 So now we're ready to go. All right. So hello everyone. Thanks for joining us tonight. This is a new experience for me. I'll make a confession. I've never given a talk this way before where I can't see my audience. So we'll see how it goes. I hope you enjoyed the last couple of talks. I know we're probably all really getting excited about gardening season. I was in the grocery store yesterday and I saw that sea potatoes were out. So that's a good even though it's snowing tonight. But tonight I'm going to talk to you about controlling weeds without chemicals. And just a little bit of background on me. I am a weed scientist but I'm also a gardener. I've been gardening for about 30 years. So I'm going to talk from the perspective of both a weed scientist and try to weave in a little bit of weed biology and ecology. And I'm also going to weave in some experiences that I've had over the years. And in this picture I'm sitting in a garden that I had when I was a grad student. I gardened in a community garden. And it was kind of neat because there are people from all over the world there and I got to see a lot of unique and effective things. And I also got to see a lot of disasters that we could all learn from. So I'll be talking about both those things tonight. So weeds are always a challenge for gardeners and in particular organic gardeners contend with many weed problems because they can't use herbicides. But in general I would say that most home vegetable gardeners whether they are strictly organic or not are probably going to rely mostly on non-chemical weed management techniques. And those are the techniques that my research focuses most on and that I'm most familiar with. So I'm just going to go through a bunch of those sorts of approaches with you tonight. All right. So this is something that I saw in the community garden time and time again. First thing in the summer everyone would get out there with their tillers and they would till the soil bear and plant their seeds and it looked really beautiful and everyone was really excited about their garden that was going to grow. And then we have the weeds. People go to the lake they forget about weeding and they come back in July and this is what you see. You'll see a big bunch of weeds and you can barely even see the crop in there. And so this is kind of a disheartening circumstance and most people don't really want to spend their weekends on their hands and knees pulling weeds. They'd rather go to the lake and I have some suggestions that can help you control the weeds before they get to this point so that gardening can be more fun and not so much of a chore. But the first thing I want to talk about is the difference between perennial and annual weeds. So this is really important and this is where I'm going to bring a little bit of the biology into play. And so it's first of all it's very important to be able to identify the weeds so that you know whether they're perennials or annuals and if you're weak on your ID I would suggest getting some books. There's a lot of good online resources and I'm also really interested in helping people identify their weeds. So if you can take a good picture you could look at my email address on the NDSU plant sciences homepage and send me a few pictures and I'd be happy to try to help you identify your weeds. So the ID is key but if you know what the weed is it's good to know whether it's an annual or perennial because the approaches you're going to use to control these weeds are very different depending on their life cycle. And the reason is that annual weeds generally have long simple tap roots and can be easily killed by hoeing or hand pulling but perennial weeds on the other hand often have complex horizontal root networks and they can't be as easily removed via tillage. Oftentimes if you till them you'll break up the roots and every little piece will grow a new plant. And so you need different techniques for suppressing or getting rid of these weeds depending on whether they're annuals or perennials. Annual weeds can be readily suppressed using mulches but even the best mulches won't usually stop perennial weeds that's why you need a different approach. So we're going to talk a little bit first about perennial weeds and usually when I give this talk in person I'll ask people to go through these pictures one by one and see if they can identify them. And so on the top left what we're looking at you can you can test yourself as we go along what we're looking at is Canada thistle. This is a noxious weed it's a very nasty character to have in your garden. It can reproduce via underground roots and if you chop up those little root pieces each piece will make a new plant. Same goes moving clockwise to the top right. This is perennial south thistle. One good thing that you can do if you're not sure about what a weed is try digging it up a little bit and if you see that you have a number of shoots connected together with roots underground then that's a pretty good sign that what you're looking at is a clonal perennial plant and you'll need to start thinking about strategies to get rid of that plant that are different than annual weeds. On the bottom left we have quackgrass. This one it can make a real mess in your garden but luckily the roots are very tough and they're not easily fragmented so you can really yank on it and pull the weeds out of the ground. On the other hand on the bottom right we have probably the weed that I'm most afraid of which is field bindweed and this is another perennial plant that reproduces vegetatively it reproduces via underground roots and the roots are very easily fragmented and it's very easy to spread and so that's just an overview of some of the common clonal perennial weeds that you might see in this area. So what I've learned over the years is that with the perennial weeds prevention is really worth a pound of