Plants to look out for in August
by Karen van Oostrum
Hornbeam (Carpinus betulus)
Our deciduous trees are worth looking at this month, as their fruits are now well on with their development. The hornbeam bears conspicuous trailing tresses of winged fruits – lime green just now, in contrast with the dark green leaves. Hornbeam and beech are easily confused, since they share a similar habit, bark and leaf size and shape - although the leaves of hornbeam have serrated edges, while those of beech are smooth. The fruits of these 2 species are entirely different though and cannot be mistaken. The individual hornbeam fruits are egg-shaped, about 0.5cm long, and each one is nestled within a leafy 3-lobed wing. The more-familiar fruits of the beech are hard and bristly on the outside, splitting open when ripe to reveal the distinctively 3-sided seeds inside.
Common Knapweed (Centaurea nigra) and Greater Knapweed (Centaurea scabiosa)
In August last year we looked at Yarrow (Achillea millefolium), a member of the daisy family, Asteraceae. In this family, what we may think of as ‘a flower’ is in fact a collection of tiny flowers, arranged into one unit, a flowering head. The flowering head is technically referred to as a ‘capitulum’, and the tiny flowers that make it up are known as ‘florets’. Hence, a single daisy, dandelion cornflower, thistle or sunflower is botanically a collection of flowers. We still tend to refer to them as ‘flowers’ though – it’s just easier that way. Many plants in this family are at their best later in summer, and this includes the Knapweeds.
Their bright purple / red flowers are hard to miss at this time of year. I am often asked how to tell these two species apart – and like a lot of botany this is quite straightforward, once you ‘get your eye in’. They differ in their overall size, the size and structure of the flowering head, and the shape of their leaves.
All photos are © Karen van Oostrum
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