Sweet peas are an easy to grow classic flower that really lend themselves to polytunnel growing. They are one of the most popular annual flowers and are great for bringing pollinators into your food-growing polytunnel. Since sweet peas grow up a trellis or another vertical structure, they are also a good choice for those seeking to employ vertical gardening techniques to make the most of the space in their polytunnel. Smaller cultivars can also be used to grow in hanging baskets or containers.
Sweet peas are easy to grow yourself from seed, though you can also buy plants easily from garden centres and plant nurseries. Some people have discovered that they have a problem with patchy germination. This is usually due to the hard seed coating. This hard coating can be softened by leaving on wet kitchen roll in a warm room and sowing once they begin to swell. Do not, however, be tempted to soak the seeds. Usually, there should be no germination problem and you should see your seedlings appearing before long.
Sow your seeds into small individual pots, or plant around five seeds in a larger container, around 12cm plus across. Cover the seeds with around 1cm of compost/ growing medium. Water in the seeds and cover the pots with clear class or plastic. Keep them at around 15 degrees Celsius until the seeds have germinated and then remove the covering. Seeds should be sown between January and April, or in the autumn in October or November, overwintering in an unheated polytunnel or greenhouse, which may give slightly earlier blooms.
Move each seedling into its own 9cm pot when they are around 3.5cm in height. If you chose to sow your seeds in the autumn, transfer the seedlings to a cold frame or your unheated polytunnel to prevent the seedlings from becoming leggy. Remember that spring sown plants will need to be hardened off gradually before you plant them out.
Plant into their final positions in your polytunnel or outdoors from April, waiting until the risk of frost in your area has passed. The plants should be spaced at around 20cm apart. Some suggest that you should pinch out the tips when the plants reach about 10cm in height, which encourages the plants to produce strong side branches. Professional growers, however, will often grow sweet peas as cordons.
Sweet peas are extremely popular for use as cut flowers, with their long stems, pretty flowers and evocative scent. They are an old-fashioned flower that has resurged in popularity in recent years. Simply cut the flowers as and when they are wanted