Posts Tagged ‘tall blue lettuce’


There are two varieties of plants around the edge of the garden and in the fields here that have been growing and growing and growing all summer. I have been waiting all season to see how tall they would get. Both have produced stalks nine feet tall and more. When Birdgirl was here last, I pointed them out to her and she got out the guides and searched out their identity. The first, shown towering above a stand of garden escapees, is Giant, or Great Ragweed (Ambrosia trifida).


There is lots of ragweed around here, and now giant ragweed as well, it seems. Hmm. No wonder my nose is always running. Ragweed is a common cause of hayfever (not goldenrod, which is often blamed). The leaves of the giant variety are quite distinctive, being large and tri-lobed.


Ragweed flowers aren’t much to look at, but they are interesting to read about. There are male and female flowers, with the male flowers positioned on short stalks along the ends of the stems. The female flowers are located below them where leaves meet the main stem. You can see some really great closeup shots of the flowers here.


Here is a sample of the other plant. I uprooted this plant and laid it out on the ground to get an accurate measurement. Nine feet.
It’s Wild Lettuce (Lactuca sp.). It is possibly Tall Blue Lettuce (Lactuca biennis), although one guide observes that due to the large amount of variation in this genus, it is often difficult to identify wild lettuce to the species level.


The genus name, Lactuca, comes from the latin word lac, meaning milk, and refers to the milky sap that the plants release when the stem is broken. The juice of lettuce plants contains narcotic components. Lettuce sap was once used to produce an opium-like substance. However, wild blue lettuce is not one of the more potent species. The leaves are deeply lobed and similar to big dandelion leaves. Below are the flowers, which top the tall stalk.


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