How to Grow the Sweet Pea Flower

The sweet pea flower is a popular annual plant. Grown for their delicate, aromatic blooms the sweet pea flower (Lathyrus odoratus) is a common inclusion in flower beds and cottage garden planting schemes. A colorful plant with a relaxed climbing habit, these classic plants thrive in pots and containers. Many people also like to grow their sweet peas as part of a cut flower garden.

Elegant and attractive, the sweet pea flower is also easy to grow. If you want to add a little old fashioned charm and fragrance to your garden, the sweet pea is a great choice. Here is your complete guide to growing the sweet pea flower.

1 The attractive sweet pea flower
Attractive and elegant, these blooms are a colorful and fragrant addition to the garden.

Different Sweet Pea Flower Varieties

There are two types of sweet pea flower: annuals, which last for one season, and everlasting perennials. These return year after year, if allowed to. Everlasting perennials are less fragrant than annual varieties.

Whether you choose to grow annuals or everlasting perennials, there are many different sweet pea flower varieties available. Some of the most popular include:

  • Lipstick, a wavy edged flower with a strong scent
  • Painted lady is a hardy annual variety, it produces attractive pale and dark pink bi-colored blooms and a strong, old fashioned scent. This is a good early flowering variety
  • Alboroseus is a hardy perennial bush forming variety which produces pink and white blooms.
  • Matucana is another reliable hardy annual cultivar. A true old fashioned variety with fragrant bi-colored purple blooms.
  • Lord Nelson is a hardy annual cultivar, grown for its fragrant blue blooms which are ideal for cutting.
  • White Pearl is a perennial white flowering climbing variety.
  • Little Sweetheart is ideal for small spaces and containers, rarely passing 14 inches in height.
  • High Scent is a strongly fragrant variety, its flowers are white with a lavender edge

For a combination of colors, try planting a mixed seed packet such as Royal Family Mix. This provides a mix of different colored plants which all share the same growing needs.

2 Flowers in different colors
These attractive plants come in a range of colors and sizes. 

While the sweet pea flower is known for its fragrance, not all cultivars are fragrant. Check the seed packet before planting. The packet also tells you lots of useful information such as the soil and light preference of the variety and their expected height and spread. All of this information helps you to select plants that are perfectly suited to your garden.

You can purchase young sweet pea flower plug plants or seed packets from garden stores.

Germinating Seeds

Despite having a reputation for being difficult to germinate, growing a sweet pea flower from seed is surprisingly easy.

I, and many others, like to soak the seeds on a damp cloth overnight before sowing. Sweet pea seeds have a hard outer shell. Soaking the shell softens it, making germination easier. Some growers avoid soaking their seeds, believing that it leads to weaker plants.

If you don’t want to soak the seeds overnight, there are other ways to help speed up germination. You can use a knife to make a slight crack in the outer coating. Alternatively, use sandpaper to gently rub away the coating. Whichever method you choose, try to mark the side opposite the black eye or scar of the seed shell.

When to Sow the Seeds

For an early display, sow the seeds in the fall, either in pots undercover or in a cool, frost free position outside. A more popular option is to sow the seeds in the spring once the weather starts to warm up. This ensures that your plants won’t fall victim to an unexpected frost.

In western areas you can sow seeds directly into the ground from August onwards. In the drier Midwest and northeast, non coastal areas sow seeds indoors after the harshest weather has passed and the ground has started to thaw. Growers in the south can sow seeds directly into their final position in November or December.

How to Sow your Seeds

Sow your seeds in seed pots or trays filled with good quality potting soil. Sow one seed per pot. If you are sowing seeds in a seed tray try to space them at least 1 inch apart.

3 Germination can be slow
Seeds can be difficult to germinate. Keep them warm and the soil moist and seedlings should emerge. 

Cover the seeds with a thin layer of compost and water well. Place the trays or pots in a propagator, for germination to be successful the soil temperature should be consistently between 55  and 60 ℉. A Propagator with Humidity Vents helps you to better regulate the temperature around your seedlings, enabling you to provide the ideal germination conditions. .

Germination takes 10 to 14 days. During this period continue to gently water or mist the soil, don’t allow it to dry out.

Following germination, remove the cover from the seedlings and continue to grow on.

Once the seedlings are about an inch in height, or have developed at least one set of leaves they can be moved to a cooler, frost free spot such as a cold frame or unheated greenhouse. If starting seeds in the fall, keep the seedlings cool during the winter to prevent legginess.

Following germination, the sweet pea flower needs about 50 days of growth in cool temperatures before flowering.

Pinching out Seedlings

Some people like to pinch out the tops of seedlings to create bushier plants. Pinching out also stops seedlings becoming weak and leggy. While pinching out is useful it is not necessary.

If you do decide to pinch out your seedlings, wait until they have developed a few pairs of full or true leaves. To pinch out simply pinch off the top of the growing tip between your fingers, breaking the stem just above a pair of leaves.


How to Transplant Seedlings

Always harden off seedlings before transplanting. This helps to create healthier, more resilient and productive plants. Hardening off takes about 2 weeks.

Transplant seedlings into their final position after the last frost date has passed.

