Thursday, 17 July 2014

Practical Session Report - July 2014

I missed the June session as I was away on honeymoon, so this is the first practical session report since May. Even including the rain, it was a lovely session. We recorded many species of plants in flower, with 29 that had started flowering this month and were added to iRecord. Our two littlest helpers were brilliant and have renamed the green 'big hands' we use to pick up grass as 'monster hands' - I really enjoy the way that children can breathe new life into everything they do. The youngest, Abel, kept bringing me snails and slugs which his mum had found - so refreshing to find a child that isn't afraid of such things.

July saw all three of our stonecrops in flower; the biting stonecrop, english stonecrop, and white stonecrop. In the past when I've seen english stonecrop and white stonecrop in isolation, I've sometimes struggled to reach the correct identification, so let's have a look at our stonecrops and see the distinguishing features are when compared to other common Sedum species.

Biting Stonecrop

This is our only yellow stonecrop and it's a perennial, which immediately rules out annual stonecrop (Sedum annuum) which at most is biennial. Being a low mat-forming plant, we can see that it's not reflexed stonecrop (Sedum rupestre (S.reflexum)), which grows up to 30 cm tall and has its' yellow flowers clustered on an umbel-like stalk.











White Vs. English Stonecrop
Now, it's with these two species that I can sometimes become unstuck. They are both mat-forming evergreen perennials and both grow in similar conditions (rocky ground and stone walls) and flower around the same time of year (June to September). Let's see photos of some features side-by-side and see what the differences are.

The photos below show the leaves of each stone crop.  We have English stonecrop (Sedum anglicum) to the left with pale green to red leaves that are often described as 'egg-shaped'. To the right is White stonecrop (Sedum album), with (what looks like to me) fuller green to red leaves that are often described as 'cylindrical-oblong'. On both species the leaves are alternate. In the books I have (see references below), which have illustrated rather than photographed images the English stonecrop tends to be shown as the plant with red leaves, with white stonecrop being shown as having primarily green leaves. This may well depend on the time of year and the population being observed.

Our english stonecrop has 6 petals, which seems quite common, but often both species are described as having star-shaped flowers with 5 petals per flower that are white or pink tinged. On our specimens we can see that the pink tinge is more easily seen on the white stonecrop with our English stonecrop showing a yellow tinge in the centre.

Finally, let's have a look at the stems. The stems of the English stone crop have large hairless leaves growing alternately up the stem, which rules out thick-leaved stonecrop (Sedum dasyphyllum), which is very similar looking.

The leaves of the white stonecrop remain cylindrical and have a much brighter and shiny look to them.


Writing this has certainly helped me get to grips with these two species and I hope it assists anyone who stumbles across this post! It's important to remember that there is always variation within and between plant populations, but using a botanical key like that in The Wild Flower Key by Rose and O'Reilly will help you understand which features are important when identifying your plant.

Our next session is Saturday 26 July. If you'd like any information about our project or you'd like to visit, please get in touch via the comments below or the contact form to the right.

Resources: 
Rose, Francis, and Clare O’Reilly. The Wild Flower Key. Rev Ed edition. London: Warne, 2006.

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