How to Grow Sweet Peas
These instructions are for guidance only and do not guarantee success. All seed is batch tested for germination and if given the correct conditions will give good germination rates.
Autumn Sown Spencer Varieties
For early flowers, sow seeds October/November. Seed sown at this time of year would not "normally" require any heat to germinate but do be aware of early frosts and cold nights, heat as required at 10/15°C Day and Night. Sow in grow tubes, pots or trays and grow either in a cold frame or cold greenhouse. If grown in a greenhouse, put the plants as high to the apex as possible to avoid 'lanky' plants and once germinated don't let them get too warm. (Open doors and windows in mild weather). Once hardened off they will withstand mild frosts.
Spring sown Spencer Varieties
Sow from January to April in a heated greenhouse or similar, at about 10/15 °C Day and Night. Once germinated, lower the temperature to about 5/10°C. If weather is mild no heat will be required but plenty of light required to stop plants from getting drawn. Once the plants have hardened off they will withstand mild frosts.
Sow seeds February to April and heat at 10/15°C Day and Night. Sow same way as the instructions below. Once germinated, lower the temperature to about 5/10°C. If weather is mild no heat will be required but plenty of light required to stop plants from getting drawn. Once the plants have hardened off they will withstand mild frosts.
Plant 6 to 8 seeds per 5 inch pot.
Plant seeds 1.5 inch apart in trays.
Sow in the ground from late April onwards.
Do not Soak or chit the seed. Take the grow tube you are going to use and ¾ fill with a general purpose compost. Any compost will do for sowing, nothing too rich. Mix with sharp sand and grit or sieved soil to keep it light and airy.
Soak the compost well.
Top up the pot with dry compost from the bag.
Make holes for the seeds.
Plant the seed ¾ inch deep into the dry compost – DO NOT water again until germinated.
Cover with newspaper to stop the compost drying out and place in a cold greenhouse or cold frame. (If sowing from November onwards place the pots in a warm greenhouse at about 10/15 °C, day and night, until germinated then put in a cold greenhouse or cold frame. Just protect from heavy frosts). Always use mouse traps to keep mice from eating the seeds as they germinate.
As soon as you see the first sign of germination remove the newspaper, even if only one has come through. Usually this happens in 7 - 10 days.
Leave the plants in a cold greenhouse or cold frame and protect from mice, slugs, heavy rain, severe frosts and heavy falls of snow . Plants started in this way will withstand down to –5/6 °C. of frost.
Keep compost moist.
When the plants have three sets of leaves showing remove the top of the plant above the 2nd pair of leaves to encourage side shoots.
Plant out as soon as the ground is dry enough to get on and the conditions are favourable, from February onwards.
When plants start to flower, cut off flowers when top blooms are open. Remove all dead flowers from plant to allow for more to grow. Cut every 2 to 3 days and do not let them go to seed as once set they will stop flowering.
To get longer stems take out the side shoots, remove the tendrils and tie the plant up.
Keep the ground moist and feed every week with a high potash feed such as Maxicrop or a tomato food.
Keep removing old blooms from the plant as the more you pick the more you get.
Problems and Diseases
For advice on problems and diseases that can affect Sweet Peas, please read our 'Cultural Information' page.