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Nitrogen fertilizers keep lawns green, lush

Q: I was very interested in a recent article about adding ammonium sulfate to one’s lawn to keep it green. Can I do this all summer long, every eight weeks?

A: The short answer is yes. Once a year use a high-quality lawn fertilizer as one of the applications. The best lawn fertilizers have a ratio of nitrogen to phosphorus to potassium of 3-1-2 or 4-1-2 with most of the nitrogen available as slow release. One example would be 21-7-14. There are many others.

The principle nutrient lawns need is nitrogen on a regular basis. Nitrogen fertilizers keep lawns green and lush. Nitrogen is the first number in the triad of numbers on the fertilizer bag.

In the case of ammonium sulfate, this is 21–0–0. A bag of ammonium sulfate contains nitrogen, hydrogen, sulfur and oxygen in mineral form. There is no “filler” in it. Ammonium sulfate is 21 percent nitrogen. The usual recommendation for lawns is 1 pound of nitrogen every 1,000 square feet.

This is applied with some sort of spreader such as a drop spreader, a broadcast spreader or hose end applicator. Since ammonium sulfate is 21 percent nitrogen, then 5 pounds of 21-0-0 delivers about 1 pound of nitrogen.

However, I find this rate is higher than necessary and lawns do just fine at half to three-quarters of this rate. This is particularly true if mowing with a mulching mower and the clippings are allowed to fall back on the lawn. Lawn clippings are very high in nitrogen and act like an extra fertilizer application.

In about 99 percent of the cases, we have two types of lawns out there; tall fescue and Bermuda grass. Both of these lawns require a high nitrogen fertilizer about every eight weeks. However, the timing of these applications is different.

A fertilizer application at Thanksgiving is extremely important if you want a dark green lawn tall fescue through the winter. It is unnecessary for Bermuda grass.

To make it simple, I recommend applying lawn fertilizers to tall fescue on Labor Day, Memorial Day and Thanksgiving. For Bermuda grass switch the Thanksgiving application for the Fourth of July.

There is no problem applying a fourth application to tall fescue during the heat around the Fourth of July as well, but it is probably unnecessary. Any application to tall fescue during the summer should be the half rate I mentioned earlier.

Q: What is causing brown spots and leaf scorch on my tomato plants? I grow about 17 different tomato plants and several different varieties in containers. I always use good potting soil and compost each year in the containers. They are drip irrigated.

A: This is the time of year that brown spots begin to develop on tomato leaves. As the season progresses, disease problems on tomatoes are often inevitable. Prevention of disease should be high on your list of things to do with tomato plants.

It’s too late this season, but some varieties are more susceptible to diseases than others. If you don’t know which variety you have, do a little homework and pick varieties more resistant to disease that give you the types of fruit you like.

Tomato cages are nice. They support the fruit off of the ground. Fruit lying on the ground is more likely to rot than fruit supported off of the ground.

Tomato cages can also be a menace. They force crowding of the interior of the plant. Leaves and vines growing in the center don’t receive enough sunlight to stay healthy. They also don’t provide good air circulation. This encourages disease. Remove the oldest leaves near the center of the plant to improve air circulation and reduce disease problems.

Drip irrigation is good. Watering at the base of the plant helps. Many vegetable plants, unlike us, don’t like showers.

Avoid overhead watering of these plants. Overhead watering keeps the center of the plant wet which encourages disease. Splashing water can spread disease from leaf to leaf.

Regular feeding of plants is important. When fruit has set, continue monthly feeding of tomato plants. They are taking nutrients from the soil as they grow. You should be replacing these nutrients as they are removed.

At the first sign of possible disease, it is important to take action. Applications of fungicides may be your last alternative. Choose a fungicide for controlling the more common tomato diseases, such as early blight. Most fungicides are preventive and don’t cure a disease once they have begun and running rampant.

Q: I put a passion fruit tree on the north side of our house. I noticed many flowers but later on, after self-pollination, the flowers fall off. What do I do to prevent it?

A: Passion fruit is a tropical and, at best, a semi-tropical vine that bears a delicious, seedy fruit with very little care under tropical conditions. It is not a tree, so it does need to be supported by a trellis of some sort. This is the cold desert so this plant is handled a little bit differently here.

In the desert, passion fruit requires more care than it does in the tropics, and it will most likely freeze back to the ground every year. But if the roots are protected from winter cold, it will grow again in the spring.

It is good you planted it on the north side of a building. but the east side would be even better so that it gets light in the morning and shade from the late afternoon sun. It likes a lot of compost added to the soil at the time of planting and to the top of the soil each year.

Wood chip mulch applied to the surface helps keep the heat off of the roots and preserve moisture in the soil. Drip irrigation works, but this plant may perform better if rooted in a large basin or donut that fills with water.

There are many different types and varieties of passion fruit, and some perform better than others in the desert. Varieties that have performed in the Phoenix area include Frederick, Incense and Blue Crown.

More can be read about their care in Phoenix at www.phoenixtropicals.com/passionFruit.html

Just remember that Phoenix has warmer winters than we have so we must apply better winter protection. They generally have better soils than we have, as well.

Passion fruit is a heavy feeder so fertilize them frequently. They set fruit easiest during the cooler times of late spring and early summer but may have difficulty during the heat.

They may need to be hand pollinated if they fail to set fruit by themselves.

Q: I transplanted my tomato plants outside April 3. I noticed holes in the leaves. I searched for insects day and night and have not found any. What could this be? It is only on a few upper leaves no damage to lower ones.

A: I looked at the pictures you sent very closely and I don’t see a disease problem. The raggedy edges of the holes do not look like insects. I think this is wind damage. I wouldn’t worry about it.

You got them out a little bit late. You should be putting out transplants no later than mid-March.

Don’t water plants with overhead irrigation, such as water from a hose. Water at the base. As soon as you see fruit, give them light fertilizer applications once a month.

The oldest leaves in the center of the plant and in the shade should be cut and removed to improve air circulation. Keep the plant open in the center which should reduce disease problems. Start watching for whiteflies and spider mites as temperatures get hotter.

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.

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