With improving sunlight, the greenhouse warms up early. Signs of growth will be more obvious under glass or polythene. The greenhouse affords an opportunity to begin the growing year a little earlier, and because it provides protection for the gardener as well as the plants.

A heated propagator in a greenhouse allows the earliest bedding flower seeds to be sown. This is not necessary for early vegetables that will later be planted out — sun heat alone is enough to give them an early start. Carrots and lettuce for pulling in late May or June can be sown in a greenhouse or cold frame in January using an early variety. A greenhouse crop of French beans can be started.

Strawberry plants potted in autumn can be brought in to flower and fruit early. A greenhouse grapevine or peach tree should have a good soak of water to get them going and to wash away surplus salts that tend to build up in greenhouse soil.