Weed of the Week: Prickly Lettuce (and Sow Thistle)

My nemesis

This weed has been driving me nuts all spring. It’s not one I’d seen a lot before this year, then — out of nowhere — it infested large sections of your backyard. Not only did it infest the yard, but I had a tough time figuring out even what it is.

After digging around on a lot of university websites and talking to people who know their weeds, I think it is prickly lettuce (Lactuca serriola). But a couple of people have also identified it as sow thistle (Sonchus arvensis L.), and it is certainly possible that I have some of each. The two weeds look remarkably similar — and they’re both trouble.

Note the spines along the leaf vein. (Click for a larger view)

Both weeds like prairie plantings (we’ve got those nearby) and make forays into home landscapes. Both of them have leaves that look like dandelions and both of them emit a white sap when cut. Prickly lettuce has spines on the back of its leaves (and many of those in my yard also have that), as you can see from the photo, which is why I think that’s what I have. The weeds spread both by seed and by rhizomes!

I also learned that if you have a big deluge of rain (say 2 inches in 12 hours), you can pull prickly lettuce with abandon. It is much easier to pull than dandelions, so last week, in between rain storms, I’ve been pulling the prickly lettuce like crazy. I’ve also added some grass patch to the especially infested areas and will likely be over-seeding this fall. However, I don’t expect this will be my last battle with prickly lettuce, or sow thistle, or whatever it is.

What weeds have you been battling this year?


Weed of the Week: Wild Parsnip

Since our early/weird spring started more than a month ago, I’ve been noticing more weeds and more unusual weeds in my yard. I hope others are not having this problem, but in case you are, I’m going to do a weekly feature on the weeds I’m finding — this could take all summer!

Let me know if you have a weed you would like to have covered.

Note the long, parsnip-like root.

This week’s weed is one that has long been a problem in parts of my yard, but has really gone crazy this spring: Wild parsnip (Pastinaca sativa).

Wild parsnip is pretty easy to identify, though it does look a bit like a native called prairie parsley or wild dill. It has fern-like leaves that come up in early spring. If you pull the weed, you can see its taproot, which does indeed look like a parsnip. According to the Minnesota Department of Natural Resources, wild parsnip will stay in this plant stage for more than one year, then flower on a tall, grooved stalk. The flowers resemble Queen Anne’s Lace, but have small yellow flowers arranged in an umbel fashion. If you see the flower heads, cut them off! Seed can survive in the soil for up to four years.

Wild parsnip also can cause phytophotodermatitis, which means if you touch the sap and are out in the sun you can get a nasty rash. Always wear gloves (and long sleeves!) when dealing with this plant.

Prevention is the best control method. The DNR says that in established prairies you can leave the wild parsnip alone and it will be out-competed by other prairie plants. In distrubed areas (this is what I have), you can pull plants. If that’s not possible, remove the flowerheads before they go to seed. Wild parsnip is a prohibited noxious weed in Minnesota.

For more information on wild parsnip, check out this page from Minnesota Wildflowers, a volunteer-run site about native  plants here.

What Gardeners Are Talking About: Buckthorn

On Saturday, I spent a couple of hours at the Northfield Home and Garden Show at a booth shared by the Northfield Garden Club and the University of Minnesota Extension Master Gardeners of Rice County. Going into the event, I was pretty sure that the most asked question would be about whether it was too early to mow or put down weed-and-feed on lawns. Nope. Many of the gardeners–especially those with larger or more rural properties—asked about buckthorn and what to do about it.

Buckthorn is a restricted noxious weed in Minnesota because of its invasive nature and its impact on wildlife habitats. Once buckthorn gets established, it takes over. There are two types: common buckthorn (Rhamnus cathartica) and glossy buckthorn (Frangula alnus). Common buckthorn came to the U.S. from Europe in the 1800s and was used for a hedge in many landscapes. By the 1930s, its negative qualities were well-known and the nursery trade stopped selling it. The glossy buckthorn is particularly invasive around wetlands.

The best way to control buckthorn is to pull it while it is still small. According to the University of Minnesota, it will not resprout from roots underground. Small plants (under 3/8th inch diameter) can be dug or pulled, but for larger ones many buckthorn removal groups use a weed wench or root talon. (The garden club has one that they have used for buckthorn remvoal.) For really large plants, the recommended control method is to cut the trunk as close to the ground as possible and then immediately treat the stump by painting on an herbicide containing triclopyr. (Garlon is the brand name most often recommended.)

You can find detailed information on identifying and controlling buckthorn at the Minnesota Department of Natural Resources website and at the U’s site. Getting rid of buckthorn can be a long process—homeowners must stay vigilant because the seeds can last five years in the ground. As you remove buckthorn, don’t forget to replant the area with a variety of native shrubs and trees that will attract birds and other wildlife. The DNR recommends plants like highbush American cranberry, nannyberry, serviceberry, chokecherry and gray dogwood.

Getting Rid of Plant Thugs

Stella d'Oro daylily in better days.

This past weekend, I dug up some of the thugs from my garden. It was an odd group, including cucumber plants, daylilies and giant ragweed. They have little in common except that I was sick of them.  Each plant earned its spot in the compost pile and garbage for different reasons.

Because it is a weed

The ragweed came out of the meadow behind our house. It is indeed giant ragweed – growing 7 or 8 feet tall and sending pollen all over the place. It took over one corner of the meadow a couple of years ago, and showed signs of moving outward from there. I’m planning to plant some grasses and other forbs in that spot in order to hold off the ragweed next year.

Because it acts like a weed

I planted my cucumbers as seed rather late this year due to the cold spring. Not expecting them to grow that well, I let about six cucumber plants survive. Big mistake! With the rain and heat this summer, the cucumbers went crazy, covering their designated trellis and bed and crawling into beds with green beans, tomatoes, even twining their foliage around raspberry plants. It had to stop. We could not eat all the cucumbers the plants were producing and they were interfering with their plant neighbors. So Sunday I harvested the mature fruit for pickles and then cut the plants at the base. It took a bit of gentle tugging, but I got most of the foliage out of the bed. I still have time to seed spinach or lettuce in that bed, which will make for some tasty fall salads.

Because it was time

Finally, the daylilies. A lot of garden writers and bloggers like to hate on ‘Stella d’Oro’ daylilies because they are ubiquitous, planted in every mall parking lot in the U.S. I’m not among them.  These prolific re-bloomers are the perfect plant for areas you do not want to have to think about much. (And, we’ve all got those spots.)  Stellas  have been hanging out on the north side of my house, blooming despite the shade and not asking for anything but an annual hair cut, for 12 years. I have some hostas that need to be moved due to a different project, so out went Stella and in went the hostas.

Fall is a good time for garden rejuvenation, and with these three spots now empty, it almost feels like the spring.

A Wonderful Weekend for Weeding

Is there any more satisfying experience for a gardener than pushing a trowel deep in the dirt and pulling out the long, long tap root of a dandelion or the mess of white rambling roots of grasses invading the vegetable garden?

With the persistent, slow rains we had for more than a week beginning in early May, this weekend’s warm temperatures dried the earth just enough and it was a perfect weekend for weeding. It was perfect for many other things, too, but I still managed to weed my biggest vegetable bed and one of the flower beds. Weeding is easiest to do and most effectively done if you wait a day or two after a steady rain. You want to soil to be moistened but not wet.