Weed ID. [Tim Miller]

Transcription

1 Weed ID [Tim Miller] Hi, my name is Tim Miller, I'm the Extension weed scientist here at WSU Extension Mount Vernon Research and Extension Center. My talk today is going to be involved in a little bit of weed identification, so we're going to be talking about some various weeds that are fairly common in the state of Washington. So I'm going to show you some of the plants that we have out here in Mount Vernon, but I think you'll find most of the plants that I'm going to be talking about are also found quite extensively on the east side of the mountains as well. So, what we are going to do is focus in on some of these particular species and then I'm going to say a little bit about them as we go along. Now, speaking of thistles, let's talk about thistles. I've got a couple thistles here that I want to show you. This is the first one, this is called bull thistle, this is a biennial thistle, this is a second year plant. Biennials live for two years and the first year you just have a rosette of leaves and then the second year you get this plant that starts to grow up and starts getting ready to flower. If you look at the plant itself you'll be able to see some pretty intense hairs on this plant. First of all it's very spiny, I'm definitely making little blood donations here as we're going along, but notice the fuzz on these leaves, very short hairs but also very cobwebby hairs in certain places, you can also see that it has what is called the arachnoid hairs, that's the cobwebby hairs that are often found at the base of the leaves as you peel them back from the main stalk. Now this is a second year plant, this is one that is not growing in a site that we would consider a good weed site. Now if you had a good weed site, you could expect the plants to look more like this. This is a second year bull thistle plant that I am not going to be picking up. You can see the size of this thing. This was found in a well-fertilized area, well-watered and growing very happily where it was at. We still have the same type of hairs on these leaves though, you'll notice we have some very bristly types of hairs on the leaf itself, and then when we go again inside here you can see some of these cobwebby hairs starting to show up here in the leaf axils. This plant will grow sometimes five feet tall, sometimes six feet tall and about the same wide, you can expect to see big thistle heads along this plant, so it's a biennial plant that will basically be dead after it flowers the second year. Okay, the second thistle I want to show you is the perennial thistle. We had the biennial, the bull thistle, this one is the perennial Canada thistle. It's closely related and in a lot of ways looks a lot the same. It tends to be one of these plants that grows out in groups so you're going to see that it's very spiny but you re also going to see that it grows in clusters so you are going to see multiple stems growing from the same stock. In fact if you look down here at this root you see a more or less horizontal root growing out of the ground at about six inches deep and then we get multiple stems come up off of that. So these are roots that would be growing in the soil much like this and you can see this root would be growing in various places, you'd get shoots out from it. So you get one big plant with multiple stems even though it looks like we maybe have two hundred plants out there, we really only have two hundred stems off the same plant, that's what makes this plant so hard to control. It is extremely spiny, that is one way that you can identify it. Generally thin leaves, not nearly as fuzzy as the bull thistle is Page 1 of 7

2 and this is a plant that will come back year after year after year. Normally the flowerheads on Canada thistle are not very spiny so you could actually pinch those and it would be fine, it wouldn't hurt you, whereas the bull thistle you would not do that, if you pinched it you would let go in a hurry. So these are the Canada thistle plants, we'll find it often times growing in lawns and places like that, obviously it wouldn't be this tall in a lawn, they'd be smaller rosette stages that just get mowed off and mowed off and mowed off. The next plant I want to visit with you about is an annual. This is an annual plant called shepherd s purse. Shepherd s purse is extremely common, it's one of the most common mustard family plants that is out in the state of Washington. If you look at the plant this is a very healthy specimen, often times you're not going to find them this tall, but I want to draw your attention in to these fruits. If you can see those fruits you notice they have a bit of a triangular shape to it, it's an unusual shape for all of our weed plants. If you look at it closely you'll see that it kind of resembles a shepherd s purse, like a marble bag, and if we were to imagine it further we could say that this stem is the drawstring of this that kind of pulls that purse shut. The plant is a mustard as I mentioned and this is a pretty classic look for a mustard plant, sometimes these seed pods are long and slender and sometimes they're short and fat, and this would be a short and fat one. The plants generally have nice white flowers although they are very very small flowers, you won't pick out too much in the way of petals or anything else on there but they tend to be maybe a quarter of an inch wide when they're in flower. And then you also get that the stem will continue to elongate all through the flowering period so that at the base of the stem you will have some seed pods that are almost ripe and at the tip of the stem you'll have the entire flower cluster still intact and it will continue to grow taller and taller and taller, flowering the whole time and dropping seed the whole time. Now in western Washington this plant is a winter annual, again it will germinate in the fall and it will usually survive and grow as you can tell this is springtime that we're filming this and this plant has been growing all winter long and it's probably about three feet tall. It will continue to grow as long as the conditions are right and as long as it has moisture. Our next plant that I want to talk to you about is another winter annual for us here in western Washington, and more of a spring annual in eastern Washington. This is common chickweed. Common chickweed is a plant that is very spindly, as you can tell it kind of all grows together in a big mass, but what you can do to identify this plant is, first of all look for the opposite leaves, notice these leaves are directly opposite each other and usually within the axils of those leaves you find a flower that then gives rise to a little seed pod. These seed pods turn into kind of an egg shape cluster of seeds that have about fifty seeds inside there, so you can tell that a plant this size would be making an awful lot of seed. If each one of those flowers will end up making fifty seeds you can do the math and see that you're going to have a lot of potential for new weed growth. The plant likes to grow in shade, it will grow in sun but it doesn't like to be desiccated out, it likes moist conditions, consequently we see a lot of this in western Washington, not quite so much in eastern Washington, in northeastern Washington we get a bit of it, but usually if it's in a dryer climate you're going to find it growing in shade almost exclusively or in a place that gets irrigated. So look for this plant to be basically in any garden kind of area. The flowers are white on this, I don't see any open flowers Page 2 of 7

