About Good Scents

The cut flower business ended in 2011 but I continue to post other items about gardening.

Saturday, March 15, 2008

Sweet Peas (Lathryus odoratus)

This post was originally written for and appeared in Project Grow's Community Gardener. I don't use sweet peas in Good Scents bouquets very often because the stems are fairly short, but I still grow them at home for the house.

Over the last few years I've become a real nut for growing sweet peas (Lathryus odoratus). It started when I became interested in growing fragrant annuals. I began reading all kinds of fragrant plant catalogs and books and they all talked about the wonderful fragrance of sweet peas. I had never seen, much less smelled a sweet pea, but they sounded great, so I bought a packet of seeds. The seeds looked like garden pea seeds only smaller, so I sowed them in early spring like garden peas. However, they didn't come up quickly like edible peas, and when they did come up, they took their own little sweet pea time growing. While the sugar snaps were merrily romping up their trellis, the sweet peas sat there poking along. Sometime in late July they finally produced a few flowers and promptly died. Needless to say, I was discouraged, but also intrigued because the scent of those few flowers was unforgettable.

Sweet peas don't smell like anything else. There is something fresh, organic and just wonderful about the fragrance of sweet peas. The scent is floral, like a rose or lily, but also sweet and fruity, like a butterfly bush, and it never carries the heaviness that you sometimes detect in lilies or lilacs. It is also one of those scents that you can catch in the air just walking near the plants. Sweet peas make nice cut flowers and their fragrance lasts for a couple days after you bring them inside. Like the smell of many flowers it can evoke old memories, and when I was growing them at County Farm many people came up to me and said the scent reminded them of their mother's or grandmother's gardens.

References to grandmother are not surprising because sweet peas are no longer as popular as they once were. My old copy of Wyman’s Gardening Encyclopedia (1977) says they were popular 50 years ago (1920’s). Compared to some flowers like roses or lilies, sweet peas have not been in cultivation very long. They were discovered by an Italian monk named Cupani, in 1699, and you can still get an unimproved "wild" sweet pea named after this monk. “Cupani” is bi-colored with the top of the flower blue and the bottom red-violet. By 1870 there were still only about 9 separate strains of sweet peas. Then, they caught the attention of breeders in the U.S. and Britain and by 1900 264 different varieties were available. The turn of the century was the heyday of sweet peas, and varieties from this time are now usually called old-fashioned or grandiflora sweet peas.

In 1904, a sweet pea mutation appeared with larger, ruffled flowers at the estate of the Earl of Spencer. This plant was used to develop the Spencer Varieties. These bloom later than the grandifloras and are less fragrant, but have larger flowers and longer stems. Most sweet peas being bred today are Spencers. I have had some success growing these newer varieties, but the fragrance, which I think is the main reason to grow sweet peas, is very faint. I have been happiest with the older varieties. You can usually spot them in catalogs even if they are not identified as grandifloras. Eleanor Perenyi writes that their names - Miss Willmott, Queen Alexandra, the Honorable Mrs. Collier - , “summon up an Edwardian dinner party”. I have been happiest with a strain called “Royal Family”. It is a mix of colors including scarlet, white, blue and pink, and has the strong heady scent typical of grandifloras.

Sweet peas, like garden peas, prefer cool weather. They are very cold tolerant, but do not grow well in temperatures over 85F. Like most true annuals, if allowed to go to seed, they quickly die. As I discovered when I first tried to grow them, in areas like Michigan where high summer temperatures come quickly, the bloom season will be very short if they are direct seeded. It works better to start the seeds inside so they have more time to grow and flower before the really hot weather sets in. I usually start my seeds under lights in peat pots or Jiffy-7’s in March and then plant them out in the garden in mid to late April. Once I started doing this I began to get sweet peas for a long season. I still found them slow to germinate until I read the following two suggestions:

  • Take a file and score the outside of the seed coat enough to see the lighter inside.

  • Soak the seeds 24 hours in warm water before planting and only plant the seeds which swell up.

I now do both of these and often have near 100% germination in a matter of days.

If you start sweet peas early inside you need to keep pinching them out or else they will start growing into tall vines too early. Pinching will also encourage them to branch into multiple stems. I usually start pinching them out after they get the first set of true leaves. After the stem branches and another set of true leaves appears on each branch, I pinch again. I continue this process until the plants are ready to go outside in mid April. If they have been hardened off in a cold frame they will easily withstood hard frosts. After mild winters they even sometimes appear as self sown seedlings. Plants started in March and set into decent soil in mid April usually start blooming in early to mid June.

All the books say you're supposed to prepare the soil in the fall to a depth of 18 inches, amend it with manure, and let it mellow all winter. I only ever manage to dig about a foot deep and add City of Ann Arbor compost in the spring. Maybe with extra preparation they grow better, but mine usually grow well enough. I usually prepare a planting bed about 18 inches wide and about 10 feet long. I then set the plants out in two rows about a foot apart, with spacing of about 6-12 inches between plants in the row.

Sweet pea vines will often reach 6 feet so you will need to provide some kind of support. I have used both 6” plastic mesh and lines of string between stakes. Anything that works for garden peas will work for sweet peas, too.

Sweet Peas All Summer
One of my favorite garden writers is Henry Mitchell, who gardened in Washington D.C. and wrote the Earthman gardening column for the Washington Post. Mitchell said he was able to keep sweet peas blooming all summer if he picked all the flowers every day so the plants never went to seed. Sweet peas all summer sounded great, and like compost or ice cream, I figured I could never have too much. So, I started about 30 plants in early March, and when I planted them out in April the 30 plants made a double row about 12 feet long.

By the first week of June I was getting sweet peas in ever increasing numbers, and by mid-June I was cutting about 75 stems per day, every day. This is about two big handfuls, enough to fill a couple medium sized vases. Because they last for awhile after they are cut, I soon found myself running out of vases. I was bringing them in to work and handing them out to neighbors and visitors. As Henry Mitchell himself might have said, I felt like a rich man, indeed.

I don’t know if they really keep blooming all summer because despite my best intentions, I never manage to keep them all picked. As the summer wears on, I start to get tired of coming home every day and having to go out and pick the sweet peas again. All you have to miss is a couple days and they start to set seed and that finishes them for the year. But, even if they stop sometime in July they are still worth the effort. Get some seeds this spring and rediscover this great annual.

It used to be hard to find many different kinds of sweet peas at local retailers and I usually mail ordered my seeds. However, this year I went into Downtown Home and Garden one day and found they had all the varieties I used to mail order plus more. They carry Royal Family in a mix as well as in individual colors, and other antique varieties to help you fill the guest list to your very own Edwardian dinner party. In addition, they have numerous newer varieties from the Renee’s Garden Seeds. Sweet peas must be making a come back!

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