The original species and the heirloom varieties derived from it have keel petals
that are turned back at the tip, thus trapping the anthers close together at the
tip of the keel. Such keels are rare but understandable abnormalities in Spencer
Sweet Pea. It is not uncommon to find keels that are split along the plane of symmetry
into two matching parts, nor to find one or two extra half-keels.
We have found two otherwise unreported abnormalities, the barge keel and the centreboard
keel. In the barge keel the cross-section of the keel is widest near the base and
the keel of the keel protrudes along its length like a longitudinal fin. We have
no photograph of the barge keel at present, but there is a sketch on p 94 of the
NSPS Centenary Celebration, 2000.
The centreboard keel (left) appeared in 2009: it is generally like the normal Spencer
keel, except that the keel of the keel protrudes increasingly from the calyx to
half way along the keel. There it ends in a shape reminiscent of the bulbous underwater
protrusion provided at the bow of modern merchant ships to reduce drag.