3 right now unfortunately or else I'd show you some, but the flowers are kind of a bright white, about a quarter of an inch across. Let's talk about another perennial weed, now many of you in various parts of the state know this plant, this is called horsetail or field horsetail. The plant itself is a native, this is one of the few native weeds that we actually have in the state, in fact anywhere, most weeds are from somewhere else. Now this plant has a perennial root system that is incredibly deep; two thirds of the plant is underground in the root system. Usually you'll see these nice black roots and oftentimes you see these structures, these are called rhizomes. This is the start of a rhizome, you can see it budding out and going in this direction and another one here and another one here. So these structures are called rhizomes and the rhizomes will continue to expand; they will go sideways, they will then come up and they'll form a new shoot at the end of that rhizome tip. Very sharp tips or at least moderately sharp tips, so they will grow through some things like tarping and things that we may throw at it. Normally what we see when we dig these up, if you dig up carefully you'll see that they, like the Canada thistle, are all attached to the same root system. We have roots that go deep and then we have more runner rhizomes that come off and then we see the shoots come off of that. So this is all within about three or four inches of the surface of the soil. We get the fronds here, these are non-fertile, they don't make any seeds. Horsetail in fact does not make seeds, it just makes spores. But these are the non-fertile ones, they don't actually make anything. All they do is have one job basically, is to make sugar to feed this root system that then grows all over the place and makes it very hard to control this plant. This is also a very primitive plant, botanically speaking. There are fossil records of horsetail-like species that are 100 meters tall, that's 100 meters, so 300 feet. Big plants that look very much like this. Our plants, thank goodness, are not that size, we have them generally within six inches to a foot tall. But they do make up for their height in their quantity, we get a lot of plants growing in a very small area and it is very difficult to get rid of them. Look for horsetail in wet sites usually, usually sites that are not very well drained and sites that generally have some type of irrigation or some type of moisture through the summer months. Okay, the next species that I want to talk to you, actually I've got two of them right close, they're two biennial species. Again two-year plant, first year strictly vegetative and the second year reproductive. And I have two reproductive plants here. This is a second year plant of what's called burdock. Burdock is kind of a dooryard weed, we see a lot of it in waste areas and kind of sites like vacant lots, places like that. Overall the plant has a superficial resemblance to rhubarb. If you look at it you think, gosh this is a large leaf, lots of leaf material there, kind of even the same groove in the petiole, you see how it's flat on one side kind of like a rhubarb. It's not even very closely related to rhubarb, this plant is closer related to a dandelion than to a rhubarb plant, but it does have that kind of look to it. Notice however, we've got a lot of hairs on this leaf, both on the backside of these new ones it looks very wooly, see how white that looks. And even on the front side there's a lot of hairs on it. So burdock has a nice root on this thing, it's fairly dense root, the root is basically what gives the plant an early start in the springtime. So this is the second year root that leads to the reproductive phase of burdock. Now this thing will continue to grow up, you can see that it would cover a lot of ground, it's probably three feet across and this plant could easily get five foot tall. Now if you look at these seedheads, I brought one of the seedheads to show you kind of what it looks like, and Page 3 of 7