cure and so don't start don't plant into established perennial weeds and I know this is going to sound a little onerous but you can oftentimes dig carefully to remove these plants, roots and all. Now it depends a little bit on your soil texture. If your soil is a really heavy clay this is going to be more difficult. On the other hand if you have a lighter, loamier, sandier soil it's going to be really easy to get a garden fork and loosen those roots. Be really careful to follow the roots carefully through the soil and get every little piece of it and this is something that I have done myself on a piece that was about an acre that was heavily infested with curly dock, Canada thistle, perennial south thistle and dandelion and over a period of two years with persistent digging to remove the plants with their roots I pretty much got rid of them and once you get rid of them unless they come back in the dandelions may come back in from seed often but the other ones mostly spread from roots and so you can largely eradicate them with some patience in a small enough area. Now if you have a larger area you might need to use some other approaches smothering with a heavy mulcher weed barrier might work to some extent especially if when you see little shoots emerging you remove them immediately. Another approach that you can use is something called solarization which I'll talk about a little bit more in a second. So this is a picture of a wheelbarrow full of weeds that I removed from one of my research sites along with that garden fork and that's a really useful tool for removing those perennial weeds and so I highly encourage you to just get out there and maybe get a bunch of kids together that have some energy and just try to get rid of some of these perennial weeds physically and then the other idea is to use a solarization approach and with solarization what you're doing is laying some black plastic down on the ground for a season and you can see in this picture how they've anchored the plastic down with some bricks and stones and maybe some pieces of wood and there's a couple different options for this. You can use clear plastic or black plastic and both have their advantages and disadvantages. It turns out that clear plastic will heat the soil up hotter than black plastic especially during the hottest months of the summertime and so it with that regard clear plastic might be better but it allows light to transmit through the plastic and so black plastic while it doesn't get as hot it blocks all the light so that the plants can't photosynthesize so if it's a little bit cooler you might want to consider using black plastic. One more idea that you might consider if you have a larger area is it and some and you have some bad patches of perennial weeds is to set aside a fallow area each year and this can have a couple of different advantages especially if you plant something perennial like a perennial legume that you can mow over and over again this will help deplete perennial weeds of their carbon stores and their roots and it will also add valuable nutrients to your soil so doing something like this if you have the room will help improve your soil and get rid of the weeds so for example out at my research site i planted a mixture of timothy grass alfalfa and red clover we mow it three times a year and it's cut down on the canada thistle and perennial south thistle i would say 80 to 90 so it's quite effective if you have the ambition to do that okay now we're going to move on to talking about annual weeds unlike perennial weeds you will never get rid of annual weeds the soil is loaded with their seeds oftentimes the seeds are very long lived and persistent and so every year you can count on no matter what you do you're going to count on having annual weeds that can emerge for instance in one of my first gardens i thought that if i kept pulling this common mallow that grew in my garden prolifically and never let it go to seed but eventually i'd get rid of it and i think i pulled it religiously for about eight years and there was never any decline in the common mallow emergence and the reason is those seeds can live for probably 30 years in the soil and so with the annual weeds you're looking at needing to either suppress them or you're going to need to remove them be a tillage hoeing mowing or hand pulling and those things are all the labor intensive approaches and so i think it's better again to prevent these weeds by suppressing their emergence and one of the best ways to do that is to use cover crops or various mulches to suppress weed emergence and growth so once again i'm going to have a little quiz to see how people do on their annual weed id starting on the top left we have a very common annual weed called common lambs quarters then top right this is a winter annual called field pennycrest it's one of the first weeds to flower in the spring on the bottom left is common purslane this is a weed that is very prolific and gardens but it's very low growing and then finally on the bottom right is yellow fox tail and you may also see green fox tail which is similar so that's a little bit of id for you there so let's talk a little bit about how to suppress these annual weeds one way to do it is with a cover crop and there's a number of different approaches one way is to try planting fall planted winter rye and this is a great cover crop for a number of reasons one is that it helps to hold the nitrogen in the system instead of allowing it to be leached out nitrogen is very mobile in the soil and if you just leave your soil bare with no growing plants in the soil the winter snow is going to melt and the water will infiltrate through the soil and you'll lose all your nitrogen another thing that rye is really great for because it's a grass and it has a fibrous root system it's really good at breaking up heavy clay soils and in the meantime