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  • Sweet Pea Cultivation for Flower Farmers

    July 11, 2024 12 min read 0 Comments

    A field of Sweet Pea flowers in white, cream, pink, and red. Jessica from Sierra Flower Farm is harvesting a large bundle of creamy green tinted flowers.

    Why We Love Growing Sweet Peas

    Nothing is better to ring in the days of spring and summer drawing near than one of the most delightful flowers we grow: sweet peas! 

    Their scrumptious scent is like no other. Until we grew sweet peas for our flower farm, I had never actually smelled a sweet pea, only knowing the fragrant lotions labeled “sweet pea,” which smelled nothing like the real flowers.

    Sweet peas are one of Sierra Flower Farm's most popular flowers. The earlier flush of stems gets tucked into mixed bouquets, but sweet peas are also incredibly charming all on their own! 

    Timing sweet peas right is the trick to getting oodles of usable stems. This post will discuss the ins and outs of growing this spring flower!

    Sierra Flower Farm’s Favorite Sweet Pea Cultivars

    Many cultivars of sweet peas produce different colors, intensities of scent, tendrils or no tendrils, and bloom at various day lengths. The main three groups of sweet peas are Winter Elegance, Mammoth, and Spencer.

    A bouquet of only white sweet peas held in the hand of a farmer.

    Spencer Sweet Peas

    Our cut flower farm mainly focuses on having sweet peas to harvest during May and June, making Spencer Sweet Peas the optimal choice for our operation. 

    Spencer varieties bloom under longer days, needing at least twelve hours of sunlight. Some of the more exciting colors are in the Spencer family. Windsor is a rich burgundy that produces incredibly long stems, upwards of eighteen inches! Jilly is another Spencer variety with extensive stems, and its creamy ivory color is lovely for wedding work. Mollie Rilstone is a creamy, almost tan variety with apricot edging. 

    These are only a few varieties we have found invaluable on our farm, especially for wedding work.

    Farmer harvesting a bunch of magenta sweet peas. The bunch is being held with stems facing up to wrap it with a rubber band.

    Winter and Mammoth Sweet Peas

    If you live in a milder climate during the shorter days of winter and spring or grow in a high tunnel, Elegance or Mammoth varieties would be better suited for your needs since they were developed to produce in less than twelve hours of daylight. 

    Elegance and Mammoth can especially become invaluable for the grower who is looking to take advantage of a mild climate to grow in winter or whose temperatures soar above 80℉ in late spring. Such consistently high temperatures will begin to shorten your sweet pea stem length and eventually shut the plants down, making growing cultivars that bloom under the shorter days of winter or early spring more ideal. 

    Sweet Pea Toxicity

    One catch to these decadent beauties is that sweet pea seeds, plants, and flowers are toxic. 

    When consumed in high amounts, sweet peas can cause intestinal distress, even paralysis, and difficulty breathing. Keep them in the vase and out of the salad! 

    A farmer planting sweet peas in deep 4-cell trays. The 4-cell trays are placed inside a Bootstrap Farmer deep 1020 tray in purple.

    How to grow sweet peas

    Days to maturity for sweet peas is 75 to 85 days from germination. 

    One of the sweet pea’s great traits is that it begins to bloom while the plants are still shorter. The plants continue to grow upwards, increasing the number of stems available for harvest. 

    Depending on the climate, sweet peas bloom from mid-winter through spring. They can even be grown throughout summer in cooler growing areas where temperatures remain in the 70s. 

    Though cold-hardy, sweet peas are also a Goldilocks, preferring temperatures above freezing but not too warm. Once they hit their stride, you will find yourself cutting from them twice daily to keep up!

    A female farmer is carrying a 1020 tray filled with 4-cell planters out of a greenhouse to be placed in the sun for germination.

    When to start and plant sweet peas

    For growers in warmer hardiness zones seven and above, sweet peas can be fall planted and wintered over. Hardiness zones below seven should start sweet peas in the winter months: ideally eight weeks before wanting to plant out. 

    Sweet peas can handle light frosts, but we find that frosts scald their leaves and can stress the plants out. Ideally, plant out sweet peas when lows hover above 34 degrees Fahrenheit and use frost blankets, low-tunnels, or micro-tunnels to help protect them and acclimate to the elements at planting until they are established after about two to three weeks.

    Succession planting sweet peas

    Sweet peas can be succession planted in three to four-week intervals. 

    We aim for two successions in our climate, with the first seeds starting in late January to have sweet peas in late May through June.

