One of the simplest flowering annuals to grow from seed is the sweet pea. In the garden, sweet peas are frequently direct-seeded. Give them a location with full to partial sun and rich, loamy soil that is deep, wet, and well-drained. To improve the soil and make it more friable, add lots of organic matter (compost, well-rotted manure, leaf mold, or humus).
When they are planted at times with colder temperatures, sweet peas thrive. The “season” for cultivating sweet peas is different depending on the location. To enhance winter and spring blossoming in western North America, sweet pea seeds should be sown from August forward. Although harsh freezes can cause sweet peas to die back, the plants can withstand frost without suffering too much damage. In the west, sweet pea blooms can be enjoyed well into the summer because of cooler nighttime temperatures.
Sweet peas can be started inside early for transplanting or planted right away once the worst of the weather has passed in the drier plains regions. Sweet peas have been successfully cultivated in Colorado’s hot summers by cut flower producers who mulch thickly as the plants mature and the temperature rises.
In the south, plant seeds in November or December for fresh cut flowers in early spring. In the non-coastal mid-west and northeast, start seeds indoors in February and transplant them outside after the ground thaws. In April, seeds can also be planted directly into prepared garden soil. The northeast’s coastline regions are also great places to raise sweet peas for the spring.
For sweet peas to bloom magnificently in your yard, you will need about 50 days of chilly temperatures (below 60 F). The seed coat of the sweet pea is tough and insoluble in water. There is no proof that sweet pea soaking will promote germination. A sweet pea seed’s outer layer can be punctured to allow for quick hydration, which speeds up and increases germination. The sweet pea seed coat can be easily nicked by scoring it with a nail cutter. When the soil is between 13 and 18 C or 55 to 65 F, sweet pea seeds will begin to sprout.
In holes that are about two inches (two knuckles) deep, plant seeds. Fill each hole with two to four seeds, and spacing them four to six inches apart. Till seeds have sprouted, thoroughly water and maintain soil moisture. Germination should occur within 10 to 21 days. Water the seedlings frequently once they start to grow to encourage robust, wholesome growth. Thin out the seedlings when they are three to four inches tall, spacing the strongest-looking plants four to six inches apart. You can enjoy your sweet peas for a longer period of time by sowing seeds once a week throughout a number of weeks.
Grow them in four-inch plastic or peat pots filled with a seed-starting mixture devoid of soil. Put two or three seeds into each container, each one being pushed an inch into the potting soil. Put the pots in a cool, dark location after covering with mix and water. Watch for new shoots to appear above the earth after about 10 days. Bring the plants outside into the sunlight at that stage. Keep them cool (below 55°F); if you keep them in a heated room, they won’t be hardy enough to move outside without a lot of time to harden off. Reduce the seedlings to one plant per pot until they have two sets of true leaves. As soon as the soil is workable, transplant into the garden about a month before the last date of frost because the shoots are hardy and won’t be affected by light frost. 12 inches should separate dwarf bushy forms, and 6 inches should separate climbing variety.
To avoid harming the roots, it is advisable to plant the stake or support with the seed or transplants when planting tall, long vine sweet peas. Although trellises are the most typical supports, there are various ways to climb. Sweet peas may climb on bird netting strung between two stakes, twine, string, or fishing line hung from the top of a split rail fence, a bamboo teepee, and brush stakes. If the support isn’t up against a wall, scatter seeds all around it to create a stunning display of blossoms that are visible from all angles. A four to six-inch layer of organic mulch will keep the roots cool and lengthen the growing season once the plants have been thinned out.
Avoid overfertilizing to avoid producing lots of very deep green foliage but few blooms. For the initial plant development, a 20-20-20 slow release fertilizer combination that is balanced works well. As an alternative, sweet peas benefit greatly from organic fertilizers. Composted manure mulching will help keep the soil moist and supply nutrients for healthy plant growth and blossoming.
When flowers start to fade, deadhead the plant if blooms are not frequently pruned. The plant will produce fewer flowers overall if seedpods are allowed to develop. More flowers will result from removing spent blooms.
Similar to other direct-sown seeds, the first difficulty for sweet peas is avoiding being devoured by rapacious birds, mice, squirrels, and other animals. Sweet pea seedlings are particularly susceptible to bird, slug, and snail damage if planted in the fall in a warm area.
Preventative actions frequently stop a problem in its tracks before it really has a chance to begin. For healthier plants, abide by these recommendations. Sweet peas should be planted in a region with sufficient airflow. Wet leaves are a magnet for fungus, so water early in the day so they are dry by dusk. Consider sweet peas as a type of food crop. Planting locations should be rotated so that sweet peas are only cultivated in one location every four years. Do not plant sweet peas where other legumes are flourishing or were previously planted. Garden peas, all varieties of beans, peanuts, and clover are examples of legumes.
