Zilker Neighborhood Gardens

Commentary by a National Wildlife Steward who helps Zilker neighbors establish native plant gardens

Tag Archives: grass

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.

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Update on Killing Grass with Newspaper

A while ago, I told you about the killing grass with newspaper and mulch method. At the beginning of March, I implemented this method in my front yard where I’m beginning to layout a semi-formal garden (more on that later). I put down the newspaper, wet it, and put several inches of mulch on top. This front yard has pretty good St. Augustine grass on it. Last weekend, I had to go through and dig out a few green grass blades that were getting through but overall, the method is working. Here’s a picture of the dead grass underneath the newspaper and mulch:

Dead grass under newspaper

So in about 5-6 weeks’ time, the grass is dying. I have not yet planted anything in the beds yet but if I wanted, I would just poke a hole through the newspaper and dig out the dead grass (which is easy to remove since it is dying) and plant a plant in it. Of course, you’ll need to do some consistent “grass weeding” until all the grass is dead and none is invading the area. To help with the grass invasion, we will be edging the bed with a sort of trench in the coming weeks. I’ll show some pictures of that soon.

One issue with this method is that it does not allow you to amend your soil. If you dig out all all the grass, you could amend the soil from the beginning. But digging is so difficult with established grass. If I wanted to amend the soil, I think I might kill the grass with the newspaper method by doing this method above. When I saw the grass was pretty much dead, I’d remove the mulch (use it in another area or put it on a tarp for use again). Then you could dig out the dead grass which is much easier to remove, amend the soil with lots of compost and other good things, plant your plants, and then put some of the mulch back on top!

Land Use Transformation with Green Landscaping

There’s a story on The University of Texas’s features website that you MUST read in lieu of any new info from me (very busy week this week!). Learn how “Wildflower Center ecologists help spur land use transformation through national green landscaping initiative.” The article discusses a nationwide initiative to bring attention to green landscaping. There are pictures, some even before and after, of the landscaping creating across pilot sites in the U.S. I will highlight some of the incredibly motivating findings from their work below.

In the six-year Santa Monica study, the native garden required 62,000 gallons less water annually than its neighbor. With little lawn to maintain, yard work took a fourth as much time and cost two thirds less. And half as much yard waste came from the native yard versus the traditional lawn with its Marathon grass, azaleas and other non-native plantings.

When my husband and I moved into our house in Zilker, we thought we were happy to have irrigation – until we got the first bill! We had not paid much attention to the watering schedule set up by the former owner, and we were aghast at the 27,000 gallons used in only one month to water – grass!!! To give you a sense of the difference, right now when we are watering very little and by hand, we use about 3-4,000 gallons a month for the household. So, about 24,000 gallons of water was being used to water our very green and lush grass. The water conservation data in Texas would be much greater than that of the Santa Monica, CA, study above because of our excessive heat and need to water more deeply and/or frequently. At my house alone, I know that we’d save about 200,000 gallons of water a year. Right now, while I’m in the process of redoing our yard and we still have grass, we water occasionally to keep the grass somewhat presentable (not at all right now in the winter, of course).

The following quote from the article highlights my post from last week on killing grass with newspaper. Clearly, you can also do the method using cardboard!

Instead of using chemicals, the landscaper snuffed out the alien, invasive, plants by mowing and covering them with layers of cardboard and mulch, topped by a nutrient-rich material and new plantings.

They also discuss an urban (Washington D.C.) university which has committed to capturing rainwater through collection, raingardens, and permeable hardscape (there’s also a great picture of a permeable walkway being installed).

Native plants such as Virginia sweetspire and American beautyberry decorate rain gardens and other sunken areas that have plantings that capture stormwater. Walkways of permeable material usher rain drops into underground tanks that supply water for the landscaping and a decorative fountain.

Clearly, underground tanks might be pretty ambitious for us home and apartment dwellers, but there are plenty of less arduous ways to capture water and reuse it. I’ll share more about that, as I’m preparing to install a small raingarden soon on my property.

