Successful flower farming is a combination of growing, marketing, and selling. I have no wisdom to share on how to market and sell during a pandemic (our sales are down 99% for 2020), but I do still know how to grow things, and I’ve been focusing on that this year. You can always hone your horticultural skills, regardless of how long you’ve been at it. As you may know, we specialize in sweet peas, so let me share my tips for success.

Autumn is the perfect time for many, dare I say most, of us to sow sweet peas. I see plenty of misinformation, or partially correct information, about sweet peas out there, so as one who lives and breathes sweet peas, let’s break it down. Pay attention to these temperature ranges and figure out when you can offer these conditions to your plants. All flowers will thrive best if you give them the conditions they prefer, rather than imposing your conditions on the flower. Few are as particular as sweet peas.

If you can keep your babies above 20F all winter, you can sow any time after you feel that fall nip in the air. Sowing from mid-September into early winter gives you a chunky, well-rooted transplant that will leap out of the ground when spring weather arrives. Southern growers especially need to start in the fall in order to have a chance at enjoying flowers before the spring and summer heat arrives.

Sowing methods: Keep ‘em cool!I prefer to use a deep 50 cell tray (I like the T.O. SureRoots deep 50 tray), but any deep cell or pot with a good volume of soil will work. In most cases they will spend most of the winter in this tray, so larger cells are better than smaller. Sow seeds one-half to one inch deep and water well. There is no need to soak sweet pea seeds before sowing. Soaking slightly reduces your germination rate and increases the chance of spreading of pathogens. 

Germinate at 55F. Sweet peas have no business on heat mats, under lights, or on your windowsill! You will see growth in 7-14 days. As soon as you see growth emerging, move these seedlings into full sun if they aren’t already in a sunny location, and maintain between 32-55F. Once you see some leaves run them even cooler. Ours spend all winter around 35F. There is no harm in letting your seedlings get frosted. Brief spells down to 20F are of no concern in this juvenile stage.
Direct sowing can work for some, but beware of mice, slugs, birds, and soggy soil.
Growing-on and transplanting

 

Southern growers will want to transplant into the location where they will flower as soon as the plants have a few leaves. Since Southern growers may have their plants in trays for only 6-8 weeks, a smaller cell tray can suffice, but choose a deep tray to accommodate the long root system. Never allow seedlings to dry out. If you have a fall heat wave coming, but you’ve already started your seedlings, put that tray in your cooler for a few days to avoid the worst of the heat. 

For those of us with wintery winters, keep your plants wherever you can maintain them in full bright natural light, but as cold as possible; 33-45F is ideal for this slow growth period. You will see short, stocky tops but the roots will be getting huge below the surface. We use a minimally heated greenhouse because we experience extreme cold here in Vermont. If you are generally above 20F in winter, growing them outside may be perfect. Don’t let them get waterlogged, but don’t worry about brief cold snaps. Growing in trays gives you flexibility. You can drag those trays into a garage if a cold snap is coming, or even put them into a cooler and keep them just above freezing for a few days. They will be fine. Again, colder is better than warmer for sweet peas. 

As spring approaches, transplant outside or in tunnels when you are reasonably sure they will stay above 20F. Cold soil is fine, but persistently wet soil is a problem. Sweet peas are heavy feeders. Apply compost and manure liberally, and feed with a liquid feed of your choice. Anything recommended for tomatoes will suffice.

Cold-grown transplants will branch on their own. If you have grown them too warm or too dark, you may have very tall, stretched plants with no side shoots. In this case pinch out the tips to encourage branching and vow to grow your transplants colder and brighter next time!

Trellising methods and stem length

We prefer plastic trellis netting as it is affordable and durable and widely available. You can use any sort of fencing or chicken wire or twine you may have on hand. Plants can easily exceed 8’ in height and can get quite heavy, so plan accordingly.

