Thursday, 25 August 2011

Bean Broomrape? (Orobanche crenata)

I spent the weekend in the Cotswolds with my wife and a friend, and this was one of the botanical highlights, Bean Broomrape (Orobanche crenata). It's not native to Britain, and is currently thought to be naturalised only a one site in north Essex. It does turn up in other southern counties however, as here in Gloucestershire. As you might guess from the name, it parasitises legumes (plants related to peas). This specimen, and the hundreds of other plants in the field, was parasitising White Clover (Trifolium repens). No doubt it was a seed contaminant that arrived with the Clover when it was sown.

The corolla with its five flared lobes (2 up, 3 down), each at almost 90 degrees to the main corolla tube, is a key feature apparently. Although on older flowers this was not so obvious.

Unfortunately this Orobanche is not included in a lot of the popular picture guides to Britain's plants, so hopefully it won't increase too much in Britain: if it does we may not notice! (And it might become an agricultural pest of other cultivated legumes, as it is in North Africa and other warmer climes).

Sunday, 14 August 2011

Red Bartsia

This is Red Bartsia, or Odontites vernus, growing at the edge of a path in Crookes Recreation Ground, Sheffield. It's not unusual to find it on waste ground or trampled path edges, but it is easily overlooked. Like all members of the Orobanchaceae it is parasitic; in this case on the roots of grasses I believe. It's green, so obviously it can still photosynthesize, so we might suspect it is only using its hosts for mineral nutrients and water. However, the line between hemi-parasitism (as here) and holo- or complete parasitism seems to be fairly thin in an evolutionary sense, so it's possible that some sugars are received from the host as well.

A nice plant to look out for in urban situations; I used to see it a lot in Birmingham along the canal in the Edgbaston area.