Happy gardening!

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!

Pictures of grass area that will be killed

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.

Picture of newspaper and mulch on top of grass

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

Picture of planting bed with mulch
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.

Planting plants in bedAll done!

Bed planted with plants

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.

Picture of garden after 5 years

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.

How to Kill Grass

If you are going to do some gardening, you might need to get rid of some grass to be able to create a nice bed for your new plants. There are several ways to do this that (a) do not use chemicals, (b) do not cost much money, and (c) do not require back-breaking work (well, maybe some – but we all need the exercise anyway).

My favorite is the newspaper method. First, you start saving your newspapers – but not the glossy pages. Design your planting bed – you can draw it out using garden hoses, flour, and/or landscape paint. Once you like your design, pick a day that is not very windy to get to work. Lay out your newspaper on your grass – about 10 sheets in thickness over the whole area of grass. Overlap the edges slightly so that no grass pokes out. I like to wet down the newspaper a bit when I have them in the right spot – especially if it is at all windy as those sheets will start flying. Once your newspaper is down, you dump about 6-8″ of mulch on top. Then you wait about 1-2 months. If you are dying to plant, just poke a hole through your mulch and newspaper and dig a hole and plant your plant. You may get a few grass stragglers coming up, but just pull any out that you see. After 2 months, almost all the grass will be gone. I used this method in MN where I used to live, and it worked like a charm. I also recently used this method in my backyard. On hearty St. Augustine, it might take a bit longer to kill the grass but it will with time. I did buy 5 cubic yards of mulch from the Natural Gardener (about $200 delivered) and had to move it back via wheelbarrow (some work), but it wasn’t that bad. Natural Gardener has a formula to figure out how much mulch you need. I just measured the beds I planned on making and did a little math. Over time, the newspaper disintegrates into the soil. Remember, you can add shredded newspaper to your compost anytime you need “browns” to balance it out. Of course, if you can coordinate your new planting bed creation with the Christmas tree mulch the City of Austin gives away in January, then you’d save some money!

Another way is to kill grass using clear plastic. However, contrary to what you think, you do not use black plastic. Instead, you use clear plastic in order to solarize the grass (essentially, that means burn it up). The plastic also needs to be somewhat thick – perhaps 6mm. The other key to solarizing the area is that you should do this in the summer when the sun is hottest and most direct. In addition, you need to keep the grass area slightly moist under the plastic. So, occasionally you need to spray some water under there. I know that you are surprised because I was surprised when one of the presenters in my training told us that clear plastic was the appropriate method. You should find a way to keep all the edges of your plastic down (logs, rocks etc.) in order to not let “cool” air within it. The experts say this approach is best, and that clear plastic + moistness creates more heat deeper into the soil under the plastic. Of course, you can use black plastic, but it will not work as quickly as the clear plastic.

The third way, which is more backbreaking, is to just cut out your sod. You could use a flat shovel and cut out your sod (if you keep enough soil on the bottom, you could use your sod in another location on your property). You could also rent a sod-cutter and use the machine to cut the sod out. I have never used these machines, but I’ve seen them used on gardening shows on TV! Neither of these approaches are easy on the back / body. If you cut your sod, you might want to use a pitchfork or twirlyfork to mix up your soil afterwards. It is always good to throw in some compost to prep your beds. Remember – always call before your dig!

Call Before You Dig is a free service that locates your underground utilities. Use this service any time you plan to excavate at your home or business. Call toll-free (800) DIG-TESS (344-8377).

The utilities will mark any underground cables/lines so you can be careful round those areas. It is also helpful to know where your sprinkler lines are, if you have irrigation, so you don’t poke your pipes and cause a leak.

The last way is to use bad, bad chemicals. I am not a fan of this, so I won’t mention it. But think: if you are intending to build a beautiful garden of wonderful natives, do you really want to put them in the ground where you just sprayed chemicals? It’s not a very “green” choice, and the NWF Habitat Stewardship aims to promote greener ways for gardening.

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