Killing Lawn to Replace with Trees and Mulch
Question from Trinidad:
I need to kill approsimately 2,000 square feet of old lawn and weeds. Since it is a large area, is my only choice to use Round Up? Please send your suggestions. After lawn is gone, the area will be designed with trees and planters. Property is located in Escondido. Thank you so much.
Answer from Pat:
Roundup is not the only way to go. Organic methods include (1) shading out the lawn by covering with several layers of newspaper and mulch over that
or (2) soil solarization, watering the ground well and then covering it with clear plastic during warm, sunny weather. Leave in place for 4 to 6 weeks. Both systems
work best if you scalp the lawn first and bag then remove all stolens and debris.
Thank you Pat!
You could also use a weed-barrier fabric to cover the ground under the mulch instead of the newspapers. This would cost more but one benefit is theoretically one can then cut X’s and plant the shrubbery straight down through it into the ground below. By the time the shrubs have shaded the entire area, the lawn and weeds should be dead. Only problem is that any bermuda grass might sneak out the holes trying to reach light. Bermudagrass, if you have that problem, will not grow in shade, thus black plastic sheeting covered by mulch will kill bermudagrass if you leave it in place about 6 months, but in that case, water could not penetrate. If you put in drip to the shrubs, then any existing bermudagrass would likely get it and try to grow up through your X slits to the light. (If you have no bermudagrass there is no problem.) Nice thing about using sheets of newspaper as your shade layer is that it eventually it rots and earthworms love it, and also you can put the drip system in first under it. Then you could get the newspaper wet and make it tight around the trunks of your shrubs to stop the bermuda from invading. This would be hard, hands-on work down on your knees but could work.
Thank you for the extended options. The area is so large, that I will go ahead and use the black plastic. I am not rushed to plant, so I will opt for the most secure way, since there is Bermuda grass. I will stop irrigation (since the area has nothing on it but weeds), then I will leave it in place for 6 months as you suggest. I will then remove everything (by then it will be fall) and I will design and plant then. Very large oak tress will go in first, then I will design the planters. I have plenty of time. The client would like an organic option, rather than spray Round up. Thank you so much for all you do. Your monthly book on Organic Gardening is my bible. The new edition was worth the effort of letting go of the old one, which I was so fond of. I will tell you how it went in a couple of months, I might have some useful feedback.
Thank you. That’s very helpful of you. In either case, scalping and cleaning up first would really help and then later on six months from now keeping the ground shaded so any existing seeds will not germinate. If in full sun soil solarization could get rid of seeds too. Soil solarization works best during the hot months. Six months beginning now would be fine, but if you opt to use soil solarization then you must soak the area thoroughly with water first. The ground then gets really hot under the plastic and kills everything under the plastic—diseases, pests, weeds, nematodes, fungus, earthworms, whatever, down a foot or two. The newspaper and mulch system would only kill the weeds and not the beneficial fungi but not the seeds either.
Oh Dear! I understand….I don’t want to kill the beneficial fungi or earthworms. Let me talk to owner and look at the whole situation before I decide. Maybe we have to compromise…I will do my very best for the environment. If I end up with the black plastic method, I can always replenish with great soil ammendments afterwards to give back what I have killed. I will be able to bring in loads of ammendment soil, since I have machinery available and all.
Thank you so much. Will keep you posted.
I think you misunderstood me. I described 2 different organic methods to you. One was soil solarization which uses water and sun to sterilize soil. (See my book page 295-296 for explanation.) This system uses clear plastic and sun to kill weeds, nematodes, etc. It works well and the beneficials come back later. You can even add them back in. The second method is to shade out the weeds with either black plastic sheeting, or newspaper covered with mulch. You are choosing black plastic. This should shade out weeds including bermudagrass, but it will not kill all weed seeds nor beneficials. This is what you chose to do and the fact that you didn’t like what I said about soil solarization, makes it sound as if you made the correct choice for you and your client.