Rock Mulches Not Bad But Present Problems for Wrong Plants

Rose growing in rock mulch.

Q. I have moved into a house that is about 3 years old with a wide variety of plants.  I have read your articles against rock mulch but I don't know which of my plants can tolerate the rock mulch that is already there and which ones I should pull the rock away and use wood mulch.

            I come from Northern Utah and do not have a clue how to handle these types of plants and all this rock.

A. I am not against rock mulch but it should not be used for everything and not all plants should be planted into rock mulch.  My personal philosophy on desert landscapes focuses on using appropriate mulches for plants which can tolerate those mulches. 

            Generally speaking, those plants which originate from arid or desert environments can generally handle rock mulches.  Those plants which do not originate from arid or desert climates probably should not be planted in rock mulch.  There are always exceptions which never help when you are trying to make rules.

Photinia growing in rock mulch.

            The problem is that we intermingle desert plants with non-desert plants and then we use rock mulch around everything.  Those plants which can tolerate the rock mulch end up, over time, to do all right. 

            Those plants which are not true desert plants tend to decline and fail over time.  Plants such as bottle brush, photinia, Carolina cherry laurel, Japanese blueberry, butterfly iris, mock orange, and others usually begin to decline in 4 to 5 years after they are planted as soil amendments used at planting are depleted. 

            If you want to learn how to handle nondesert plants in rock mulches please visit my blog and search this topic.

Bottlebrush growing in rock mulch.

            The other reason for decline would be improper watering.  Make sure you get your irrigation intervals and the amount that you apply each time to be adequate for the plants.  Improper watering will cause plants to look terrible as well.

I Want to Plant a Necta Zee Nectarine. Will it do well here?

Q. I want to plant a necta-zee nectarine tree. will it do okay in Las Vegas? I looked on your fruit tree list and it shows its under review.

A. You are right it is under review. It is expected to do very well but to date it is only about three years old so it is very new for us. I like to see about three years to five years of production before I determine how it will do in southern Nevada. It is a Zaiger Genetics release I would expect the fruit will be good to high quality. Watch for thrips damage to the fruit (scarring) in the future if you plan to go ahead with it.

Necta Zee Nectarine

Preventing Weeds From Growing on Top of My Weed Barrier

Q. Weeds that infested an area of my yard - there is a screen like barrier just under the top soil. My question is what can I do to prevent this in the future without killing the shrubs in this area and what is the best method to eliminate the weeds that do emerge. I pulled and dug these and don’t want to have to do that again in the future.

Weed barrier or geotextile under nursery containers to
prevent weeds from growing

A. I am assuming the screen like barrier may be a geotextile used to prevent weeds that might germinate and grow up underneath and through it. These are frequently laid on the soil surface with a 2 to 4 inch surface mulch applied on top of it. The surface mulch helps to shade the barrier and prevent the germination of weed seeds beneath the barrier. We do not use sheet plastic for this purpose. That is a huge no-no which is another topic in itself.

Weeds such as bermudagrass and nutgrass can grow through the barrier and the mulch but it can be very effective in preventing other weeds. If bermudagrass and nutgrass weeds are close to a source of water such as a drip emitter or a leaky hose they will have no difficulty growing through the barrier and through the mulch.

Weed barrier down. Lets air and water through to the soil.

The other problem with textile barriers covered in mulch is that windblown dirt is trapped by the rock mulch and falls on top of the textile barrier. Over time, this windblown dirt accumulates and forms a soil layer on top of the textile barrier in amongst the rocks. Weed seeds then blow over the rock mulch or might be carried by birds where they fall between the rocks and onto the soil on top of the barrier.

If there is rain or a source of water, weeds will flourish and the textile barrier appears to fail. The barrier has not really failed. The accumulation of windblown dirt on top of the barrier is a major culprit. Weed seeds below the barrier are still prevented from penetrating the barrier and making it to sunlight.

Geotextile barrier

There are three things which you can do to help prevent weeds from getting established. The first is to make sure your sources of water are limited to only where the plants are growing. If you have water that is spraying onto the rock mulch or puddling into open areas from other sources than you are going to have problems. It is imperative to make sure water is contained in the area where plants are growing.

Secondly, it is best that mulches are deep. A 4 inch layer of mulch is much more effective at controlling weeds than a 2 inch layer. Coarse mulches are more ineffective at controlling weeds than fine mulches. By a coarse mulch I mean rocks that are at least 1 inch in diameter.

          Thirdly is the point you are probably not going to like and that is staying on top of weed growth. We have an old saying as gardeners that basically says one year of weeds leads to seven years of weeding. This just means that if you fail to control weeds in your garden area and let them go to seed then the seeds released by these weeds will lead to seven years of weeding.

It is so very important to stay on top of your weeds and get them removed before they form flowers. There are several types of garden hoes that are very effective. For bare soil or very fine mulch I like the diamond hoe. For larger mulch pointed hoes or even a shovel works well. If the weeds are relatively large, spraying the area with water from a hose and hand pulling weeds about 15 minutes later is very effective as well.

