Q. I have vegetable garden. Do I have to cover with a sheet if it freezes?   A. It depends on the vegetables and the site. Vegetable gardens located in warm areas of the yard with reflected heat and very little wind are much warmer. They may not need to be covered or covered less often than those that are exposed. Vegetables growing in these locations are not as likely to freeze during the winter. Freeze damage to tomato plant Freeze damage to tomato fruit      Of course any of the warm season vegetables like tomatoes, peppers, eggplant, squash, etc. are going to freeze as soon as temperatures drop below freezing. In fact, they can suffer some damage when temperatures drop to the temperature of your refrigerator.             Some warm season vegetables like beans may freeze to the ground at the hint of a freeze while others like peas, spinach and radishes may sail through the winter with no problems. Sorry that I can’t give you a definite answer on that because there are so many variables. Bush bean collar rot due to cold soils             To be on the safe side get yourself a 1 ounce or more frost blanket and cover your growing area when temperatures are predicted to drop below freezing. Depending on the frost blanket, it can allow 50% or more of the light to reach the vegetables and it also breathes while it can raise the temperature under the blanket five or 6° F. It also keeps the wind off of the vegetables. Crop cover (frost blanket) on raised bed for improved germination during cold weather             Follow the direction and tack it down tightly so the wind doesn’t get under it. Or put some weighted objects along the perimeter of the blanket. Don’t use burlap or plastic sheeting. Spend the money, buy the 1 ounce or heavier frost blankets and they will last for three or four seasons or more. De Witt makes a good one. So does Agfabric.

Q. I heard the Israelis established a low desert apple tree. A few orchards have been established in the Phoenix area. I would like to learn more with the intent to purchase.   A. There are a couple of apples suitable for the low desert developed in Israel but the quality of the apple is typically not the best, in my opinion, unless you are a big fan of ‘Yellow (Golden) Delicious’. Both “Anna’ and “Ein Shemer’ apples were bred in Israel as a “low chill” apple for warm climates, not necessarily hot desert climates. Anna grown in Las Vegas, Nevada in the Eastern Mojave Desert             “Low chill” refers to the chilling requirement required by some fruit trees to flower and produce fruit the next growing season. A chilling requirement is a specific number of hours below a threshold temperature, usually around 45° F, so they “recognize” winter has passed.             Just because a fruit tree has a low chilling requirement does not necessarily mean it produces good fruit in a hot desert climate. Hot desert climates are not the best places for apples. It doesn’t mean necessarily that an apple tree won’t grow but may have trouble producing fruit and decent yields and the flavor, texture and keeping qualities may be inferior. Apple fruit frequently sunburn in our hot summer climate and develop thick skins and high sugars but lower acidity. These climates are more suitable for stone fruit such as apricots and peaches. Immature apple in the early stages of sunburn            Apple fruit with severe sunburn from lack of protection from late afternoon sun (West)   Hot deserts without cool nights close to harvest don’t develop a good balance of acids and sugars for flavor development. Cool nights are important for this. A 4000 foot elevation adds cooler nights which is very important for flavor development.             The orchards in Arizona that I know of such as those near Wilcox, Arizona, are at a 4000 foot elevation or higher. Compare that with Phoenix at an elevation of around 1000 feet. These higher elevations and can handle some popular apples like Granny Smith, Fuji, Fuji, Gala and Pink Lady.             Some lower chill apple varieties to try in hot desert climates include Dorsett Golden, Anna, Ein Shemer, Mutsu, Pink Lady and Sundowner. From my experience, try but proceed with caution with Fuji, Granny Smith, Gala, White Winter Pearmain, Winter Banana, Gordon, Yellow Bellflower and Pettingill. All of the apples do better with protection from late afternoon sun.

