January 14, 2010 - 10:00 pm
A Landscape Design with the Desert in Mind series of classes is being offered by the University of Nevada Cooperative Extension every Monday from 9 a.m. to noon starting Feb. 1 and running through March 22. For more information call the master gardener help line at 257-5509.
Q: I have a double trunk Chilean mesquite that is about eight years old. It is in a raised bed in front of my home, gets lots of wind and therefore the limbs are a little weird. For the past two years, this tree has a yellow tinge to it and doesn’t seem quite as healthy as past years. I called a master gardener and told him of the yellowing. He said these trees don’t need fertilizer. I love this tree even though it is a little misshapen. Can I do anything else for it? I sent a picture of the tree.
A: I really did not see the yellowing from your picture. The tree actually looks quite healthy. If the tree did not lose its leaves last year from the winter cold, the leaves will turn an off-color yellow-green due to winter cold damage. That is nothing to worry about.
I did notice that there has been some recent construction around the tree to build the raised bed. This type of construction had to result in some root damage. There isn’t really any way for that type of construction to not affect the roots.
The master gardener is right in that mesquite are capable of producing their own nitrogen fertilizer from the air. Their roots do this for the tree by taking nitrogen from the air and converting it to nitrogen, which it can use. There are microorganisms that live in the roots in a very close and mutually beneficial relationship with the tree that perform this function.
However, although this may work perfectly fine in the wild it does not necessarily mean that it will work to the satisfaction of an urban dweller who wants that tree to be the focal point of a yard. For this reason we usually give these plants extra care that will take them to the peak of their performance and looks. This requires extra water and extra fertilizer along with some artistic pruning.
So with fewer roots due to construction and the desire for a top-performing tree in your yard, you will have to add fertilizer to achieve this. So I would give it a shot of fertilizer in January to give its looks an extra boost.
You will have to be careful of your watering since the tree probably has fewer roots now to take up water. You also will have to be careful in strong winds so that the tree will anchor firmly after root pruning. Water mesquites deeply but not too often to get deeper rooting.
To keep the canopy of the tree full and dark green, water as you would most other landscape trees. Watering with small amounts of water or watering infrequently will cause the trees canopy to thin and become sparse. Overwatering will cause very rapid and explosive growth, which you want to avoid as well.
Any good landscape fertilizer for trees and shrubs would be safe to use and it is usually a balanced fertilizer with all three numbers the same. Examples are 10-10-10 or 16-16-16. Keep the fertilizer away from the trunk of the tree but distributed under the tree’s canopy.
Q: I want to plant some Indian hawthorn shrubs in my raised beds. A local nursery has these shrubs on sale right now. If I buy them now, is this a good time to have them planted or should I wait until spring? If it should wait until spring, is it a good idea to buy them now and try to keep them healthy in their pots until planting time or just wait until planting time to buy them? If it would be OK to buy them now, which side of the house would it be best to keep them on? Do they need to be more sheltered (such as on a porch with my other potted plants) or is it best to keep them in the elements?
A: There’s nothing wrong with buying plants right now if they are a good deal. They will overwinter better in your home landscape than they will in a nursery container. Go ahead and buy them and plant them. But remember you will be treating the plants like they are overwintering so there’s no need to water them frequently, perhaps twice a week at most with a thorough irrigation by hose.
To give you a simple rule to follow, for 5-gallon plants give them 5-10 gallons per irrigation. For 15-gallon plants, give them 15-20 gallons per irrigation. This is just a rule to follow, even though the gallon designation of nursery containers has nothing to do with the gallons of water they will hold.
Just because you are getting a good deal on the plants does not mean you can skimp on the amendments going into the hole. Make sure you prepare the soil with compost and phosphorus and settle the amended soil around the rootball with plenty of water at planting time.
Leave a basin around the plants for hand watering. I would hand water them this winter and check the planting hole for further settling of the soil around the rootballs and fill in this settled area as needed.
They will do better if they are mulched as well. Don’t water too often and make sure the plants are planted the same depth they were in the container. If unsure about whether to water, stick your finger in the planting hole and feel if it is moist or use a moisture sensor. If you are planting and watering them all the same, then sampling one plant should be enough to gauge the others.
Q: I reside in Mesquite and I plan to plant a fig tree this fall or winter as a memorial to my husband, who was particularly fond of figs. Additionally, is one variety better than others for growing figs espalier?
A: As far as figs go, two very good figs are Black Mission for a dark fig and Kadota or Janice for a white or yellow fig. Most figs do quite well here as long as they are getting adequate irrigations when fruit is developing, which is most of the season.
This year at the orchard we did get three crops off of our figs. Any of the figs can be trellised or espaliered, but they get massive trunks and limbs.
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 firstname.lastname@example.org.