4 you get these burr-like seedheads, hence it's name burdock. The hooked hairs on the tips of these heads are much the same as Velcro. If you look at them very closely you'll see that each one has a little hook right at the very tip so it hooks very nicely to pants, to sleeves, to dogs, to cats, to dogs, to cats, all over the place. These things move all over. In fact they say the name for this plant, burdock, gave rise to the person who invented Velcro got it from this particular plant more so than from a cocklebur, which is the other plant that kind of has these burr-like fruits. So burdock is found throughout the state, we see it on both sides of the mountains, probably a little more prevalent on the eastern side than on the western side but we certainly have some out here as well. Okay, another biennial plant that I'd like to show you is poison hemlock. This is a very good specimen of poison hemlock, particularly for this time of year. Now you can see how tall this thing gets. This is a very robust plant, it can grow easily to ten or more feet tall. It is a biennial, so the first year plants are strictly foliage down low and you don't notice anything like a seed stock showing up on it. You can see that this plant is just barely starting to move into flowering, so right at the tips of these stems you'll see just the beginnings of where the umbels will be. It does have umbels, it's in the Umbelliferae or the Apiaceae family, the same family as carrots and some of those so if you've ever seen carrots like a Queen Anne s Lace kind of carrot this would be very similar to that. The entire plant, however, is extremely toxic. This is one of those that the Hemlock Society actually gets its name from, this is poison hemlock. It's also thought to be the same species that Socrates was forced to consume in order to dispatch him back in the old days when they got into trouble they had to eat hemlock or drink a cup of hemlock, of crushed leaves. It doesn't take very much, actually about this much leaf material, about ten to twenty ounces is probably enough to kill a full-grown cow, so we're talking about a pretty intensely toxic plant. Look for the shiny glossiness of these leaves; you can probably see that even in this video how shiny the leaves are on one side. They look very lacy, very fernlike, but they do have that glossy sheen on the outside. The other thing that you should look for that's on this plant, see the kind of a purple mottling on the stem, it's got a waxy bloom to it so you can wipe it off but the mottles stay right where they are. You can see it all through the leaf that the plant is essentially spotted with these purple spots. The Latin name for the plant is Conium maculatum and if you think of something that is immaculate, it's spotless, it's clean and that's where it gets its name maculatum because it has these spots all over it. Look also for the base of the leaves, see how it kind of wraps around the stem, it kind of moves around there and you have this sheath at the base of the stem that kind of wraps around, very unusual for most of the plants that we have, but not unusual for the plants in this particular family. Now while we're speaking of plants that have unusual, easily identifiable characteristics, look at this plant. This one's called curly dock, it s Rumex crispus. It has a fairly unique look to it. We have a lot of this plant located on both sides of the mountains. The base of the leaves have what is called a sheathing stipule that actually wraps around the stem itself. So you can kind of see the stipule here, you can see the stipule here, here's an old sheath that's hanging off of there that's kind of dried up and you notice that it is on the base of these leaves. Each one of these stems will have quite a few of those things that are located at each node. Very unusual for the Polygonaceae family, when you see that you know you're looking at some type of a polygonum. This one is Rumex obtusifolius Page 4 of 7

5 so it's actually broadleaf dock, very similar to the curly dock that is more common on the eastern side of the mountains. Both of them will continue to grow up and these are closely related to rhubarb, so they have a similar type seedhead when they get up to three or four feet tall we'll have something that looks very much like the seedhead of a rhubarb plant. It is a perennial, grows from yellowish roots that come up in a simple way, they don't have the spreading rhizomes, they re a simple perennial that grows from this overwintering root. Each year the plant will die down to the base for the winter time and then it will send up new shoots each spring. Another type of plant that is a burr-like plant, but it's not really burr-like in that sense that the entire plant is basically one that sticks to about anything, this is called catchweed bedstraw. It's an annual, for us in this side of the mountains acts almost like a winter annual, but on the eastern side of the state it's more of a spring annual. Usually you'll get the seeds germinate and then the long growth. Overall the plant is very sticky, not in a glandular way, but in a burr-like way because it will stick to your clothes very easily, in fact this is a favorite of the kids to throw on the people in front of them when they're out in a line looking at things and they don't tell the people ahead of them. Overall the plant has a very distinct look, if you look at it closely you'll see first of all that you have whorls of leaves and long internodes between those whorls. Notice too what those whorls consist of. We have usually six to eight leaflets, I think this one has nine leaflets on it that wrap around the stem and the stem is very angled, you can kind of pick that up from this view of it, there's strong ribbing on the side so it gives it an angular feel. Sometimes it's square, sometimes it's got five sides, so it's not strictly a square stem. I don't know if you can see it or not but on the edges of each of these are very tight hairs that are like prickles, they're kind of like a cat claw that is backwards facing so that it's a retrorse angle as we say in the botanical business. That's what causes it to stick tightly to clothing or to hair, and that's how this plant spreads around. It also is a great way for this plant to grow up on itself. Notice that I'm not really holding up more than one of them, but I am, I'm holding up three different stems that are all closely pulled together because they are intertwining themselves. It's not strictly viny, it doesn't wrap around things, it doesn't have tendrils or anything, but the effect is the same. It tightly sticks to itself using those prickles and it can get sometimes to very tall heights. You may see a plant that could be four, five, or six feet long and still upright just by supporting itself or by sticking to some other type of vegetation that it's growing next to. Now these plants will make small white flowers later on when the days get a little warmer around here, and then each one of those flowers will give rise to two fruits, two round fruits, that are just as Velcro-ey as these plants are and those seeds will stick to just about anything, in fact if your pet or your livestock get into any of this plant that time of year they will have a face that is just completely covered in the seeds. And that's a great way for seeds to get around, and this plant is definitely able to get around. Another plant that I wanted to show you is a perennial, this is one of those creeping perennials though, it's very common throughout the state, it's often in fact grown as a crop. This is white clover. Frequently grows in lawns, we find it in garden areas, not always intentionally, and sometimes it's not all that bad of a problem, some people like to have it in their lawn because it's at least green, whereas the lawn sometimes may go in the summertime back to a more dormant state. This plant is able to grow in very droughty type conditions and pretty much stay green the whole year in the western part Page 5 of 7