Black plastic when laid under rock starts to poke through
in a couple of years. Very ugly. Black plastic is a
temporary mulch and rock is a permanent mulch.

          To aid the gardener chemical companies have developed weed killers that can kill seeds as they are germinating or kill the plants after they have grown from seeds. Many of them are very effective however you are applying and unnatural chemical which is potentially, and in varying degrees, dangerous to other plants, animals and our environment.

          Check with your local ordinances but there are devices which use fire to control weeds. These frequently operate off of LP gas with some sort of torch. These are also potentially very dangerous and should be used with extreme caution.

          In a nutshell, there is no magic bullet except to make sure water goes where you needed to go, increase the depth of your mulch layer and stay on top of your weeds and do not let them go to seed.

Which is Better? Miracle Gro or Compost?

Q. Compost or Miracle Gro? Which is better?

A. No question that good quality compost is usually the best choice. Problem is finding a good quality compost and using it appropriately. Good quality composts are expensive.

            There are potential problems with compost. These include unwanted salts that can come with the compost, its potential problem with food safety issues like E. coli and other microorganisms that accompany the use of manures, the development of some insect problems such as fungus gnats and grubs and potential weed problems if the compost was not handled properly.

Yellowish brown leachate (liquid) from the compost.
A compost tea full of lots of stuff.

            High quality agricultural fertilizers can be big help in our landscapes. They can be applied to the soil and usually to the foliage as well. They can supplement a good fertilizer program whether you use compost or not. I will talk more about this on my blog.

 

fecal matter safety compost -

Trees Growing But Lacking Leaves and Not Full

Crepe myrtle lacking leaves

Q. I am one of your long-time readers and fans. I am attaching pictures of four different trees from our backyard in Queensridge (basically Summerlin) that seem to be challenged.  In each case, the tree is definitely alive, but simply lacks enough leaves – or so it seems to us.  All of the trees have received plenty of organic matter, fertilizer (possibly not enough, fish and iron chelate is what they get), water, and all are mulched in with organic mulch (compost under-layer and wood chips on top).  The backyard faces North and West and, as you can see, is quite open as it is surrounded by a golf course.  Why are there so many naked branches, weak-looking leaves, and not enough leaves?  Thank you for your help. 

A. Thank you for the great pictures and breaking them into two emails. That helped quite a bit. Here are some comments on what I saw.

First general comments. The plants are actually doing quite well, maybe even a bit too well. There is plenty of new growth which is what you want but because they are so “happy” they are growing very quickly and thus you are getting big spaces between leaves and buds. This results in an “open” appearance.

Persimmon tree with open appearance

Many of your plants, now that they are getting lots of nutrients, water and in a great growing condition are now growing as fast as they can. This will result in larger plants that will start to flower or fruit further and further from the ground as they get closer to their mature size. Plants do this naturally because in nature they are always competing for sunlight and other resources that keep them alive.

How do slow them down? We focus on two things: reduce those “goodies” they are getting that encourage a lot of growth (water, fertilizer) and (this next part is harder to realize a bit) get the plant to reduce its own growth in each of its growing branches by increasing the total number of branches it has to support. This then causes the “goodies” that encourages growth to be divided up among many more growing points and slows it down. It’s like having an income of $50,000 a year and having to support three children or 20 children; your resources are divided up many more times  so each “child” gets less.

Generally speaking, reduce “goodies” by reducing your watering frequency (how many times you water per week if possible) and cut your fertilizer application in half (but not to the point where it is starving or gets leaf scorch) and (increase your children) prune. The type of pruning you will mostly do this winter will be what I call “heading cuts” rather “thinning cuts”. Heading cuts increase the total number of shoots in a tree while thinning cuts typically do not. If you want to see the difference, please visit my Youtube video on this subject

http://www.youtube.com/watch?v=yKDSzCfvqe0

Now your individual trees, you must decide what you want for the ultimate height on these trees. If you want them to be large (such as flowering trees for beauty, shade or screening) then let them go and don’t do much pruning. If you want trees to be smaller and more compact (fruiting and harvest for instance) then you will cut them back pretty hard and take away from them their luxurious growth. You will prune these trees twice each year; once in the winter and again (taking away new fast luxurious growth) in April (summer pruning).

Magnolia with open canopy.

Crepe myrtle. I would assume you want a larger tree, perhaps with multiple trunks (3 to 5) coming from the ground. Don’t reduce the height. Let it go. Pruning will focus on removing dead, twiggy growth (it has lots of these due to flowering) and use thinning cuts to eliminate branches growing too close together, one branch growing on top of another, branches crossing each other, etc.).You can reduce the height by making thinning cuts and removing the tallest limbs and branches back to a “crotch”. I would not do much of this until it gets closer to the height you want it to get. You will fertilize in January with an all-purpose soil applied fertilizer such as 16-16-16 or even a rose fertilizer. You will see benefits from adding iron chelate to the soil in January and foliar applied fertilizers such as Miracle Gro about two or three weeks after the leaves emerge in the spring.

