What Are Sweet Peas?

Sweet peas (Lathyrus odoratus) are among the most rewarding flowering annuals. Valued for their delicate blooms and exceptional fragrance, they produce flowers over several months. Native to Sicily and southern Italy, sweet peas have been cultivated for centuries and have become garden favourites.

The original sweet pea in Sicily needs a minimum twelve hours day length to flower. Many modern sweet pea cultivars retain this genetic programming and will not flower in New Zealand until early October when the day length becomes long enough. These are known as summer flowering cultivars.

Some sweet peas have been developed that flower with as little as ten hours of daylight and some that need around eleven hours. We call these winter and spring flowering sweet peas respectively.

Winter flowering sweet peas are very useful as cut flowers as they can be sown in autumn and winter for flowering from early August, providing cut flowers well before the summer flowering sweet peas are available.

Spring flowering sweet peas fill the next flowering period, from early September, and provide a succession of flowers before the summer flowering cultivars start from early October. Winter sweet peas can also be sown in mid summer to flower in autumn, another valuable time for cut flowers.

When to Sow Sweet Peas in NZ

Sweet pea sowing time varies according to whether the cultivar is winter, spring or summer flowering. Our web site has filters so you can easily see which cultivars fall into which group and plan your sowing accordingly.

Winter flowering sweet peas can be sown from April through to August for flowering from late winter to early summer. They can also be sown in January for autumn flowers. These cultivars include 'High Society', 'Paradox' and the 'Solstice' range of colours.

Spring flowering sweet peas can be sown from June to September for flowering from early spring through to mid summer. These cultivars include 'Equinox Mix', 'Mahogany', 'Enigma', 'Pandemonium', and many more.

Summer flowering sweet peas should be sown from July to October for flowering from late spring through to late summer. Most cultivars fall in this group, including 'High Scent', 'Chocolate Flake', 'Almost Black', 'Erewhon' and the 'Kaleidoscope Mix'.

While spring and summer flowering sweet peas can be sown early like the winter flowering cultivars, they will simply produce more and more growth before the days eventually become long enough for them to flower in mid to late spring.

How to sow Sweet Pea Seeds

Sweet peas can be planted directly in the soil or can be started off in small biodegradable pots - our recommended method.

Step 1 – Choose the Right Position

Sweet peas prefer:

• At least six hours of full light each day, some afternoon shade in hot areas
• Free-draining, humus-rich soil
• Good airflow around the stems and leaves to prevent mould
• Something robust to climb up - a trellis, fence or bamboo wigwam
• Protection from strong winds

Step 2 – Prepare the Soil

Loosen the soil before planting and improve heavy ground by working in plenty of quality compost.

Sweet peas like a good feed, so work some fertiliser into the soil as well. They also prefer a neutral pH, so a couple of handfuls of powdered lime should be worked in as you go. Lime and gypsum react very slowly in the soil, powdered lime is faster acting so is always our preference.

Step 3 – Sow at the Correct Depth

Whether you're sowing directly in the soil or into small compostable pots (recommended), the same process should be followed.

• Sow the seed around 2cm deep.
• Keep damp but not soaking wet.
• Seeds should be emerging within ten days, but can take as long as eighteen days.

Step 4 – Plant out your seedlings

If you've started the seeds in small biodegradable pots then they should be planted out once they are 5-6cm tall.

• Plant them out in a suitable location, into prepared soil as described above.
• Biodegradable pots made from compressed fibre are planted out as they are, the roots just grow through the pot
• Water them in after transplanting.
• Keep them damp, but not wet over the next few weeks as they establish.

Sweet pea care while growing

Once the sweet peas are 15cm tall it's time to check a few things are in place.

Flowering and Cut Flower Tips

By carefully choosing cultivars with different day length responses, you can have sweet peas flowering from late winter through to mid summer.

• Picking the flowers often will encourage the plants to keep growing and produce more flowers.
• For the longest vase life, pick early in the morning.
• Pick when the first flower on a stem has opened and the upper buds remain closed.
• Use clean, sharp snips and place the cut stems into water immediately.
• Refresh vase water regularly for the best vase life.

After Flowering Care

As the plant comes to the end of its natural flowering period it will stop growing and begin to yellow off.

Remove the old, dried vines from your trellis or netting so it is ready to use the following year.

Common Sweet Pea Problems

Common Questions

Final Advice

Success with Sweet Peas comes down to just a few essentials:

1. Free-draining soil with plenty of compost and some lime added
2. A trellis, mesh or fence to climb up
3. Full sun with protection from intense summer heat
4. Planting the right cultivars to get a succession of flowers
5. Feed well and pick flowers often to keep the plant growing and flowering

With those basics right, Sweet Peas can reward you fragrant blooms from late winter to mid summer.