it will suppress weeds another idea is to use a legume like sweet clover that's really great for adding nitrogen to your system mustard family plants are really good for getting rid of soil pests a lot of mustard family plants exude glucosinolates that are toxic to soil pests so they can help with weed suppression and cutting down on soil pests and then another suggestion is annual buckwheat which grows really quickly you could plant that in the spring and one thing that's neat about buckwheat is it helps to make the soil phosphorus a little bit more available something that's kind of an unusual idea is to use weeds as a cover crop or maybe a mulch so a dense stand of annual weeds can be cut or pulled before those weeds go to seed and just laid on the surface as a mulch i did this with a garden in wisconsin once where we were gardening that's to a huge patch of giant ragweed and we would use a mower to just cut that ragweed before it went to seed and we'd plant our garden we'd pile up the ragweed plants everywhere and we would literally plant it on memorial day and come back on labor day we never did a thing we never had to pull a weed we just planted it mulched it came back on labor day and harvested and so a weed mulch is really great because it's free it'll suppress your weeds it'll break down and add nutrients to soil like any other mulch and then we can talk a little bit more about other types of mulches that you might use plastic mulch we talked about a little bit with regard to perennial weeds it'll also work fine for annual weeds you can use clear black or even some colored plastic mulches sometimes they make a red mulch or a green mulch those mulches have sometimes been shown to help certain plants like tomatoes for example some of the advantages are that plastic mulches are relatively inexpensive they do suppress most annually weeds pretty well but on the other hand they don't decompose they don't improve your soil and plastic mulches can attribute to plastic waste disposal problems and I think that's really an important thing to consider if you're going to use plastic mulches I think they work best for crops that are planted as seedlings like tomatoes peppers and squashes warm season crops where you can lay that plastic out and then just cut a little hole where you want to drop your seedling in but besides those crops I would probably always lean toward using organic mulches like hay straws leaves and things like that usually there's some cost involved except for leaves weed suppression can vary a lot another thing to consider is the carbon nitrogen ratio so every material has sort of a characteristic carbon nitrogen nitrogen ratio and you need to consider that we're just run through some of these options really quickly straw hay is a very common mulch material needs to be pretty thick it does decompose relatively quickly and it adds a lot of nutrients to the soil hay will add more nutrients than straw but something you need to watch out for is that hay and straw especially hay can contain weed seeds so we need to make sure that the hay isn't loaded with a bunch of weeds and sometimes these mulches can harbor pests like rodents and they can sometimes be a little expensive too wood chips are another option they are oftentimes free I know the landfill here gives them away for free two or three inches deep usually can do it there's some thought that as wood chips decompose they change the soil biology and shift it more to a woodland type biology with more fungal dominance as opposed to bacteria like you would see in a grassland which is what we would want more in vegetable production they can be coarse they don't decompose very easily they're hard to move aside they might interfere with vegetable seedling emergence and they also may acidify the soil they also may rob a little nitrogen from the soil as they can decompose because they have a high carbon nitrogen ratio and then you also need to be careful with some tree species like black walnut because they contain compounds that are toxic to vegetables tree leaves are another option that I've used a lot because they're free and they do work really well to suppress annual weeds they can be easily moved around imagine the garden one drawback is they tend to form really thick mats that can hold in a lot of moisture slugs really love leafs mulch so if you have a slug problem I'd probably not go with this one and again leaves have a pretty high carbon nitrogen ratio so you might need to add some extra nitrogen to make up for that newspaper and cardboard are another other materials that are very commonly used in the garden they both also have high carbon nitrogen ratios they work well to suppress weeds but they can blow around so they use usually are anchored down people will anchor them down by putting some compost on top or maybe some straw or hay so they don't work as well all by themselves but they can work well as a base layer that's really cohesive and impenetrable and then you might not need quite as much thickness of hay or straw on top of that some unusual materials are cocoa bean holes and hemp herd these are neat materials because they're finer textured and you don't need as much of the material to get good weed suppression they might be a little bit more expensive the cocoa bean holes are really beautiful and they add some nutrients to the soil the hemp herd is an unusual material that's not widely available yet I just mentioned it because I've done some research with it and it worked really great to suppress weeds but it did seem to rob some nitrogen from the plants so the next thing I'm going to try is mixing it with some compost in manure to get that nitrogen content up okay so that's enough of mulches and the last talk you heard all about starting your own seedlings and I'm going to make a pitch for that any plant that you can start from a seedling and