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Saturday, April 20, 2019

Prune Plants Heavily When Transplanting Them

Q. I transplanted a dozen Rosemary from the planter in front of my house into pots to see if I could salvage them. I know Rosemary likes full sun, but I’m curious if they could use some shade because of the shock of transplanting?

A. Yes, you should shade plants in containers after removing them from the planter, but you should also severely cut them back. Let me explain.

Prune Transplants Hard

            General rule of thumb, when you transplant any plant from the ground to a new location, including containers, cut back the top about 1/3. In other words, reduce the amount of top growth the plant has because it loses so much of its roots during transplanting.
            I've read estimates that as much as 80% of the roots remain in the ground when moving plants to a new location.  The older the plant, the more roots remain in the ground.
            If the plant is watered with drip irrigation, the roots grow closer to the plant and transplanting is more successful. For these reasons, and my own personal experiences, when plants are more than 3 or 4 years in the ground, the chances of successfully moving it to a new location are fewer. Root pruning helps.

Plan a Year in Advance

            Transplanting plants from the ground to a new location or container is more successful if you can plan a year in advance. One year ahead of its move, cut the roots with a sharp shovel as deep as possible where you’ll be digging the following year. “Root pruning” causes roots to grow closer to the mother plant and improves the chance of transplanting.

Shade Helps

            If moving a plant into a container, put them in the shade the first growing season before moving them into intense sunlight. Remove one third of the top by eliminating entire branches rather than cutting these branches into a “butch haircut”.

Large Cactus Has Blown over. What to Do?

Q. I have a cactus I bought as a start from a little nursery in 29 Palms that grew a foot a year for the last 15 years. It finally tore out of the ground and fell over causing the ground to quake. It towered to 17' and was spectacular. The cactus had no water supply but was irrigated by water runoff from the roof.
Not this readers cactus but another cactus which is blown over because the roots have not spread out due to localized irrigation.
A. I suspect the cactus had a very small, spreading root system that finally just couldn’t support it anymore and fell over because it was top-heavy. Cacti and other desert plants have extensive, relatively shallow roots, that spread as much as eight times their height! This extensive root system provides a very efficient way of gathering sparse rainwater and provides substantial support for taller cacti.
            Non-desert plants, sometimes referred to as “mesic” trees and plants, are reported to have spreading roots as much as 2 to 3 times their height. Still quite extensive but not like desert plants. Cacti have more extensive roots that are not terribly deep for gathering sparse rainwater as quickly as possible. Desert plants convert this unexpected water into rapid growth and producing flowers. They are good at that.

Water cacti infrequently but in a large area

            So, I think it's important to periodically irrigate cacti large distances from the mother plant as they get taller. Plants get water where it’s the easiest to find it. Desert plants are opportunists. By that I mean, when water is present, they grow quickly and then shut down when water is no longer available.
            By watering these plants close to their base (e.g. rainwater from the roof) they tend to fall over as they get taller because the small size of the roots can’t support its massive top growth. Of course, I'm not mentioning how often you should water these plants. That's an entirely different topic. But when they are irrigated, water should be applied over a large area.
            I probably don't need to tell you that plant roots don't actively "seek" water, but they grow towards sources of applied water because of soil moisture. With cacti, and many of the other succulents, it doesn't take much soil moisture to get them growing in its direction.
            In my opinion, I think it's beneficial to use a hose and hose-end sprayer periodically and spray the surface of the soil around cacti to get their roots spreading outwardly and anchor them in the soil as they become larger. Of course, water should be applied at times of the year, or in intervals, that don't encourage Bermudagrass growth, a terrible scourge to landscapes.

Remove Sago Palm Brown Fronds or Not?

Q. I'm sending pictures of the Sago palm I transplanted. The top ring of fronds died after I transplanted it but remain on the plant. I left this brown ring of fronds around the crown of the plant and it looks like new growth coming from the center is okay. Should I trim off the dead fronds without disturbing the crown or just let them fall off?
Leaves yellowing and turning brown on Sago palm after transplanting
Healthy central Bud of Sago balm that will push new green fronds when it starts growing. The older fronds can be clipped off or left on. It's up to you.

A. That’s an aesthetic decision more than a plant health decision. I can't think of a reason why removal of dead fronds would affect the plant one way or another. Someone might claim possible “disease” problems that might emerge, but I don’t know of any.
            Another option is to "paint" the fronds a green color with one of the green plant paints or dyes used for lawns and make the dead brown fronds appear green and look alive or just remove them. There are several paints or dyes available on the market. Your call on that.
            Personally, I would cut them off and let the growth from the center take over as it emerges the spring and in following years. Remove the dead fronds to within about half inch or less of that center crown. The brown, dead fronds will probably stay there for several years or until they’re removed. But that's my call on your situation.

