Cold winter temperatures are detrimental to growing citrus

Q: Why does your list of recommended fruit trees have no citrus? I understand the problem with freezing during the winter, but nurseries and garden centers here sell citrus. If I could provide some sort of wind block from cold winter winds and some frost protection, would lemons or oranges have a chance or are they just generally doomed?

A: Generally, I do not recommend growing citrus in the Las Vegas Valley. Is citrus grown here? Yes, it is grown successfully in many backyards. So why don’t I recommend growing citrus? Because many planted in our valley die during freezing winter temperatures. Some don’t.

Successfully growing citrus is better than a crapshoot. The overall climate of the Las Vegas Valley is too cold during the winter to recommend citrus. However, there are protected nooks and crannies in people’s backyards that allow for citrus to be grown. These protected nooks and crannies are called microclimates.

The major limitation for citrus here is cold winter temperatures. Cold winter temperatures are made more lethal when accompanied by strong winds. Remove these two obstacles and citrus does well.

After an ideal microclimate is found, citrus must be healthy to survive our extremes of heat and cold. Amend the soil with compost at planting time. Do not apply citrus fertilizers after Aug. 1. For long-term health of the tree, avoid surrounding it with rock and desert landscaping.

And finally, choose fruit that you want that is tolerant to freezing temperatures in your microclimate. Tolerance to winter temperatures is best with kumquat followed by mandarin orange, Meyer lemon (only Meyer) and grapefruit. Least tolerant to cold are the limes, true lemons like Ponderosa or Eureka and some of the specialty oranges.

Planting citrus here is not for everyone. Proceed with caution and look at it as a fun experiment in gardening.

Q: We are considering planting sissoo or raywood ash in our front patio which is covered with pavers. Are root problems a concern for sissoo? I have concerns about dieback in raywood ash because of diseases described in Northern California and Europe. Does our climate reduce the chances of disease problems?

A: To me, the choice between sissoo or raywood ash is like picking between an apple and an orange; they don’t do the same job in the landscape. People choose sissoo as a fast-growing personal shade tree, while the raywood ash is not fast-growing and is not much of a personal shade tree.

Sissoo is much more likely to freeze during the winter here than raywood ash. Because of their mature size, I don’t consider either one of them as good choices for a single-story residence in a desert climate.

I observed a few sissoo planted at homes in Las Vegas, but most of what I know about this tree’s performance after planting is from homeowners in Arizona. The major complaints are its large size, limb breakage in strong winds, heaving of sidewalks and patios by its roots, general litter from leaves and fruit, and root suckering throughout the landscape.

There seems to be two opinions about this tree; people love it or they hate it. Not much in between. Homeowners who planted it in Las Vegas were surprised by its size and considered removing it after a few years.

Raywood ash is not fast-growing like sissoo but easily handles our winter temperatures without damage. However, the trunk can be damaged by intense summer sunlight. It does not produce root suckers. Raywood ash is more ornamental” with its beautiful fall color.

Raywood ash is susceptible to a disorder — disease if you want to call it that — called ash decline. This disorder has been a problem in Las Vegas since the 1980s beginning with modesto ash and later with raywood ash. I generally don’t recommend planting ash trees susceptible to this disorder in the Las Vegas Valley.

Both trees should not be planted in a desert landscape surrounded by rock. You’re asking for trouble if you do. Instead, plant them in lawns or surrounded by other plants that require moderate to high amounts of water.

Q: I changed my drippers to adjustable types and have problems with them working in my backyard. I fix them either by adjusting or removing the heads. Now they work fine. This happens throughout the year, but I have never seen so many fail at the same time. My front yard also uses adjustables but don’t have the same problems. I was thinking about going back to drippers for reliability.

A: I call dippers “drip emitters” or “emitters” but I think we are talking about the same thing. I work with drip irrigation all over the world. The major reason drip systems fail is that the system is not cleaned and flushed regularly. Flushing and cleaning drip systems must be part of a regular maintenance schedule.

When cleaning and flushing a drip system, the primary filter or screen must be cleaned thoroughly; every “dead end” must be opened and flushed with several gallons of water and emitters should be inspected for plugging when they are operating. If emitters are plugged, they must be cleaned or replaced if they cannot be cleaned.

A major problem is created when drip systems are repaired and but not flushed afterward to remove dirt that enters the drip lines. If drip irrigation lines are cut and repaired, I guarantee dirt entered these drip lines. It is mandatory that the “dead ends” associated with the repair are flushed immediately afterward.

Drip system filters are cleaned and the system flushed because dirt or sediment in the water collects inside the filters and eventually plug drip emitters. Flushing the irrigation lines removes algae and bacteria that plug emitters as well.

How frequently to clean and flush a drip system depends on the quality of the water and how much water flows through the system. Irrigation systems should be flushed more often in summer than winter.

How long it takes to flush and clean depends on the design of the system. Poorly designed drip systems take longer to flush and clean. When designing drip irrigation systems, minimize the number of dead ends so that flushing the system takes less time and there are fewer places that accumulate dirt and slime.

Most drip irrigation systems attached to municipal water are flushed once a month if the municipal water delivered is clean. Sometimes it is, sometimes it isn’t, depending on the age of the municipal system.

Even though filters must be installed as part of every drip system, small amounts of sediment pass through these filters and eventually become a problem if the system is not flushed and cleaned regularly. Failure of drip systems is gradual, not like an on and off switch.

Drip systems attached to well water should be flushed more often because this water is dirtier. How often depends on the quality of the well water, which varies from well to well. Typical cleaning and flushing might vary from weekly to bi-weekly during the summer months.

Algae and bacteria (you might call it slime) grow inside every irrigation system. Algae and bacteria are not problems with most sprinkler systems but can be problems with drip emitters because the emitter holes are so small.

In my opinion, drip irrigation systems must be flushed and filters cleaned on a regular basis depending on the quality of the water and the gallons used. The drip emitters used should be easy to clean and inexpensive. Variable drip emitters are inaccurate in their delivery of water but are subject to the same plugging as all other drip emitters.

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