Starting Nasturtiums From Seed: Your Quick Answer
To grow nasturtium from seed, sow them directly into well-draining soil after the last frost, or start them indoors 3-4 weeks prior. Plant seeds about 1.5-2.5 cm deep, spacing them 20-30 cm apart, and water gently. Nasturtiums germinate quickly, often within 7-14 days, in warm, sunny conditions.
- Sow directly outdoors after frost or start indoors 3-4 weeks earlier.
- Plant seeds 1.5-2.5 cm deep, 20-30 cm apart.
- Germination typically takes 7-14 days with adequate moisture and warmth.
- Ensure well-draining soil and ample sunlight for best results.
- Nasturtium flowers and leaves are edible and add colour to dishes.
Nasturtiums (Tropaeolum majus) are wonderfully forgiving plants, renowned for their trailing or bushy habit, vibrant trumpet-shaped blooms, and peppery edible leaves. They are a superb choice for beginners and experienced gardeners alike, bringing colour and culinary interest to borders, hanging baskets, and even vegetable patches. Sowing nasturtium seeds is straightforward, and with a little attention, you can enjoy a continuous display from early summer until the first autumn frosts.
When and Where to Plant Nasturtium Seeds
Understanding the optimal timing and location for sowing your nasturtium seeds is crucial for a flourishing display. These plants thrive in conditions that mimic their native South American environment, favouring warmth and sunshine but tolerating a little shade.
Direct Sowing vs. Indoor Starting
The most common and often most successful method for growing nasturtium from seed is direct sowing. This involves planting the seeds straight into their final growing position in the garden. Nasturtiums dislike root disturbance, so direct sowing minimises stress, leading to more robust plants. It is best to wait until all danger of frost has passed in your area. The soil temperature should ideally be around 18-21°C for good germination. If you're in a region with a shorter growing season, or simply wish to get a head start, you can begin your nasturtium seeds indoors.
For indoor sowing, use biodegradable pots (such as peat or coir pots) to further reduce root disturbance when transplanting. Sow 1-2 seeds per pot about 3-4 weeks before your last expected frost date. Keep the pots in a warm location, around 20-25°C, and ensure the soil remains consistently moist but not waterlogged. Once the seedlings have developed a couple of true leaves and the risk of frost has completely passed, they can be carefully transplanted into their outdoor positions.
Soil and Sunlight Requirements
Nasturtiums are remarkably adaptable to different soil types, but they perform best in well-draining soil. Avoid overly rich, heavily manured soil, as this can encourage lush leaf growth at the expense of flowers. In fact, nasturtiums often flower better in poorer soil conditions. If your soil is heavy clay, incorporate some grit or compost to improve drainage. For container growing, a standard, good-quality potting compost is usually sufficient, provided it has adequate drainage.
Sunlight is a key factor in successful nasturtium cultivation. Aim for a spot that receives at least 6 hours of direct sunlight per day. While they can tolerate partial shade, particularly in very hot climates, they will produce fewer flowers and potentially become leggy. In hot summer conditions, afternoon shade can be beneficial to prevent scorching. Ensure the chosen location is also protected from strong winds, which can damage their delicate foliage and stems.
How to Sow Nasturtium Seeds for Germination
The process of sowing nasturtium seeds is uncomplicated, designed to encourage rapid germination and healthy seedling development. Following these steps ensures you give your seeds the best possible start.
Preparing the Seedbed
Whether sowing directly outdoors or in pots, good soil preparation is paramount. Loosen the soil to a depth of about 15-20 cm, removing any weeds or large stones. If the soil is compacted, this will help the emerging roots penetrate easily. For direct sowing, you can lightly fork in some compost or well-rotted manure to improve soil structure, but remember that nasturtiums do not favour overly fertile ground, which can lead to abundant foliage but fewer blooms. Ensure the area has good drainage.
For container planting, select pots with drainage holes. A pot diameter of at least 20-25 cm is advisable for individual plants, or larger for trailing varieties meant to cascade. Fill the pots with a quality potting compost. If using peat-free compost, sometimes adding a little perlite can further improve aeration and drainage.
Planting the Seeds
To plant nasturtium seeds, create small holes or furrows in the prepared soil or compost. The general rule of thumb for depth is twice the width of the seed. For nasturtium seeds, this means planting them approximately 1.5 to 2.5 cm deep. The seeds are relatively large and have a distinct shape, often described as resembling a tiny wrinkled cannonball.
Spacing is important for air circulation and to allow plants to develop fully. For bush varieties, space seeds or seedlings about 20-30 cm apart. For trailing or climbing types, you might want to provide support and allow slightly more space, perhaps 30-45 cm, as they will spread more widely. If sowing multiple seeds in a pot, thin to the strongest seedling once they have established.
Watering and Germination Care
After sowing, water the area gently but thoroughly. A watering can with a fine rose attachment is ideal to avoid dislodging the seeds. Keep the soil consistently moist throughout the germination period. This is vital; allowing the soil to dry out completely can prevent germination or weaken the seedlings.
Nasturtium seeds typically germinate within 7 to 14 days, provided temperatures are favourable (between 18-24°C) and moisture levels are maintained. You should start to see small green shoots emerging from the soil. Once germinated, you can slightly reduce watering frequency but ensure the soil doesn't dry out completely, especially during warm, dry spells.
For the most prolific flowering, avoid over-fertilising. Nasturtiums are naturally vigorous and prefer leaner conditions, which encourage blooms over foliage.