then plant as a seedling and not a seed that gives your crop a head start on the weeds and so that's a really great idea that you can utilize not only to save some money but to get a jump on the weeds and this is just a picture of a little tiny cold frame that I made that I use at home to grow my starts. Finally the last idea is just to bypass pests that live in the soil all together and there's a couple of techniques for doing this one is called no-till or lasagna gardening and that's pictured on the left and what you do there is and you can even start a garden like this right on top of grass without even having to kill the grass and what you would do is lay down some newspaper and then maybe I think there's a layer of brown material like leaves or peat moss and then a layer of green like vegetable scraps yard waste grass clippings and then another layer of brown another layer of green and then over the top you would add some compost or some compost and manure and you just plant directly into that and that way you don't have any weeds at all if your materials that you're using your green and brown layers are weed free and that way if you have a really bad weed problem you can just bypass it all together and it also will help bypass some disease or other soil pest problems that you have in the soil. Another idea is something that a guy named Joel Karsten who's over in St. Paul, Minnesota came up with and I believe he wrote a book about this and gives workshops about it it's called straw bail gardening and what you do is you get bails of straw just really briefly I'm not going to go through it in detail because we don't have time but really briefly you just lay those bails of straw cut ends up you water them and add some fertilizer to help get them decomposing a little bit and then you put a little compost or manure on the top and plant your crops into it once again that's a really neat trick because you're just bypassing all of the weed seeds that are in the soil and over time the straw bales decompose and do help to add nutrients to the soil and so that is a basic rundown of a lot of the ideas I have for making gardening more fun by cutting down on weed problems and not spending so much time on your hands and knees pulling weeds just to recap with perennial weeds I think the best idea is to remove them via digging as much as possible or you can try suppressing them with heavy mulch plastic mulch or potentially using a fallow period with some kind of perennial crop or cover crop that you mow periodically with the annual weeds you're always going to have the annual weeds you need to suppress their emergence by covering the soil that's really key we always want that soil covered with cover crops or organic mulches or our crop plan into clean plots consider using starts instead of seeds because this will give your plants a head start on the weeds and also consider using soil free techniques like lasagna gardening or straw bale gardening and that's all I have and I'll be happy to take some questions if you have any thank you thank you we do have several questions here how about let's start with an asparagus planting that has quackgrass in it any special tips with that oh boy well this is a problem asparagus is a tricky crop because it's a perennial crop and over time it's going to become infested with perennial weeds if you have an asparagus bed that's already heavily infested with quackgrass I think that what I would probably do is start over unfortunately I I think that starting over and doing the work ahead of time to get those weeds out of there before you plant and consider maybe um submerging some kind of barrier around the edges of the plot so that weeds can't encroach in from the sides you might be able to use say pieces of plywood that you dig into the soil to create a physical barrier around your edges kind of like edging that you use in your lawn to keep the grass from spreading into the flower beds but it needs to be just a little bit deeper um I would just start over again um luckily with the quackgrass it's pretty easy to remove especially if you do it first thing in the spring after the soil thaws when it first has thawed and dried out it tends to be more friable because the action of the freezing and thawing has loosened it a little bit and that's when I would go in and try to pull all those quack roots out of there and just start over again once you've already got a bed that's totally infested with it it's going to be really hard to get those weeds out of there without seriously disturbing the asparagus too okay when we use the solarizing treatment how long do you put down the plastic and at what time of year okay that's a great question the idea with the solarization is that you pretty much want to leave it in place for a season so that you take advantage of the hottest part of the summer that's what's going to really kill the weeds and so I would lay it down as soon as you can get out there in the spring and just devote an area to that process and leave it for an entire season and then come back the next spring and see what happens I did this once with a really bad patch of Canada thistle had a garden that was pretty much solid Canada thistle and we just covered it with black I think we use black plastic for a year and it got down on it considerably something to keep in mind though is with some of those perennial weeds they can poke through that black plastic so make sure you use a heavy gauge of black plastic and if you start to see weeds poking through there you might go lay some boards on top of them or try to pull them out a little bit or just clip them off because every time you see any green poking through anywhere that means the plant is photosynthesizing sending carbon to the roots and it's perpetuating your problem right how about a lot of gardeners have questions about using grass clippings for