Soil Solarization … Update on the New Garden

 

In March, I wrote about solarizing a new planting bed in the front of my house. In that post, I described with pictures our process of scalping the lawn, watering the area, and covering it tightly with plastic (black or clear is fine; generally clear is better). I put the plastic down around mid-March and it lasted just fine through June. Occasionally a blade of grass might poke a hole through the plastic (didn’t know grass was that sharp!) but I would just readjust the plastic and put more rocks down on that area to cover the hole.

In June, I finally had time to tackle the bed. The first job was figuring out what I was going to plant. I had measured out the front yard and made a paper layout of the garden bed, to size, so I knew how many inches equaled a foot of space. I read up about native plants, pouring through resources I have, books, and checking against LadyBird Johnson Wildflower Center’s native plant database. I considered the plants that were already planted in the front yard on the other side as I hoped to create some symmetry of color. I also wanted a little bit of height, but not as tall as a tree because this bed sits immediately in front of the front door of the house. I did not want to block the sight-line of the front door from the stree/sidewalk with a tree. The area is in full-sun, so I had to choose plants that could withstand the heat.

I came up with the following plan. The plan includes:

• Lamb’s Ear
• Purple coneflower
• Silver ponyfoot
• Black-eyed susan
• Gayfeather
• Henri Duelburg Sage
• Jerusalem Sage
• Mexican Feathergrass
• Firebush
• Texas heartleaf hibiscus
• Tall Rosinweed
• Grandma’s Rose (yellow)
• Martha Gonzales Rose (red)
• Globemallow
• Yarrow (white)

On my paper version, I take care to estimate out the plant’s mature size in order to give it enough room. Thus, when you plant initially, your planting bed might look a little spare. But don’t worry, plants seem to grow so fast here in Texas that your garden will soon be lush. I was going for a color scheme, from front to back, of white, red/orange, orange, yellow, purple, white, purple. It didn’t quite work out exactly like that but good enough. The yarrow introduces white at the front, then the globemallow (orange), red roses and hibiscus, and firebush have reds. The yellow comes from Grandma’s rose, Tall Rosinweed, black-eyed susans. Purples come from Jerusalem sage and Henri Duelburg sage, gayfeather, and purple coneflower. (Note: Gayfeather was not available at time of planting.)

Once I had my plan, I decided that this time I’d hire some strong people to dig out the dead grass for me. I killed myself the last time and my husband was not too keen on doing it either. What a good decision! It took 2 men about 2 hours to completely dig out the grass and turn the soil a bit.

Here’s what the area looked like when we removed the plastic and after the dead grass had been dug up.

Dead grass revealed after plastic removed (above)

   

After dead grass dug out (above)

Soil amendments added (above)

After the hired guys dug through and rid the area of most grass, I went through and broke up big pieces of dirt and also checked for grass roots (they are so invasive!). We added a lot of compost, green sand, and corn gluten as I recall. We raked the amendments into the soil, catching more pieces of grass root. My husband installed edging along the grass side of the bed in order to reduce the invasion of grass, which is inevitable.

We had this work done on Saturday. After the bed was prepped, I went out and bought my plants and planned to plant on Sunday after the sprinklers had moistened up the soil.

Planting was super fun! I bought all 4″ pots if I could find them. The plants grow SO fast – there is no need to buy bigger plants unless you are impatient. The roses were a splurge and I did buy larger roses. Here are the pictures of the garden planted in mid-June.

Purple coneflowers and Lamb’s Ear (left, above)

Front of bed. Mexican Feathergrass, Lamb’s Ear, Yarrow (left to right, front)

Globemallow (center); roses (right center)

Symmetry in the beds at last. Getting closer to my semi-formal garden.

The last task, of course, was to put mulch around all the plants and on the bed to reduce weeds and to retain moisture. Lucky for us, Home Depot had a great sale on mulch. I also designed in a small, dry creekbed. On the other side of the sidewalk (not in picture), a gutter downspout had typically dumped water onto the driveway which flowed to the street. I added a different endpiece and now the downspout dumps water onto the sidewalk that flows into the small creekbed within the planting area. Silver ponyfoot is planted at the right corner of the sidewalk/driveway near the creekbed.

Soil Solarization – Killing More Grass (without chemicals)

Well, I implemented the newspaper and mulch method to kill grass/weeds on part of my front yard and my back yard, which I described in an earlier post. The backyard worked pretty well requiring only a little weeding here and there – mostly because squirrels buried oak acorns into the ground, and they are popping up.

