Starting nasturtiums indoors is a practical strategy for gardeners aiming to get a head start on the growing season. These vibrant, edible flowers are renowned for their ease of cultivation, yet the decision to begin them in pots or directly sow them outdoors depends heavily on your specific climate and timing needs.
Understanding Nasturtium Growth Habits
Nasturtiums (Tropaeolum majus) are classified as annuals in most temperate regions and are notably sensitive to cold soil and frost. They originate from the cooler, high-altitude regions of South America, which means they thrive in cooler temperatures but cannot survive freezing conditions. Because of this sensitivity, sowing seeds directly into cold ground often results in poor germination or rot. Starting them indoors allows you to control the initial environment, ensuring that delicate sprouts emerge in warmth and stability before being introduced to the variability of the outdoor garden.
The Benefits of an Early Start
One of the primary advantages of starting nasturtiums indoors is the significant extension of the flowering period. By sowing seeds in pots 2 to 4 weeks before the last expected frost date, you can have mature plants ready to transplant as soon as the soil warms up. This head start is particularly valuable in regions with shorter summers, allowing the plants to establish a robust root system and begin blooming earlier than if they were sown directly into the ground later in the season.
Step-by-Step Indoor Sowing Guide
The process of starting nasturtiums indoors is straightforward and requires minimal equipment. Select biodegradable pots or seed trays filled with a light, well-draining seed-starting mix. Plant the seeds approximately 1/2 inch deep, ensuring they are situated in a warm location with indirect light. Maintain consistent moisture without waterlogging, and you should observe germination within 7 to 10 days. Once the seedlings develop a set of true leaves and the threat of frost has passed, they are ready for hardening off and transplanting.
Transplanting and Aftercare
Hardening off is a critical step that should not be skipped when moving indoor-started nasturtiums outside. This gradual acclimation process involves placing the young plants outdoors in a sheltered spot for increasing periods each day over the course of a week. This adjustment helps prevent shock and ensures the plant can adapt to direct sunlight and wind. When transplanting, choose a sunny location with poor to average soil; rich soils can actually promote excessive foliage at the expense of flowers.
While nasturtiums are generally low-maintenance, there are scenarios where starting indoors might be less advantageous. In very mild climates where the soil warms early and the last frost date is unpredictable, direct sowing might be just as effective and eliminates the need for transplanting, which can sometimes cause root disturbance. Additionally, because nasturtiums have a taproot that dislikes being moved, using biodegradable pots is essential to minimize root shock if you choose to start them indoors.
Comparing Indoor Starts vs. Direct Sowing
| Method | Best For | Key Advantage |
|---|---|---|
| Starting Indoors | Cool climates with late frosts; maximizing bloom time | Extends the growing season and flowers earlier |
| Direct Sowing | Warm climates with stable soil temperatures | Simpler process; no transplant shock |
Ultimately, the decision to start nasturtiums indoors comes down to resourcefulness and climate awareness. For the majority of gardeners in temperate zones, the indoor method proves highly effective, turning a simple seed into a cascade of colorful, peppery blooms well before the season officially peaks. By controlling the initial environment, you are not just planting a flower; you are strategically leveraging time to create a more vibrant and prolonged display in your garden.
