Understanding Your Nasturtium Seedling
A nasturtium seedling is the tender young plant that emerges after germination, poised to grow into the familiar, prolific flowering annual. These seedlings, characterised by their rounded, sometimes shield-shaped leaves and delicate stems, are the foundation for the striking blooms and peppery foliage nasturtiums are known for. They represent a crucial, albeit brief, stage where careful attention can significantly influence the plant's future vigour and flowering potential.
Why focus on the seedling stage? Because this is when the plant is most vulnerable but also most receptive to the right conditions. Establishing good root development and healthy foliage early on means your nasturtiums will be better equipped to withstand pests, diseases, and environmental stresses later in their life cycle. Proper care now translates directly into a more robust plant, more abundant flowers, and a longer blooming season throughout the summer months.
Nasturtiums (Tropaeolum majus) are wonderfully adaptable, making them ideal for novice gardeners. They thrive in a range of conditions but show their true potential with a little understanding of their needs during their formative weeks. Unlike some more demanding plants, nasturtium seedlings are relatively forgiving, yet providing them with optimal conditions from the outset will significantly enhance their display.
The seedling is the starting point for vibrant, edible blooms.
Consider the two main growth habits: bush types remain more compact, ideal for pots and borders, while trailing varieties spill over edges and walls, creating a cascade of colour. Recognising which type you have can influence planting density and location, but the fundamental care for the seedling remains consistent.
Essential Care for Growing Nasturtium Seedlings
How do you nurture a young nasturtium seedling into a flourishing plant? It begins with understanding their fundamental requirements: light, water, soil, and space. These elements, when managed correctly during the seedling phase, lay the groundwork for success.
Light Requirements
Nasturtium seedlings need plenty of light. Ideally, they should receive at least six hours of direct sunlight per day. If you've started them indoors, a bright, south-facing windowsill is often suitable. Insufficient light can lead to leggy, weak growth, where the stems stretch searching for light, becoming thin and prone to snapping. If natural light is limited, consider using grow lights, positioning them a few inches above the seedlings for 12-14 hours a day.
Watering Wisely
Watering is critical. Seedlings require consistent moisture but must not sit in waterlogged soil, which can lead to root rot. Water thoroughly when the top centimetre of soil feels dry to the touch. Aim to water the soil directly rather than the leaves, especially in the morning, to help prevent fungal diseases. As the seedlings grow, their water needs will increase, but it's always better to underwater slightly than to overwater.
Soil and Potting
Nasturtiums prefer well-draining soil. While they aren't overly fussy, a good quality potting mix is recommended for seedlings. If planting into the garden, ensure the soil isn't too rich, especially with nitrogen, as this can encourage leafy growth at the expense of flowers. For container growing, use a potting compost that offers good drainage. When transplanting seedlings that have become pot-bound, gently loosen the roots before placing them in their new home.
When transplanting nasturtium seedlings, disturb the root ball as little as possible to minimise transplant shock.
Feeding Your Young Plants
Nasturtium seedlings generally do not require heavy feeding, particularly if started in good quality compost. In fact, over-fertilising, especially with high-nitrogen feeds, can result in lush foliage but few blooms. If your soil is poor or you are growing in containers and notice signs of nutrient deficiency (pale leaves), a balanced liquid feed, diluted to half strength, can be applied sparingly every 4-6 weeks. The key is moderation; nasturtiums are naturally vigorous and can perform well with minimal intervention.
Consistent moisture and ample light are paramount for healthy seedling development.
Transplanting and Acclimatising Nasturtium Seedlings
When is the right time to move your nasturtium seedling from its nursery pot or seed tray to its final growing position, whether in the garden or a larger container? This transition, often referred to as 'hardening off' and transplanting, is a vital step that requires careful management to ensure the young plants thrive.
Hardening Off
Before transplanting outdoors, seedlings started inside need to be acclimatised to external conditions. This process, known as hardening off, gradually exposes them to wind, sun, and cooler temperatures. Start by placing them in a sheltered spot outdoors for a few hours each day, gradually increasing the duration over a week to ten days. Bring them in at night if frost is a risk. This toughens their stems and foliage, making them less susceptible to shock and damage once permanently planted.
When to Plant Out
The ideal time to plant out nasturtium seedlings is after the last frost date in your region has passed. Nasturtiums are tender annuals and will not tolerate frost. Check your local weather forecasts to ensure the risk of frost has significantly diminished. Young plants should have developed several sets of true leaves and a reasonably sturdy stem by this point.
Planting Techniques
When transplanting, dig a hole slightly larger than the seedling's root ball. If planting multiple seedlings, consider their mature size and growth habit. Bush varieties can often be spaced 20-30 cm apart, while trailing types may need a little more room or can be planted closer if you want a denser cascade. Place the seedling in the hole so the top of its root ball is level with the surrounding soil. Gently firm the soil around the base, and water thoroughly. Avoid planting too deep, as this can lead to stem rot.
Acclimatising seedlings to outdoor conditions prevents transplant shock.
Container Planting Considerations
For container planting, choose pots that are at least 20 cm in diameter for bush types and larger, perhaps 30-40 cm deep, for trailing varieties to allow for ample root growth. Ensure containers have drainage holes. Nasturtiums grown in pots can dry out faster than those in the ground, so monitor watering closely, especially during hot weather. A well-draining potting mix is essential.
Troubleshooting and Alternatives
Even with the best intentions, sometimes nasturtium seedlings encounter issues. Understanding common problems and potential alternative approaches can help ensure a successful display.
Common Seedling Problems
Leggy growth: As mentioned, this is usually a sign of insufficient light. Move seedlings to a brighter location or supplement with grow lights. You can try repotting them slightly deeper to support the weak stem, but prevention is key.
Yellowing leaves: This can indicate overwatering or nutrient deficiency. Check soil moisture levels; if consistently wet, reduce watering. If the soil is appropriately moist but leaves are yellowing, a weak liquid feed might be beneficial.
Pests: Aphids are common on nasturtiums. They can often be washed off with a strong jet of water or treated with insecticidal soap. Encourage beneficial insects like ladybirds to help control aphid populations.
Considering Alternatives
While nasturtiums are a favourite for their ease of growth and vibrant colours, other annuals offer similar benefits. If you're looking for easy-to-grow, colourful flowers, consider planting marigolds, petunias, or even sunflowers. For edible flowers and foliage with a peppery note, nasturtiums are somewhat unique, though borage also offers edible blue flowers.
If you've missed the seedling stage or are short on time, purchasing larger, established nasturtium plants from a garden centre is a viable alternative. These plants, while potentially costing more initially, bypass the delicate seedling phase and offer a quicker route to colourful blooms. Remember to check their health for any signs of pests or disease before purchasing.
Plant nasturtiums near vegetables like brassicas; their strong scent can deter common pests like cabbage white butterflies.
Addressing common issues early prevents them from becoming major problems.
For gardeners seeking specific effects, bush varieties of nasturtiums are excellent for filling gaps in borders or providing ground cover, while trailing types are superb for hanging baskets or tumbling over raised beds. Each offers a unique aesthetic, but all begin with the care of a healthy nasturtium seedling.