Landscape Fabric or Deeper Rock Mulch?

 

Q. About a year ago your newspaper column had a clip about stopping annual weeds & it’s in your column in the RJ this past Saturday. I had my yard re-rocked & took your advice over the advice of the landscaper who wanted to put down a screen to stop weeds. I paid extra to have him put down a 3 inch layer of rocks. I believe last year you said 3 inches & this year 4. So, now I have a lot of weeds in all of the rock areas! What happened?

Black plastic mulch under a rock mulch and eventual unsightliness.

A. Great questions and I apologize for any misunderstanding I may have created. I don’t have any pictures to go on so I’m using my imagination. Let me tell you my thoughts about this.

Do you know that the time (and money) spent to control weeds beats out time (and money) spent to control insects or diseaseor both of these combined? It's true in agriculture, too. Weed control is timely and expensive.

Here plastic is applied under rock mulch bordering a lawn. The plastic is suffocating the roots of Italian cypress and causing it to yellow.

There is some research done on the use of thicker rock mulch versus using a landscape fabric (sometimes called a weed barrier and you call it a screen). There are a number of recommendations about what to do when laying down any type of much whether it is rock or wood. The information I see on using both is either from marketing and sales of landscape fabric or from landscaping companies promoting it. 

Landscape fabric starting to poke its head out from under rock mulch in a couple of years.

Using landscape fabric under rock or woodchip mulch looks good in the beginning.

Pro landscape fabrics

The Spruce - How to install landscape fabric

Bob Villa - Landscape Fabric 101

There are some sites that are against its use. This can be from informational sites or landscapers. Its not a "magic bullet" when it comes to controlling landscape weeds.

Con landscape fabrics

Linda Walker-Scott - The Myth of Landscape Fabric

Garden Rant - Is landscape fabric ever not horrible?

Plenty of contradictory information out there and I think the main reason for using landscape fabrics AND mulch is hope. This includes landscapers as well.

Black plastic under rock mulch and planting.

First of all, don’t ever expect total weed control from anything whether it’s by mulch, a weed fabric or both. Wherever water is applied there will be weed growth. The most common places whether there is fabric applied are not is where the drip irrigation is applied. Weed barriers do nothing to prevent bermudagrass, nutgrass and many other weeds from growing. 

Whenever installing mulch, whichever method you use, take the time to kill weeds first before using landscape fabric or not.

Spray marker (paint) is used to mark where weed control spray is applied to a landscape to reduce spraying weeds twice.

Origin of Landscape Fabrics

Weed control barriers had their start in commercial agriculture. It was then adopted to landscapes.

Here black plastic mulch is used as a temporary mulch for weed control and warming the soil early for lettuce production in Kosovo. Straw is used between the beds as a temporary mulch.

The most effective depth for rock to cover a surface is at least 2 inches deep. Nothing is gained by having the rock deeper than four inches. The problem in making a rock mulch two inches deep. evenly, is it takes precision. Higher areas are one inch deep and low spots are three inches deep. The best choice is probably three inch depth but certainly not more than four! That's a waste of money.

Best depth for rock mulch

Hence, landscape fabrics are not recommended for weed control practices in landscape planting beds. 

Non-chemical Weed Control Strategies for Nurseries and Landscapes: Part I

Reason for Justifying Landscape Fabric

A reason for applying landscape fabric is weed control. One reason for applying a mulch is weed control. They are supposed to do the same thing. Why apply two things for the same reason? 

Applying rock mulch is a permanent layer. Landscape fabrics or weed barriers are temporary weed barriers. You are applying a temporary weed control barrier under a permanent layer. Do you see the problem that will arise if the temporary barrier fails? This doesn’t make sense to me. Using two things for the same purpose? And applying something temporary under something permanent?

What to do? 

If you have it under rock or wood mulch then it is there. Nothing you can do about it but it will be a big job if it has to be removed because of unsightliness. Hopefully it is not a solid sheet of plastic but a fabric that allows air and water to plant roots. That's better but it can still be unsightly over time.

Hand weeding. Most, probably about 90% of the weeds that you see at first will be annual. They can be easily removed with some hand labor and a hoe before they flower. Another option (one that I use with rock mulch) is a fire weeder like Red Dragon and propane. Make sure your municipal ordinances allow its use first.

