How to Grow Sweet Peas

February 29, 2016

sweet peas on trellis

There's an old wives tale that says you should sow your Sweet Pea seeds on St Patrick's Day (March 17th). Whether you're a believer or not, it's definitely a tradition many Australian gardeners follow.

Soil Prep

When we talk about preparation we're referring to your garden's soil. So unless your soil is naturally alkaline rich (not many of us are so lucky) you'll need to do a couple of things prior to sowing.

  • Adding Lime. Lime will raise your soils pH levels and improve it's over all quality
  • Adding a generous amount of compost with a slow release fertiliser. This will ensure your flowers have nutrients for a longer period of time. Try to avoid high nitrogen fertilisers.
  • You'll find that your Sweet peas are happiest when their heads are in the sun and roots are deep in cool, moist soil. So if your garden gets a lot of sun, plant low-growing annuals in front to shade your Sweet peas roots

Sowing Seeds

After roughly 2-4 weeks you should be ready to sow your seeds. Give your soil a good watering so it's nice and damp and dig a trench no deeper than 3cm. Roughly measure the depth using your finger or even a pencil and place your seeds into the holes and press down firmly.

Unless the weather is particularly hot and dry; further watering won't be needed. Sweet Peas hate having 'wet feet' and is the reason we don't recommend soaking the seeds prior to sowing.


Germination can take anywhere between 7 - 15 days depending on the soil temperature. Gradually fill in the trench with soil the more your seedlings grow. When determining if your plants require water put your finger into the soil bed to roughly the first joint. If dry, water them at soil level and do so in the morning. Sweet Pea flowers suffer from bud drop so be careful not to over water.

Climbing Options

It doesn't take long for your Sweet peas to climb, so supports should be added at the planting stage.
Except for the bush types, it's a good idea to give at least 1.8m of good support. You'll find that trellises are most commonly used however alternative options can be chicken wire, bushy stubbly twigs, fishing line hung from above. It's really anything that your plant can climb.

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