We demonstrate that the operation of taking disjoint unions of
J–holomorphic curves (and thus obtaining new J–holomorphic curves)
has a Seiberg–Witten counterpart. The main theorem asserts that, given
two solutions (Ai,ψi), i=0,1 of the Seiberg–Witten
equations for the Spinc–structures W+Ei=Ei⊕(Ei⊗K-1) (with certain restrictions), there is a solution
(A,ψ) of the Seiberg–Witten equations for the
Spinc–structure WE with E=E0⊗E1, obtained
by "grafting" the two solutions (Ai,ψi).