In particular, certain specialized nurseries or garden centers may sell sweet pea plants. There might be sweet pea plantings in ready-made containers, creating an instant garden. When buying sweet peas, search for plants in individual peat or earth-friendly pots as they require special care when transferred. The better, the bigger the pot. Snip off any blooms or flower buds just before planting. Now is the moment to establish the roots thoroughly so they can support the needs of the developing plant. You will gain larger plants with a profusion of bigger flowers even though you give up early blossoms.
Plant in a pot or in garden soil that has been prepared. To protect the priceless roots from damage when transplanting, it is even more crucial to place the support first. Attempt to maintain the root ball’s unity. It should be planted at the same depth as when it was first emerging. Water it after gently firming the dirt around it. A week to 10 days should pass before mulching. Till the plants are well-established, make sure to maintain the mulch at least an inch away from the stem of the plant. Otherwise, you run the risk of suffocating the stem or potentially fostering bugs, illnesses, and insects.
Sweet peas entered the world of containers when “Cupid,” the first dwarf sweet pea, was introduced at the turn of the 19th century. Their small size makes them ideal for use in pots, urns, hanging baskets, window boxes, and other types of containers. Numerous varieties of dwarf sweet peas are offered in store-bought seed packets or through mail-order catalogs.
Sweet peas that climb are excellent container plants as well. Instead of placing one or two seeds in the center of the pot, place a circle of seeds an inch inside the rim of the pot, spaced a few inches apart. It is simplest to plant the support first, then scatter the seeds around it, in the constrained space of a container. Tomato cages make excellent supports for larger containers; the legs can be pressed into the potting soil. You can put a container of sweet peas in the garden in the early spring because sweet pea shoots aren’t affected by frost (at the same time youd plant seeds outside.)
Start trimming flowering stems for indoor bouquets when the first blooms show. You’re encouraging the plant to produce more flowers in addition to enhancing the lovely scent in the home. Every other day, during the morning hours when they are freshest, trim the stems. For climbing kinds, trimming lateral shoots that emerge from the base of the leaves will slow vegetative development, boost flower production, and improve airflow around the plant.
When you first arrange the stems, they will appear full. As the early blooms fade, the remaining buds will open. Make sure to get rid of any leaves in the vase that are submerged in water. If the base of each stem is trimmed off by 1/4 to 1/2 inch, a bouquet of sweet peas will easily last a week indoors. The water should also be changed every day.
The National Garden Bureau provided permission for this information to be republished. The person who wrote this fact sheet is Cathy Wilkinson Barash. Renee’s Garden provided the sweet pea image “Pastel Sunset,” while Bodger Seeds Ltd. provided the sweet pea images “Ocean Foam” and “Streamers Mix.”
When should I indoor-sow my sweet pea seeds?
In regions with warm winters, you can start seedlings inside in late January. (For the following year, prepare to immediately plant the seeds in the garden in the fall; they will develop throughout the winter into roots and bloom early in the spring.) Sweet peas should be planted inside about six weeks before the anticipated last frost date in areas with cold winters. Les Brake, an Alaskan gardener, offers tips on growing sweet peas. As soon as the soil can be worked in any location, transplants can be placed outside. Light frost won’t harm sweet peas. The majority prefer cool weather, while certain species, such the heirloom Lathyrus matucana, can tolerate mild heat. Since sweet peas often bloom in the spring, you should plant them as soon as you can. Lathyrus belinensis is a plant that blooms later and has interesting coloration.
Sweet peas should be sown in containers indoors:
Use a sharp knife to make a small cut in the tough outer shell of the seed coat. The seed will sprout more quickly as a result.
Fresh seed-starting mix should be poured into four-inch plastic pots or pots made of biodegradable materials (such as newspaper or Cowpots) and properly dampened. With your finger, a dibber, a pencil, or something similar, make a 1-inch-deep hole, then place one to three seeds within. Add extra mixture on top.
If more than one seed sprouts, cut off any more seedlings at the soil line so that each container only contains one plant. The seedlings should be grown in a sunny area, such as next to a window that faces south or on a light stand. The tops of the seedlings should remain 6 inches away from the bulbs if artificial lighting is being used.
Pinch or prune seedlings when they have four sets of leaves, right above the third set. The plant will become bushier and more branched as a result of this.
