Freezing temperatures could prove lethal

Saturday I will be teaching how to prune peaches, nectarines and miniatures at the University of Nevada Cooperative Extension Master Gardener Orchard in North Las Vegas from 10 a.m. to noon. The class is open to the general public. If you plan to do some pruning with our volunteers afterward, please bring your pruning shears and loppers. For information on how to get to the orchard call the master gardener help line at 257-5555.

During this past week we saw some unusually cold temperatures for this time of year. Not only were the temperatures low, but in some parts of the valley these temperatures were subfreezing for several hours.

Several factors can combine to make freezing temperatures more lethal, particularly to tender fruit trees like citrus. These other factors include the amount of time these temperatures were subfreezing and the amount of wind. Subfreezing temperatures at the orchard lasted for several hours in some cases and the wind was substantial for at least one of the freezing nights.

Plants that could withstand one hour of freezing temperatures might not survive several hours at these temperatures, particularly combined with wind. Succulent plants, like many vegetables, might see the damage first appear as wilting several hours after temperatures warmed. Some with cold sensitive citrus might see damage to the trees several days or even a week later. This is why it is important to plant citrus in protected locations here in the valley.

Q: I just put down some sod two weeks ago. Should I winterize my lawn or give it some type of nutrient?

A: I like to see an application of high nitrogen on fescue lawns right about Thanksgiving.

I am hoping it does not get too cold right now, which is unusual. An application of nitrogen before it gets too cold will help keep fescue green through the winter -- provided we don't get a real bad cold snap. If it gets too cold earlier, then the fescue might take a dip in its color and quality. If that happens, then it is hard to get it to recover until some warmer temperatures come along.

Fescue has better tolerance to cold and maintains its green color better if it is fertilized just prior to winter.

Q: How long during the winter should I water the lawn with the subsurface system?

A: How long to water with subsurface drip depends on how it was designed. During establishment you will have to irrigate when you start to see the lawn develop those blue, gray or smoky-colored spots that tell you those sections are too dry.

The best I can tell you is to run it long enough to get the water from the drip system to a depth of about 10 inches or so. You can use a long screwdriver or piece of rebar to judge the depth of watering. These devices will push easily into shallow wet soil and with more difficulty in the lower, drier soil.

Push it into soil midway between drip lines. Be careful not to puncture your subsurface drip tubing when you do this. The subsurface drip should have been installed around 4 inches deep.

Hopefully the water will come out of the drip system fast enough to cause upward movement of the water toward the soil surface. Otherwise you may have to water by hand until roots from the sod can reach the subsurface water.

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 morrisr@unce.unr.edu.