Leaf odor can differentiate bay laurel, Carolina cherry laurel

Q: I found your blog, Xtremehorticulture of the Desert, and am hoping you can tell me if my tree is a bay laurel. I looked at pictures of Carolina cherry trees that look similar. This tree has supports that I know need to be removed at some point. The tree was planted by my builder in February of last year.

A: It looks like bay laurel to me. Bay laurel is a Mediterranean tree and more tolerant of our desert climate than Carolina cherry laurel. Carolina cherry laurel is native to the southeastern U.S. and not tolerant of desert conditions without proper site selection, soil preparation and watering.

One easy way to tell the difference is to crush the leaves and smell the herbal (bay) aroma. Bay laurel leaves have a pungent aroma. When you crush the leaves of Carolina cherry laurel, they have an aroma of maraschino cherries rather than herbal.

The second way is to look for round glands at the base of the Carolina cherry laurel leaf where the leaf is attached to the petiole (leaf stem). These glands are characteristic of many plants in its genus (Prunus) like plums, cherry, peach, etc.

In 98 percent of the cases, the supports or stakes should be removed after one growing season. There are a few cases when the trees do not establish rapidly due to grower mismanagement or poor planting practices and need support longer than this.

Q: The bottom layer of my palm fronds turned an orange-yellow color almost overnight. Is this from too much water or not enough water?

A: Neither. The cause of these fronds turning orange or yellow is natural. These orange and yellow colors are already there, masked by the strong green color that the chlorophyll provides.

The bottom layer of fronds die naturally. As these lower fronds approach death due to old age and shade, some of the minerals in the leaves are absorbed back into the palm, first turning the lower fronds orange or yellow and eventually brown.

Sometimes these color changes occur quickly and other times more slowly. How fast depends on how hot it is.

The nitrogen, phosphorus and potassium move out of the frond first followed by magnesium, chlorine, zinc and molybdenum. Lesser mobile nutrients are left behind, which include sulfur, iron, boron, and copper.

These mineral remainers dominate the content of palm fronds. This color change is your signal to cut and remove palm fronds.

Q: We have three Japanese blueberry trees in our yard: two in the back and one in the front. All three have dead branches that snap off when you bend them. Yet there are scattered green leaves above the dead branches and far more green leaves at the bottoms of the three plants. Is it possible this is due to a lack of water? They were all planted about 4½ years ago.

A: Sounds about right. Sounds like the trees went through a dry spell and then regrew. Oftentimes when trees come back from drought they sucker from the base. If the drought lasts quite a while, the top can also die back. There are trees that sucker from the base naturally, but this tree shouldn’t unless it was stressed.

Whatever caused the stress (maybe a lack of water), suckers grew from the base of the tree. The top may have fried during the drought and then grew leaves again from leaf buds on the stem when water was reapplied.

You are aware that Japanese blueberry is not a great choice for desert climates. It is not a desert-adapted tree. It does great in coastal California but not the desert.

Make sure the trees are planted in the mildest microclimate you have (probably east or north side of your home), the soil was amended at the time of planting, water applied under the canopy 18 inches deep and the top of the soil covered with woodchips and not rock.

Locals can get free woodchips at University Orchard in North Las Vegas or the Cooperative Extension office just south of the airport. and load them in plastic bags, a car or a pickup truck. Call the master gardener helpline at 702-257-5555 Monday through Friday and see if any are available and where.

Q: I have a well-established, prolific peach tree. About this time every year, it loses some of its immature fruit and I know that is normal. However, this year it’s losing an abundance of fruit. I’m literally picking up 50-100 peaches a day. I have checked the irrigation and it seems to be fine (drippers, 15 minutes per day, twice a day).

A: I don’t like that you are applying water every day — twice a day, in fact. Is there any way that can be changed to less often? That irrigation frequency sounds like watering a lawn or vegetable garden when it’s hot and windy out. I don’t know about the amount you are applying, but you are applying water way too often.

Fruit trees should have water applied to them twice a week in May and growing in most soils. The applied water should wet the roots to a depth of about 18 inches each time it’s watered.

For fruit trees growing in the desert, I like to see a layer of woodchips on the soil surface 3 to 4 inches deep. These woodchips provide a layer that protects the roots from getting too hot, conserve water, prevent most weeds from growing and help keep the soil dark and rich.

I imagine the tree roots are growing about 2 inches deep if watering is this often. They should be growing 18 inches deep. Roots like this are cycling back and forth among too dry, too hot or too wet.

Roots can’t grow deeper because they are drowning (if you are watering a lot) or getting too hot and dry (if you aren’t watering enough). I need to know how many gallons you are applying, not the minutes, and where it’s being applied.

What to do? Cover all the soil under the tree’s canopy with 3 to 4 inches of woodchips. Apply water to the soil 12 inches from the tree trunk all the way to the edge of the canopy. This can be done by constructing a donut around the tree trunk 6 to 8 feet in diameter.

Fill the inside of this donut with a 1-inch layer of compost with woodchips on top. Fill the inside of this donut with water once a day.

At the end of August, begin watering every other day. At the end of September, water every third day. By December you should be watering once a week.

Q: How often should I water my trees and shrubs with all this heat? The weather got hot so quickly, I’m not sure when to water. I have a California pepper tree, two big palm trees and five Japanese boxwood shrubs.

A: First off, don’t violate your water purveyor’s directions. These policies are in place to coordinate community water use and lower the costs of supplying water to end users like you.

All the plants you mentioned are called “mesic” plants and require more frequent irrigations compared to “xeric” desert plants. The amount of applied water depends on the size of the plant. As plants get larger, more water is applied to a larger area (even though the water wets the same depth of soil) under the plants’ canopy.

Apply water to all the area under the plants’ canopy. This advice might be difficult to follow with larger trees like your California pepper, so apply water to at least half the area under a plant’s canopy when it is big.

Lawns, annual flowerbeds and raised beds for annual vegetables require daily, or near-daily, applications of water. Sometimes they need water twice a day. These plants should receive water that wets the soil to a depth of about 6 to 10 inches with each watering.

Shrubs and patio trees should be watered to a depth of 18 inches. Medium-sized trees around 30 feet tall should receive enough water to wet the soil to a depth of 24 inches. Large trees need the soil wet to a depth of 36 inches after an irrigation.

How to know if the applied water went deep enough? Use a straight, 4-foot-long steel rebar and push it into the soil after an irrigation. It stops going deeper where the water stops.

How to water deeper with the same number of minutes? Add more drip emitters under the plant.

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.