Q. I have a fruit bearing plum tree approximately 2 years old. I noticed an amber hard substance on the trunk. I think it’s borers. If it is, what can I do to save it and still be able to eat the fruit?  A. The most effective way to kill borers is to apply a systemic pesticide and let the tree distribute this pesticide everywhere inside it. There is a very popular systemic insecticide available nearly 100% effective at killing borers if they are present.             This insecticide is distributed everywhere (systemic) inside the tree and lasts for nearly 12 months. And yes, it is labeled for fruit trees that are bearing fruit as well as vegetables. This pesticide applied to food bearing crops makes me nervous for obvious reasons.             Let me present to you an idea that does not require pesticides but a little work on your part. I have observed it to be about 80% effective. This requires a sharp knife and a method to sanitize it such as alcohol, butane lighter or even Pine-Sol. Plum sap from a pruning cut in the spring Sap oozing from the trunk of a fruit tree due to overwatering             Plums are very sappy trees. Any injury to living parts of the tree cause sap to be produced. The production of sap is a defense mechanism against “intruders”. The tree does not differentiate between damage from boring insects and damage caused by pruning, invading diseases or environmental damage. Extensive damage to the trunk of plum and bark is peeling from the west side             To a plum tree, it’s all the same. It reacts by producing sap. If it is an intruding insect like a borer, sap engulfs and frequently suffocates it. If the damage by boring insects is extensive, loose bark easily lifts away from the damaged area because that area is dead.  Borer damage under the bark leaving behind “debris” in the tunnels just under the bark from eating             Damage from boring insects most first appears on the west or south facing sides of the trunk and limbs or on their upper surfaces. A tree may have damage for one or two seasons before you see parts of it suffering outwardly. On plums, sap is a good indicator something is going on.             The only way to find out if a boring insect is involved is to inspect the wood under the sap for damage. It is easiest to do this after the leaves drop in December. You can wait. It’s cold now and they are not active.             When you are ready, take a very sharp, sanitized knife and remove the sap along with the bark just under it. Look for damage to the trunk or limbs in the exposed wood. Boring insects leave debris from feeding, in tunnels, just under the bark. Borer damage removal using a sharp knife removing all the damaged bark to fresh wood             If you do not see damage to the wood under the sap, then this damage is not due to borers. Leave it alone if the limb appears otherwise healthy. If you see insect damage in the wood under the bark, cut and remove ALL bark from the damaged area with your sharp knife and let it heal on its own. If the damage is extensive and the limb is weak, remove it.             There is no pesticide you can apply to the tree that will kill the borers AND leave the fruit safe to eat in my opinion even if it’s on the label and you can use it for that purpose.

Q. Last November my next door neighbor’s African sumac trees were pruned to a trunk and branches. They were cut back so much I was sure they were being removed but was told they would leaf again. They did and are green and a lovely, smaller shape. I am planning to take the plunge with my tree but was advised to wait until February to avoid freezing damage. What should I do? A. I will get to the February pruning. There is a right way and wrong way to radically prune large trees to a much smaller size. African sumac trees will survive this kind of pruning and you can get a much smaller tree. But the resulting growth from this tree will be weakly attached to the main trunk and large branches. This results in a lot of future wind damage to the tree and will cost more money to have this repaired later.             Radical pruning that dramatically reduces the size of a tree must always be done during the winter months. Winter freezing damage to this tree does not happen very often here so I am not overly concerned about waiting until February. Not a bad idea though if the tree will look ugly until it regrows.             We are talking about African sumac now. This type of pruning will not work on all large trees. If this type of pruning had been done to most ash trees, it would’ve killed them.             The acceptable method for reducing the size of larger trees is a technique called “drop crotching”. This technique identifies the tallest limbs and removes them at a “crotch” in the tree, using a clean cut that leaves no stubs. When cutting trees in this way, the height is reduced but strong limbs remain to support the canopy and reduces future wind damage.             Basically, “drop crotching” can be done to any large tree, not just African sumac. The type of pruning you saw done to your neighbor’s trees only works on trees that sucker easily from larger limbs.             Dramatically reducing the size of trees by pruning is best left to tree care professionals, certified arborists, who have passed rigorous exams demonstrating that they understand and can practice highly specialized form of pruning correctly. They are more expensive but they know how to do it correctly.

Q. Can you please tell me if it is possible or not to use volcanic rock dust on a Venus fly trap to promote its growth? A. Rock dust is a marketing term which means a very finely ground powder from different sources that contains dozens of minerals in small quantities. It is thought that soils which are used for a very long time become depleted of some minerals that cannot be replaced with fertilizers. Recently, this term has become a hot topic among gardeners in the social media like YouTube and some gardening internet blogs.             I became interested in it because I was getting questions regarding its use. I experimented with three different kinds of rock dust and compared them for one growing season in some raised vegetable beds. All of the raised beds were composted, as they would be, normally, at the start of a growing season.             Perhaps it promotes growth in soils that do not have enough nutrients but I did not test that. I have not seen any advantages to vegetable growth when it is applied to raised beds and the soil has been composted and amended correctly.             It does not hurt anything to apply it in small quantities and it can be inexpensive insurance if you want to be sure. You don’t need much.             Venus flytrap in nature grows on very poor soils. It gets its nutrients primarily from the soil when it can get it. Alternatively, they also take nutrients from small insects that walk or fly into their trap. They evolved this way because of the poor soils. But catching insects and devouring them is an alternative to getting nutrients from the soil or leaves.              Regardless, the soil must drain well when growing these plants. Lava rock, perlite or pumice will help in that regard. They like high humidity so growing them in an enclosed terrarium will help. Adding rock dust to the soil will not hurt it. But help it? Perhaps if the soil is lacking in any of the plant nutrients found in the rock dust.             Personally, I would use liquid fertilizer sprayed on the foliage much like you would orchids. This plant would like very much compost tea applied this way. They do not like rich, wet soils.

