The sweet pea, Lathyrus odoratus, is an annual climbing plant known for its intense fragrance and rapid growth. While it quickly covers trellises and supports, its growth timeline is highly dependent on environmental factors and initial preparation. Understanding this cycle from seed to bloom provides a timeline for anticipating its display. The speed of development is governed by germination rate, vertical growth, and conditions for sustained energy production.
Initial Preparation and Germination Timeline
Accelerating growth begins with seed preparation due to the sweet pea’s tough outer seed coat. Many growers recommend scarification, which involves gently nicking the seed with a file or nail clipper, followed by a 12 to 24-hour soak in room-temperature water. This process allows for rapid water uptake and initiates the sprouting process.
The seeds require specific thermal conditions to germinate efficiently, ideally soil temperatures between 50 and 65 degrees Fahrenheit. Under ideal conditions, the initial sprout can emerge within 7 to 10 days, though some varieties may take up to three weeks. Starting seeds indoors approximately four to six weeks before the final outdoor planting date gives the plants a significant head start over direct sowing. This method ensures a robust root system develops before the plant is tasked with rapid vertical growth outdoors.
The Vegetative Growth Phase
Once seedlings establish their first set of true leaves and are planted out, they enter the vegetative phase. This is the period when the plant focuses on producing stems, leaves, and tendrils for climbing. The growth rate can be substantial, with mature vines often increasing in height by over a foot per week in favorable weather.
Sweet peas are natural climbers and require immediate support to maximize their vertical speed. Providing a trellis or netting for the tendrils to grasp prevents the vine from tangling and slowing its upward ascent. Depending on the variety, vines can achieve a height of three to six feet or more within a single growing season. Growers often pinch the central growing tip when the plant is a few inches tall to encourage lateral branching, resulting in a bushier plant with more flowering potential, even though this may temporarily slow vertical growth.
Optimizing Speed: Environmental Factors
Achieving the fastest growth rate for sweet peas depends on providing cool-season conditions. The plants flourish in full sunlight, requiring at least six hours of direct light daily for energy production. However, they are sensitive to heat; temperatures consistently above 80 degrees Fahrenheit will slow growth and shorten the blooming period.
The soil must be rich, deep, and well-draining, with a slightly alkaline pH between 6.0 and 7.5. Sweet peas are heavy feeders, benefiting from incorporating aged compost or manure into the planting bed to provide sustained nutrition. Consistent moisture is also necessary, as the rapid growth rate demands a steady water supply, especially around the roots. Fertilization should favor high-phosphorus and high-potassium formulations over those rich in nitrogen, as excessive nitrogen encourages leafy growth rather than flower bud development.
Transition to Bloom: The Flowering Timeline
The final phase of the growth cycle is the transition to flowering, which typically occurs between 10 and 12 weeks after the initial sowing of the seed. This period allows the vine to accumulate sufficient energy reserves to support blossom production.
While the vine grows rapidly, the plant must reach a certain maturity and size before it can sustain flower production. The flowering period can be extended significantly by consistently harvesting the open blooms, a practice often referred to as deadheading. Removing spent flowers prevents the plant from setting seed, which signals the end of its life cycle and diverts energy away from producing new buds. Regular cutting encourages the plant to continue its reproductive efforts, speeding up the production of subsequent flushes of blossoms.