Bitter orange can be hard to find in Las Vegas

A: They aren’t very popular here. I understand why you might want to grow them.

We are talking about Citrus aurentium. They are used as a landscape highway plant or landscape hedge in the Phoenix area, where it’s warmer during the winter.

Here, they are mostly used as a low-temperature rootstock for citrus when shipped to our area by wholesale nurseries. Trifoliate orange is used primarily as a freeze-tolerant rootstock for our area, but sour orange is also used. I don’t have the information on their low-temperature tolerance for the winter, but I think it’s around 20 degrees, so it would be a good choice for planting in the Las Vegas area.

Meyer lemon and kumquat, two more commonly grown citrus here, get down to about 24-25 degrees once established. In protected backyards, Meyer lemon, grapefruit and kumquat survive most of our winters. So, my guess a 15-foot sour orange will reach at least those temperatures, if not a bit lower.

This tree should start flowering in about year four to six. You still will lose fruit because of early spring freezes combined with open flowers in some landscapes depending on its exposure to early spring freezes and wind. But the tree should survive our annual fluctuating freezing temperatures for about 25 years or more.

Remember all citrus are from Asia. This means the desert soil needs to be amended at the time of planting and amendments periodically added. No citrus are xeric, so they will need about the same amount of water as regular fruit trees of a similar size.

For your information, bitter orange occasionally gets a deadly disease, but it’s usually not prevalent in non-orchard citrus areas, so you should be all right. Buy the tree smaller and protect the tree from sun damage by shading it while it gets established. Buy a tree that is shrublike.

You won’t find it locally. It is not as popular as a tree on its own. I think you will have to order it online.

Places outside of the desert Southwest don’t have to worry much about sun damage to the trunk, so it is limbed up higher into a tree. For this reason, you want to buy it grown into as much of a bush as possible. Limb it up later when it gets older and acclimated to our desert.

The best places to order it are from Arizona nurseries such as Whitfill or Greenfield if they will ship it to you. Both are in the Phoenix area.

Plant it when temperatures are cool, but spring planting is best in the case of citrus. Because of digging and availability, most nurseries sell bare-root trees in the spring. Bare-root trees need to be planted as early in the spring as possible.

Potted or container trees can be bought anytime, but planting them is always best in the spring. If it were totally freeze-tolerant, or you were sure it will not get extremely cold this winter and you can find it available, then fall planting is always best.

Q: What causes the brown tips on some strappy-leaved plants like iris or agapanthus? Should I cut it off?

A: You didn’t tell me which plant you’re concerned about because some plants are less tolerant of certain locations than others. This browning of the leaf tips is called plain old “leaf scorch.” It can be caused by many issues: bright sun, low humidity, windy locations, poor periodic soil amendments, watering too frequently or watering not often enough.

For instance, mondo grass — it is a form of Liriope muscari or grape muscari — is a small plant with strappy leaves that has lots of different common names such as border grass, monkey grass, grape hyacinth and others. It gets leaf scorch in the desert in all locations. That’s the way it looks in the desert. When in doubt, call it by its scientific name (or Latin name) and understand where it is from.

Getting back to your plant, do what the gardeners in the hotels do to indoor plants. They cut the leaf scorch off and make the ends of the leaves resemble others. This makes the plant leaves look more natural. If most of the remaining leaves are pointed, then cut them off in a point. If you end up not liking the look, remove the entire leaf by cutting it off at its base and hiding the cut.

I know I sound like a broken record but, when pruning, always sanitize the blades with at least 70 percent alcohol before starting.

Consider moving the plant to a more hospitable location. If it looks like the leaves are scorching, then move it to a shadier spot. If that doesn’t work and you remove it, then lesson learned. Consider it part of your education. Learn the name of the plant and buy something different.

Remember, plants that have showy flowers need more light than those that don’t conspicuously flower. If you planted a nonflowering plant and it was planted at the lowest level of light available, then the same plant will not work in that spot. Either that or more light needs to be made available.

Q: I have several large pine trees that have been in the ground since 2002. Due to heavy winds, one was felled, and the trunk broke. Upon inspection, it looked like root rot. Can you advise how much water these trees need in winter and summer. I want to be sure this does not happen to others.

A: Make sure the trees have water applied to a wide area, equal to about half the spread of their canopies. Tree roots follow applied water in the desert.

Pine trees are relatively deep-rooted. For this reason, apply water to them deeply. But if the soil is hard and the water is applied too rapidly, the water may start puddling and the tree can blow over easily. Watering plants in the desert indicates where you want their roots to grow.

The other problem is watering. If they are given small drinks of water frequently (think planting in lawns), they develop roots that are shallow and will not hold them upright during strong winds.

When planting pine trees, it may be a good idea to plant other smaller shrubs around its canopy. Pine tree roots will grow where the shrubs are as well and help support it. Unless you know what you are doing, it may be a bad idea to have a pine tree planted all by itself surrounded by desert soil that is not irrigated. These trees will blow over.

Place plants around the pine tree that are throughout its canopy as it grows larger. Putting irrigated shrubs around pine trees helps the pine tree roots to grow into the surrounding soil and become more firmly anchored. It is not something mystical about the surrounding plants. It is because these plants are irrigated, and they share water with the pine trees.

Q: When should you stop cutting asparagus? We’ve had a good crop in the past, but they seem to have quit harvesting too soon in prior years so want to go as long as possible. We enjoy eating them.

A: The textbook answer is six to eight weeks of cutting, and then you should let it go and rebuild its crowns beneath the soil for next year’s harvest. That information was given back when asparagus spears were thought to be marketable only if they were the diameter of your thumb. That has changed, and now we see asparagus sold much smaller in diameter than that and marketed as such.

The other answer is to continue to harvest until you see a noticeable decrease in the diameter size of the spears. When they start to get too small for harvesting (don’t just look at one spear but take an average), stop and let the roots and crowns of asparagus rebuild themselves.

Asparagus will rebuild itself better if you can provide some nutrients as the crowns are putting away storage for next year. After harvesting, apply at least an inch of rich compost or you can also use manure.

The crowns should be 6 to 10 inches deep depending on the soil, so laying manure on top of these areas should cause no problems. (Some manure is high in salts.) Planting the crowns deep makes sure the spears don’t come up too early. Make sure you water it after planting. After planting, don’t water too often because the crowns are deep. Apply water on a similar irrigation cycle as fruit trees. The roots and crowns should have water available at the same depth.

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.