weed control or for a mulch do you have any guidance for that that can be a good option one of the problems one of the good things about grass clippings is that they have a lot of nitrogen and so they do add a lot of nitrogen to the soil however grass does tend to decompose pretty quickly so it doesn't create a really long lasting barrier to weed emergence but if you have the clippings by all means use them but if you put chemicals on your yard you cannot use them and I would especially caution against getting any grass clippings from places that you don't know how they were treated because those residual herbicides can harm your garden plants another thing is that if you don't use the herbicides then maybe your clippings are loaded with dandelion seeds and that's something that you might not want to be introducing into your garden either but as long as you've got clean grass clippings that are free of chemical residues and also weed seeds they make a pretty good mulch that adds nitrogen but they decompose pretty quickly okay we have uh just maybe a few focused uh bullet points for a few weeds here first one is Canada thistle any special tip on Canada thistle control uh with Canada thistle I have gotten rid of it by digging it so just the roots are pretty tough they hang together pretty well just dig it out carefully and try to remove every little bit of root and it's pretty easy to eradicate that way how about wormwood any special tip with wormwood wormwood is something that I have not really dealt with very much in a garden setting I don't know as much about that one it doesn't reproduce vegetatively I don't believe so just pulling it would probably suffice and you don't have to worry about the roots as much how about bindweed any special tip on bindweed really with that one I think that you just need to be very persistent about it and you might need to learn to live with it a little bit too it's more difficult to dig up and remove the roots and get rid of it completely because the roots are really fragile and they fragment easily and every little fragment can create a new plant but I have gotten rid of it by using really heavy mulch and every time I saw a little emerging shoot I would pull it to deprive the plant of carbon how about uh this you've inspired someone to try the fall planted rye as a cover crop so how do we manage this come springtime great question yeah it's really good to catch that at about the right time in the spring I would say when the grass is about four to six inches tall I would get out there with a garden spade or shovel and just flip it over and it would be really good to wait until the soil is dried out a little bit so catch it when the soil is just right flip it over let it sit for a couple weeks and it should decompose and then you'll be able to maybe till it and plant into it or sometimes you can just plant into it just like that what uh Greta what's the difference between wood chips and shredded bark does that make a difference in your garden situation I don't think there's a huge difference they're both wood products um you know I think sometimes you have to be careful with the shredded bark because it can be dyed and I don't think you'd want to use that those dyed materials that are for flower beds and landscaping in a garden so I think of wood chips is more of a raw product that's just um chipped wood that's wood that's gone through a chipper you know and not so much the bark there bark is different than wood bark is like the outer covering of a tree right so I'm talking more about wood wood okay I think this is our last question good luck I have a chicken coop with straw as the floor cover how long does that straw need to sit so it's not too hot before putting it in my garden a really good question yeah that would be a great thing to use on the garden but you're right that you need to compost it first so I would put it in a compost heap and turn it just like compost for a season and then wait till that next year to put it on and that would be a great addition for nutrients and it might help some with weed suppression too do you have a feeling about cypress mulch I've used cypress mulch in my flower beds but I do not think that wood chips or any kind of wood product makes a very good mulch in the vegetable garden you can I think in pathways if you want to delay down a weed barrier in between say raised beds and line that with any kind of bark or wood chips that would be great it's a problem with wood chips cypress mulch any kind of wood project product those all have very high carbon nitrogen ratios they rob nitrogen from the soil which you don't want right how about corn gluten meal for weed suppression that has shown some ability to reduce emergence of annual weeds it's been tested for uses in yards a little bit another good thing about it is it does add some nitrogen but it has a relative it's relatively short lived I think it's relatively expensive and it's not something that that I can highly recommend it does have some weed suppressive ability but I don't think that the efficacy really warrants the cost or expense of it okay I think we got all the all the relevant questions answered so thank you very much that was very interesting thank you everyone all right so now thank you everybody if we had a great first session we had over 500 gardeners here tonight learning about gardening and we're going to keep it going next week we're going to stay in the garden we're going to learn about using horticulture as therapy we'll talk about growing ornamental grasses and we'll also see what's happening in the North Dakota State University display gardens and our freebie next week will be some packets of herbs that you can try in your garden so so thank you again tonight and we hope to see it next week tell your friends about it everybody's welcome to join the forums thank you everybody good night