Leaves Yellowing and Burning Up

Q. What’s wrong with my plants? The leaves are all yellow and starting to burn up.
Readers plants are yellowing and looking pretty ugly because of rock mulch and some poor pruning practices.

A. I couldn’t see exactly from your pictures, but the plants appear to be either Photinia or Mock Orange. Regardless, I bet they were planted about five years ago and the soil was covered with rock. Desert landscaping without using desert plants. That leads to problems in a few years.
Yellowing of Photinia in desert soils because of rock mulch

Mock orange originally came out of Japan and Korea and the Photinia came out of non-desert areas in China. However, both plants are very adaptable to different climates and that’s a reason why they are used in many places including here. I have had several people ask me which landscape plants are desert or desert adapted and which aren’t. I will put together a list and put it on my blog.

Bottlebrush yellowing because of rock mulch

            However, non-desert plants will struggle in desert soils, so the soils need to be improved at planting and under constant improvement as these plants get older. Yes, they look good for about five years after planted in amended desert soil but when they are incorporated into desert landscaping, surrounded by rock and not maintained properly, they don’t do as well when the organics eventually disappear from the soil.

Mock orange yellowing because of rock mulch

            The cause of the yellowing is a combination of soil reverting to its desert chemistry and suffocation of plant roots. Amended desert soil but covered in rock becomes a desert soil again in three to five years. The time difference, I think, depends on how much amendment was added to the soil and what kind was used. Unless you plant desert plants in desert landscapes and cover the soil and rock mulch, many start to decline in a few years. Photinia and mock orange are two that will.

What to do? 

You can try the Band-Aid approaches and spray them with iron foliar fertilizers multiple times each year. You can apply iron chelate fertilizer, called iron EDDHA in January of each year. You can spread some sulfur soil amendment and see if you can adjust the soil alkalinity so the iron already in the soil is available to the plants. Or you can replace these yellow plants with desert plants that can tolerate desert soils, our climate and the rock mulch.
            There are several lists of desert plants used in landscaping in the desert Southwest and Las Vegas that can be found on the Internet. Consult these lists and go to your local nursery and see if you can find some that will fit your situation.

Desert Horticulture Podcast: Yellow Leaves, Black Spots, Bougainvillea, Fruit Trees

Join me today as I talk about yellow leaves on fruit trees and why it may or may not be a fertilizer issue. A friend contacted me about a black spot developing on the surface of his saguaro and if he should be concerned. How to prune bougainvillea when it does survive the winter or when it doesn't. And where to get some of the fruit trees I recommend and what time of year you should do it. Join me as I talk about these topics and more on Desert Horticulture.

Thursday, April 18, 2019

What to Do to a Saguaro with a Black Spot on the Trunk

The reader sent this picture to me after following the directions found in the Arizona publication below. He told me the outside had a black spot on the surface of the "trunk". I sent him a link to the publication and this is what he did. Just make sure you use a sanitized knife.

Q. I’m growing a saguaro cactus in my yard and it’s developed a black spot on its surface. Do I need to be concerned?

A. Yes, you should be concerned. As you know, this is not saguaro country, so our location poses some problems when growing saguaro here. At planting time, make sure the soil drains well and amend the backfill around the roots with a small amount of soil amendment. Be very careful not to damage the plant in any way when planting.

I use the publication provided by the University of Arizona on this topic and it can be found here.

            First, let’s find out if there is a problem or not related to that black spot. Take a sharp, sanitized knife and cut the black spot out of the saguaro. Look at the “flesh” inside the cactus and under the black spot you removed. If the “flesh” is green and clean, there is no problem. Leave it alone and let it heal. It will.
This was a picture sent to me by a reader several years ago and I don't remember the specific question. But looking at the brown discoloration on the trunk I would be thinking about cold damage or someone trying to wrap the saguaro during the winter to protect it.This is not the black spot that I'm talking about. I don't have a picture of that.

            But if the “flesh” under the black spot is black or brown and oozing like it’s rotting, then this could be a problem called Bacterial Necrosis of Saguaro. If this infected black spot is low on the saguaro, there may be nothing you can do except wish it well and hope for the best. But it will probably die.
            If this disease is caught early and all the infected “flesh” is removed with a sharp, sanitized knife, there is a good chance it will heal and recover.
            This disease spreads easily from infected plants by insects landing on open wounds or being careless during planting. So be very careful not to damage the plant in any way during planting.

