Nasturtiums (Tropaeolum majus and T. minus) are cheerful, easy-to-grow annuals prized for their vibrant, edible flowers and unique shield-shaped foliage. These plants are popular with gardeners for their quick growth and ability to thrive in less-than-ideal conditions. Knowing the typical development cycle is helpful for planning a garden and setting expectations for when their colorful blossoms will arrive.
The Nasturtium Timeline: Seed to Flower
Nasturtiums typically take six to eight weeks from the date of sowing until the first blooms appear under favorable conditions. This relatively short period makes them a favorite for quickly adding color to a garden or container. Germination, the initial stage, usually occurs within seven to twelve days after the seed is planted.
Germination involves the seed absorbing water and the tiny root (radicle) emerging from the tough seed coat. Optimal soil temperatures, ideally between 55°F and 65°F, are necessary for this rapid sprout. Once the seedling establishes its first true leaves, the plant focuses energy on developing the foliage needed to support flowering.
The remaining four to seven weeks are spent in vegetative growth before the plant produces its first flower buds. While six to eight weeks is the average, cooler temperatures or non-ideal conditions can extend this period, sometimes delaying the first flower until ten to twelve weeks. Gardeners should consider this range when planning planting dates relative to the growing season.
Optimal Sowing Methods for Timely Blooms
Direct sowing the seeds into the garden soil is the preferred method because nasturtiums have fragile roots highly sensitive to being moved. Avoiding transplant shock ensures the plant dedicates its energy directly to growth, maintaining the fastest schedule to bloom.
For gardeners in regions with short growing seasons, starting seeds indoors can provide a head start, though this requires careful handling. If starting inside, use biodegradable peat or coir pots, which can be planted directly into the garden without disturbing the roots. Seeds should be started just two to four weeks before the last expected spring frost, as starting them earlier can result in leggy, stressed seedlings.
To speed up germination, which is slowed by the seed’s thick outer shell, gardeners can prepare the seeds beforehand. Soaking the seeds in water for 12 to 24 hours helps soften the coat, allowing moisture to penetrate. Alternatively, gently nick the seed coat using a nail clipper or small file, a process known as scarification, which accelerates the emergence of the sprout.
Environmental Factors That Accelerate or Delay Flowering
Once established, several environmental conditions influence the speed at which the plant moves from foliage development to flower production. Sunlight is a primary factor, requiring a minimum of six hours of direct sun daily to flower efficiently. Plants grown in partial shade will develop leaves but often have delayed or significantly fewer blooms.
Warm temperatures are necessary for quick growth, as nasturtiums are not tolerant of frost and thrive once the soil has warmed. Cool soil temperatures in early spring can slow the plant’s metabolism, delaying the entire process for up to two weeks. Planting when the soil temperature is consistently above 55°F promotes rapid development.
The composition of the soil strongly affects the bloom time. Nasturtiums flower best in lean, average, or poor soil that drains well. Soil rich in nitrogen, often from heavy fertilization, encourages excessive lush, green leaves at the expense of flowers. This significantly delays the blooming period, so gardeners should avoid adding high-nitrogen fertilizers.