The front yard has been more of a challenge. As I wrote about earlier, some grass is popping through my newspaper and mulch area in the front yard. I’m a bit disappointed with this. The method has killed the St. Augustine grass that was below it. But what seems to be growing is some bermuda grass, one of 24 most invasive plants by the City of Austin. I have decided to remove the mulch and newspaper, dig up the dead grass, till compost in the soil, then plant, then put mulch back on. This will be a chore, but I am certain I will be much happier with the planting bed. At this point, I’ve only planted trees in the beds, and I’m still having a hard time deciding on my plant choices.

I have a semi-formal plan for my front yard and the garden bed I prepared with newspaper and mulch is only HALF of the plan. So I still have another half of the yard to kill grass on. I have decided to try soil solarization on the other half. One of the speakers in our Habitat Steward training discussed this method, and I know many of you have used it.

The point of soil solarization is to get the sun to heat up the top 6″ or deeper of soil and kill all the weeds (or grass for my purposes). Contrary to what many people think, you should use clear plastic that is 1-6 mil in thickness. Some sources say 1-2 mil is better as it lets more of the sun through. In our climate right now, soil solarization is the perfect way to go since it is so hot and the sun so direct. (In cooler climates, one can use black plastic but I won’t go into that here for Texas. Use clear plastic, especially in a sunny area in the summer.) Might as well take advantage of our heat wave!

BENEFITS

Solarization during the hot summer months can increase soil temperature to levels that kill many disease causing organisms (pathogens), nematodes, and weed seeds and seedlings. It leaves no toxic residues and can be easily used on a small or large scale garden or farm. Soil solarization also speeds up the breakdown of organic material in the soil, often resulting in the added benefit of release of soluble nutrients such as nitrogen (N03^–, NH4⁺), calcium (Ca⁺⁺), magnesium (Mg⁺⁺), potassium (K⁺), and fulvic acid, making them more available to plants.

Plants often grow faster and produce both higher and better quality yields when grown in solarized soil. This can be attributed to improved disease and weed control, the increase in soluble nutrients, and relatively greater proportions of helpful soil microorganisms. (http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn74145.html)

Before you put the plastic down, the ground should be soaked with water, as wet soil conducts heat better than dry soil. Having the soil moist seems important, and you might to wet it during the process (life up and edge and spray water in) – sources indicate this might reduce the temperature for a time, but overall is important for the solarization to occur.

One of the keys to success is getting the plastic as tight as possible to the ground. So I plan to mow the current grass as low as possible in the area I want to solarize. I will also edge the area deeply so I can secure the plastic tight down the ground. You can also use bricks or rocks etc. to keep the edges down. It will be hotter if there’s less billowy air pockets inside. We do get a fair amount of wind, and you don’t want your plastic to set sail.

Then you wait 5-6 weeks. Have a few cool drinks and know that you’ll get to the gardening when it is cooler outside!

An excellent resource on soil solarization can be found from the University of California. They have further, very detailed downloadable packets of information here.

The Natural Gardener also has a short description of soil solarization. They have slightly different advice on the preferred thickness and length of time to keep the plastic on than the UC source.

I welcome comments regarding this approach – have you done it? How effective was it? Any challenges? Personally, I sure hope this works as the alternative of digging the grass out by hand is not optimal.

Photos: Killing Grass with the Newspaper Method

As a followup to my post about how to kill grass, I wanted to show some pictures of the process. I have done this twice – first in Minnesota where I lived for 7 years (and which are reflected in the pictures below) and second, here in Austin just in December, 2010. I used this method to setup some planting beds in my backyard. I have planted a few things there but have not yet finished.

Step 1: Identify the area where you want to make your planting bed. I chose this area where I had already planted a flowering crabapple tree. You can design your bed using a garden hose to see it before you destroy it!

Step 2: Layout your newspapers in 10 sheet thickness, spray with water and put 6-8″ of mulch on top. See the black hose in picture below to see how I outlined my bed before laying out newspaper.

Step 3: Wait for 1-2 months for the grass to die.

Step 4: Plant your plants. Just dig a hole through the newspaper, remove any grass if it still exists, and plant your plant. You may have to remove some of your mulch because it is so deep.

All done!

Step 5: Let it grow. Here’s what my garden looks like about 5 years after I planted it. I have since moved, but I was back in Mpls and took a picture of my beloved garden last May, 2010.

Gardens with native plants absorb much more water run-off than the grass they replace. This is good because it reduces storm run-off. Plus, I think this garden looks a million times more interesting than the former grass that was there.