Q: I pulled out my old, bent crepe myrtle and bought a new one from a grower. It’s still small, but I noticed the trunk is already curving. Is this going to be a problem like the old one? Is there something I should do now, or will it straighten itself out as it grows? When I plant it, should I put the root ball in the ground at an angle so the trunk is pointing more or less straight up?
A: As soon as you plant it, it will start straightening as it grows. The light will come at it from all different directions unlike in the nursery. When you plant it, plant it as straight as possible and let the plant figure it out with new growth. You can help straighten it out with pruning. As you guessed, the plant will figure it out as it grows.
Leaves and buds are light receptors. The side that is open will fill in with new growth as long as the plant gets enough water and fertilizer to push this new growth. The top growth from leaves and buds (where it sees light which determines where and how stems develop) is what we call “positively geotropic” which means it grows upward.
Roots are negatively geotropic. which is a fancy way of saying roots grow down. Of course, root growth is encouraged by water, air and fertilizer. Top growth is encouraged mostly by light but heavily influenced by irrigating it and fertilizer to push new growth.
Q: I got two differences of opinion from a local professional and my own handyman. It concerns watering my 50-foot-tall mondell pines. One told me I am watering too much, and the other said they are not getting enough water. In the summer, they are watered seven days a week for 45 minutes. They have clusters of brown needles on the bottom and green needles at the top. I sent you some pictures. What do you think?
A: It looks like a combination of shade from these trees and not enough water applied. Each tree is affected by the neighboring tree (sunlight, wind, temperature and humidity). The trees should be no closer than about 30 feet apart, and all parts of the tree should get at least six hours of full sunlight every day.
The two primary drivers of tree water use are intense light from the sun and wind. All parts of the tree need about six hours of full (intense) sunlight every day. As trees get bigger, the shade from neighboring trees may be too much, and the lower limbs begin dying over time as the amount of shade increases.
Water-use research studies assume the trees have no shade and wind is unobstructed. How much water does yours use? I don’t know. Your tree water use should be something less than the research predicts.
Both professionals may be right. It is possible to not give them enough water even though you are watering seven days a week. It is the total amount of water that is important to trees, not what you think they need. If the trees were given little sips of surface water daily, then the total amount of water still might not be enough.
Hence, one guy said you should water twice a week (he is right) while the other guy may be forced to give them little sips of water because of the way the irrigation system was altered over time (he is also right).
What to do? Put the trees on a separate valve from everything else. This valve should be alone so you can water all the trees and large bushes separately from other plants under 3 feet tall. Increase the time and/or size of the emitters so that the water applied wets the soil to a depth of three feet each time it is applied.
Follow this watering schedule for the trees and large shrubs:
June, July, August, early and mid-September: three times each week
April, May, late September, October: two times each week
February, March, November, December: one time per week
January: every 10 to 14 days.
Adjust the number and size of the emitters so that each tree and large shrub gets the same number of minutes each time you water. Just change the days of watering each week.
Make sure water is applied to at least half the area under the canopy. Water to a depth of 3 feet for these trees each time you water. Give trees at least one day off from watering each time you water. To increase the amount of light on each tree, top to bottom, remove every other tree.
Q: Three years ago, my 25-year-old front lawn started dying. A small spot slowly grew larger over time and is now about 600 square feet in size. No matter how much fertilizer, water or new seed was planted, it died. A gas leak was discovered. A gas company representative told me that natural gas leaks will kill vegetation. I would like to replant, and I need to know how long will my front yard dirt be toxic.
A: My understanding is that natural gas is nearly entirely methane. What other contaminants are in natural gas, I don’t know. Methane is toxic to plant roots. In an underground gas leak, the methane replaces the air in the soil and kills plants in that spot or a larger one if not fixed right away. Once the roots are dead it doesn’t take long for the rest of the plant to die.
As far as the methane goes, once the leak is stopped and the air replaces the natural gas in the soil, the plants will recover. This may take a few days but no longer than a couple of weeks. My question would be other contaminants besides methane. How fast they leave the soil and how depends on the toxin.
Plant some landscape plants in the location of the leak and see how they perform. Signs of soil/plant toxicity would be first leaf drop, followed by branch dieback and finally plant death. If all is well, go ahead and finish the planting.
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.