Lawns best fertilized around Memorial Day
As the heat sets in, here are some questions I've encountered:
Question: Do I fertilize my lawn now or wait until fall?
Answer: Fertilize around Memorial Day to get your lawn through the summer. Use a fertilizer containing nitrogen, potassium and iron to put the finishing touches on your lawn.
Q: Why did brown blotches show up on my older tomato leaves? It is not typically scorched leaves. We transplanted them in March and water every day.
A: Thanks for the picture. My first reaction was alternaria, but it's not a problem in our dry climate. I strongly suspect it is mesophyll cell collapse. After transplanting your tomato, the root ball's interior dried out because it wasn't getting enough water. To protect the plant, the cells within the leaves collapsed. By now your plant is most likely doing fine.
Q: Do you know of a vine to cover my west-facing wall?
A: Consider cat's-claw, creeping fig, grape, Hall's honeysuckle, Lady Banks rose, trumpet vine or the vegetable vine luffa.
Q: Can you provide me with a list of plants to attract hummingbirds?
A: Visit the Mountain States Wholesale Nursery website at www.mswn.com/mswnhummerattractors.htm for a list of hummingbird-attracting plants. Then Google the suggested plants to see if you like them.
Q: Will thinning my fruit-loaded pomegranate increase its size?
A: If your goal is to make juice, syrup or grenadine, thin them. It's easier to process larger fruits than small ones.
Q: Can we grow cotton in Las Vegas?
A: Master Gardener Don Fabbi grows it every year, and you still have time to plant it. Fabbi grows it more for its tremendous ornamental value: It produces gorgeous flowers in a couple of months, and in the fall the cotton ball bursts open. Then, after a frost, the foliage drops to expose the decorative cotton balls even more.
Q: We saved a small irregular patch of grass when converting our yard to a Water Smart landscape. We want to surround it with shrubs to take advantage of sprinkler overflowing. Will the shrubs get enough water for this arrangement? We're following the Southern Nevada Water Authority watering guide.
A: No. Grasses are shallow-rooted and shrubs are deep-rooted. Shallow irrigations do not encourage deep rooting of your shrubs. Put in a drip system for your shrubs to meet their needs.
Q: Two years ago we converted our yard to desert landscaping, and now our ash tree is in decline. We placed eight 4-gallon-per-hour emitters around it and run them for two hours a week. Do you think it's getting enough water?
A: When you removed the grass, you removed a major portion of the tree's feeder roots. Provide additional waterings and deep soakings occasionally. It takes a couple of years for decline to set in, and by then you forgot about removing the roots.
Q: What is the white, fluffy, sticky stuff at the base of my apple trees?
A: It is woolly apple aphids growing in masses on the roots and near pruning wounds. You'll also find clear, sticky honeydew and black sooty mold on foliage. Wash them off with a strong jet of water or apply neem.
Q: Our bougainvillea is flowering beautifully, but something is eating the leaves. What's causing it?
A: It is the leaf-cutter bee, one of our major pollinators. The bee builds a nest somewhere in your yard to lay its eggs for next year. This is how this insect carries over from one year to the next. These bees love bougainvilleas and roses along with other plants, but their damage doesn't kill plants.
Q: Why is my agave shriveling up even when I water it?
A: You are describing agave weevil damage. They attack mature agave and yuccas, and eventually plants succumb. Look for black, three-quarter-inch long adults crawling around and stomp on them. Wiggle the bottom leaves and if they come loose, look around the plant's base for round entry holes. If the plant wiggles freely, the entire plant might be infested. Choose an insecticide for beetles and grubs. Drench each plant and the surrounding soil and other agaves to prevent their aggression.
Q: What are the white fungus spots on our prickly pear cactuses?
A: It's cochineal scale. It will degrade your cactuses if not hosed off with a strong jet of water. Don't be alarmed if you see a blood-red substance coming from these spots. People use this substance to dye things.
Linn Mills' garden column appears on Sundays. He can be reached at
linn.mills@springspreserve.org or (702) 822-7754.
