Q: What is the best fertilizer to use on lantana? I have yellow and purple, and the yellow just never seems to keep the flowers long in the summertime; they come and go and do no not look very vibrant. Is there such a thing a mild fertilizer to use?
A: Lantana is not particularly fussy about fertilizers but all plants benefit from improved soil health. Fertilizers only replenish some of the minerals in the soil that plant roots remove.
Plants growing in desert soils covered in rock improve if organic materials are applied to the soil rather than only fertilizer. Ideally, organic materials should be mixed with the soil at the time of planting, but these disappear in a couple of seasons and need to be replenished with surface applications on a regular basis.
The ideal organic application is 100 percent compost applied to the soil surface, not a soil mixture containing compost. Soil mixes commonly contain a large percentage of sand that adds volume to the landscape when applied. Compost, on the other hand, doesn’t add volume because it dissolves into the soil.
Pure compost, 100 percent compost, can be difficult to find in stores. However, 100 percent compost can be purchased from composting facilities such as A1 Organics or a compost supplier such as Viragrow in North Las Vegas.
Applying compost is simple. It is applied to a soil surface, or rock mulch, and simply watered in with a hose. Compost dissolves into the soil giving the plants nutrients and improves soil health. Improved soil health, along with the nutrients it contains, makes new growth darker green with larger leaves and larger, more vibrant flowers.
Q: After this last rain and gusty winds, some sunflower leaves are scorched. The sunflowers are 3 feet tall and sown from seeds saved from last year. The leaf scorching runs between the veins but not on all the plants. Is this normal after this kind of weather?
A: This had nothing to do with the weather. Look at the bottom of the leaves. Sunflowers are notorious bug traps. If this scorching is from bug damage, you will find lots of bugs feeding on the bottom side of the leaves.
Bug damage is noticed on the lowest leaves first and progresses up the plant. Usually, insecticidal soap sprays applied to the bottom of the leaves kill these critters but will not repair the damage they created.
If the lower leaves turned yellow, it could be from not enough nitrogen fertilizer. If they are 3 feet tall, they have already removed a lot of nutrients from the soil to get that large. Feed them once a month with fertilizer or they will run out of food causing the lower leaves turn yellow and scorching.
Another possibility is irrigation or damage from salts. They go hand-in-hand since water washes salt from around the roots and pushes it deeper. Little plants only require small amounts of water. Big plants require more water so make sure they are getting enough water and it is applied often enough.
Improve the soil at the time of planting with compost, feed the plants regularly with a fertilizer, water them enough and check for bugs. Then they will be healthier.
Q: I was going to plant a grape vine directly in front of my cement block wall. I decided to check the Internet to see how far away from the wall I should plant. The site said grapes should not be planted close to walls because the roots cause structural failure. Is there is a minimum distance from the wall to plant the grape?
A: Roots of grapes are not a big problem for walls, particularly when grown in the desert with drip irrigation. However, do not plant a grape vine immediately against the wall.
Put them on a trellis at least 1 foot away from the wall. Place drip irrigation away from the wall to encourage plant roots to grow away from the wall as well.
Grapes need to be pruned and harvested. Planting directly against the wall makes these practices difficult. Generally speaking, table grapes grow more vigorously and are more aggressively than most wine grapes. Wine grapes might be a better choice for smaller areas and they are more versatile as a food.
Q: We planted new oleanders a month ago and fertilized them with Epsom salts and gypsum. They have yellow leaves that are dropping already. What can we do to stop the yellowing of the leaves?
A: Oleander should be one of the easiest plants to grow in this climate and soils. Something is definitely wrong. Gypsum and Epsom salts are not complete fertilizers. They contain a lot of calcium and sulfur as well as some magnesium but nothing to encourage plant growth.
Select a fertilizer that contains nitrogen, phosphorus and potassium such as 16–16–16 or some type of fertilizer for trees and shrubs.
You didn’t mention mixing compost with the soil when it was planted. I hope the soil was amended with organic matter like compost at the time of planting. This is extremely important for plants growing in our desert soils.
Make sure the planting hole is filling with water at planting time. This practice is not as important in soils found in wetter climates but can be an extremely important practice for our soils.
Add enough water at each irrigation to thoroughly wet the soil surrounding the plant roots to a depth deeper than the container. Build a donut or moat around the plant that can be filled with water. Irrigate with a hose, filling this moat, the first three weeks after planting.
Q: My tomatoes have blossoms all over. When should I cover it with shade cloth?
A: Tomatoes do fine without shade cloth. Be careful using shade cloth because too much shade stops plants like tomatoes from flowering and producing fruits.
Shade cloth is best used for leafy vegetables and herbs. Shade decreases bitterness and improves tenderness of leaves.
Many people use shade cloth that produces too much shade. Never use shade cloth meant for people when growing vegetables. Shade cloth for vegetables and herbs should not produce more than 30 or 40 percent shade.
Generally speaking, grow tomatoes, peppers, eggplant, cucumbers, squash, melons and other flowering vegetables without shade. Also include onions, garlic and potatoes on that list. Use shade cloth for lettuce, spinach, collards, basil, parsley and other leafy green types.
Q: I am responsible for maintaining a bermudagrass lawn at a church where the foot traffic is pretty high. The lawn gets 25 minutes of water three days a week, all in one watering because the lawn is very flat. But it still looks thin in spots. Can you tell me if this is the right amount of water?
A: Water is tough to measure in minutes. It is usually measured in gallons or inches of applied water. Right now, March and April, lawns need about ¼ inch of water per day. After four days, apply 1 inch of water.
To translate 1 inch of water to minutes put several cans out in random places, measure how much water is applied in five minutes and then in 10 minutes. Translate the lowest amount caught in cans into minutes.
Another method is to water the lawn for 15 minutes. Take a long pointy device, like a long screwdriver or piece of 3/8 inch rebar, and shove it into the lawn in five different places. Measure how deep the water has penetrated. It gets harder to push when it is dry and pushes easily when it is wet.
Run the irrigation long enough for water to penetrate to 1 foot. When the water penetrates to this depth, then this is the number of minutes to run the sprinklers. These minutes aren’t changed much throughout the year.
What is changed is how often the sprinklers come on. Three times a week seems quite often for bermudagrass this time of year. It should be about every three or four days between irrigations when watering a foot deep.
Applying enough water helps fill in bare spots. But what really causes bare spots to fill in quickly is enough water plus a nitrogen fertilizer. Apply ammonium sulfate, 21-0-0, to the lawn every eight weeks. Use 3 to 5 pounds of this fertilizer for each 1,000 square feet of lawn.
Apply it with a handheld spreader over the entire lawn and water it in. Apply it more heavily in bare areas. Mow it somewhere between ½ and 1 inch in height. Taller grass is more wear resistant.
Bob Morris is a horticulture expert living in Las Vegas and professor emeritus for the University of Nevada. Visit his blog at xtremehorticulture.blogspot.com. Send questions to Extremehort@aol.com.