Published by Brian Wagner on 10/9/25 in “Growing Flowers from Seed.”
Lathyrus latifolius (commonly known as perennial sweet pea) is a perennial in many climates, but an annual in its native Sicily (where it behaves like a winter annual, germinating in autumn, flowering in spring, dying in summer). Among cottage gardeners, annual sweet peas (Lathyrus oderata) are an essential treasure – valued for their flowers and scent – but this perennial variety might interest you as well.
The perennial sweet pea has showy flowers (magenta, pink, white), and it scrambles up trellises, just like its annual (oderata) siblings. However, it has almost no fragrance, which is certainly unfortunate. If you have an area of your garden where sweet peas would thrive (bright sunlight, cool soil, ample moisture/nitrogen) but you won’t miss the fragrance, then this is your pea. (Many gardeners, sad as it is, are also allergic to flower fragrances, so this could be a selling point for some.)
Lathyrus latifolius is thought to be native to central Europe, although its story is lost to time. Like many plants, we have old memories in ancient botanical texts (for which we are thankful), but the records are spotty. It is hardy to Zone 5, which makes it attractive to gardeners in both the UK and eastern United States.
In their native geography they thrive at the forest edge – i.e., the transition zones between forests and grasslands/scrublands. It’s here that they get a balance of nutrition (i.e., from nitrogen cycling in the forest), water (less heat than open areas) and part sun. They also grow in scrubland areas typical of Mediterranean climates, but they are happier where it is cooler. In the garden setting, they’ll be happiest if their feet are kept cool (e.g., shaded in some way) while their heads are in full sun most of the day. In hotter climates like Texas they will cower under the summer heat; they’re much better adapted to mild climates with full sun.
Growing From Seed
Seeds of Lathyrus latifolius have a physical dormancy (abbreviated in the literature as ‘PY’), which means that the seeds are impermeable to water. In other words, if you were to weigh the seeds and then soak them in water – and then after drying them off with a towel, weigh them again – they would weigh the same as they did before. With seeds that have physical dormancy, typically all they need is to experience damage to their outer shell in order to germinate.
There are many creative ways to damage a seed shell. You can get your grandkids to shake them in a can for a few hours (fun), or you can also simply poke a small hole through each of the seeds (they’re quite large). You can also nick them with nail clippers. If you’re adventurous try sulphuric acid, but only if you’re a chemist. After doing so, soak the seeds for 4 hours in warm water, and then rinse.
Seeds should germinate within a few days after doing this. They do not need light to germinate and can be buried an inch or so below the surface.