How to Grow Stunning Sweet Peas in Fall
If you're a warm climate gardener in Zones 8 and higher, you can plant sweet peas in the fall for gorgeous blooms in winter and spring. North Florida gardener Melissa Strauss shares her method for growing swoon-worthy sweet peas in autumn.
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Living in the South, I don’t see many sweet peas in local gardens. These plants need a significant amount of cool weather to make growing them worthwhile. Spring in the South just doesn’t provide that. Fortunately, stunning sweet peas will be frost tolerant, and we can successfully grow them in the fall.
If you’re a warm-climate gardener, Zone 8 and higher, you can plant your sweet peas in the fall. The farther south you are, the later in the year you should plant them. Since they need a significant period of cool weather, growing them in the spring won’t result in a good bloom.
Here in Zone 9, mine are already in the ground and have some growth. But don’t worry if you’re just getting started. There is still plenty of time to get your seeds in the ground. Let’s discuss how you can grow these sweet-smelling beauties in warm climates by planting them in the fall.
Step 1: Choose Your Varieties
Aside from seeing them flower, choosing varieties is my favorite part of growing flowers from seeds. There is an assortment of sweet peas available in many colors along with other desirable attributes. Here are some basics to consider when making your selections.
Color— Sweet peas come in an incredibly wide range of colors. You will find varieties of nearly every color of the rainbow, as well as bi-colored types. Some have picotee edges (edges darker than the petals), stripes, and even streaked and speckled. Some, called shifters, even change color as they age.
Size—The original sweet pea plants had smaller, less flashy flowers. They are still beautiful and have a sweet scent, but modern hybrids tend to have larger blooms, many with ruffled petals.
Fragrance—These flowers are famously fragrant. Not all varieties smell the same, however, and it’s nice to know which varieties have a stronger scent. In general, the scent of these blooms varies between woody, fresh, floral, and oriental (or spicy). Some of the most fragrant types include ‘High Scent,’ ‘Heaven Scent,’ and ‘More Scent,’ as the names indicate.
Step 2: Prepare Your Beds
I prefer to directly sow my sweet pea seeds because it creates stronger roots, which produce stronger plants. As such, before you prepare those seeds, it’s a good idea to get your garden ready for planting.
These plants prefer fertile soil with good drainage and plenty of nutrients. If you’ve got some compost ready to go, this is a great amendment for your beds. Otherwise, pick up some manure, worm castings, or other nutrient-dense amendments.
Dig a trench between the spaces that will be your rows. Go down about one foot, or nearly, and fill this trench with your compost or other soil-enriching amendments. As your plants set down deeper roots, they will come in contact with this trench and get a serious boost.
Step 3: Nick Your Seeds
Whether planting in the fall or spring, sweet pea seeds germinate best when nicked. The seeds have a hard outer covering that can make it more difficult for water to penetrate the seed and initiate germination. Many seeds benefit from soaking ahead of time, but these need an extra step if you want fast, vigorous germination.
To speed up and enhance the germination rate of your seeds, gently and carefully nick the hard outer cover. You can use an emery board or nail clippers to make a small cut or scrape off a small amount of this hard coating. A pocket knife works, too. Just be careful not to go too deep and damage the embryo.
Some gardeners like to soak their seeds overnight before planting. This won’t cause any harm, but it’s not really necessary with these seeds. As long as you keep the soil moist, nicking the seeds will help them hydrate and, therefore, germinate fastest.
Step 4: Direct Sow the Seeds
Sweet pea shoots are tough little things, tolerating frost and plenty of sun right from the start. In fact, the young plants will be more cold-tolerant than mature ones.
I like to direct sow seeds whenever possible, because it eliminates transplant shock. It also allows the roots to grow as deep as they want, as quickly as they can. Plants with deep, strong roots are the healthiest, as they are more capable of taking in water and nutrients.
Space your seeds about six inches apart, with at least six inches between rows. Use your finger or a pencil eraser or other tool to make one-inch holes in the soil. Drop two or three seeds in each hole and gently cover.
When your seedlings are three to six inches tall, thin them out so that there is one plant every six inches. Identify the strongest seedling and remove the others from that space.
Step 5: Pinch Your Seedlings
If you want to increase the yield of your fall sweet pea vines, it’s a good idea to pinch out your seedlings. Pinching seedlings helps promote branching, makes bushier plants, and makes them produce more flowers. Not all plants need pinching, but sweet peas perform best if you do.
Pinching simply means removing the top set of leaves from the shoot. This will make the lower buds branch, creating two vines or more where there was only one.
Wait until your shoots are about six inches tall or have three sets of leaves. Then, remove the top set of leaves and the stem to just above the set below. The vines are tender at this stage, so you can choose to pinch with your fingers. Or, use a small pair of scissors or shears if you’re more comfortable with that.
Step 6: Feed Your Young Plants
Sweet peas are heavy feeders, so you’ll want to fertilize them often throughout the fall and mild winter. Wait until about four weeks after your seedlings sprout to begin fertilizing. If you’ve amended your soil ahead of time, they will have plenty of nutrients to get started on.
These plants are nitrogen-fixing, so they don’t need much additional nitrogen in the way of fertilizer. Rather, it’s best to use a formula with higher phosphorus and lower nitrogen. This will encourage more flowering and less green growth.
Thereafter, fertilize them once every two weeks throughout the growing season. Stick to a high phosphorus formula if you want to maximize their flowering potential. A liquid formula will deliver the most immediate dose.
Step 7: Water Regularly
These are moisture-loving plants, and allowing the soil to dry out will slow down their growth. They are especially vulnerable in warm weather. If you experience a warm spell after planting, make sure to water deeply every two to three days.
Expect to see growth slow during the warmer weather. They will speed back up when the temperature drops again. Sweet peas need about 50 days of cool weather to flower, so be patient if you plant early and have to contend with warm weather.
Drip irrigation and soaker hoses are good tools for watering. These direct water down to the roots rather than on the foliage, helping to prevent fungus and water waste from evaporation. Although sweet peas are different than edible peas, you can use similar trellising structures and growing methods like the ones described in this video:
Step 8: Support the Vines
Sweet pea vines are tender and delicate, so they need support to stay happy. There are many ways to do this, and how you choose to do it is entirely up to your taste.
A trellis is a good tool for growing these plants. You can also use an arch or teepee made from bamboo canes. If you’ve ever grown vining peas in your garden, you can use the same methods to support sweet peas.
Step 9: Deadhead or Harvest Regularly
Deadheading is an important factor in increasing the yield of your vines. The more you cut the blooms, the more they will produce. Deadheading also prevents your vines from going to seed. This is most important in times of rising temperatures.
When the weather warms, your vines think it’s time to bolt so that they can re-seed themselves. If you leave pollinated flowers on the vine, this will occur, and as a result, the vines will begin to die back.
I grow these specifically for cutting purposes. They make wonderful cut flowers and bring much charm and cheer to the indoors when most blooming is over for the season. The more you cut, the more they produce, so cut often and enjoy these wonderful-smelling blooms.
The best time to cut your stems is before the top two blooms open. This will extend their vase life. The flowers will continue to bloom after you cut them. If you decide not to cut while the flowers bloom, make sure to deadhead by removing spend stems after the flowers drop.