    The hand of a farmer is holding sweet pea seeds, showing that they are round, brown and a little smaller than dried peas.

    How to grow sweet pea seedlings

    Sweet pea seeds are round spheres, often in variations of brown, but can also have some mottling on the seed. 

    They germinate in soil temperatures of 50-60 degrees Fahrenheit in ten to twenty-one days. 

    Plant seeds ½ inches to an inch below surface level, as darkness aids germination. 

    Keep soil damp but not soggy to avoid seed rotting. 

    We find an increase in algae growth in the winter months; sprinkling vermiculite on top helps to suppress algae. 

    A flower farmer's hand is planting sweet pea seeds into deep 4-cell trays. The hollows for planting are around 1/2 an inch deep.

    Tips for growing sweet peas from seed

    Growing sweet pea transplants is one of my most treasured winter tasks. Watching their little green tendrils reach and clamor on each other is a treat in the greenhouse during those bleak cold days. 

    • Starting sweet peas in the greenhouse gives us more control over when they will begin producing for harvesting.
    • When direct sowing outdoors, consider placing a frost blanket, insect netting, or a micro tunnel over the rows for protection from birds who like the seeds as tasty treats.
    • Be sure to keep the soil wet but not soggy to encourage germination.
    • Even as seedlings, sweet peas like to be watered consistently and don’t tolerate being dried out.
    • Ideally sweet pea seeds should be smooth without cracks.
    A farmer's hands are filling planting trays with a planting mix of coco coir and perlite to provide a good moist base for starting sweet pea seeds.

    Sweet peas do not like to be waterlogged. Use a quality substrate with plenty of perlite to keep the sweet peas happy. 

    Since sweet peas have a long tap root, growing in deep-celled containers will result in a healthier transplant. We prefer deep-celled propagation trays for propagating berries, tree saplings, or 4-inch tall cell inserts to best accommodate its long root system. 

    We prepare the trays with our chosen seedling substrate, watered like a wrung-out sponge.

    A jar of water holding sweet pea seeds to soak before planting.

    To Pre-Soak or Not to Pre-Soak Sweet Pea Seeds

    Depending on your seed source, the seed packet may recommend stratifying your sweet pea seeds by soaking them in room-temperature water for up to twenty-four hours. 

    There is controversy surrounding whether or not soaking the sweet pea seeds helps aid germination versus harming by causing fungal disease. 

    We have tried both methods and found, especially with sources who recommend soaking their seed, sped up germination without fungal problems compared to not soaking. When soaking, we opt only to soak the seed overnight, for about eight to twelve hours.

    When it comes to soaking seeds when the source recommends not to, we did find better germination when following their directions and not soaking the seeds. 

    Use your discretion or experiment to see what works best for you, but ultimately, we rely on the direction of the supplier from whom we source the seeds. 

    white sweet peas on a flower farm

    Should you pinch your sweet peas? Branching vs. the Cordon Method

    Sweet pea seedlings prefer to grow on the cooler side, between 40 and 50 degrees Fahrenheit, to encourage a more robust plant. The cooler temperatures allow the sweet peas to focus better on root growth and cause the plant to branch out naturally. 

    If you grow the sweet pea seedlings on the warmer side, the plants will push their growth upwards with one central stalk. Depending on your preferred growing method, this can be ideal or not. 

    Commonly, sweet pea growers prefer the plants to branch since it will push the plants to yield more stems. Some growers, especially those growing sweet peas in high tunnels, may use the Cordon Method.

    The Cordon Method is where the grower pinches the side shoots to encourage one main stalk. This is similar to the pruning done by some tomato growers. The advantage of using this method is tidier plants and longer-stemmed sweet peas. The plants will produce fewer stems, but the ones they do are believed to be more premium. 

    Most small-scale growers don’t necessarily have the time to put into the Cordon Method and may be looking to get the most stems possible out of the space given to the sweet peas. As mentioned, growing the seedling on the cooler side will encourage it to branch out without pinching. 

    If you have a seedling with one central stalk and want to force it to branch out, once the seedling is 4-6 inches tall, you cut the stalk down to the second or third set of true leaves. 

    If you want to increase the sweet pea plants, don’t toss the clipped sweet pea cuttings yet!

    An orange air prune tray holding sweet pea starts grown from cuttings.

    Propagating Sweet Peas from Cuttings

    Sweet pea seeds are not inexpensive, especially if you are looking for more specialized varieties. One way to increase the number of plants without purchasing more seed is to take sweet pea cuttings to propagate. 

