Nitrogen stimulates green growth

For those of you interested in the Slow Food movement in Las Vegas, I will be speaking on its development here along with Giovanni Mauro of Nora's restaurants, who is the chairperson of Slow Food Las Vegas. Our presentation will be at 7:30 tonight in the Barrick Museum Auditorium at University of Nevada, Las Vegas. We will discuss the Slow Food movement in general and specifically some of the issues surrounding its evolution in Southern Nevada.

Q: A couple of years ago I thought I got and used a "wake-up" fertilizer formula. I thought it was from a Review-Journal column. Does this ring a bell and if this did come from you, could you direct me to where I can get the ingredients and amounts again?

A: I don't believe that I have ever used the term wake-up fertilizer. I am not quite certain what this means, but I can take a guess. My guess would be that it is a fertilizer that is rapidly taken up by plant roots in colder soils.

Nitrogen is the principal fertilizer that is used to stimulate new, green growth such as stems and leaves. There are different forms of nitrogen that can be applied to plants. Most commercial fertilizers that are not organic have nitrogen available to plants in either of two forms: ammonium or nitrate.

Nitrate is taken up by plants more rapidly than ammonium nitrogen, particularly in cooler soils. So my guess would be that a so-called wake-up fertilizer for plants in the spring would contain the majority of its a nitrogen in the form of nitrate.

Labels must state the nutrient content of the fertilizers, so you should be able to determine the percentage of nitrogen contained in the bag and whether it is in the ammonium or nitrate form.

For rapid plant intake, you should get a fertilizer with a higher percentage of nitrate nitrogen.

Q: I have a sick willow tree that is 15-20 years old. The tree was diagnosed with "slime flux" last fall. What is the prognosis for this tree?

A: Slime flux is a bacterial disease that in most cases is pretty benign and causes foul-smelling sap to ooze from the trunk or limbs and usually attracts flies. Flies can carry the bacteria to open wounds where it can infect other plants. The disease can hit a number of different plants but usually they live with it with no ill effects except they look and smell bad.

The usual method of treatment is to drill a hole where the sap is coming out and insert a tight-fitting tube that allows the foul sap to drip a few inches beyond the trunk and not run down the side of the tree. The treatment is cosmetic. The disease persists in the tree for its life, which is still quite long.

There is a different form of this disease that attacks the round-canopied willows we usually call Navajo globe willows. This disease has been called frothy flux and it will frequently kill the tree in a short time.

To my knowledge there is no cure, but it only attacks Navajo globe willows. I have never seen it in Southern Nevada; it is more common in Utah, Colorado and New Mexico. This particular disease has only been around for 30 years.

The cure for frothy flux is to cut the tree down. If there are other globe willows in the vicinity, then cutting it down is best since it can be a source of infestation for other trees .

If this is a weeping type of willow, frothy flux is not supposed to infect it. You can leave it, treat it with the tube or have a certified arborist take care of it for you.

Q: For four years now, our live oak tree drops many leaves around this time of year. It fills out later and looks much better. I have been told that I am overwatering so I shut one dripper off. I fed it twice in the past six or seven weeks. Slap my hand, I didn't follow directions precisely on fertilizing for the trunk size.

Also, I have very prolific Mexican evening primrose plants that seem to give birth frequently, even in the area of our holly oak. Is that harmful?

A: It is normal for many so-called evergreen trees to drop a considerable number of leaves in early spring. Normally, this would occur just before or during new spring growth.

If this were my tree, I would probably give it about 30 gallons of water each time I watered. Because it is on drip irrigation, I would water it only once on the day I had it scheduled for getting an irrigation. I would try to distribute the water in an area that is at least half the size of the tree's canopy. I would want to apply enough water so that it would penetrate to a depth of 18-24 inches every time I have watered.

Around the first week of May, I would increase the irrigations to twice a week. However, if it got hot early in the season, I would increase the watering sooner. When temperatures consistently break 100 F and climb to 110 F, I would increase the watering to three times a week.

The key here is to water deeply and then hold off on water so that the upper layer of soil begins to dry and forces roots to grow deeper. You are going to have to apply math to your situation and do some calculations based upon the number of emitters that you have, the size of the emitters and the number of minutes they are running.

Mexican primrose, in my opinion, is basically a very pretty, invasive weed. Once it gets established it can be very difficult to get under control. It will not hurt your holly oak.

Bob Morris is an associate professor with the University of Nevada Cooperative Extension. Direct gardening questions to the master gardener hot line at 257-5555 or contact Morris by e-mail at