A Prickly Subject

I was initially stumped by the aster I found growing in the Courtenay Airpark. I photographed the plant and was particularly struck by the distinctive row of spines down the midrib of the leaf. With a leaf like that I assumed that the field guides would definitely use it as a field mark and it would be easy to identify.

Prickly Lettuce (Lactuca serriola) Leaf
The line of spines down the midrib of this Prickly Lettuce (Lactuca serriola) leaf is an obvious field mark.

An initial look through Pojar and MacKinnon’s Plants of Coastal British Columbia turned up a couple of possibilities but nothing really fit. I thought that the flowers sort of looked like they belonged to the hawkweeds (Hieracicum sp.) but the leaves didn’t fit with any of the common plants in this genus. Instead, I thought that the leaves looked more like sow-thistle leaves (Sonchus sp.) but the flowers didn’t work with any of those species. I’m not great at keying plants out and tried the Illustrated Flora of British Columbia. I was quickly overwhelmed.

Prickly Lettuce (Lactuca serriola) Flowers
Prickly Lettuce (Lactuca serriola) flowers lack disk flowers.

Back to the photographs. I looked at the shape of the leaf and tried to ignore the nasty looking spines down the rib of the leaf and had a thought – the leaf sort of looked like Wall Lettuce (Lactuca muralis) in shape. I returned to Plants of Coastal British Columbia and read through the notes  for this species (often similar plants are described in this section even though an image isn’t usually provided). Sure enough, one of the species described was Prickly Lettuce (Lactuca serriola)! A quick check of eFlora, British Columbia’s on-line database of plants confirmed that my aster was indeed Prickly Lettuce – mystery solved!

Prickly Lettuce (Lactuca serriola) Leaf
The pinnate lobed shape of the leaf of Prickly Lettuce (Lactuca serriola) is somewhat similar to the leaf of Wall Lettuce (L. muralis).

This distinctive looking plant is one more introduced species from Europe that can be found at the Courtenay Airpark Lagoon. The leaves have a network of veins with a very noticeable line of spines down its midrib. The yellow flower consists of ray flowers only – no disk flowers are present. While Wall Lettuce is considered edible, if bitter, I’d have serious doubts about trying Prickly Lettuce!