Older Agave Yellowing and Not Looking Healthy

Q. My agave is 10 years old and just isn’t looking healthy. I’m afraid of losing it and the surrounding plants. Can’t figure out if it’s too much or too little water. Your expertise would be appreciated.

Not a whole lot of information but I am guessing it's a watering issue. Agaves are usually from the desert Southwest. But it could be agave weevil that damaged the plant earlier in the year.

A. Most problems with agaves are from boring into the trunk and roots by the agave weevil and less to do with water. Eventually the immature forms of this insect tunnel into the base and trunk of susceptible plants. Look for them.

Agave weevils give birth through their eggs to destructive smaller grubs about 3/8 inch long. They infest the trunk and roots of agave and a few yucca. Look for their damage on older plants later in the year.

This is one of the many types of American agaves showing collapse of the leaves due to probably agave weevil.

All agaves should have a systemic insecticide applied by spray or soil drench in the spring, no later than March or early April. With spray insecticides it’s important to spray the lower leaves and the surrounding soil at this time. With soil drench insecticides it’s important to apply it to the soil immediately around the plant at the appropriate time. American agave, in particular, is very susceptible to this pest. Be sure the appropriate insecticide is used by reading the label.

Example of a liquid garden systemic insecticide that gives at least a couple of months control of insects (picture taken from Amazon)

            The agave weevil lays its eggs in susceptible agaves and some yucca when temperatures begin warming in the spring. These eggs are laid by the agave weevil inside the lower leaves, close to the trunk, around that time. A single application of a systemic insecticide is needed around that time. I don’t know of any proven organic methods that control this insect.

            If you are still concerned about watering and drainage, make sure that these plants are not watered daily. All perennial plants need the soil to drain away from their roots. Some plants like agave and cacti should never be planted at the bottom of a ridge. Tops are usually okay but not bottoms. Too much water accumulates in those low spots for agave. Other plants may need a continuous moist soils not most agaves and other plants that originate from the desert Southwest.

Star Jasmine Needs Sun and Watered Like a Shrub

Q. I am hoping you can tell me what is wrong with my "star jasmine". These plants are approximately twenty years old. The wall they are growing on is north facing. I have pulled the rock mulch away from the base. I mix in compost to each plant every spring when I fertilize. Could it be the irrigation is too close to the trunk?

Star jasmine is from the area of Japan. The great deserts of Japan...not!!! It is not a xeric plant and so it can get yellow, iron chlorosis, in rock. Plant it with compost in the soil and build up the organic content.

A. Without looking at the pictures I was expecting them to be yellow. That’s usually what happens to star jasmine in rock landscapes. Your addition of compost to the soil is keeping them green and healthy.

Bare wooden stems can sometimes happen when it is in poor health or covered with shady growth on top.

Perhaps Watering too Often

Bare stems on older growth can be a natural occurrence. I don’t think it is in your case. It is possible if the water applied is too close to the stems AND it is being applied too often then you can end up with bare stems. It is best if the water is applied at 12 to 18 inches from the trunk (stems, base) of the vine.

Water, when it hits the soil, spreads out. In soils that are very sandy then this distance might be 12 inches from where it is applied. If the soil has a small amount of clay in it then the spread is about 18 inches from where it is applied. In soil with lots of clay (most of the soils in Las Vegas do not have that much clay) then water can spread out from where it was applied from 4 to 6 feet. A happy medium is 12 to 18 inches from the stems or trunk.

Be careful of applying water too often. It can keep the soil wet too long. This can result in leaf drop followed by bare stems. It is always best on plants that have deeper roots (like your jasmine vine) to apply water less often. Vines like star jasmine are deeper-rooted, like medium sized shrubs. Water should wet the soil 12 to 18 inches deep each time is applied. Water your vines like they are medium sized shrubs.

What to Do?

What can you do with bare stems? Cut them back no closer than three or four inches and they will send out “suckers” and those suckers will fill in open spaces if the vine is alive. You may have to cut alot of stems back and start over if it is bad.

Bamboo Can Be Cut Back to Repair Winter Damage

Q. I have bamboo that was damaged last winter as you can see from my pictures. New growth is emerging from them but they are still yellow and brown. Should I fertilize them or give them iron?

New Tomato Seedling Transplants Not Growing

Q. I started seedlings in a greenhouse and transplanted them into my raised beds. but they are not growing at all. It's been 2 weeks, and a couple have died but the rest have not even continued growing.

Ash Trees Do Not Normally Need Applied Iron

Q. Should I give my ash trees the same iron treatment as fruit trees?

Sago Palm All Stressed Out

Q. I have four sago palms and two are turning yellow. The two which look best were bought from a local nursery and the two which don’t were bought from a building mass marketer, They are all planted in rock mulch and watered on drip. They each get about 15 gallons each a week. They are now pushing new growth. I screened the soil they were going into when planting them and put in a lot of peat moss to amend it. They get sun all day long. I tried some local supplements but they don’t seem to be helping.