There are weed control chemicals you can use to control weeds around your landscape plants without hurting them. Try applying fusilade weed control products for grass control growing in non grassy landscape plants if bermudagrass is the problem. Look for fusilade (fluazifop-p-butyl) to be listed in the active ingredients on the label. In some cases the product is simply called Fusilade. (I agree its a lousy name to remember). 

Permanent Weed Control

Permanent control of weeds is impossible but you can reduce the amount of time you spend weeding. Persistence. 

1. Never let weeds flower. This makes seed. "One year weeds, seven years of weeding." (old gardening adage). Remove them before that happens.

2. Remove weeds when you first see them. It will begin starving your worst weed problems out and you will see a reduction in your efforts the first months of your efforts! If you do this, the amount of weeding time spent on your property will become less. It will never be nothing, but it will be less.

Bottle Tree, Leaf Drop and Sun Damage

Bottle trees (Brachychiton populneus and locally called Kurrajong) are Australian native trees found in the northern tropical and subtropical climates there. They are classified as “drought deciduous”. Drought deciduous just means they start dropping leaves when the soil gets dry from September through December every year. For B. populneus the swollen roots are thought to store water for dry periods.

The other common Bottle Tree, (Brachychiton rupestis), does this as well and has a trunk with more of the traditional "bottle" shape. Both grow too tall and large for most home landscapes. They can be grown in lawns if not overwatered and you make sure the soil will drain fast. If these trees are watered too often or the soil does not drain well, the roots of the trees can suffocate and the trees die.

Bottle tree with horizontal limbs and thin bark gets sun damage and can drop its leaves if the damage is severe. This tree has thin bark that should be protected from intense sunlight and vandals.

They are thought of as "desert trees" but they aren't. The intense sunlight of the desert can burn their horizontal limbs and, if enough damage is done by the sun, the leaves will drop. 

Use Florel to Eliminate Fruit You Dont Want

Q. I have a 25-year-old fruitless cherry plum tree in my backyard. It is a beautiful tree, and has grown wonderfully through the years, however it has not been fruitless.  Some years have had more fruit than others, but the last few years it has been covered, with tons of fruit, making a real mess and attracting ants and rats. I was told that there is a spray that will stop it from bearing fruit. I found something called Florel, which you apparently spray on with a hose, at the perfect time between mid and full bloom in the spring. Will this work? Will it hurt bees?

This is a cherry plum called 'Sprite' , a Myrobalan plum used for fruit production. The fruit has a very high sugar content but very sour. Some types of Myrobalan plums are used as ornamentals.

A. You did some good investigating. It must be applied when it is flowering. It is safe to use around honeybees and other pollinators that might be present during the flowering time. 

For any of these "fruit eliminator sprays" it is important that the flowers are open so the spray can reach inside the open flowers and cause the ovary to abort. 

This is a fruit eliminator product, Florel, that can be used as a spray to eliminate fruit and seed of plants. The spray will not hurt bees.

Yes, Florel will work. It is best to spray when the flowers are starting to open (20% of the flowers are open) and repeat the spray when the first flowers that open are shedding their petals (80% of the flowers are open). Flowering can take two to three weeks for all of the flowers finish. The first flowers to open are those in the warmest parts of the tree (usually south, west and tops of trees) and the last to open are on the north side and those in the shade. Follow the label directions for mixing the spray with water. It won’t get all the fruit 100% but most of it. 

It is sometimes called flowering plum and it is a fruit tree. It has been selected as an ornamental because of its beauty. In the fruit tree industry it is sometimes used as a rootstock for fruiting plums and peaches and called Myrobalan plum or just plain old Myro. The fruit has wonderful flavor, very tart but full of sugar and makes a wonderful jam or jelly. 

Choosing the Right Vegetable Varieties are Important and Other Tidbits

Q. Can you also guide regarding quality of seeds and plants and recommendation for places where to get them from? Any guidance how I can improve my crop for next season?

