Lactuca serriola
...from down the road, fortunately NOT on our property!
This is my current nemesis in the prairie restoration--Lactuca serriola, aka "Prickly lettuce." The really bad stuff out there is gone--no more field bindweed, Canada thistle, poison hemlock...but Prickly lettuce is formidable. It was pervasive when I moved here, with many years of spreading seeds, of which there are many in every plant, as you can see above. As I have battled it, I have learned of its extraordinary powers, but now I seem to have gained the upper hand.
One of its weapons is persistence. Here on the WA/ID border, they start sprouting in April (though some that sprout in fall will winter over and can start growing by March), and will continue through the Spring. If you clear all of the plants in, say, late June, the sprouting throughout July and into August will get you. In a serious infestation, seedlings will begin to sprout after the first few rains in fall. I was just at my dentist's office yesterday, and we got to talking about the weeds (between cleaning and suction... usually the conversations are pretty one-sided). He was saying that after the little spray of rain we had the other day, he was seeing little seedlings of Prickly lettuce seem to spring up, bloom, and go to seed in one day. Still, they all do at least mostly bloom at the same time, July into August.
As with many aspects of this project, my process was trial-and-mostly-error. I did discover that if you have a substantial patch of it, mowing can be effective just as they start to bloom. Many will survive, but if it's during a hot dry period, some will give up the ghost, and you get rid of a lot of future seeds. Similarly, in the years where they just got past me, I cut down a standard hoe for a shorter handle (better for whacking), sharpened the blade and would hack off as many flowering/seeding heads as I could. The trick was to strike so that the blade would encounter the plant down into the root a bit--often I'd get enough of the root to take it out. While doing this with a perennial weed like bindweed would be pointless, I found that, like mowing, I could get Prickly lettuce seeds out of the system, and some plants would eventually quit trying. Unless you have a small area to work, or you are crazed, this method will not work to eradicate Lactuca serriola.
You know what's coming, right?
Yep, as I have mentioned in these posts before, I am not above using herbicide. I understand that some people are horrified by this, but there is no prairie restoration without it, and as I have seen here, there is no. consequence. whatsoever. from its use in this project. I have used glyphosate and 2,4-D, and they really work to get rid of invasive noxious weeds I couldn't have eliminated otherwise. Here, I must recognize the guidance of my awesome father-in-law, Frank Abderhalden, retired farmer of 250 acres of spectacular farmland beside the Willamette River near St. Paul, OR, who walked through the prairie with me for the first time in 2006, and said in a way I wish that you could hear--"So, are you serious about this? Would you like my advice?" Yes, I wanted his advice.
"You have to be willing to use herbicide." OK.
I adjusted my schedule for the difference between the wet climate of the Willamette Valley and the drier and colder Palouse region, but in late May/early June, after some rain, I walked through the prairie, spraying every Prickly lettuce I saw with 2,4-D. Any living Lactuca at that point will be toast. Ideally, I had native grass growing in that area, and so the 2,4-D would not disturb it. This is the most profound effort by this plant, and 2/3 of your problem will be gone. The next important time to go through was around the first week of July, hoping for summer rain we would often get, and spraying a day or so afterwards. This would be the last time I could use herbicide until fall. In this instance, I would use what I called "kill juice"--OK, yell at me, but... whatever. "Kill juice" is mixing as much glyphosate as would be appropriate for that much water, and then mixing 2,4-D into that same liquid, appropriate for that much water. It is very effective, and used in spot spraying applications. In fact, the bindweed, poison hemlock, and Canada thistle I mentioned earlier? That takes it out. With the glyphosate, it will also take out grass, so into those spots where I had grass, I would again use pure 2,4-D. I should say that this method is also how I rid myself of another similarly-invasive weed, Salsify (except for the odd one blowing in from the neighbors). Salsify (Tragopogon porrifolius) was easier because it doesn't have as much of a long period where the plants will sprout.
This will eliminate 80%-90% of the Prickly lettuce, but the 10%-20% of it remaining will ruin everything. One single plant, unmolested, can spread (hundreds? thousands?) of seeds--each one of those little pods that were flowers you can see in those plants above is loaded with a bunch of tiny seeds. It will--this is the years of trial-and-(mainly) error talking here. So, then comes the bucket-and-shovel. Now, I know some people around me here want to be organic about things, and OK, I do the same in my vegetable garden. A small space can be cleared (not of field bindweed, poison hemlock, or Canada thistle, but...) through this ritual of physical control, but the weird thing is that I have never seen my neighbors using the classic dig-the-actual-weeds method. But I start up in July, and keep going. I have a five-gallon bucket, and I go out in the mornings before it gets too hot (I have been thwarted by smoky conditions as well... sigh...)--I discovered that blooming Prickly lettuce closes up its flowers in the middle of the day--if you go in the morning, the pale yellow flowers of blooming Lactuca will tell you where they are. This is important. Some years I have dug more than 75 gallons of weeds in this way.
I take my little shovel (I had a cool Army-surplus trench-digger from my ancient boy scout days that did a great job until the blade cracked through), and dig right alongside the Prickly lettuce plant in question, pop the dirt sideways as my gloved hand gently pulls the plant stem, and it nearly always pops out with enough roots to take care of business. Into the bucket, and from there to the burn pile. In early July, the plants are not that resourceful, and I can break off the top blooming part to put in the bucket, and drop the roots, lower stem, and leaves as compost on the ground. By the end of July, you can see the blooms/buds popping out of the leaves all the way up the plant, and you've got to put the whole thing in the bucket. Now in mid-August, the plants come up blooming and you have to get all of it in a hurry. It has been so hot and smoky here that on the rare days I can get out there, I've got to go. Weirdly, in this smoky drought, I think that many of these plants gave up on the future and sprouted earlier than they normally would have, and thus... I have cleared them. In this bizarre time, I have to say that I'm optimistic. For the first time I've gotten ahead of them, and most of the prairie is completely free of weeds. I still go out most days, but there are less and less of them in a few areas that had been impossible for years, but now... I get my five-gallon bucket maybe a third full.
So, the next step may not be necessary this year, but in the past, after the first rains (October), I would go through and spot-spray any Lactuca that sprout with the notorious kill-juice, or I would use pure 2,4-D where there was grass, or plain glyphosate where I was preparing ground to plant native grass seed. I think this year there will be so few that I can walk through with the bucket and shovel in late October and get the few that show up, from seed that blew in and sprouted. It has been a few years, but satisfying to know you can get there.
That's the method. Good luck!
