Birdsfoot Trefoil

2016 December 17

These rather bright yellow flowers are very common along road margins and bloom through most of the summer, this particular plant was next to our road on June 29, 2016.


This is Birdsfoot Trefoil, Lotus corniculatus. The flowers grow in a radiating cluster at the tip of the stem, and their odd, asymmetrical blossom shape is pretty similar to other legumes like beans and peas.



The “Birdsfoot” part of their common name comes from the appearance of their seedpods after the flowers drop off. Each blossom makes a single pod. The pods are long, thin, and radiate from a central point, looking rather strikingly like the foot of a small bird.



The “Trefoil” part of their name comes from the leaves. While each leaf consists of five leaflets, there are three prominently projecting out (trefoil = three leaves), while the other two are smaller (sometimes so small as to be almost invisible) and remain closer to the stem.


So, these are another non-native species, but unlike a lot of the others they were imported on purpose, as a forage crop. As legumes, they help to fix atmospheric nitrogen into the soil, which they then use to produce proteins. This both makes them very nutritious, and allows them to grow in nitrogen-poor soil without much fertilizer. As an added bonus, birdsfoot trefoil does not cause bloating[1] in cattle that eat them, unlike a lot of other legumes.

Birdsfoot trefoil has gotten popular for growing on soils that are too poorly drained, acidic, dry, or nutrient-poor to support alfalfa or clover.

[1] Bloating is a big problem with ruminants, like cattle. If they eat too much of certain plants, particularly fresh, green alfalfa[2], the plants make a foam that traps gases in their first stomach (the rumen). The rumen is a fermentation chamber where the ruminant breaks down cellulose, and the fermentation process produces a lot of carbon dioxide and methane. Normally, the animal will just belch frequently to relieve the pressure, but if the alfalfa foam traps the gases they will just, well, not explode exactly, but close to it. As you can imagine, one doesn’t want bloating to occur, so we fed our cows these “bloat-guard” blocks alongside their salt licks. These were blocks of molasses, mixed with an antifoaming agent, and were evidently pretty effective. Another remedy is to force-feed them vegetable oil or mineral oil, again to break up the foam in the rumen. In extreme cases, as a last resort it is necessary to use a tool called a trocar to punch a hole in a cow’s side to let the gases out. We never had to do this on our dairy farm when I was a kid, but we had a trocar handy just in case.

In any case, the option of feeding cattle a “non-bloating” substitite for alfalfa is obviously pretty attractive.

[2] If the alfalfa is dried and baled up to make hay, then it doesn’t have this problem.

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