hatch and live as underground grubs for three years. They emerge from quarter-size holes under the tree in the early evening much like cicadas. They attack stressed trees, so keep your trees healthy. To avoid attracting them, turn off your outside lights.
Q: How do we get rid of suckers coming up from a large tamarisk tree we cut down?
A: Suckers are very difficult to eliminate because of their aggressive root system. Let the suckers get about 3 feet tall and spray them with Roundup. After the suckers die down, more will emerge, so spray them. Repeat the process until you exhaust the energy from the roots.
The reason for letting the suckers get about 3 feet high: Roots are using up energy to generate more suckers. At about the 3-foot height, suckers begin returning energy to the roots. With this spraying, the tree takes the medicine “hook, line and sinker.”
Q: Will it hurt our mesquite tree if we raise the soil level under it a foot to plant shrubs?
A: You can add 2 inches but no more. Any greater depth shuts off the tree’s natural oxygen supply to the root structure.
Q: What are the small drops of liquid oozing from my okra leaves?
A: It’s a natural secretion from leaf and stem glands and doesn’t cause any damage.
Q: Why did two of my many gopher plants die but the others are OK? We found some slimy worms in one root ball.
A: Gopher plants need good drainage or root rot sets in. Get a Ross Root Feeder, which is sold by nurseries, and drill holes through the rooted area to open up the soil so drainage can occur. The bugs most likely were scavenger bugs starting the decomposition process.
Q: Why are my Early Girl tomatoes so small?
A: Whenever I’ve grown them the fruit has always been small. I assumed the variety has sparse foliage and with the sudden buildup of heat the plant wasn’t able to generate enough carbohydrates to satisfy its needs. Remove the smaller fruit so the remaining fruit will size up. I contend that gardeners don’t fertilize tomatoes enough and small fruit is often the result.
Q: Why is my avocado pale yellow and stretching? It seems to be getting plenty of light.
A: It’s not getting enough light. Place your hand a foot above your plant to observe its shadow. If the shadow is blurry, move it to a lighter location and it will stop the stretching. It’s getting enough light if you see a very distinct shadow.
Q: What is the gray white powdery stuff on my squash plants?
A: It is powdery mildew and is common this time of year. This disease doesn’t require moisture to get started. It robs the plant of nutrients and blocks out the sun, hurting photosynthesis. It occurs most where sun-loving plants are planted in shaded locations. If necessary, apply fungicide as a preventive measure before it becomes a problem.
Q: Are the mushrooms coming up in my yard edible?
A: There are many edible mushrooms but also many that are highly poisonous. Be on the safe side, destroy them and buy mushrooms from stores.
FOR SHADY GARDENS
Finding sensational plants for shady niches in your garden is a challenge as our landscapes mature. Learn about the many suitable specimens that will brighten up those shady spots. The tour is at 8:30 a.m. July 28 and 29 at the Springs Preserve, 333 S. Valley View Blvd. Visit www.springspreserve.org for more information.
Linn Mills’ garden column appears on Sundays. He can be reached at email@example.com or 702-526-1495.