For the discerning gardener, selecting sweet pea (Lathyrus odoratus) varieties is a pursuit of sensory perfection, balancing intoxicating fragrance with vibrant color. From a botanical perspective, these traits are not mere aesthetics but are deeply rooted in the plant's evolutionary biology and genetics, developed to attract specific pollinators and ensure reproductive success.
The signature fragrance of sweet peas is a complex bouquet of volatile organic compounds (VOCs), primarily benzaldehyde, linalool, and phenylacetaldehyde, which are produced and released by specialized cells within the petals. This scent is most potent in the older, heirloom or "Grandiflora" types, which often prioritize fragrance over bloom size. From a plant's perspective, this powerful aroma is a long-distance signal to attract its primary pollinators, bees. The compounds are often produced in higher concentrations during the cooler parts of the day, such as dawn and dusk, to maximize their travel through the air and conserve energy during the heat of the day.
The spectacular color range in sweet peas, from pristine whites to deep, almost black purples, is governed by anthocyanin pigments. The specific color expressed is determined by the pH of the cell sap and the interaction of multiple genes controlling pigment type and distribution. For instance, the 'Matucana' variety exhibits a deep maroon and violet bicolor pattern due to a combination of cyanidin-based pigments and a genetic mutation that causes a break in color, creating a distinctive "wing" pattern. This visual spectacle is a close-range attractant, guiding pollinators precisely to the nectar and pollen rewards at the flower's center.
Several varieties are celebrated for achieving an exceptional balance of these botanical traits. The aforementioned **'Matucana'**, an heirloom from the 1700s, is renowned for its exceptionally strong fragrance and striking deep purple and magenta bicolor blooms. **'Cupani'** (often considered synonymous or very similar) shares these legendary scent credentials. For a different color palette, **'North Shore'** offers a powerful perfume alongside stunning deep blue-purple flowers. The variety **'April in Paris'** provides a strong, sweet fragrance with unique creamy-yellow blooms, a color achievement in sweet pea breeding. Meanwhile, the heirloom **'Painted Lady'** attracts with a soft orange-pink and white bicolor pattern and a reliably sweet, honeyed scent.
To maximize the genetic potential of these varieties, certain horticultural practices are key. Consistent moisture and rich, well-drained soil are essential for healthy root and flower development. Crucially, regular harvesting of blooms is not just for bouquets; it is a direct mimicry of the plant's goal of setting seed. By deadheading spent flowers, you signal the plant to continue producing more blooms in an effort to achieve reproduction, thereby prolonging the display of both fragrance and color throughout the season.