Caring for Young Nasturtium Plants
Once your nasturtium seeds have successfully germinated and established into young plants, ongoing care ensures they thrive and deliver their characteristic vibrant display. This stage is critical for building a strong foundation for flowering.
Watering and Feeding
Young nasturtium plants need consistent moisture, especially during their first few weeks and during dry periods. Water them thoroughly when the top centimetre of soil begins to feel dry. As they mature, they become more drought-tolerant, but regular watering will promote continuous flowering. Avoid letting the soil become waterlogged, as this can lead to root rot. Water at the base of the plant to keep the foliage dry, which helps prevent fungal diseases.
Regarding feeding, nasturtiums are not heavy feeders. In fact, too much nitrogen-rich fertiliser can result in an abundance of dark green leaves and very few flowers. If you started with reasonably fertile soil or compost, additional feeding may not be necessary. If your plants seem sluggish or pale, a light application of a balanced, low-nitrogen liquid fertiliser diluted to half strength, applied sparingly during the growing season, should suffice. This is more about maintaining health than encouraging rapid growth.
Weeding and Mulching
Keeping the area around your nasturtium plants free from weeds is important, especially when they are young. Weeds compete for water, nutrients, and light. Once the plants have grown larger and have begun to fill out, their dense foliage can help suppress weeds naturally. A light mulch of compost or straw around the base of the plants can help retain soil moisture, suppress weeds, and regulate soil temperature. Ensure the mulch does not touch the stem directly to prevent rot.
Nasturtiums are relatively pest-resistant, but occasional issues can arise. Aphids can sometimes be found on the undersides of leaves or on new growth. A strong jet of water from a hose can often dislodge them. For more persistent infestations, an insecticidal soap solution can be used. Slugs and snails may also nibble on young plants, so consider protective measures if these are a common problem in your garden. Generally, their peppery scent deters many pests.
To encourage bushier growth and more flowers, pinch back the tips of young nasturtium plants when they are about 15-20 cm tall. This redirects the plant's energy into producing more stems and blooms.
Support and Pruning
Most nasturtium varieties, particularly the bush types, do not require any staking or support. They naturally form attractive mounds or trailing cascades. However, if you are growing the climbing varieties, such as 'Climbing Nasturtium' or 'Scarlet Emperor', they will need something to clamber up. Provide a trellis, obelisk, netting, or even support them to grow up a wall. Gently tie the stems to the support as they grow, using soft plant ties. They will twine their own leaf stalks around supports naturally.
Deadheading isn't strictly necessary for nasturtiums, as they tend to drop their spent flowers and produce new ones. However, removing any yellowing or spent leaves promptly helps maintain the plant's appearance and health. If plants start to look tired or stop flowering by late summer, a light trim can sometimes encourage a final flush of blooms before the season ends.
The key to abundant flowers is ensuring they get enough sun and aren't overfed.Harvesting and Using Nasturtiums
One of the unique pleasures of growing nasturtiums is that virtually the entire plant is edible, offering a peppery, slightly sweet flavour that brightens up salads, garnishes, and other dishes. Understanding when and how to harvest ensures you make the most of these versatile plants.
When to Harvest
You can begin harvesting nasturtium leaves and flowers once the plant is well-established and actively growing, typically a few weeks after sowing. The younger leaves, especially those at the centre of the plant, have a milder flavour and are ideal for salads. Larger, older leaves can be used in cooked dishes, similar to how you might use spinach, though their flavour is more pronounced.
Flowers can be picked whenever they appear. It's best to harvest them in the morning after the dew has dried, as they will be at their freshest. Gently twist or snip the flower from its stem. Continuously harvesting flowers encourages the plant to produce more, extending its blooming period throughout the summer and into autumn. Avoid harvesting if the flowers appear wilted or have been rained on heavily, as they might be prone to rot or be less appealing.
Culinary Uses and Preparation
Nasturtium flowers are incredibly decorative. Their vibrant colours – ranging from bright yellow and orange to deep red and even some bi-coloured varieties – make them a stunning garnish for desserts, cocktails, and savoury dishes. They add a visual flourish that is hard to beat. The flavour is subtly peppery, akin to watercress, which pairs well with creamy or mild flavours.
The leaves, particularly the young ones, also possess a distinct peppery bite. They are excellent chopped into butter, mixed into cream cheese spreads, or added to pesto. Larger leaves can be blanched or sautéed. The seeds, when green, can be pickled and used as a caper substitute, offering a unique tangy and pungent flavour.
To prepare nasturtiums for consumption:
- Leaves: Rinse them gently under cool water and pat them dry. Use young, tender leaves whole in salads or sandwiches. Chop older leaves for cooking.
- Flowers: Rinse gently if necessary and pat dry. Remove the green base of the petals if the flavour is too strong for your liking. Use as a colourful, flavourful garnish.
- Seeds: Pick the green seed pods before they fully dry and harden. Pickle them in brine for a unique condiment.
Alternative Plants with Edible Flowers
While nasturtiums stand out for their ease of growth and dual culinary/ornamental use, other plants offer similar benefits. Consider 'calendula' for its sunny, slightly peppery petals, or 'borage' for its cucumber-scented blue stars. Pansies and violas offer a mild, sweet flavour and beautiful decorative appeal. Marigolds (Tagetes spp., ensure they are edible varieties) provide bright colours and a citrusy note. These can complement nasturtiums in a culinary or ornamental garden, offering a diverse range of flavours and aesthetics.