If you are planting or seeding wildflowers into a confined or small garden with limited space please read Wildflowers in Small Spaces. The information below is tailored for larger wildflower plantings and naturalization projects that will be going into a site currently occupied by perennial weeds, invasive grasses or something similar. We strongly suggest preparing your site by following one or more of the methods described below in an effort to provide the best conditions possible and aid the wildflowers in establishing themselves and prospering in a timely manner. However, it is not always possible or necessary to provide the optimum growing conditions so understanding what you should be trying to achieve and why will help you decide how much site preparation is right for your particular project. Large scale projects that take a lot of time and money deserve the attention to detail that is described below. Plugs have an advantage over Seed as they will be less affected by competition from germinating weed seed present in the soil. If you only want to plant a few wildflower plugs in a small area you may choose to spend less time in preparing the site.
Site preparation is probably the most important part of establishing a wildflower garden and taking the time to prepare the site properly will save you time and money later on. The first step in site preparation would be to remove the existing vegetation. Established weeds and grasses will have a leg up on the new wildflowers in the competition for light, moisture and nutrients. A large site which has well established perennial weeds and grasses may take a whole summer to clear. Remove the vegetation by smothering, herbicide, cultivation, or a combination of these methods.
Smothering is a simple, chemical free way to remove vegetation but it requires a full growing season to be effective. Use plastic, carpet, plywood, a thick layer of mulch or anything that completely blocks the sunlight to cover the entire site. Black plastic will speed the process slightly by adding more heat to the equation.
Cultivation is another chemical free way to prepare the sight, but again a site with well-established perennial weeds and grasses may need an entire growing season of this treatment. Pitchforks, rototillers, sod-cutters, plows, disk or harrow can be used depending on the size of your site. When cultivating you should begin in the spring and consistently redo the site about every 10 to 14 days to a depth of 4-5”, this cycle will allow perennial weeds to recover and grass rhizomes to re-sprout. Continue on this cycle until all existing established vegetation is dead.
Herbicide can sometimes be the only way to deal with aggressive established unwanted material. Use herbicides as part of a bigger plan to address maintenance issues and not as an on-going solution to unwanted plant material.
Even with all that you have done to clear your site weed seeds are still present in the soil and every time you work it you will bring them to the surface. These seeds will germinate quickly providing unwanted aggressive competition for light, space, moisture and nutrients. One method suggests allowing weeds to germinate and grow to approximate 2-3” then applying herbicide, followed 10 days later by a shallow tilling not more than 1” deep will clear the surface soil of weeds without bringing more seeds to the surface. A chemical free method suggests that tilling the soil 1 week after the first good rain of the season to a depth of one inch will kill the seeds after they have germinated but before they have sprouted. These techniques work best in the spring on sites prepared the previous season by one or more of the above methods. Planting or seeding out immediately after tilling will give your seedlings a good head start on the competition.
When creating a garden or a wildflower planting site preparation is half the job, and spending the time doing thorough job at this point will provide you with better results. Existing plant material, whether it be weeds or grasses will compete with wildflower seedlings for resources and space, delaying and/or impeding their ability to grow and establish themselves. Once established your wildflowers will provide you with years of low maintenance pleasure by bringing color, fragrance and wildlife into your spaces and therefore enhancing your surroundings on multiple levels. It is well worth the effort.