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Busted: 4 gardening myths revealed

by Timber Press on June 17, 2015

in Gardening

Weeds love landscape fabric!

Weeds love landscape fabric!

From harpin to xeriscaping, How Plants Work author Linda Chalker-Scott breaks down four common gardening misconceptions.

1)  LANDSCAPE FABRIC (Geotextile, Weed Barrier)

The product
Landscape fabric is laid on top of soil to keep weeds out while letting water and oxygen in.

The supposed benefits
Because the fabric is porous, water and oxygen will pass through to the roots of desirable plants but weeds can’t poke through.

How plants respond
Unlike the claims right on the packaging, these products do not let water and oxygen through for very long. Those little holes are quickly filled with soil particles, and water puddles on top of the fabric, only slowly dripping through to the parched roots below. Dust and soil blow in along with weed seeds, and within a few months—Voila! Weeds spring up like magic. Likewise, aggressive weeds like bindweed and horsetail slip underneath and pop right through the holes and seams. I guess they didn’t read where the package claimed “permanent weed control.”

Meanwhile, your tree and shrub roots are desperately seeking water, oxygen, and nutrients. They will creep up to the soil surface, sometimes growing through and on top of the fabric. This causes the fabric to break down even faster. If you try to remove it, you damage your trees and shrubs in the process. Do yourself a favor and don’t buy this stuff!

Leaf wilt can be caused by many factors, not just lack of water.

Leaf wilt can be caused by many factors, not just lack of water.

2)  WATERING AND LEAF WILT

The product
Interpreting leaf wilt as a signal to add water.

The supposed benefits
Leaf wilt means that water levels are low in the leaf, so that must mean they are low in the soil, too.

How plants respond
While it’s true that leaf wilt is generally due to lack of water in the leaf, the underlying cause is not necessarily lack of soil water. What leaf wilt does tell you is that the roots are not doing their job in taking up sufficient water. Soil that’s too wet, too dry, too hot, too cold, compacted, or salty can injure or kill roots. Pathogens, insects, and rodents can do the same. Poor root systems—those that circle, kink, and generally tie themselves in knots—don’t take water up well. You, the gardener, realize there’s a problem when the leaves droop like steamed spinach. Root around the roots a little and try to diagnose the trouble. Don’t just turn on the hose!

A protein from the bacterium responsible for fire blight helps plants fight disease in the laboratory, but not in the garden. Image: Sebastian Stabinger

A protein from the bacterium responsible for fire blight helps plants fight disease in the laboratory, but not in the garden. Image: Sebastian Stabinger

3)  HARPIN

The product
Sold as Messenger, harpin is derived from a protein isolated from fire blight bacteria (Erwinia amylovora).

The supposed benefits
Harpin acts like a vaccination to prepare plants to fight environmental stress and disease.

How plants respond
When it enters a plant cell, harpin turns on biochemical pathways that produce anti-stress compounds. It’s a process that works great in the laboratory, but has little success with real plants in the landscape. The reason is pretty easy to understand. Remember that cell wall and those layers of waterproofing compounds on the leaf surface? It’s really difficult to force the harpin molecule through the cuticle and cell wall. If harpin can’t get into the cell, it can’t turn on the necessary biochemical pathways. This is a product that’s a good idea, but with limited practical use.

Drought-tolerant plants are often water hogs.

Drought-tolerant plants are often water hogs.

4)  XERISCAPING

The product
Using drought-tolerant species (xerophytes) for landscaping in arid climates.

The supposed benefits
Drought-tolerant species don’t use much water, so homeowners will save money on irrigation.

How plants respond
Xerophytes are fascinating plants. They survive quite nicely with little water, but they are fierce competitors for water when it’s available. In response to extra water (what we call luxury consumption), they reward gardeners with a flush of leaves or a burst of flowers. But once the water is gone, they often drop some or all of their leaves and go dormant. This is typical for plants in stressful environments. However, gardeners don’t like this and will usually water the plants again to get that aesthetically pleasing response. You can end up using as much or more water keeping xerophytic plants lush-looking than it takes for drought-intolerant species. So by all means use xerophytic species, but realize you are creating a landscape that is naturally slow growing—unless, of course, you add lots of water.

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chalkerscott_lLinda Chalker-Scott is an associate professor and extension urban horticulturist at Washington State University. She has written three other books and has published extensively in American Nurseryman, Organic Gardening, Fine Gardening, and more

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Click image for a look inside this book.

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“Loads of tips on planting, watering, fertilizers, weeds, what causes plant problems and much more. Yes, it will help you change the way you garden.Garden Design

{ 7 comments… read them below or add one }

1 Leo Chance June 21, 2015 at 5:08 am

Good advice, I have been trying to point out how counterproductive landscape fabric is for a long time. It always ends up exposed where it tears and breaks down. It ha sno purpose except to make money for the manufacturer.

2 Brian Ridder June 22, 2015 at 9:36 am

The stuff is pretty unsightly, huh? Thanks for the comment, Leo!

3 Marc Daniels June 29, 2015 at 11:53 am

About 25 years ago, I did consumer market research in Germany with organic gardeners who were very skeptical about any commercial plastic weed fabric, woven or non-woven. Easy Gardener had a new embossed micro-funnel technology in which the sunlight would reflect against the angles of the funnels, while channeling moisture into the ground. The membrane served as a liner for bark chips…. For the most part it was accepted. As long as the top dressing did not contain mulch, weeds did not penetrate.

4 Brian Ridder June 29, 2015 at 5:03 pm

Interesting. We’ll have to check that out. Thanks for the comment, Marc.

5 Guilherme Goncalves July 2, 2015 at 11:03 am

Landscape fabric can be very useful if used as part of an IPM strategy. It is much safer than pesticides, and, when used correctly, it is very efficient.

I take care of a large area in a public park, and I use landscape fabric as a TEMPORARY weed control strategy. I lay it down in small areas, cut open some spaces, plant there, and, as the plants grow I remove the landscape fabric. Think of Heliopis for example. As it spreads and colonizes, I remove chunks of the fabric. It won`t keep all weeds down, but it does slow them down. For example, Mugwort will poke through but now as much as in a place without the fabric.

I do not use fabric in my backyard. There, all the weeding I do is by hand.

6 Brian Ridder July 2, 2015 at 1:29 pm

You make a good case for the temporary use of landscape fabric, Guilherme, thanks for the comment!

7 Veronica Marks December 18, 2015 at 10:17 am

I’ve seen landscape fabric before and wondered how well it actually works. It’s interesting that they actually don’t keep weeds out for very long. I also don’t want to starve my plants of water and oxygen! I’ll be avoiding these kinds of ground covers for sure.

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