    If you need to pinch your seedlings, this is a great way to use those cuttings!

    What you need to propagate sweet peas from cuttings:

    • Cell tray-we like to use a 72-cell or 50-cell tray.
    • A dome lid
    • Rooting hormone gel or powdered
      • You can also use coconut water or aloe.
    • Potting soil (substrate), preferably with mycorrhizae, moistened 
    • Clippers, sanitized
    • Spray bottle of water
    • A cool, shaded location 
    • Sweet Pea seedlings

    To take a cutting for propagating:

    1. Take a cutting of about five inches 
    2. Cut right above a leaf node
    3. Remove all but the first set of true leaves 
    4. Dip the cutting into your chosen rooting hormone 
    5. Place the cutting in a prepared pot or tray with a damp but not oversaturated substrate. 
    6. Spray the cuttings with water.
    7. Place a dome lid over it and put the tray out of the direct sun, where soil temperatures will be 45-55 degrees Fahrenheit. 

    You should have new root growth in a matter of weeks! 

    Sweet peas will also grow roots in water, but roots are stronger when they are started in soil.

    Once the sweet pea cutting can easily be lifted from the cell, it is ready to be bumped up or planted out.

    Transplanting Sweet Pea Seedlings in the Field

    Sweet pea seedlings can be planted into their growing beds six to eight weeks after germination.

    Properly hardening off sweet pea seedlings is essential for successful transplants. They should be exposed to the outside elements for one to two weeks before planting in their growing beds. 

    On planting out day, we thoroughly water and drench the sweet pea seedlings in kelp to provide them with additional phosphorus, which will help them better cope with the stress of being transplanted. 

    Sweet peas are one of our most hungry plants. To keep them fed, we prepare their growing bed with quality compost and a slow-release fertilizer mainly comprised of feather meal. 

    We have their growing bed ready with drip irrigation and weed cloth since sweet peas are thirsty plants and do best with consistent and deep watering. Before planting the sweet peas, we finish prepping their growing bed by running a water cycle and hand watering to ensure they stay adequately hydrated from the start. 

    The weed cloth not only helps us get a handle on combatting noxious weeds but also helps keep the sweet peas from drying out. We are in an arid climate that gets windy, and we have found that weed cloth helps hold the moisture in the soil better.

    Purple sweet pea buds shown at the stage just before they have bloomed enough to be harvested.

    The recommended spacing for sweet peas is between 4” and 8” apart. 

    Since sweet peas are a vine crop, we plant them with our vining spacing, two rows of plants 7” apart. In our 45-foot rows, we can fit 154 plants per row. Two sweet pea rows usually produce way more than we need, making them an excellent crop for small-scale farms.

    Lastly, when we plant them out, we install a micro frost cloth tunnel over them and sometimes an additional low tunnel, depending on our temperatures. Though sweet peas can handle temperatures in the low 20s, this is not without damage. We want to protect them with temperatures that dip below 35℉. 

    The sweet peas are under the low tunnel for about four weeks. We remove the tunnels once the seedlings are acclimated and temperatures have stabilized. 

    Once the tunnels are removed, we must install one final piece of infrastructure.

    Vertical Trellising for Sweet Peas

    Sweet peas need vertical trellising to support them. The trellis needs to be strong enough to handle the weight of the plants. We use lightweight, strong, UV-resistant trellis netting for the sweet peas. Chicken wire and hog panels are other strong plastic-free choices but can be tricky or expensive to install and store. 

    Unlike peas grown for eating, sweet peas are not the best at holding themselves to the trellis. Therefore, corralling them around or tying falling vines to the trellis keeps them neat and upright. 

    Proper trellising results in high quality flowers. When the vines fall over, we find that their tendrils, though they do poorly at grasping a trellis, quickly clamor and grab themselves or flowers, resulting in damaged stems.

    Related: How to Install Plastic Trellis Netting. 

    Maintenance of Sweet Pea Plants

    Sweet peas can be finicky, but by addressing their primary needs, they will produce a bounty of quality blooms for you. 

    Feeding Sweet Pea Plants

    Sweet peas can also benefit from being set up on a fertigation system to provide supplemental nutrients weekly or bi-weekly. If you don’t have a fertigation system, foliar spraying with fish emulsion and kelp works, too. In their active growth phase, we foliar spray sweet peas weekly with a fertilizer high in nitrogen. 