Q. We have a 9-year-old Chitalpa tree which has deeply cracked bark. The tree is in the front yard of our south facing home and provides shade. Is there anything we can do to save it? Chitalpa. Not the readers. A. This tree easily gets sun damage, sunscald, on the trunk on the west and south sides if the trunk is fully exposed to the sun. Sunscald causes deep cracks in the trunk as the trunk dies on that side and begins drying.             The trunk is dead on this side and as the trunk dries out, it cracks. It is not dead on the north and east sides and this may be enough to keep the tree alive. It is possible for the tree to recover from this type of damage. Not the readers tree but vertical cracks developing on the trunk due to sunburn and partial trunk death on the sunny side.             Not much you can do about the damage already done. When growing this tree, it is best to leave lower limbs to help shade the trunk until it gets older. At this point, all you can do is make sure it has enough water and fertilize it in the spring to help it recover.             Fertilize once a year with something like 16-16-16 in late January or early February. This helps push new growth which shades the trunk.             If there is new growth coming from the trunk, don’t remove it. Remove it when this new growth gets larger than pencil diameter. Otherwise, leave it alone.

Q. Two out of three of our beaver tail cactus clumps have multiple dying paddles. We don’t fertilize the cactus and all three are watered the same, extreme heat, every 1.5 weeks; moderate heat, every 2-3 weeks, and nothing in winter. All receive approximately 1.5 gal. each time and all are on mounds that drain.   Freezing damage to beavertail (Opuntia) cactus A. If I were only shown your pictures with no explanation I would have come to two conclusions: freezing damage from previous winters because damage to the edges of the paddles, no soil improvement combined with watering, and poor growth due to a lack of nitrogen fertilizer. Light freezing damage to nopal (Opuntia) cactus on the edge of the pad and regrowth in the spring from nondamaged areas.             Most of the damage to the pads are environmental in nature. The condition of the pads can be improved with a change in soil amendments, watering and applying fertilizers. They like soil improvement at the time of planting. If they are watered too often they will die.             When I plant beaver tail cactus from a single pad it is during the heat of the summer, not the fall or winter months. I amend the soil with either compost or manure before planting. I use about a 50/50 mix in the soil. Planting a single pad of nopal cactus. Moisture meter used to make sure soil is not too wet for next irrigation in about three weeks.             I’m glad to hear they are planted on a mound if drainage is a problem but I usually plant them on level ground as long as the soil is amended at the time of planting. Amending the soil does two things besides providing nutrients; it holds water in the soil but at the same time improves drainage. This can be difficult to accept but this is the magic of soil amendments used in our very poor soils. Nopal cactus planted in an irrigated bed with compost applied on top of the soil. Not the best way of using compost. It is better if the compost is mixed with the soil at the time of planting.             I harvest mature pads at their “joint” or nodes making sure I do not damage the pad I am harvesting and do not leave any traces from the mother pad. The joint or node is smooth and not raggedy. Nopal pads are harvested at the “joint” or where the harvested pad is joined to the mother pad             Harvesting a pad can be done most easily by grasping the pad with newspaper and bending the pad almost to the point of splitting through the joint. Then lightly touch this joint with a very sharp, sanitized knife.             When done this way, the harvested pad separates easily and quickly from the mother pad right at the joint. If it doesn’t and the joint is “raggedy”, then trim it being careful not to cut into the harvested pad. There should be no remnant of the harvested pad remaining on the mother pad. Remove it.             Remember, this is done in the early summer, not in the fall or winter. Put the pad in the shade for three days to a week, oriented either upright or turn the pad over daily to keep it from curving. The pad will continue to grow after harvesting so keeping the pad from curving is important at planting time. If you leave the pad lying on its side for even a day it continues to grow and curves the pad making it very difficult to plant or sell.             The other option is to dip or dust the cut end of the pad in a fungicide such as a copper fungicide. The pad is planted in the amended soil upright so that the edges are oriented north to south. This gives an equal opportunity for one side of the pad to receive morning sun and the other side of the pad to receive afternoon sun. Mature harvested pad healed, dipped in copper based fungicide and ready to plant. Wont qualify for “organic” but it helps prevent pad losses after planting due to overwatering or poor soil drainage.             Once planted, water deeply every three weeks during the summer, not more often than this. To do this, put a basin around the planted pad about 2 feet in diameter to hold the irrigation water. Fill the basin with 2 to 3 inches of water and let it drain into the soil. Commercially harvested nopal pads for green vegetable     I like to harvest them much younger when they are more tender for personal use          The next irrigation in the same way is three weeks later. If you water more often than this the cactus can become so large, so quickly, there is a danger it will fall over because the roots are not large enough to support the top.             Planting and watering a single cactus pad should get the new cactus 3 feet tall in one growing season. Once the cactus is the size you desire, water less often and remove pads if it gets too tall.             Once the cactus is established, fertilize them once a year. If pads and height are desired, use a high nitrogen fertilizer. Once the cactus has the size you desire, switch to a low nitrogen fertilizer such as the kind you use for roses or growing tomatoes. From a single pad your cactus should be at least this tall in the first season if managed correctly             In addressing your questions, I would not do anything to your cactus until next March or April. At this time I would prepare a new hole, the soil amended with compost, and plant some harvested mature pads, as free from blemishes as possible, in these locations. I did not see anything that looked like a disease or insect problem. However, to be on the safe side I would