Readers sago palm or cycad

A. On your cycads, or sago palms, it is stress. Looks like the yellowing is from high light combined with high temperature stress. The rocks are not helping since it makes the area hotter from radiated heat.

Put some shade over it but the damage is done and those fronds cannot repair themselves. You have to rely on new growth to cover the damaged growth. So it will look bad until that happens. That is my best shot at it.

 They will not do well with rock mulch. They don’t do well if the soil doesn’t drain easily either. They really want to have rich, organic soils, mixed with their roots, to do well. Even though they are somewhat tolerant of dry soils, they are not drought tolerant.

The worst exposures for sago palm will be hot south or west facing exposures near heat reflecting walls with rock mulch at their base. The best exposures are east or even north exposures with lots of indirect light with wood mulch at their base and plenty of air movement.

The best soils have been amended richly with compost and the soil covered in wood mulch (not bark mulch) that decomposes with time. Be careful of watering too often since they will get root rot if the roots stay wet for too long. In that type of environment they can handle full sun but still not the rock mulch.

Yellowing of Meyer Lemon Tree Leaves Hard to Correct

Q. We went and talked to nursery folks a couple times about this tree. First we got the water cycle correct, then iron was suggested which we did as directed. Then a soil amendment was suggested. Online I read possibly the tree suffers from a magnesium issue. I thought these photos would give a better picture. We did as directed and the tree is not responding in fact it is getting worse. I am wondering if it is because of where it was planted which is a confined root growing area. Any insight would be appreciated.



Readers lemon tree with yellowing leaves

A. By looking at the leaves I have to assume this is a Meyer Lemon (which is, by the way not technically a lemon but an unknown hybrid found in a Chinese back yard by USDA researcher D. Meyer in the early 20th century).

Your pictures are all pretty good with the exception of not showing a critical view of the trunk where it is just out of the soil. Just for future reference always look at and show this interface of the trunk and soil. W/o that view I have to only guess that the rootstock/trunk union is well out of the soil and we can eliminate that issue. And, a shot of the soil might show how the plant is getting watered. I have to assume drippers and I would guess they are in the same locations as when the plant was planted.



Closer look at readers yellowing leaves

The leaves show two distinctive symptoms that often occur in concert: 1. There is some salt burn and 2. The common symptom that comes with salt issues is the magnesium deficiency. Just FYI Iron deficiency only occurs on the new leaves.

For the salinity (salt) issue we usually look first at the watering and with watering comes knowing if the water can even be applied uniformly all around the edge of the canopy, sometimes called the 'drip line'.

Citrus are botanically a shrub with shallow and wide spreading roots that are tough to grow to maturity with drippers unless they are closely spaced in a wide band around the canopy's edge. There is one picture showing the plant is right next to a step wall with no water being applied in that zone of the root system.

Clear look at the yellowing or chlorosis problem
on readers citrus

I would not worry too much about adding any supplements and see if you can begin to manage a watering system of application that would give a long deep soaking water application out near the drip line. The 'soaker' hoses could be laid out on the ground out near the drip line and let it run for hours and hours to try and leach out the excess salts that may have accumulated over time with the drip system. Drip systems are fine but, due to their limited water output salts can begin to accumulate thus impacting citrus' sensitivity to salts.

Give it a long deep watering about once every few weeks from now on all during the growing season (May through October)  to supplement the regular water to leach out the salts that inevitably are deposited with the limited volume of drip systems . .This leaching watering is also the great time to add fertilizer and get it into the soil evenly all around the active roots near the drip line.

-Terry Mikel

Orange Tree Leaves Losing Green Color (Yellowing) With Green Veins

Q. I have 9 orange trees on my property and pamper them like my “kids”.  One of them (perhaps two) is losing the green color in the leaves although the veins are staying green in color.  I would like to send you a couple of leaves for your inspection as I have tried to trouble shoot the problem using the computer and pictures. A local nursery disagrees with my request for manganese sulfate to resolve the problem. Would you send me an address so that I can send a few leaves for your inspection and suggestions?

A. A picture of the leaves will work just as well as sending me a sample. I will be out of the country and so samples will probably not reach me.

            Nine times out of 10 a yellowing leaf with green veins, particularly if it is the newer growth at the ends of the branches, is iron chlorosis and not typically manganese or zinc. The manganese sulfate would be used for a manganese deficiency or you could use a manganese chelate.

            You can sometimes take an iron solution with a few drops of Ivory liquid detergent and, making sure the iron solution is slightly acidic with a little bit of vinegar, dip the leaves in the solution for a few minutes. You should see a color change in the leaves in about 24 hours or less.

            Otherwise you can take some liquid iron chelate with a little bit of detergent like Ivory liquid and spray the leaves three or four times over a period of a couple of days. This will also turn them a darker green if it is iron.

            If it is something other than iron, it won't do anything. Then go ahead and try your manganese application.

            If this color change occurred during the winter it is possible it could be cold damage. This appears more like a bronzing of the leaves rather than yellowing. I hope this helps.