Plum
Cultivars and varieties:
Prunus domestica 'Czar' - Doesn't need sun to ripen, will grow and fruit on a north-facing wall.
Prunus domestica 'Early Rivers'
Prunus domestica 'Marjorie's Seedling'
Prunus domestica 'Oullins Gage' [AGM] (Dessert) - Self-fertile.
Prunus domestica 'Victoria' - The most commonly grown plum. It's self-fertile and will grow well on a north-facing fence or wall.
Seeds to sow now:
Indoors or in a heated greenhouse
Cress
Ornamental pepper
Outside
Alpine wallflower
Basil
Beet, Beetroot, Chard
Beetroot
Cabbage
Canterbury bell,
Carrot
Common wallflower
Cress
Double daisy
Foxglove
Kohl rabi
Onion
Pansy
Radish
Spinach
Spring onion
Sweet William
Turnip