Magnolia. This is another tree you could elect to let it grow. Having a multiple trunked tree will help to keep it smaller. You realize that this tree is not a terribly good choice for our climate so you will spend more effort and money on this tree than many others. It will need the mulch which you are doing. This will give it some soil improvement near the soil surface as it decomposes. It will require a fertilizer application in January to push new, healthy growth. It will also benefit from an iron chelate. It will not most likely need a foliar fertilizer but it will not hurt it if you chose to apply it in February or March. Your choice but it might do better if it is kept smaller than the mature height it will try to reach. Perhaps if you can keep it in the 25 to 30 ft. range it will be easier to keep healthy. Perhaps saucer or star magnolia might work better in the future. Not as pretty but still pretty. There is a southern magnolia called Little Gem that is smaller.

Persimmon. Cut this tree back hard if you want your fruit closer to the ground. Your tree is too lanky. Cut back into older wood about half way in where it is too long in late January or early February. Don’t be afraid to do this. It will handle the hard cuts. Fruit is produced on current season wood so it will flower and fruit from new growth.

Young Apricot Leaves Drying Up and Liquid Oozing

Q. I planted a Blenheim Apricot in March.   At first it did not seem to take but within four weeks it began showing growth whereas all the other fruit trees took almost immediately.  Its been doing fine until just recently when I noticed some of the leaves on the main truck were drying up.   I check the moister level regularly.   Looking closer at the graft there seems to be some liquid oozing out.   Enclosed are some photos of the liquid, drying leaves, and tips of higher leaves.   Any thoughts on what I’m up against.   Rootstock is Citation Hybrid if that helps.

All my other fruit trees planted in the same general area are doing just great.

Iron chlorosis, inter veinal chlorosis, or yellowing
between the veins typical of new growth when iron
chlorosis is present

A. Some great shots and I would like to post them on my blog. Your photos tell a nice story I dont get to tell very often. But first lets look at the obvious and the is the discoloration of the leaves.

The yellowing between the veins is called "interveinal chlorosis". Chlorosis just means "yellowing" so it is yellowing between the veins. The most common reason for this in our alkaline soils is nutritional and frequently it is a lack of iron. Other nutrient deficiences that can cause similar types of chlorosis can include manganese and zinc deficiencies. I would guess this is an iron problem.

The picture of the sap at the place where the rootstock (in this case Citation) meets what we call the scion (in this case yours is Blenheim apricot) we see some damage. It is very close to the bud union or dogleg (where the two meet).

Bud union or dogleg. Where the Blenheim apricot was
budded or "grafted" on to Citation rootstock and sap

The damage may have started at the time of planting and is most likely from sun damage or sunburn. This area should have been painted with whitewash or any diluted white latex paint. Dilute 1:1 with water. Or you can put anything in front of that area that would give it some shade until the tree puts on some canopy and shades itself. You can use wooden shingles, cardboard, anything to cast a shade on the trunk.


Usually, if the trunk gets sunburn then it is highly likely it will also draw borers to the damage and you will get borer damage there. It is very likely this is what you are seeing. YOu can find out easily by bending the canopy of the tree over. If the trunk breaks, it will break at the borer damage and you will most likely see them there. If it does not break when you bend it, it may just be sunburn. If the sunburn is not extensive, it is posssible it could heal itself but rather unlikely. You may have lost the tree.

Interestingly, this dunburn and damage at the dogleg can also lead to the chlorosis or yellowing of the leaves as well. The sunburn damage can interrupt the flow of nutrients including iron up the tree and the interruption may be enough to limit the supply of available iron and lead toward iron chlorosis. However, some iron chelate sprays on the leaves a few times, along with a teaspoon of Ivory liquid per gallon of spray, may be enough to green the leaves up. I would guess 4 to 6 applications made in the wee hours of the morning when it is cool.

Next time whitewash the trunk at the time of planting or provide some shade on the trunk until the canopy gives enough shade to protect itself.

Snake Squash Growing in Mesquite Tree Not Fruiting

Q. This is the second year I planted Snake squash. As you can see by the attached picture they are very healthy and happy growing up my Mesquite tree. Last year I tried growing them in my garden and had the same problem, beautiful plants and no fruit. The blossoms appear, open then shrivel and fall off. What am I doing wrong?

A. I think you are always going to have problems with any plant that produces vegetables from flowers when it is growing in such low light levels with so much shade. Vegetables that you grow for their leaves do not require very high levels of light but vegetables grown for something they produce from their flowers usually requires much higher light levels.

If flowers do appear, try to discern the difference between male and female flowers. Like most squash, male flowers come first followed by female flowers. The female flowers need to be pollinated either by hand or by insects. If bees are few and far between then this may be a problem. Also they have a tough time setting fruit at high temperatures. All or any of these might be a problem for your plant.

I would recommend that if you want a vegetable that you consider enriching the soil and try to orient the plant so it gets a minimum of six hours of full sunlight. The of course  you want to fertilize it so that it can handle this type of production.