    There is a balance of providing enough nitrogen but not too much, which can lead to too much vegetative growth and not enough blooms or, even worse, burning the plants and encouraging fungal disease.

    Watering Sweet Pea Plants

    Not only are sweet peas hungry plants, but as mentioned, they are heavy drinkers that thrive with consistent watering. Drip irrigation is best for sweet peas, especially in drier climates. 

    To aid in their water uptake, we will also do a yucca drench monthly.

    We usually need to give them an extra daily watering cycle for a couple of weeks during their peak growth.

    Season Extension with Shade Cloth

    In early June, we sometimes get heat spells in the 80s, which will shut the plants down and force them into seed production. 

    To extend our sweet pea season, we have successfully covered the rows with shade cloth to help keep them cooler, thus producing blooms. 

    Pests and Diseases

    Sweet peas are not without their foes. Some of the biggest pests we battle are:

    • Aphids
    • Caterpillars
    • Thrips 

    If you have slug pressure, they, too, find sweet peas tasty. Keeping the plants from stressing out too much earlier in life has helped to keep them from falling prey to these pests in conjunction with encouraging beneficial insects such as ladybirds and praying mantis. 

    Sweet peas are vulnerable to powdery mildew, especially towards the end of their lifecycle. Removing lower leaves on mature plants can help provide additional airflow. Aphids spread various mosaic diseases, resulting in mottled leaves, with the plants eventually withering and dying. 

    Root rot and damping off are common, especially in the seedling stage. Using proper substrate and keeping from over-watering and over-fertilizing to help prevent fungal disease.

    A field of Sweet Pea flowers in white, cream, pink, and red. Jessica from Sierra Flower Farm is harvesting a large bundle of creamy green tinted flowers.

    Harvesting sweet peas

    Once sweet pea flowers bloom, you will quickly become inundated with them! 

    We harvest sweet peas at the plant’s peak in the morning and evening. Sweet pea flowers are ready for harvest once the first bloom on a stem is open. 

    Cut the stem where it meets on the vine. Later in the season, when the stems begin to shorten, we will cut the vine with the stems. The vine extends the vase life of the sweet pea and makes a lovely filler.

    Our bunches of sweet peas are in fifteen-stem increments. 

    Sweet peas are harvested and placed directly in a clean bucket of water. CVBN tablets or a splash of bleach can be used, but they do decrease the scent of the sweet pea, which is why we prefer to keep them in plain water. 

    Place sweet peas in a cool, dark location or cooler to hydrate. 

    Sweet peas are very ethylene-sensitive and do not store well for more than a couple of days. Storing in a cooler will also decrease their fragrance. We try to hold the sweet peas for no more than a day before moving them to provide a better vase life for the customer. 

    With flower food, sweet pea vase life is, on average, about five days.

    female flower farmer harvesting white sweat peas for market

    Sweet Peas in Floral Designs

    Sweet peas are excellent on their own and can perform as a filler, linear or “spike” flower, and even as an airy competent, depending on your product and design. 

    At farmer’s markets or as a pop-up, sweet peas have sold well for us as a “posy” of about fifteen stems as a novelty offering. These sweet pea posies would often sell with our giant mixed bouquets or multiple bunches bought up since they are relatively unique. Our spring subscription members rave about the delicious smell. 

    Related: Structuring a Flower CSA

    For wedding work, I love to add them on the vine to bring light and airiness to the bouquets, not to mention their fragrance. Olfactory memories are strong. By incorporating sweet peas in the wedding work, my goal is to tie the scent of sweet peas to the couple’s wedding day, should they come across sweet peas again. 

    Sweet peas have a strong fragrance. A few stems are more than enough. You can tuck them into bud vases and arrangements without overusing them to avoid overpowering the guests.

    Sweet peas are a novelty flower. Their poor storage and shipping abilities make them a fantastic offering for the local flower farmer to provide to florists and direct to customers. They elevate the designs in appearance and fragrance. Once a garden staple that, over the decades, has declined in popularity, leaving it as a luxurious and unique offering for a flower farmer. Their fragrance in the field alone will lift your spirits. 

    Sweet peas are one of our most beloved and versatile varieties for mixed bouquets, especially for wedding work. Their generosity in producing stems was pivotal in our early years, providing a much-needed volume of stems with a minimal amount of space. 

    Written by: Jessica Chase, Sierra Flower Farm, Photography by: Graham Chase, Sierra Flower Farm

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