6 of the state. Obviously it has the same type of trifoliate leaf that we associate with clovers. Sometimes it will have fairly large leaflets with these little water marks on there, sometimes it won't. It just depends on the kind of growth that it's in and the breeding that was behind where these seeds came from. One thing that we can say is that the plant always creeps along the soil surface and tends to put down roots at the nodes. If you see this particular site you can see that these leaves were in the soil, so as it was lying on the soil it sent out the adventitious roots that then allowed it to cover a larger area. It also makes it very hard to hand pull because if you pull it up you usually will leave a fragment somewhere on the ground that will then root and continue to spread. And then each of these pieces, if we are not careful with where they end up, they will become new infestations somewhere else. Now generally speaking, clover is one of those that some people will like and some people won't like depending on the situation it's in. Some folk s lawns, they want them to be immaculate and in those conditions it's a very different texture than what a lawn would be and so they may not like it for that reason. The other thing that is commonly called a problem with this plant is that it does make nice white flowers that bees love and so if you like to walk barefoot in your lawn or if you have kids that really like to walk in the lawn, they don't much like to step on bees or other stinging insects that are attracted to the flowers of the white clover, so that would be a reason to maybe try and control it although if you don't have either of those issues maybe it's not one you want to control. Okay, what we're going to look at now is another perennial plant, this is a vegetatively propagating plant that tends to like to grow in lawns. This is a good western Washington lawn that is very typical actually, we have a lot of this creeping buttercup. If you can see the leaves that are very different in texture than the grass that's grown up through it, and then obviously if you let it grow to long you start to see the buttercups themselves, which makes it very easy to identify this particular plant. Notice it also does not stop at the lawn s edge. We have lawn right here, we have buttercup in the lawn, we also have more open space on this side that is into a planting and the buttercup likes it very nicely there, too. And so consequently we get a plant that can grow from one to another and really not miss a beat. The competition of the grass is really not enough to knock the buttercup out; rather the reverse is true, usually what these buttercup plants do is coalesce into very large infestations and you start seeing the grass disappear in those infestations. Again if you re not one of those people who like to have a completely all grass lawn, this is not an overall bad plant. The problem is that it tends to not stay put, it tends to move around every time we mow the lawn, it roots very effectively from stolons that root at the nodes and then continue to creep out over the course of the lawn, and so we end up with very large patches of this. If it just stayed where it was then we probably wouldn't be as concerned about it, but this is one that likes to roam and we find it growing in many of the lawns in western Washington. Okay, the next plant I want to show you is another winter annual, and this is a classic plant that we have a lot of in the state of Washington. This is called common groundsel. It is frequently found in garden sites or even along roadsides and places like that. What is interesting about it is that this plant is in full bloom in this particular specimen. If you look closely at the flowerheads you'll notice that they are heads, so it is in the composite family, but it also has little bracts that are right at the base there and also at the tip of each flower. These small black bracts make it pretty easy to identify any of the Page 6 of 7

7 particular plants in this genus, Senecio. Now this plant tends to be one of those that lives for longer than what we consider a usual winter annual, so actually it's classified as a spring annual in the big sense of the word. It will, however, continue to flower, it will continue to make seed, and it will continue to grow and develop as long as conditions are right for it, so a plant could survive for quite some time. If we look at some of these plants that are a little older, notice it's got the same seedheads as dandelion, which will then tell you that it's in the same family as the dandelion, the Compositae family. And each of these fluffy tipped seeds will blow all over the place as these are, and have new infestations all over the place, this is how this plant tends to get around. The other thing I want to show you about this plant is that you'll often see rust spores growing on it. Now this is a plant disease that is fairly important in world agriculture as far as being a problem in crop plants, we often will get them on weeds as well. Unfortunately this particular rust in not really hot enough to kill this particular weed until after it's gone to seed and done some things that we probably didn't want it to do in the first place, so it's not really a good biocontrol agent but it does show up and it will eventually probably kill this particular plant. Page 7 of 7