It is called 'Scarlet Tunic' after the distinctive apparel of the Chelsea Pensioners.
The name was decided after a public online vote and a ballot of the pensioners themselves.
Mr Fothergill's will donate 25p for every packet of seed sold to the Royal Hospital Chelsea.
The seed company's supportive retailers and gardeners have already helped Mr Fothergill's raise more than £45,000 for the Royal Hospital Chelsea through sales in 2015 and 2016 of its poppy Victoria Cross. Sweet pea 'Scarlet Tunic' continues that backing for the veterans of the United Kingdom's armed forces.
Mr Fothergill's joint-managing director David Carey said: "Our stockists have been fantastic in promoting this wonderful cause, and we look forward to building on the great success of the poppy Victoria Cross campaign."
The Royal Hospital Chelsea was established in 1682 by Charles II to provide a safe home for military veterans 'broken by age or war'. The Christopher Wren-designed Royal Hospital admitted its first pensioners in 1692.