Rock Dust and Venus Fly Trap

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.

Saving Chitalpa Tree With Deeply Cracked Bark

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.

Opuntia Cactus Damage and Not Growing

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 spray the pads with an alcohol spray or soap and water mixture before planting. The fungicide you are suggesting, I don't think there is a role for it unless you see some soft rotting occurring somewhere on the roots or the pads.

Fall and Winter Perfect Timing for Grub Control

            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.

Fall and Early Winter Perfect Timing for Bermudagrass Control

           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.

Late Fall Fertilization Requires Proper Timing and Plant Selection

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.

Cut Back Lantana After Leaf Drop

Q. You said trim Lantana in February.  Wouldn't it be OK to cut them back in December, or when they appear to be dormant?  

Lantana cut back in the winter by landscape company. It could be cut back more than this with no problems. See where it is growing from at the base? You could cut it back this much.

Lantana spring growth after cutting back in the winter

A.  Yes, any time after leaf drop. I give people a specific date so they can mark their calendar and get it done. Those of you more involved in your landscape should understand the principles better so you can apply them just as you are doing.

Early Leaf Drop Can Be Dry Soil or Fertilizer

Q. My young fruit tree suddenly lost its leaves. This happened after I changed to the fall watering schedule. A couple of weeks ago I had tree service fertilize all my trees and shrubs including fruit trees.  They said there is nothing in their mixture that could have caused this.

A. Trees and shrubs are normally fertilized in early spring, not in the fall. There is nothing wrong with fall fertilization but it should never be done in the fall to plants that are sensitive to freezing temperatures.

            When fertilizing in the fall, it is best to wait until all growth has stopped with only a few weeks remaining before the leaves change color. The month of November is usually a good time to do this.

            There are typically two reasons for sudden leaf drop if temperatures are still warm; soils are overly dry or improper fertilizer application. I agree with your tree company. There is nothing in their fertilizer mix that would cause leaves to drop BUT if fertilizer is applied incorrectly, or the soil is dry when it is applied, then the tree might experience unexpected rapid leaf drop.

Desert Dawn nectarine leaf drop after drought

            If the soil dries out too much, leaf drop should be gradual in the fall. Leaves wilt, they turn gray because they are drying out and they fall from the tree in about a week’ s time. If fertilizer is applied too close to the tree’s trunk or applied when the soil is dry, leaf drop would be sudden; “overnight”. Always fertilize when soils are wet and at least 2 to 3 feet from the trunk.

            Regardless, I don’t believe the tree has any long-term damage. To be sure, bend small branches from where the leaves dropped. They should bend easily without breaking. Supple branches after unexpected leaf drop in late summer or early fall is a good indicator. This means they will most likely come back.

            The worst time for unexpected leaf drop is in the spring during periods of active growth. Leaf buds for the following year have not yet been initiated. In the fall, when the tree has stopped growing but already formed leaf buds for next year, it would grow new leaves in a couple of weeks if temperatures are warm and the soil moist.

What to do?

            Irrigate the soil above the tree roots with a hose, flooding the areas where fertilizer was applied. Apply 15 to 20 gallons of water slowly to these areas. Do it again in one week. New leaves will emerge in 10 days to two weeks. Enough leaf buds will remain unopened for next spring’s growth.