Highly versatile, and gracing gardens with their beautiful flowers and divinely rich scents, the Sweet Pea (Lathyrus odoratus) is quite understandably a quintessential annual plant. For every garden, there is the perfect sweet pea; you can choose from flowers ranging from lilac to plum in colour, and can even opt for a dwarf variety if you don’t wish to provide support. Primed for the beginner gardener, read on to understand how to grow flourishing sweet peas.
How to Plant Sweet Peas
Sweet peas can be grown from seed in both autumn and spring; although if you are sowing them in autumn, it is wise to grow them in a location that is sheltered from the frost.
As you would for most annual plants, sow your seeds in 9cm pots (or a tray if you prefer), and use a peat-free compost. We do believe that a tall pot is best, as their added depth is optimal for the roots.
Once sown, your sweet peas are best stored in either a greenhouse, warm windowsill, or cold frame. One aspect that gardeners find appealing about sweet peas is that they will germinate very easily. However, you can nick the seeds to provide an added boost. This is done by delicately making a cut on each seed. The cut should be shallow enough to resemble a light graze, but deep enough to allow the water to penetrate the seed. As long as you don’t harm the structures beneath the seed’s coating, you can nick with either a knife or nail file.
After any risk of frost has passed, your sweet peas can be safely planted in your garden. Nonetheless, we advise that you harden them off for up to two weeks to accustom them to the less predictable conditions.
Depending on your preference, you may wish to pinch out your young sweet pea plants. Some believe that this can hinder the size of the bloom, while others are convinced that it allows for bushier growth and prolific flowering. If you are unsure, why not pinch out the tips of some sweet peas, and leave the rest to grow naturally?
How to Care for Sweet Peas
Come spring when the weather begins to warm up, any sweet peas grown from seed can now be grown outdoors. Whether you are planting in pots, or into your garden’s beds, we encourage you to use a rich, water retentive potting compost (ideally a mix of both rich potting and loam-based compost). Make sure you firm down the soil once your sweet peas have been planted, but be gentle, as you could otherwise prevent their roots from properly growing.
Do sweet peas need support?
Because of their vining habit, the majority of sweet pea plants will need support. Dwarf varieties, such those belonging to the ‘Cupid’ series, are an exception to this rule. Typically growing to no more than 30cm tall, they can be grown in low troughs, and even be used as a bedding plant. Why not plant them in a hanging basket for a floriferous display?
Before you plant out your sweet peas, you should have their support readily set up. You can support your sweet peas by making a wigwam out of bamboo canes. However, to allow for straight stems (which are desirable if you want cut flowers), you should have bamboo cane that is positioned at a 90 degree angle.
As sweet peas grow vigorously, you should tie them to their support every few days. Using a piece of regular string, tie a double knot around the cane. From the remaining string, gently tie your sweet pea to the cane, and secure with another double knot. Try to rescind any side shoots that emerge, as this enables the plant to leverage greater energy into their stem.
You should repeat these steps throughout their growing season, and provide plenty of generous waterings.
Do sweet peas need full sun?
To really thrive, sweet pea plants will need full sun or light dappled shade. Due to being perfect for pots, you’ll have more freedom in where they can be grown; better enabling you to provide a sunny site.
Do I need to deadhead sweet peas?
To enhance the flowering of your sweet peas, you should remove any spent flowers. Try to do so before any pods of seeds have formed, as these will encourage the plant to conclude flowering.
Using Sweet Peas as Cut Flowers
As long as you adopt the cordon method, your sweet pea plants will offer an abundance of cut blooms. Aside from being highly perfumed, their vibrant, frilly petals will look stunning in a bouquet or vase. As such, they’ll make pretty indoor accents, and thoughtful gifts for loved ones.
To keep your sweet peas looking their best, you should replace the water in their vase once a day, and cut their stems once every two days. Why not begin growing a mix of varieties now to enjoy a colourful bouquet come summertime?
Growing Sweet Peas: Common Questions
Before you begin growing your sweet pea plants, the following questions may spring to mind:
Do sweet peas self seed?
Annual plants, sweet peas will die after setting seed. Nevertheless, this doesn’t mean you can’t keep the seeds they produce. Simply bring the pods indoors and collect the seeds. Allow them to dry for a few days, and transfer to an airtight container to keep moisture out.
Do sweet peas grow peas?
Although their name implies this, the pods that sweet peas form are not the same as the pods you see on a runner bean for example. It is important to know that the seed pods on a sweet pea are poisonous so must not be consumed.
Are sweet peas poisonous to dogs?
Sweet peas contain a chemical called ‘aminopropionitrile’, which eventually causes ‘lathyrism’ (a condition developed by ingesting seeds from the Lathyrus genus). The symptoms can affect humans and animals, so you should keep your sweet peas out of reach from children and pets.
Are Sweet Peas available as a perennial?
Yes, typically in the form of plug plants, but many gardeners still prefer growing annuals because their flowers are more fragrant. The flowers of a perennial Sweet Pea have a scent that is much less noticeable.