The easiest way to find a suitable plant (that gives the right feel for your piece) would be to go to B&Q or a garden centre and look at seed packets. They will tell you when and how to plant.
For instance, your character might be the kind of man who'd plant lettuce, or he may be more of a root veg person. Going and looking yourself would give you loads of choice, and the chance to find something 'just right'.
However, as an example (and in case you can't be bothered to go look):
'Sweet Basil: Sow between early March and late May, directly into finely raked, warm, moist soil at a depth of 6mm, thinning the resulting seedlings to a final spacing of 23cm. Alternatively sow inside into pots or trays fo moist, quality compost. Maintain 10-15 degrees C. Thin to 5cm apart and grow on prior to planting out when danger of frost is past. Easy to grow and very tasty.'
Basically, if you're planting them directly outside then you need to do it later in the suggested window rather than earlier. Late April should be okay for directly outside.
Any more questions, just shout...
Deb
<Added>I have some more seed packets here if you have any particular requests, Emma... ;)