Sweet peas are easy to grow, come in a range of rich colours, are prolific bloomers - the more flowers you pick, the more the plant produces - and its flowers bring a fresh perfume indoors.
New Zealand has a strong history with sweet peas, both in terms of seed production for English and European seed catalogues and sweet pea breeding. Dr Keith Hammett is the godfather of sweet pea breeding; he has a passion for these blooms that is captivating. Keith’s interest in the sweet pea started off as a teenager, when his uncle decided he wanted to separate his flower and vegetable garden, doing so by planting a dividing row of sweet peas. As Keith recalls it, it was love at first sight. This love has only continued throughout the years, as sweet pea varieties bearing the Hammett name are now sold all over New Zealand and around the world.
Keith says “Sweet peas are the ultimate ‘cut and come again’ flower”, meaning that the more you pick from the flower stems, the more they will produce. This is a total win-win for those at home who can never have too many of these gorgeous blooms.
“The ones with the larger, frilly flowers have longer stems than, say, some of the smaller flowered forms with the strongest scent,” says Keith. His most highly-scented varieties are ‘Original’, ‘High Scent’, ‘More Scent’, and ‘High Society’.
When, Where & How
- Plenty of sun needs to be on the menu – while sweet peas will bloom in half-day sun, the results are always best when they are planted somewhere that gets rays all day.
- Sow seeds now or look for seedlings, as they are in the shops throughout August, September and into October.
- Seeds can be sown directly where they are to flower provided the soil is well drained, in a sunny position, and you are able to protect against slugs, snails and maybe birds.
- If sown into pots for planting out later, seeds do not need to be grown inside or in the glasshouse, simply sow and place outside in full light. Keith advises to never soak seeds before sowing.
- Provide support – sweet peas are a tumbling vine and need something to cling to when climbing. This support can be as simple as bamboo canes, wigwams, or old bike wheels, while netting against a fence or wall is an enduringly popular choice. Keith often suggests making a simple tepee by selecting tall bamboo canes or finding some tall slender prunings from apple or plum trees, then poking them into the ground in a circle about 70cm in diameter, tying the tops of the bamboo or branches together and weaving string around the structure so the sweet peas have something for their tendrils to cling onto.
- Sweet peas need plenty of nutrition to keep blooming and prefer a soil that can lock in plenty of moisture to maintain active growth. As soon as the soil dries out for any period of time, the plant thinks its life is nearing the end and it begins to wilt and prepare to set seed, so avoid this with regular watering. This can present problems with tubs and planters.
- Mildew or grey mould can be an issue, especially early in the season before the days become longer. It often appears if humid weather allows the plants to dry out, and can be counteracted with a monthly drenching with Seasol, although some recommend spraying with baking soda on a weekly basis instead.
Homemade baking soda spray
A weekly spray of the following mix can slow mould spread and prevent further attack.
- 1 litre of water
- 1 tsp baking soda
- 1 tsp cooking oil
- 2-3 drops dishwashing liquid
Did you know?
Summer-flowering sweet peas need 12 or more hours of daylight each day before they are able to flower. If sown too soon, plants grow very tall before they come into bloom, and similarly, if they are sown when days are long, they will not flower until they have been through the following winter.
Tougher than they look
As Dr Keith Hammett will tell you, sweet peas may look delicate and feminine, but they are surprisingly tough. These fine flowers will germinate and grow at low temperatures. In northern New Zealand, delay sowing seed until June at the earliest.
What you need to know
When to sow
It is possible to have flowers year-round.
- Summer-flowering types: March-May.
- Winter-flowering types: May-July.
- For autumn blooms: sow spring and winter types in November-December.
When to plant
Plant out seedlings in August-September.
Where to plant
Full sun in fertile soil. Ideal as patio and tub plants.
Allow 20-50cm between most hybrids or as directed on plant label.
Where to buy
Garden centres, hardware stores, or online nurseries.