A. Use tried and true vegetable varieties that have performed well in desert locations in the past. Make sure your vegetable seed and transplants are in good shape at the outset. Avoid purchasing seed from open locations unprotected from the elements. Dont buy transplants that appear sickly or have a problem. You are not a plant "rescuer" when it comes to problem plants. They wont perform very well. Usually the east side of walls or buildings in full sun give the best protection from late afternoon damage from sun and heat.

I get emails from newcomers to vegetable growing in the desert that try vegetable varieties with marketing claims of "amazing results" from newer varieties. Introduce newer untested varieties in small numbers and notice which do well. 

Some suggested varieties to start with include:

Vegetable Varieties

Asparagus - UC 151

Beets - Detroit Dark Red

Bush Beans - Contender

Broccoli - Packman

Cantalope - Hales Best

Carrots - Chantenay

Cauliflower - Snowball

Cumber - Straight Eight

Eggplant - Thai Long Purple

Garlic - California Early

Hot Pepper - Jalapeno

Kale - Russian Red

Lettuce - Red Sail

Onion - Yellow Granex

Peas - Knight, Cascadia

Sweet Corn - Sweet Rhythm

Sweet Pepper - Red Beauty

Potato - Red Pontiac

Radish - Cherry Belle, French Breakfast

Spinach - Melody

Tomato - Sweet 100, Roma

Watermelon - Bush Sugar Baby

Zucchini - Black Beauty

Windbreaks

Desert climates can be finicky. High and sometimes erratic temperatures can be a problem along with wind and low humidity. Probably the most overlooked climate variable that will improve production and vegetable quality the fastest is controlling the wind. 

Did you know the best production occurs just downwind of a windbreak? They slow wind speed down considerably to a distance of about five times its height. 

Four foot tall chain link fence with PVC slats work well if installed downwind of the growing area's prevailing wind and doesn't require much maintenance or any water! 

Windbreaks made of chainlink and PVC slats slow the wind enough to qualify as a nonliving and waterless windbreak in desert climates.

Grow in Containers

Growing vegetables in containers makes it easier when there is a problem.

Five gallon containers and larger give the plants enough soil volume to hold water in the soil for at least one day during the summer. When you want to increase your growing area try containers first. They are best located on the east side of a wall or building and the container shaded from the hot sun by the raised bed, other plants, or double potted. 

No crop rotation is necessary. Just use the soil from the container for a different crop or cropping season and reuse the soil somewhere else and clean the container, if you use it again, when it gets "worn out", full of diseases like Verticillium or nematodes.

Conks Can Tell You Disease Severity

 Q. A friend has a beautiful, large, old (and productive) fig tree on a property she owns in an older neighborhood. She just observed for the first time large conks. Is there anything that can be done to save the old guy? She loves the tree and is pretty devastated, and is willing to invest to save it if possible. She would definitely have you out to consult if that could be productive. Thank you, and I have been loving your blog for years!

Conks, or bracket fungi, can be diagnostic on trees as to which disease is present and how aggressive it might be.

A. Nice pictures. My presence there wont help her or the tree I think. It is possible this "rotting disease" was brought to your tree on dirty equipment. Your decision to remove the tree is probably necessary at some time. When, I am not sure. If the tree develops weaknesses that could lead to damage or other safety issues, it is time for pruning or removal.

The conks are because of some internal rotting. The color, shape and size of the conks may be an indicator of what disease it has and how aggressive it is. To my knowledge, there is no armillaria root rot locally. To me it looks more like oyster mushroom type of internal wood decay.  Presence of conks low on the tree can mean the rotting is in the roots or crown of the tree. In this case they seem to be higher on the trunk. Try identifying which disease it is by the conk.

Figs regrow very easily from new suckers coming from the base if it has to be cut down. The internal rot CAN be an indicator of a problem and how serious it is. If you an invite an arborist to look at it, of course they will recommend removal. If the tree looks otherwise healthy, then I would knock them off if not wanted and watch the tree for safety weaknesses. It would be a loss to lose fruit but it could be fruiting again in a fairly short time after cutting back.

Make sure any pruning is done using sanitized equipment. Eventually, most likely, the tree will have to be removed. How soon you have to do that depends on how aggressive the disease is. (think cancer, some are more aggressive than others). Maybe removal as soon as a few months to a few years.