Protect flowering plants from freezing temperatures

Looks like there might be a freeze coming up for some parts of the valley. If you have citrus, take a close look at the plants and see if they are getting ready to flower, they are flowering now or made small fruit already.

Citrus like Meyer lemon can start flowering as early as late December, through January and into February. Throw a light blanket over the tree at night if it’s going to freeze and take it off the next day. Flowers and small fruit will die with the slightest freeze. Freezing temperatures can eliminate all or some of the fruit you normally would harvest this next fall or winter.

Last spring we had two pretty hard freezes come through the valley in February, with snow, that wiped out a lot of fruit that we expected in 2019.

Watch the weather forecasts this January and February and pay attention to your other fruit trees. Flowering of other fruit trees starts the first week of February. Peach, apricot and nectarine are usually the earliest. It’s the same story with these fruit trees. We don’t see fruit loss typically as much because they flower later when there is less chance of a freeze.

The flowering period for a tree lasts two to three weeks depending on the temperature. Early flowers open first at the top and on the south or west side of the tree. Later, flowers in colder locations in the canopy open sequentially with flowers opening last on the north side of the canopy toward the bottom.

The flowers of some varieties seem to handle a tiny bit of freezing temperatures better than others. Flavor Supreme pluots and plums like Elephant Heart, some peaches, nectarines and apricots can’t handle any freezing temperatures at all.

If there is a light freeze, some or most of the fruit can be lost. That happened the last two Februarys in colder parts of the valley.

Q: I have a spider that killed my house plant. I couldn’t find it, but I found the webbing in the leaves. I took a sample to the nursery for identification, but they couldn’t find anything either. What is it?

A: I doubt it’s a spider. Most spiders are carnivorous. It sounds more like spider mites. Spider mites will damage plants or even kill plants and spin webbing just like a spider. They feed on plant juices and cause the plant to appear like it’s dying and can even kill it. They are difficult to see.

Spider mites are not insects, but they are related to spiders, just extremely small so they are hard to see. They are about the size of a period at the end of this sentence. They will spread from plant to plant, so keep an eye on any other plants you might have.

Symptoms of plant damage from spider mites can be the leaves turning a grayish silver, a scorching or browning along the edges of the leaves, or a dusty appearance on the bottoms of leaves. Sometimes it looks like it’s only a lack of water.

If any part of the plant is still alive, check for them and confirm my guess. Do this by checking the undersides of leaves and looking for that dust I was talking about. Spider mites will always give this dusty appearance on the bottom sides of the leaves.

Take a white piece of paper and slap the dusty leaf against the white paper. Hold it still under a bright light for about 10 seconds. If there are mites, you will see these little dots crawling on the white paper. Lightly brush your fingers over these dots, and they will smear against the paper. Voilà, you found spider mites.

Soap and water sprays will control spider mites if it’s applied three or four times about three or four days apart. The problem with soap and water sprays is they are not always 100 percent effective.

Neem oil, canola oil or even the lightweight horticultural oils will suffocate them. But they can be toxic to some house plants, so test a leaf with the spray before you apply it to the whole thing.

Q: Where can I send a soil sample to have it tested?

A: I usually send my soil samples to an agricultural soil testing laboratory in Modesto, California, by the name of A and L Soil Testing Laboratory. The cost of sending in the soil sample is about $75 for a complete analysis.

A soil analysis tells you which minerals are in short supply for plants. It’s a good idea to have one of these done in a raised bed every three or four years, but I certainly wouldn’t do it every year unless you were farming and spending a lot of money on fertilizer.

A soil test will not tell you if there is something in the soil killing your plants such as a disease or industrial chemical. The test measures the nutrient supply in the soil.

If you go to its website, there are instructions on how to take a soil sample. If you have questions that aren’t answered in these instructions, give them a call and they will explain it to you. It’s very important to send them a composite sample that represents the entire area where you’re growing plants. That is the only way to get an accurate understanding of the nutrients in your soil.

There are soil testing kits available that are reasonably accurate at telling you the major nutrients available to the plants, but most kits will not analyze the soil for many of the nutrients needed in tiny amounts by plants.

Q: Is it time to spray or fertilize plants yet? What fertilizers and sprays would you recommend using?

A: The only spraying I would recommend now is the dormant oil application made for controlling pests that will cause problems in the spring and summer months. Dormant oil can be mixed with other pesticides, but it’s not necessary considering the pests that we have here. It might be necessary in other parts of the country. By the way, there is a spray sold called a Dormant Spray for diseases, but it’s not necessary here usually.

Dormant oils have no effect on borers or the alien-looking, leaf-footed plant bug that damages pomegranates, almonds, pistachios and vegetables. But it will suffocate aphids that are trying to hide until spring, mites and other problem insects. It’s probably the most important spray of 2020.

The spray is a petroleum oil called Dormant Oil or Horticultural Oil in the nursery and garden center. If you buy this oil, it is emulsified, so it will mix with water for spraying. If you use one of the substitute oils like soybean oil or olive oil you will have to emulsify it in water before you use it. Emulsifying it can be done in a blender.

Mix the equivalent of one-quarter cup of oil per quart of finished spray. Put this amount of oil with a cup of water and blend it together until its white. Then put enough water in the emulsified oil to make one quart of finished spray. The spray can be sprayed directly on plants. The plants should have no leaves on them when you apply the spray.

It is time to fertilize landscape plants and fruit trees before the end of the month. Plants like roses should get an application of iron fertilizer alone with a normal fertilizer application. Those plants that don’t start growing until later can receive a delayed application around the end of February.

Q: Is it time to fertilize my lawn?

A: Lawns are fertilized three or four times each year. The first fertilizer application to a fescue lawn can be done at the end of January. If your lawn is a Bermuda or warm-season grass lawn, then wait and make the first application at the end of March.

Bob Morris is a horticulture expert and professor emeritus of the University of Nevada, Las Vegas. Visit his blog at xtremehorticulture.blogspot.com. Send questions to Extremehort@aol.com.