Before transferring seedlings outside, harden them off by gradually exposing them to sunlight and open air over the course of a week or so, leaving them out for a little bit longer each day. Put them on a soil that drains well and is rich. When moving plants, take care not to harm their roots. Squeeze the pot’s walls to help the root ball slip out. Handle the plants by their leaves and hold the entire root ball in your palm. You can simply plant the entire container in the ground if you used peat pots or anything similar.
Seedlings should be planted 6 inches apart and at the same depth as they were in their pots. Use a watering can with a rosehead to water softly. Sweet peas are annual climbing flowers. Give your sweet peas something to grow on, like a lattice, a twine frame, or netting with holes that are at least 2 inches square.
Before planting, should I soak the sweet pea seeds?
- Sweet peas can be seeded in the fall in warmer places (Zone 7 and above) where the winters are generally not too harsh. Other than that, plant seeds in late winter or early spring. Before planting, give the seeds a 24-hour soak in water. By doing so, the seed coat is softer and the sprouting process is accelerated.
- Fill your planting containers with high-quality potting soil while the seeds are soaking. Use the deepest pots you can find because sweet peas develop a lot of roots. Ideal containers are 4-inch (10-cm) pots and root trainers.
- In each container, plant two seeds by pressing a fingertip into the soil and a half-inch (1.25 cm) deep.
- To boost humidity and hasten germination, cover pots with a plastic dome covering. Place in a warm greenhouse or a house window with good light.
- Pinch out the center growth tip, just above a leaf joint, once plants are 4 to 6 inches (10 to 15 cm) tall, leaving just two or three leaf nodes. The plant will be encouraged to branch out strongly from the base as a result.
- Because they use a lot of food, sweet peas need a little more care to produce in large quantities. Apply bone meal, a thick layer of compost or well-rotted manure, and a generous amount of natural fertilizer to planting beds to prepare them. Incorporate these elements thoroughly into the soil.
- Vines require a sturdy foundation to climb and grow quickly. Affix Hortonova netting or 6-foot (1.8 m) tall metal fence to the tall poles spaced approximately 8 feet (2.4 m) apart down the row for them to climb.
- Around the time of the final spring frost, plant seedlings outdoors in two rows, one on either side of the trellis, spaced approximately 8 inches (20 cm) apart down the row. It’s crucial to keep the vines bound to their supports as they erupt into lush growth. Sweet peas can grow more than a foot (30.5 cm) per week once the vines begin going.
- Sweet peas adore water, and they can’t survive without regular watering. Set up soaker hoses as soon as you plant them to prevent their luxuriant development from being restrained. It’s important to maintain their thirst quenched during warm weather. Use diluted fish and seaweed emulsion to feed plants once a week.
- Pick flowers when there are at least two unopened blooms remaining on the stem for the greatest vase life. To extend the life of the vase, add flower food to the water. It’s crucial to prevent plants from going to seed in order to prolong blooming, so be sure to regularly harvest and deadhead the flowers.
How long does it take for the seeds of sweet peas to sprout?
To avoid mildew, sweet peas require a location in full sun, rich soil that drains very well, and sufficient air circulation. Increased organic material must be worked into clay-rich soil in order to improve drainage. Consider using raised beds for successful results if the soil is excessively wet.
If you are aware that summer heatwaves can come on suddenly, plant your sweet pea seeds where there will be some afternoon shade. For best results, carefully read the instructions on the seed packet. Proper plant spacing is essential. Slugs and snails should be kept away from seedlings. Use netting suspended over seedlings until they are 4 to 5 inches tall if marauding seed and seedling-eating birds are an issue.
Adequate water is a crucial requirement for all sweet pea varieties. If summer rain is insufficient to keep them evenly moist, be sure to water germination-stage seeds, seedlings, and vigorously growing older vines on a regular basis. If the soil is dry when your finger is inserted up to the first joint in the soil bed, water the plants.
Sweet peas are strong feeders, so add plenty of rich compost or well-rotted manure to the soil before planting. At least twice during the growing season, fertilize the soil with a thorough soil drench made up of one tablespoon of liquid kelp and one tablespoon each of fish emulsion. (Every few weeks, sweet peas grown in containers require regular fertilization.)
Aphids can be a problem for sweet peas; spray them off frequently with water. Sticky pheromone traps placed among the vines to attract and capture thrips, an opportune pest, can be used to efficiently control them. Mildew can be avoided with enough airflow and by not watering in the late afternoon and evening ( until the plants succumb to it naturally at the end of their bloom period.)
