From a botanical perspective, the common garden sweet pea, known scientifically as Lathyrus odoratus, is classified as an annual plant. This classification is fundamental to understanding its life strategy. An annual plant is one that completes its entire life cycle—from seed germination, through vegetative growth and flowering, to seed production and death—within a single growing season. For sweet peas, this entire process typically unfolds over the course of a spring and summer. The plant's primary evolutionary goal is to produce as many viable seeds as possible to ensure the propagation of the next generation before the arrival of unfavorable conditions, such as winter frost, which it cannot survive.
It is crucial to distinguish Lathyrus odoratus from its close relative, Lathyrus latifolius, commonly known as the everlasting pea or perennial sweet pea. While they belong to the same genus and family (Fabaceae), they employ different life strategies. Lathyrus latifolius is a true perennial. Its root system, often featuring rhizomes or a hardy crown, persists through the winter dormancy period. The above-ground growth dies back with frost, but the plant's energy reserves stored in the roots allow it to regenerate new stems, leaves, and flowers for several consecutive years. This perennial strategy represents a long-term investment in a specific location.
The annual nature of Lathyrus odoratus is a specific adaptation to its native Mediterranean climate. It thrives in cooler conditions and completes its most vigorous growth and prolific flowering before the intense heat of midsummer can cause it to decline. The plant invests its energy not in building durable, overwintering structures but in rapid vegetative growth to climb and access sunlight, followed by a massive reproductive effort characterized by its famously fragrant blossoms. Once pollination occurs and seeds develop, the plant has achieved its biological purpose and senesces (dies). This strategy is highly effective for colonizing disturbed ground and taking advantage of seasonal rainfall.
Understanding this life cycle explains common gardening practices. Since the individual plant is genetically programmed to die after seeding, gardeners often practice "deadheading"—removing spent flowers before seeds form. This tricks the plant into a state of "prolonged youth," diverting energy away from seed production and back into creating more flowers in an attempt to achieve its reproductive goal. However, this only delays the inevitable. The plant will still succumb to the end of the season or heat stress. True perpetuation of Lathyrus odoratus in a garden relies on the seeds it drops or those collected and sown by the gardener the following spring, not on the original plant returning.