Plant in a full sun or lightly dappled shade position. The soil should be rich and well draining. While you are hardening off the seedlings, take the time to prepare the soil. As well as weeding and raking over the soil, work in lots of organic matter such as compost. If you struggle to keep your soil weed free, here is a list of easy to use, durable weeding tools.

If you are growing in containers use good quality peat free compost. Work a slow release fertilizer into the soil before planting.

When you are ready to transplant, make a hole in the soil large enough to hold the seedling. Position the seedling in the center of the hole and backfill. Water well. Space your seedlings 7 to 8 inches apart.

How to Care for the Sweet Pea Flower

These are climbing plants. This means that you will need to provide some form of support such as a trellis for the plants to climb up. This is best installed when transplanting. You can also use bamboo canes to make a wigwam. The plants send out tendrils to help them climb so they do not need tying. However, sweet pea support rings, such as ZeeDix Plant Support Cages, can be used to help train their sprawling growth.


When to Water

Water to keep the soil evenly moist. This usually means watering deeply once a week but it can vary depending on the weather and your growing conditions. Unless they are planted in a self watering pot, plants growing in pots may require more regular watering.

Keeping the soil evenly moist helps to prevent the plants from setting seed. It also prolongs flowering. If you are unsure whether to water, stick your finger into the soil close to the plants. If the soil is dry to the first knuckle it is time to water.

How to Fertilize

These are not particularly heavy feeding plants. Apply a dose of high potash fertilizer, such as tomato fertilizer, when flower buds start to form. Apply a second dose halfway through the flowering season. Alternatively, a compost tea can be applied.

Pruning your Plants

You can prolong the flowering period by cutting away the spent flower heads on a regular basis. Deadheading also helps to promote and prolong flowering. Deadheading is best done before the bloom starts to fade and set seed.

If spent blooms are allowed to remain on the plant seed pods will form. These should be cut away before they mature and split to prevent the plants from reseeding around your garden.

4 Deadhead to prolong flowering
Pruning is minimal. Cut away spent blooms to prolong flowering and prevent seed pods from forming. 

Common Sweet Pea Problems

These are pleasingly problem free plants. Try to space the plants out correctly when sowing seeds or transplanting. Planting too closely together, or in an overly dark position can cause mildew issues. If your sweet peas develop mildew thin out the affected plants to improve air circulation. A fungicide can also be used.

Slugs and snails can target plants. Organic and chemical free solutions such as copper bands, beer traps, and diatomaceous earth can all be used to deter these destructive pests. Diatomaceous earth can also be used to deter cutworms and caterpillars. Simply sprinkle it evenly around the base of the plant.

Aphids can also target the foliage. Should you notice an infestation, treat the affected leaves with neem oil or homemade insecticidal soap.

Finally, don’t allow the soil to dry out. This can cause blooms to fall from the plant.

Keeping the Seeds

In late summer or early fall allow some of the sweet pea flowers to remain on the plant and go to seed. As the blooms fade, seed pods form.

5 Allow pods to brown
Allow pods to brown and dry before harvesting the seeds. Ripe seeds will be dark brown or black in color.

Allow the seed pods to remain on the plant until they turn a light brown color. Typically the ripe pods will be the same color as a paper bag. When they are ripe, cut the pods from the plant. Take the pods inside and open them. Carefully remove the black seeds and store in a dry place, such as an envelope or air tight jar until you are ready to use them. Remember to date and label the envelope or jar. The older the seeds are the more difficult it is to germinate them.

Cut Sweet Pea Flowers

The sweet pea is a reliable member of the cut flower garden.

Cutting at the right time helps to improve their life span. Cut the blooms as soon as they completely open. Alternatively cut when the stem has at least 2 unopened buds at the very tip.

Cut sweet peas early in the morning before they have time to dry out. You can also cut your blooms late in the evening.

After cutting, take the stems inside as quickly as possible. Cuttings can be kept fresh in a bucket of water for a little while, but ideally they should be prepared as soon as possible. To prepare the stems, hold them underwater and cut the stems 1 to 2 inches above the initial incision. Cutting underwater prevents air bubbles from forming and blocking the flow of water into the stem.

Place the prepared stems in a vase or bucket of fresh water. The water level should come up to the neck of the stem. Allow the cuttings to sit in the water for several hours. When you are ready to arrange, remove any foliage that would otherwise be underwater.

6 A fragrant ornamental flower
A fragrant addition to the ornamental garden, lathyrus is a versatile and easy to grow plant.

A colorful and fragrant member of the flower garden. Sweet peas thrive when planted alongside roses, catmint, lavender, alyssum and lobelia. They can look particularly effective if planted on their own in a pot and allowed to cover a bamboo wigwam. Despite their ornamental elegance these attractive blooms are amongst the easiest to grow in the garden. This makes the sweet pea flower ideal for novice and nervous gardeners.

The versatility of the sweet pea flower  means that it can be incorporated into a range of different planting styles and schemes. Wherever you chose to grow your sweet pea flowers, these fragrant blooms are a fantastic, low maintenance addition to the summer garden.

Sweet pea flower 1 Sweet pea flower 2