This early in the year to germinate seeds it is essential to create a warm, benign environment for both germination and the early stages of the seedlings. Very few gardeners can afford the luxury of a heated greenhouse which means bringing seed trays into the house, not ideal, or using a heated propagator mat and site the seed trays in a porch or unheated conservatory. Seeds will need to be placed into a sealed propagator to create a warm atmosphere which will not dry out, and once germinated, removed and kept frost free. Light levels are very low in February, so seeding is not easy and plants need to be turned regularly to keep even growth.
The benefits of seeding in February is if it goes well, the plants will mature earlier. Sowing in March and April is easier because of the extra light and warmth. Lots of information and advice at How to Sow Plant and Veg Seeds, 10 top tips for successful sowing and germination and what to do with weedy seedlings.
Video advice on sowing seeds and germination.
Suitable for seeding under glass in February are: Aubergines, Beetroot, chilies, Broad beans, lettuce and rocket and tomatoes. Flower seeds, many of the popular garden plants such as Ageratum, Antirrhinum, Calendula, Cornflower, French Marigolds, Nigella, Rudbeckia, Salvia, Scabious, Sweet Peas and Zinnia.
The hardier plants such as Broad Beans, Lettuce, Sweet peas will be easier to sow early because they will be able to withstand the cooler temperature. Equally the more tender plants, courgettes, cucumbers, ipomoea are best left to later.
Towards the end of the month and into March it is easier to germinate and grow on seeds because of the increasing light and warmth. The further north you are in terms of prevailing weather and chill factor the more you may wish to delay first sowings.