In message , Pam Moore
writes
white convolvulus flowers

Calystegia sepium and Calystegia silvatica usually (but not always) have
white flowers, by Calystegia pulchra has pink flowers, and Convolvulus
arvensis can have white or pink flowers. (Around here Calystegia sepium
and Calystegia silvatica are much the commoner - over 10 times commoner
that Calystegia pulchra, and Convolulus arvensis appears to be even
rarer - but I've seen suggestions this isn't true everywhere in the
country.)
--
Stewart Robert Hinsley