04 Dec 2021

Kildare Wildlife Watch: Black medick can help improve nitrogen levels in your soil

With the Irish Peatland Conservation Council

Kildare Wildlife Watch: Black medick can help improve nitrogen levels in your soil

Black Medick. Picture: Nuala Madigan

This week I came across a low growing, pretty yellow bright flower on a gravel area in my garden and I have since identified it as black medick (dúmheidic as Gaeilge).

Reading about this native wildflower, I have learnt that it is typically found growing in nutrient poor soils, especially those that are low in nitrogen.

Black medick is part of the clover family, and when looking at the oval green leaves of black medick and its low growing nature, it shares these similarities with other members of this family including red and white clover. But it is what happens beneath the ground that is interesting about black medick and other members of the clover family, as they have the ability to fix atmospheric nitrogen.

Why is this important? All growing plants need nutrients including nitrogen to grow. As plants grow, they absorb nitrogen and over time this can deplete the soil of this chemical.

Our atmosphere is made up of approximately 78% nitrogen but this nitrogen cannot be used by plants to grow. Some plants, like black medick, have adapted to use this atmospheric nitrogen with the help of a group of bacteria in the Rhizobium genus.

Rhizobium bacteria have the ability to fix atmospheric nitrogen into a form plants can use, but to achieve this they need a host plant. Black medick offers its roots to Rhizobium bacteria and in return, once fixed, the nitrogen is shared with black medick. This is not a parasitic relationship between the species — instead it is mutually benefical and is referred to as a symbiotic relationship.

The value of these species is that soil that was once poor in nitrogen can be improved by introducing members of the clover family.

The flowers of black medick are low growing, small, clustered together in a round head 3 to 8mm in diameter.

Even though these bright yellow flowers are small, they are valuable for biodiversity and are visited regularly by the honeybee.

If you would like help identifying or to learn more about a wildlife species contact me via e-mail

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