            Fall and early winter are excellent times to prevent insect problems that occur next year. I received a few reports of “worms” or grubs now feeding on the roots of plants. The most common are “white grubs” feeding on a variety of different plant roots tasty to them. White grubs removed from the soil where they feed on plant roots             These white grubs found now pupate, or change into adults, over the winter. The adults of these white grubs are sometimes referred to as “chafers” or in a much larger category of scarab beetles. Common midwestern June Beetle             The most common one too many Midwesterners is the June beetle. To desert dwellers, like myself, who have lived here a long time might think of the metallic green June beetle that attacks soft fruit. But these pests come in a variety of colors, sizes and even racing stripes! Our common metallic june beetle that attacks soft fruit             The easiest way to control these insects is to sprinkle granular insecticides that are specifically labeled for “grubs” or insects feeding on the roots of plants. Follow the label directions but normally the insecticide impregnated on the granules is washed into the soil with a light application of water after they are applied. If you can’t find granules, then use a liquid applied to the soil as a drench that protects the roots. Ten-lined june beetle that is an occasional pest in our desert             For those of you who prefer an “organic” or more natural approach then look for beneficial nematodes or bacteria that can be applied to the soil around these plants. This approach gives a “slower kill” but can be just as effective as commercial insecticides over time with an added benefit that they persist in the soil for a much longer time.             The most common plant attacked and reported by many readers is Lantana. Evidently white grubs love the roots of these plants. It is a safe bet, if these plants were struggling this past summer, the roots were probably attacked by white grubs.

           Control of Bermudagrass and other nasty weeds that resist removal by hoeing are better controlled during the fall months than any other time of the year. Just make sure that these weeds are “happy” before applying systemic weed killers. This bermudagrass has gone dormant due to a lack of enough water. It is still alive. Water it. Fertilize it with nitrogen. Mow it and then kill it when it is growing strong.               Water and even fertilize them lightly a week before applying systemic weed killers. Apply weed killers at the label rate, do not exceed it. Applying more than what is recommended on the label is not just wasteful but can work against the effectiveness of these chemicals. Common bermudagrass. Remember, chemicals like glyphosate (Roundup) kills all grasses when it is applied. Apply it carefully to only the grasses you want to kill. Fall is a great time for control.

Q. I have heard you mention applying fertilizer to trees and shrubs in the fall rather than the spring. Is now the right time to do that? A. The concept is called “late fall fertilization”. I have mentioned it before. It first came to light in the management of lawn grasses. It was found the “effects” from applied nitrogen fertilizers in late fall could be stored over the winter. In the spring, these effects would “kick in” and get the lawn off to an early start without fertilizer applied in the spring.             This concept was applied to landscape plants. The same seems to hold true. If high nitrogen fertilizers are applied late in the fall the effects from nitrogen fertilizers can be delayed until the following spring. This must be done after growth has stopped in the fall but before leaf drop or even change in leaf color. This concept can be applied fruit trees as well. Too late for fall fertilization             Outside of being a novelty, why would this be considered? Why not just apply the fertilizers in the spring? The primary reason, commercially, is labor. Frequently, springtime is a very labor-intensive time of the year for professionals. Late fall months, before pruning begins, is usually a slow time of the year. Taking a spring operation and moving it to the fall redistributes labor. Saves money for landscape companies. Maybe it is a better time for homeowners who do it themselves. Nice cocktail talk. Bragging rights. The lawn on the right was fertilized in the late fall. The one on the left was not. In Salt Lake City, Utah. Bluegrass mix.             Timing is critical. Time late fall fertilization to a time when growth has stopped or nearly stopped but before leaves have begun losing their color. Plants should no longer be growing but the leaves should still pull water from the soil to distribute the fertilizer throughout the plant for storage. Avoid late fall fertilizing on winter tender plants that are woody such as citrus, bougainvillea and Cape honeysuckle.