This Week’s Weed – Prickly Lettuce
ChiloquinNews article October 1st, 2012
I’ve saved my most dreaded weed ‘til last. Prickly Lettuce (Lactuca serriola) is commonly considered a weed of orchards, roadsides and field crops, but in fact, it will grow anywhere from dry to wet, bright sun to deep shade, in grasslands or through thick shrubs. It is found in the temperate regions of all major continents. It has been just horrible in my yard this year. I’ve pulled hundreds, perhaps thousands, and didn’t come close to winning the battle.
It has leaves with prickles along the margins and on the midveins of the lower leaf surfaces. Additionally, all parts of the plant bleed a milky sap when cut. These characteristics help to distinguish prickly lettuce from similar species, such as sowthistles. When the plant are young, the prickles are quite soft, but as the plant gets older, the prickles get much harder, and beware trying to pull an older plant with bare hands. It will flower when 6 inches tall out in a hot, dry pasture, or will grow to 6 feet tall to rise above a thick shrub, and no matter how many times it is cut, it will try, try again until it sends up a flower stalk.
In the sun the leaves twist round to present a flat face the sun, and are quite pretty with the sun shining through the forest of neatly lined up leaves, and a forest it usually is, because there are always SO many of them. It has a flowering stalk with dozens of small yellow flowers, and each flower develops into a puffball of seeds, which are dispersed by the wind. The only advantage this weed gives us is that it doesn’t flower until well into the summer here in Chiloquin, so there is time, if you act quickly, to pull them out before they flower. Like many other successful weeds though, once they have a flower bud, they will go on to produce seeds even if you pull the plant out of the ground, so at that stage, they have to be gathered up and put in a trash can.
Prickly lettuce is the closest wild relative of cultivated lettuce (Lactuca sativa). Young, tender leaves of prickly lettuce have been eaten – raw or cooked. They are said to taste mild and can make a good salad, but the whole plant becomes bitter as it gets older, especially when flowering – as does cultivated lettuce. Eating large quantities has been known to cause digestive upsets. Young shoots can be cooked and used as an asparagus substitute.
The whole plant is rich in a milky sap which hardens and dries when in contact with the air. The sap contains lactucarium, which is an agent that has been used in medicine for its properties of being mildly pain-relieving, antispasmodic, a digestive aid, urination-inducing, and for its hypnotic, narcotic and sedative action. Lactucarium has similar effects to a mild opiate, but without being addictive. It has been taken internally in the treatment of insomnia, anxiety, neuroses, hyperactivity in children, dry coughs, whooping cough, rheumatic pain. The sap has also been applied externally for treatment of warts. Because of its mild narcotic properties, even normal doses can cause drowsiness, while excess doses cause restlessness, and very large overdoses can cause death through cardiac arrest.
Even though concentrations of lactucarium are highest when the plant flowers, I’m not about to eat this plant at any stage, when lettuce is so much prettier, not to mention prickle-free, but it definitely causes restlessness in me when I look at how much is out there to be pulled. Hopefully though, I won’t get carried away with so much excess weed-pulling that it will cause death through cardiac arrest!