We generally cordon train our plants, where each plant is restricted to one leader, and all side growth is removed. This results in very long flower stems. It is highly labor intensive and probably not worth it for most growers. Naturally-grown plants are simply plants that are allowed to climb and branch as they please. Early in the bloom cycle you will still get some long stems. As the plants get larger and weather warms you will see stem length shorten. At this point you can cut them with a bit of the vine to achieve a usable length. Many florists love the leaves and tendrils. Cut EVERY open flower off of the plant at least once a week to keep the plant producing. 
The longest stems occur when plants are given a 45F/65F night/day cycle. While variety selection is important, there are few cut flowers that are more dependent on their growing conditions for size and quality. We all like to blame our seed/bulbs/plugs for poor results in a crop, but with sweet peas, the blame almost always falls squarely on the grower!

 

Daylength

 

Sweet peas are naturally long day plants, needing 12 or more hours of sun to flower. Of course the long days of summers come with heat, so luckily there are varieties that will bloom under shorter days. “Winter” varieties bloom with 10+ hours of light, and “spring” varieties need 11+ hours of light. Don’t be fooled into thinking winter or spring varieties are somehow more cold hardy—it just designates their daylength response. All sweet peas are identical in their desired temperature range. Southern growers will want to stick with winter types so the plant will bloom when temperatures are favorable.
Primary types of sweet peas

 

Grandifloras These most closely resemble wild sweet peas, and for the first 200 years in cultivation were the only sweet peas available. They have small rounded flowers, 3-4 per stem, are often very fragrant, grow well outdoors, and produce in abundance. They are generally too short for cutting as individual stems, but are perfect for cutting with a bit of the vine attached. Very few grow grandifloras for cutting, but they should be considered. Some grandifloras are very old while others are recent creations. ‘Mrs. Collier’, ‘Dorothy Eckford’, ‘Almost Black’, ‘Turquoise Lagoon’, and many others fall into this category. 
Spencers The first Spencer sweet pea showed up as a mutation around 1900. ‘Countess Spencer’ was the first variety to have large ruffled flowers, and all Spencer-type sweet peas since then have been bred from this initial discovery. These can have very long stems for cutting, generally produce up to 4 flowers, and come in a huge range of colors and patterns. They are most often summer flowering, needing 12 or more hours of daylight. Thus they are not well suited for winter production but will do well in cool summer locations. ‘White Frills’, ‘Windsor’, ‘Mollie Rilstone’, ‘Nimbus’, and ‘Jilly’ are just a few of the hundreds of desirable varieties available. 

Multifloras As you might assume, these are the types with 5-6 or more flowers per stem, and understandably have been bred for cut flower producers. Many multifloras are also “winter” or “spring” types, making them a good choice for Southern growers in winter. Generally speaking they do just as well for northern growers producing in the summer, and they will often come into flower a week or two before Spencers. Since these have historically been bred as commercial cutting strains they tend to have the longest stems of all. They tend to have slightly less ruffled and slightly smaller flowers than Spencers, but can be forgiven on account of their stem length. ‘Sunshine’, ‘Elegance’, ‘Bouquet’, ‘Solstice’, and ‘Mammoth’ are some of the multiflora series you may encounter, with many colors available in each series. We use mainly the ‘Sunshine’ series in our cutting beds all season. You are advised to buy seed from a sweet pea specialist as oftentimes cheap seed has deteriorated genetically and won’t live up to expectations.  

 

Pests

 

Aphids and thrips are the primary insect pests to watch out for, and powdery mildew and botrytis are the fungal pathogens of most concern. Be ready to act at the first sight of any of these, or employ preventative measures to prevent them from taking hold. Mosaic virus is spread by aphids, so aphid control will prevent viral pathogens as well.

 

Postharvest

 

Cut when one-half to two-thirds of the flowers are open. We cut directly into Chrysal AVB, to protect them from ethylene damage, and stems go right in the cooler. After 3-12 hours in AVB, we transfer to Chrysal Professional 3, which has more sugar than a standard holding solution. Stems handled in this manner will hold in the cooler for up to 5 days, and then last an additional week out of the cooler. If you are opposed to anti-ethylene treatment, your flowers will last only about 3 days, which may be fine for sales to local wedding designers. Cutting them on the vine seems to offer a bit of natural ethylene protection.

Yes, sweet peas are divas and require more fuss than most any other cut flower crop. Maybe they don’t make commercial sense for your operation, but at least plant a small patch for personal enjoyment. Treat yourself. You deserve it.