There are, in fact, five species of bindweed in Britain but I’ve only encountered three so far. One, the Field bindweed (Convolvulus arvensis) is, I think, the easiest to identify: it’s quite small, and its flowers are a delicate swirl of pink and white (as shown below).
Then there are the two bindweeds that have large white flowers, Hedge bindweed (Calystegia sepium) and the aptly named Large bindweed (Calystegia silvatica). To my untrained eye, these two look remarkably similar but I have recently learnt how to tell them apart so I thought I’d share that little snippet of knowledge. My wildflower key tells me that Hedge bindweed has an epicalyx of 2 bracteoles that don’t (or scarcely) overlap, whereas the Large bindweed has strongly inflated, overlapping bracteoles. Okay, so you might now be thinking, “Huh?” Well, the photos below show the difference: Hedge, left, and Large, right. Easy now, right?
Oh, and one more thing I found out while looking at all those bindweeds. The flowers often look like a little fairy has come along and snipped pretty patterns in their petals with miniature scissors. A fanciful idea I admit, but it’s almost true – these have been created by bees and other insects desperate to get at the sweet nectar inside so they cut their way into the flower bud before it opens.