Site Preparation for Native Plantings
Why Prepare the Site?
The number one thing to keep in mind when it comes to site preparation is that native plants will never or rarely outcompete weeds or any other non-native vegetation. This non-native vegetation is all around us. If you look at a grassy field or along the road, chances are very few of the plants are native. The same goes for your lawn and any sunny areas of your property you may have let "go wild."
Most of the vegetation we see nowadays in fields and roadsides are exotic plants, mostly grasses, introduced from Europe primarily for the purpose of pasturing livestock and horses.
That is one of the main reasons why there are so few remnant prairie plants left.
It is very rare to see an area of remnant native vegetation on a full- or partial-sun upland site. If you do it’s probably because the soil is so poor that not even weeds can grow. Our native wetland and woodland habitats have fared a little better and a little longer because these introduced agricultural grasses don’t readily invade these habitats. However, even they are being taken over by other exotic plants such as Reed Canary Grass and European Buckthorn that were introduced later for other purposes.
All this means is that if you want to plant an area with native plants, you will most likely have to kill off any existing vegetation first. This will eliminate competition and make the establishment and growth of the native plants possible.
You could try to plant some extra hardy wildflowers in a stand of field grasses, but you'll most likely end up with a weedy looking patch with very low species diversity.
But if you do think you may actually have some native plants on site, please do everything you can to preserve them.
The How To:
There are generally four methods for eliminating existing vegetation that are commonly put forward:
1. Sod cutting and removal
2. Continuous tillage
3. Application of an herbicide
For most plantings, applying herbicide and smothering are going to be the best approaches. These disturb the soil the least and are probably the most effective at ridding the area of non-native species.
For the Application of an Herbicide, please carefully follow the directions on the bottle. We recognize that some people are not comfortable with this method but it can be an effective trade off for getting native plants into a large area. Please use caution, check your surroundings and understand the process of the product you are using.
Smothering is the preferred pesticide-free method of site preparation. It entails covering the vegetation you want to kill with some sort of light-blocking material. Since it can take a long time to kill some of the most persistent weeds, like quack-grass and thistles, you'll want to smother for most of a growing season.
Cover the area with cardboard, old carpet, black plastic sheeting, or heavy duty landscape fabric. If the area only contains lawn grass and tender weeds, covering in the spring, should mean planting can happen by fall. If the area has tough weeds and brush, you may have to leave the material on for an entire season or more.
Some sources recommend removing the cover periodically (2-3 times throughout the season), letting the weed seeds germinate, then replacing the cover. This process could help to exhaust even more of the stockpile of weed seeds that has likely built up in the soil over the years.