I’ve been spending a LOT of time weeding this year. I like weeding—or at any rate, I find it very satisfying. Yet, there are lots of other activities that I’d rather pursue, so I am trying to understand WHY my yard is so much weedier this year. Let’s explore.
Anytime you dig in your yard, especially with heavy machinery, you expose thousands of weed seeds to the oxygen and light they need to germinate. Many of those seeds have lain dormant in the soil for years, just waiting for an opportunity like this. In my case, that happened last fall when half of my front yard and boulevard were torn up for a sewer line project.
Changes in growing conditions
When a dramatic change occurs in your yard, expect a flush of new weeds. For example, my southerly neighbor cut down his large crimson king maple about a year ago. It had deeply shaded the southern half of my back yard, to the point where very little grew there at all. But apparently seeds of sun-loving weeds had been collecting in that soil for years because we’ve had flush after flush of new weeds back there.
We’ve had great growing conditions most of the late spring and summer this year in South Minneapolis. Everything is flourishing! We’ve had plenty of rain, and it’s been warm by day and cool at night. (Until this week’s heat wave. Wow.) Weeds flourish just as much as other plants in these conditions.
So what to do about all this weed madness?
For one thing, and this is especially true if you grow native plants, you need to decide which plants are weeds. Note that deciding is different than simply figuring out. I highly recommend the book Common Backyard Weeds of the Upper Midwest by Teresa Marrone. It will help you identify weeds and understand which ones are edible (you’d be surprised how many you can eat).
If you grow natives, many will reseed themselves all over your yard, and most wildflower gardeners find this desirable. But you will need to learn how to identify seedlings of those coneflowers, Wild Columbines, and Black-Eyed Susans. Google is your friend here. If you see a plant and can’t identify it, do a google image search on what you think it might be, e.g. “Wild Columbine seedling.” You will get very skilled, very quickly at identifying certain prolific re-seeding plants, native or non-native. I’m looking at you, dill.
Getting rid of the weeds
So obviously to start with you need to just get rid of these plants that you’ve decided are weeds. I’m not into spraying chemicals on my yard but I issue one plea with those who do: when it comes to herbicides, the label is the law and you should carefully read the instructions of any herbicide before using it. One of the most critical rules is to only spray it at dawn or at dusk when there is little to no wind. Otherwise it blows over to my yard and I get VERY UPSET with you.
It’s also worth noting that even if you Roundup the heck out of your weeds, they will still come back in a few weeks. Roundup does not destroy the weed seed bank in your soil, nor does it prevent new weeds from blowing in via seed or creeping in via underground rhizomes from nearby areas once it has left your soil.
I have poured boiling water on my paver paths and found it to be pretty effective, but if you have a large paver path area you might need to boil several pots’ worth before you can get it all. It takes more than a few drops.
I’ve always hand-pulled weeds. But I heard Larry Weaner, author of the meadow manifesto Garden Revolution, speak this winter, and he made a pretty powerful case for trimming weeds to the ground rather than pulling them out. The idea is that every time you make a disturbance in the soil, you give new weed seeds a chance. This works on a micro-level when you pull weeds, as well as a macro-level when you dig up your sewer line.
So he recommends successive mowing or trimming of weeds—making sure they never get a chance to flower and continually weakening the plant until it just gives up and dies, without ever disturbing the soil and creating conditions for a new weed to grow in its place.
Preventing the weeds in the first place
An ounce of prevention in the native wildflower garden is complex, because you have some process-related and aesthetic decisions to make. The best way to prevent weeds is to have a thick growth of hardy, healthy weed-suppressing perennials (this is true of lawn grass as well). But in order to have that, you’re going to need to overcome this particular American Garden Aesthetic:
Create a sea of mulch with annuals and perennials tucked here and there, and—congratulations!—you’ve created a maintenance project for yourself. Many people, desperate to maintain this unmaintainable look, turn to plastic sheets of landscape fabric under their wood mulch, hoping they’ll suppress those weeds. (Do not talk to me about rock mulch. That’s a subject for a much longer post, some other time.)
But wood mulch over landscape fabric is also not a good long-term solution because weed seeds will land on top and start growing in the mulch as it decomposes. Furthermore, landscape fabric makes it more difficult for your short-lived but self-seeding native wildflowers (like Wild Columbine) to spread their offspring around. You’re creating conditions that do NOT favor wildflowers.
If you are creating a new garden where there was once turf, sheet mulching is a good choice that will suppress the weed seed bank.
If you are planting into bare ground, mulch with something that you know will break down relatively quickly. Two great choices are lawn clippings (my neighbors are happy to share theirs with me) or fall leaves. Plus one if the fall leaves have been mowed over and collected so that they’re chopped up.
Both of these options break down within a year, allowing your native plants to spread their offspring around, and move around among each other as they please, filling in and creating a thick, lush landscape that weeds eventually will not be able to thrive in.
I use a thick mulch of straw on my vegetable gardens. It takes two years to break down but is easy to move around when you want to harvest or plant something new.
Wood chip mulch is good on a temporary basis while plants get established, because it also breaks down over time. But be wary of cheap bagged mulch from big box stores or gas stations. I get free municipal wood chips from the city of Minneapolis. They’re not as pretty, but they work just fine.
A quick how-to on sheet mulching:
Obtain uncoated cardboard and lay it down in the contours of your new bed—look at it from close-up and from far away to make sure you’ve got your scale and shape right. Cover with at least 2-3 inches of wood chips. Wait at least 6-8 weeks or up to 6-8 months before planting. If you wait weeks, you may need to spade through cardboard and water your new plantings frequently until the cardboard breaks down. If you wait longer, it will be easier.
This is why I like to sheet mulch in the autumn. I can spend my winter researching plants. Come spring, the cardboard has disintegrated and I simply pull back a small circle of wood chips where each plant will go and dig the holes with a trowel.
The chips break down within another year or two, just as the new native plants are ready to start spreading around.
The end goal: mulch with living plants
The eventual goal here is to not need mulch at all. It’s OK to sprinkle some wood chips on a walking path, like this:
This is an area of my back yard that I unintentionally filled with two plants that were far more aggressive than I initially realized. Virginia Waterleaf and Wild Sarsparilla slowly filled this area completely in; the only parts that stay open are the little path where we walk to the garage door, and a little path by the canoe (behind the rain barrel). The rest is completely full of lush green plants, and they suppress weeds better than any mulch ever could. I spend only several minutes per year weeding this area.
Here’s a very weedy little area that also serves as a walkway around my raised strawberry bed (bricks to the left), and also provides access to this end of my vegetable garden. I often place a pot of peppers or two here, but the path has been VERY weedy despite getting walked on. Earlier this year I added a rather invasive plant—peppermint (center right)—to crowd out the weeds and provide a “trap crop” area for four-lined plant bugs. The peppermint doesn’t mind if I step on it occasionally. Eventually it will become a living mulch for this area.
In the foreground, an established perennial garden filled to the brim with a mix of natives and non-natives. It’s easy to maintain. In the background, my new shade garden, planted this year after my sewer line tragedy/opportunity. I’m trying to keep it mulched with grass clippings until the tiny, barely-visible plants have a chance to fill in. It’s required some maintenance weeding, but in a few years it will be as lush and beautiful as the nearer garden.
So there you have it. I set out to explore the world of weed management in my own garden, and I ended up writing a weeding manifesto. How has your weeding been going this summer?