Almost any vertical support structure will allow all tall vining kinds to naturally grow up it. They will develop into strings, netting, wire, wooden, or pretty much any other sort of trellis. In the soil you can also utilize long branches that were left over after tree pruning. Wrap them in twine or netting so the tendrils can grip because they cannot twine around heavy poles like bamboo. It’s usually advisable to stay away from wire fencing in really hot climates like Texas. Before you sow the seeds or once they are a few inches tall, erect your securely anchored supports.
Between 75 and 85 percent of sweet pea seeds will germinate. There is always a little fraction that goes dormant, giving Mother Nature a refuge in the wild in case of bad weather. Only plant the seeds that have swollen and soak them in tap water for no longer than one night prior to planting in order to leave out the dormant ones. Never soak seeds; rather, nick them to let moisture seep into the seed coat for the highest possible germination rates. To accomplish this, simply cut a small hole with nail clippers in the seed’s outer layer; no chunk needs to be gouged out; this will allow moisture to enter the seed naturally. Although this nicking procedure takes more time, it will ensure excellent germination.
Plant seeds 2 to 3 inches apart and 1 inch deep. Depending on the climate and soil temperature, seeds can fully germinate between 10 to 28 days. Dig down to check if the seeds are still present if your sweet peas do not germinate well. Plant more immediately soon if they have decayed or been eaten since they will quickly catch up. It’s crucial to thin seedlings when they are several inches tall so that they stand about 5- 6 inches apart. This will provide the plants room to develop and flourish. Pinch off the top set of leaves when seedlings have three or four sets to encourage plants to branch out. Avoid significant changes in soil moisture during the active growing season by keeping sweet pea plants evenly moist. Mulching is a wise tactic.
Picking bouquets early and frequently can help you enjoy the longest season of spectacular bloom; the less you pick, the later the plants will go to seed and wither. Harvest flower stems frequently as the lowest blossom on each stalk just starts to open. Although stems may get shorter as the season goes on, the flowers are still large and gorgeous.
Sweet Peas Species
Our common garden sweet pea is the annual species Lathyrus odoratus; you can find them in a variety of colors and growth patterns, including:
tall varieties of vines
Depending on the region and season, these robust vines can grow to be 5 to 10 feet tall and produce numerous flower stems over a six to eight week bloom period. Tall vining plant species come in a variety of floral shapes:
Intense breeding efforts have been made in England to produce tall vining “Spencer” cultivars with bigger, waved and ruffled exquisite flowers. Because English breeders typically have been more focused in petal shape, form, stem length, and color than in perfume or weather tolerance, some Spencers are quite fragrant while others are very faintly so. Nowadays, Spencer kinds can be used to describe the majority of large-petalled, ruffled sweet pea cultivars. We stock the scented Spencer type “Blue Celeste.”
Mammoth and Royals are two American cultivars developed in the middle to end of the 20th century that have good-sized flowers, a light perfume, and are widely available. Since our only area of expertise is scented sweet peas, we do not provide these varieties.
Variety of Containers & Window Boxes
These tiny plants look great in containers and have stems that are 8 to 10 inches in length or have spreading and mounding characteristics. The heirloom varieties “Windowbox Cupid” and “Cupid Color Palette” are available from us.
Short, unable-to-climb Dwarfs
These sweet peas are short and don’t require vertical supports, with some varieties being tendril-less. It’s “Explorer” for us.
Other Species of Sweet Peas:
In the West, the perennial Lathyrus latifolius is frequently observed as a naturalized roadside wildflower. The cultivated form of this perennial, which is far more drought tolerant than annual sweet peas, can be trained to grow into an appealing and dependable permanent hedge plant. Although the flowers are plain, small, and odorless, their shape makes me think of miniature orchids. They come in rose, pure white, and shell pink. We market these colored mixtures as “Garden Orchids.” In zone 4 at Sweet Pea Gardens in Surrey, Maine, where they are quite hardy and over ten years old, Susan Keating has planted perennial sweet peas as a tall blooming screen on the side of her garage. Their flowering stalks also make lovely arrangement flowers.
This diminutive sweet pea, Lathyrus sativus azureus, features 1 inch dazzling azure-blue flowers and tangled grassy leaves. Plants only reach heights of 3 to 4 feet. attractive landscape accents in pots with minimal supports. We offer “Electric Blue” for sale.
Dr. Hammett is attempting to stabilize hybrids between several annual species in order to bring together lovely form and scent with fresh colors and heat tolerance. For home gardeners, the next ten years will bring some interesting new advances, such as real tricolor sweet peas and non-fading orange and apricot colours, all of which have potent fragrances.