Hints on growing

Hints on growing

There are many ways to grow Sweet Peas, but what follows are suggestions that have been proved to work for summer flowering varieties in the UK.

Sow seed in October, if in the south or midlands, or from January to February. Later sowings are possible if growing for garden decoration and cutting for the house.


Seeds should be sown and covered with 1 cm of compost. A general multi-purpose compost is sufficient. Seed composts often have insufficient air spaces and are best avoided. There are three options for container:

  1. Put 8 seeds in a 12.5 cm pot, reducing to the best 6 following germination. These can be left in the pots until planting time.
  2. Put one seed per cell in deep Rootrainers, which have 8x4 cells. These are 12.5cm deep and the plants are left in them until planting time.
  3. Put 50 seeds in a standard seed tray, arranged 10x5. Once the seedlings are about 2.5cm high, they will need to be transplanted into one of the above containers for growing on.

Do not soak seeds in water before sowing as this may reduce germination. Germination is best at about 15C to 18C and can take place in 7 to 14 days.


Seedlings emerging in root trainers




Early growth

Gently water in your seeds after sowing. Further watering is then best avoided until germination can be seen, in order to reduce the risk of disease.

Autumn sown seedlings should be placed in a cold frame or cold greenhouse to over-winter. They will stand moderate frost and must be kept cool on sunny winter days. Spring sown should be kept in a cool greenhouse. Protect against mice.


Seedlings growing on in cold greenhouse



Spring sown plants should have the growing tips of the primary stem pinched out after two pairs of leaves have been produced, to ensure the development of side shoots. Autumn sown plants will normally produce side shoots naturally but the primary stem should be removed before planting out.

Plant pinched out showing side shoots


Planting out

The planting area should have been prepared in Autumn. Autumn-sown plants should be planted out about mid-March and spring sown a month or so later, depending on your location. Individual plants should be placed in holes and the soil level brought back to a level below the first side shoot and planted firmly but lightly to ensure good soil contact.


Before planting out


Seedlings ready to go out



Growing on

If plants are to be grown on the cordon system, once the side shoots are about 20 cm long decide which is the strongest stem, not necessarily the longest, and then remove all other side shoots. (Sometimes two stems may be retained).

As growth progresses the stem(s) should be tied to their canes, using rings or other methods. Side shoots and tendrils should be removed.

Only Spencers for showing have to be grown by this method. Otherwise use netting or wire supports and leave tendrils in place to allow the plants to climb.

Once flowers appear they should be cut regularly or dead headed to ensure no seeds are produced, otherwise flowering will cease.


Sweet peas planted out and tied in


Picking a bloom


Layering will be necessary for cordon grown plants. Untie the plants and lay them along the ground; retie several canes further along, depending on height. This will prevent them from growing taller than their supports.

Layered cordons


Non-cordon plants grown more for garden decoration require less intensive care, but still need tying in as the side branches develop and perhaps a little thinning out.


Sweet peas flowering in a garden border


Growing in a polytunnel


Feeding and watering

Little feeding is needed if the ground has been suitably prepared. These plants fix nitrogen from the atmosphere so additional fertilisers should be high potash and phosphate, to encourage flowers rather than green growth. Liquid feed at dilute concentrations (half or even quarter strength) can be applied at root level or as a foliar feed. Care should be taken to ensure that roots do not dry out. Under very warm conditions it can be beneficial to spray, below flower level.