Q: If a fruit tree gets infested with borers in the main trunk and seems likely to die, can I cut off the trunk and allow the tree to grow back from this stump?
A: Yes, but it depends on the fruit tree where the new growth occurs and the kind of growth that results from damage. In my opinion, it’s worth the effort since you will know whether or not this is successful in a couple months after you cut off the trunk.
Most fruit trees are grafted. If you look at the trunk of the tree near the soil surface, you will see that the trunk is slightly crooked, perhaps 2 to 6 inches above the soil. This crooked part of the trunk is called the “dogleg.”
The dogleg is the place where the top of the tree — that gives us good fruit — was grafted to the bottom part, or rootstock, to give us good roots. This was done when the tree was very young.
New growth growing from the dogleg or below it must always be removed. But new growth, or suckers, coming from above the dogleg may be kept. But deciding which to keep depends on the type of growth.
Keep the new growth growing from above the dogleg if this new growth (suckers) is at a wide angle from the trunk. The angle or space between the trunk and sucker, where it is attached to the trunk, is called the “crotch angle.”
A wide crotch angle is important for strong future growth and fruit production. If this angle is too small, the point of attachment to the trunk is weak and will not support the weight needed in future years.
Whether to keep a sucker or not is decided only after a few weeks of new growth. It all depends on the crotch angle of this sucker. If this crotch angle is wide or strong enough, keep the sucker. In fact, keep several of these suckers if you’re lucky enough to get that many. You can decide later which one you will keep.
Growth of these suckers will be extremely rapid and strong because the roots of the old tree are providing the water and nutrients for this growth. Without the top of the tree to feed, all the water and nutrients are being fed into this new growth.
At the end of the growing season, during winter pruning, decide which sucker to keep and remove all the others. Remove the trunk above this sucker.
Cut this remaining sucker at knee height (about 28 inches) during winter pruning. This cut will force several new suckers to form below this cut in different directions the following spring. This new growth will be the foundation limbs — future scaffold limbs — of your new tree.
Peach and nectarine trees sucker from the trunk very poorly and may, in fact, die after cutting trunk. This is a risk but if you don’t see any new growth by the end of March, following your winter trunk removal, buy a replacement tree. You will lose maybe a couple of months of growth.
The best luck is from plum or pluot, apricot, apple, pear and many others. With these trees, wait until April or May to make your decision about whether to replace the tree or not since spring growth is later than peach.
Q: Should drip irrigation run during daylight hours or at night? I’m assuming there would be less water loss from evaporation if they run at night, but that makes finding bad emitters more difficult.
A: Time of day doesn’t matter if you’re using real drip emitters and not adjustable emitters that flood water on the soil surface. If there is standing water after using your drip emitters, then evaporation is a problem and it’s best if it’s done at night.
Drip irrigation is designed to slowly release water in one small area so this water enters the soil and doesn’t puddle on top. When adjustable emitters are used, the kind that can be adjusted to release more or less water, then this water may form water puddles on top of the soil.
The key to evaporation is whether there is standing water. If it is truly drip and not adjustable drip emitters which flood the area, then evaporation is minimal.
Always check first with local laws, regulations or policies regarding when it is lawful or advisable to irrigate.
Consider applying wood chips to the soil surface instead of rock to conserve water. Wood chips on the surface of the soil where water is released will slowly rot and improve the soil in only a few months. This soil improvement helps water released from drip emitters to enter the soil more quickly and reduce puddling and evaporation.
Free wood chips are available from the University Orchard in North Las Vegas or the Cooperative Extension office south of the airport. Call the master gardener help line at 702-257-5555 to get directions where to get it.
Q: Please give some tips on pruning my young sweet lime planted in 2015: when to prune, how tall to keep its growth on my limited backyard space, fertilizing and if pruning should be done every year?
A: Most information on pruning citrus will tell you to prune very little. Citrus of any type have few problems corrected by pruning. They seldom need to be pruned to improve fruit production, unlike other fruit trees.
However, they will need to be pruned to keep them smaller. Prune to reduce their size to about 60 percent of their mature size.
Pruning to reduce size but maintain production must be done every year. Prune these trees after harvesting the fruit so that it doesn’t interfere with next season’s fruit production. This is also the best time to apply fertilizer.
To control the height, identify those stems contributing to an undesirable height. These, most likely, will be almost vertical. Follow the stems along their entire length and remove them completely at the point where they become vertical.
This may be at a point deep inside the canopy. It doesn’t matter if they do. Remove them with a clean, close cut.
The tree wants to become tall and bigger. You want the tree to produce fruit but stay small. This is where you are at odds with the tree. Control the tree, don’t let it control you.
The best fruit production comes from stems not growing vertically. Consistent fruit production comes from stems closer to horizontal, no more than 45 percent above horizontal. Upright stems favor growth over fruit production.
If the width of the tree is a problem, reduce the length of these horizontal or near-horizontal stems. To do this, follow the length of the offending stem toward the inside of the tree. Remove a portion of this stem that is offensive at a juncture with another stem. Do not leave stubs.
Finally, remove any stems that are crossing or broken in the interior canopy.
Adding fertilizer to plants, particularly those high in nitrogen (the first number on the bag), should be done every year to maintain a high level of fruit production, but the amount applied should be adjusted according to the needs of the plant. If the tree is growing excessively, reduce the amount of fertilizer applied but don’t eliminate it.
If you see the beginning of undesirable growth, pull it out when you see it. If you pull it young enough, you will not need to cut it.
Pull it with your hands. Pulling is better than cutting but this technique needs frequent visits to the tree and exploring the inside of the canopy in order to see it early enough.
Q: My schedule was to fertilize my citrus plants on Presidents’ Day, but because of the drop in the temperatures, I decided to postpone. It has stayed cold. So when should I fertilize?
A: Everything has slowed down because of the temperatures. As soon as it warms up would be fine. If they need some extra help, consider foliar feeding them with a tomato-type fertilizer in three or four weeks. Don’t forget to apply iron either in the soil or combined with your foliar feeding.
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.