Please make sure that any knife you use is sanitized before cutting into living, plant "flesh". 

Apply Fertilizer Once or Multiple Times to Fruit Trees?

Picture of tree sent by reader. He thought this might be a nitrogen deficiency or nutrient of some sort. But look at how green all the other growth is and how much it is growing. Its healthy but there is a problem with one shoot.

Q. I see many times where you've said fruit trees only need feeding in the spring.  However, without periodic applications of nitrogen my three-year-old peach tree leaves become yellow.  Could there something going on I should investigate?

A.  Yellowing can be from lots of different things, not just fertilizer. If enough fertilizer is applied in the Spring, you should get dark green leaves and lots of new growth. Enough for the whole year. You want lots of new growth in the spring and the fertilizer to slowly disappear from the soil. This should take about two months.
This plum tree has severe iron chlorosis. It affects the entire tree. This was corrected with three foliar sprays of iron a few days apart. It became dark green again.

            There is one reason why you might apply fertilizer frequently to plants. Extremely sandy soils. This soil would be like planting in a sand dune. I haven’t seen any of it in Las Vegas, but I have in Bullhead City, Arizona. When the tree is planted in extremely sandy soils, fertilizer is applied lightly every couple of weeks and water daily, sometimes twice a day.
This is iron chlorosis in ornamental or purple leaf plum. Notice all the leaves are not yellow because of all of the purple pigments in the leaves. It shows itself as chlorotic because it turns from a dark purple to a lighter pink. I am guessing the reason it became chlorotic is because of over watering the lawn and root rot beginning in the deeper rooted plum tree.

            Running out of fertilizer in a couple of months from a spring application gives the tree time to set up fruit production for the next year. Fertilizing the tree continuously pushes lots of new growth but may cause low fruit production. The tree sets up its fruit production for the next year any time from about late June through September. It depends on the fruit tree.
This is borer damage to peach in July. The weather is hot and so the branch where the borers are located was cut off from its water supply and turned brown. If this happened during the cooler months or in a cool climate, you might see some yellowing occurring on this branch first.

            The tree should grow about 18 inches each year when they are young and established. No more than that. Excessive growth is frequently caused by over applying fertilizers. Too much growth and it’s just is wasted since it is cut back during winter pruning. After fertilizer is applied in early spring, the tree will grow dark green leaves for the first two months and then the leaves will become a lighter shade of green as the season advances, but they shouldn’t be yellow.
Peach tree yellowing in a lawn probably because it's receiving too much water and the deeper roots are suffocating. I like it that they have cleaned the lawn grasses away from the trunk. This helps to minimize damage from line trimmers and mowers. But it would be nice if that grass were removed to about 2 feet away from the trunk rather than only 10 inches.

            If yellowing is caused from a lack of nitrogen fertilizer, the older leaves become yellow, not new leaves at the ends of branches. If yellowing is caused by a lack of a micronutrient fertilizer such as iron, yellowing appears in leaves at the ends of branches. The yellow leaves in both cases becomes worse as the season progresses unless the correct fertilizer is applied to correct it.
Leaves are still yellow and showing interventional chlorosis (leaf blade is lighter color than the veins) which means the leaves don't have enough iron in them to cause them to green up. The only way to cure this is to spray it with an iron solution multiple times a couple of days apart until the leaves become a darker green. You stop spring when the leaves have gotten the deep green color you want. Kerex was applied to this tree earlier and it still remained chlorotic.

            Yellowing leaves can be from watering too often or poor soil drainage or both. This leaf yellowing also appears at the ends of branches, like iron. Yellowing can be from planting too deeply. The tree should be planted the same depth it was in the container or grown at the nursery.
Here several trees are showing a lighter green color than the surrounding trees. I could spray the leaves of these trees multiple times with an iron solution until the greened up or I could apply an iron fertilizer to the soil just before new growth begins in the spring. A single application of an iron fertilizer in early spring is enough usually for the entire year. Leaf sprays have to be applied multiple times on fruit trees to get them to green up.

            Yellowing can because by early borer damage. Borers damage the trunk or limbs by their feeding which interrupts the flow of fertilizers, like iron, to the leaves. Because the leaves lack iron, they turn yellow.
            Investigate all these possible situations before jumping to the conclusion it’s lack of fertilizer. If you’ve applied your spring application of fertilizer and the leaves are dark green, it’s not a fertilizer problem.