Perennial sweet pea flowers can be yours with a little work and a few good plants.
This flowering plant is a good one for the beginner gardener because it is easy to grow and quite hardy into gardening zone 4. Sow 2 seeds in a single pot or one seed to a plant cell (plastic cell packs) and keep the soil slightly damp.
This is an excellent plant for part shade conditions in poor soils. It will not flower if put into deep shade gardens and will eventually die out.
Clay soils tend to kill it as well as they hold too much moisture around the roots; this plant loves good drainage (which may be why it is commonly found along the edges of ditches in sun or part shade spots).
Let me point out that the more sunshine you give this plant, the more sweet pea flowers you’ll get in return.
Germinating Sweet Pea Flowers
The seeds, if kept at a soil temperature of 70F will germinate in 2 weeks (give or take a few days) and send up a single shoot. Grow this shoot in full sunshine until it is time to put outdoors. I generally sow the seed in January as the plant is a slow grower (a good fast germinator but slow after that). I put it outdoors in May after the last frost.
Sweet pea flowers can be expected the second year from sowing and the vine will be full of them.
The flowers are not overly fragrant on this plant but they do come in a wide range of whites, pinks and mauves when you’;re growing the commonly available Lathyrus latifolius. This is the plant commonly found in seed racks and garden centers in the spring and you’;ll be able to grow this one right up into USDA zone 3.
This species has also escaped from gardens and is now naturalized in North America.
Other Common Varieties
L. palustris or marsh pea is for warmer gardens (zone 6). This is a bog type perennial sweet pea with purple-blue flowers. It is not L. sylvestris or narrow leaved everlasting pea, or flat pea is another good plant with sweet pea flowers. It is a little more tender than L. latifolius. Sporting dark mauve-red flowers, it grows to 6 feet in height. It is more of a garden plant than a climber.
L. vernus or spring vetch is a bushy type of perennial sweet pea that grows to 24 inches tall. The flowers are reddish-violet and you’ll be pleased if you put it into the perennial border between other plants to support it. You’ll be able to find seed of this plant in smaller seed companies and you may even carry distinct cultivars such as ‘Roseus’ a rose-red or ‘Albo-roseus’; with lovely rose-white sweet pea flowers.