Nasturtiums are classic, easy-to-grow flowers that attract pollinators, are fairly drought tolerant, are deer and rabbit resistant, and begin blooming 8 to 12 weeks after sowing. While usually grown as an annual, nasturtiums are perennial in USDA zones 10 and warmer. The genus, Tropaeolum, is Greek for 'trophy', in reference to its shield-shaped leaves. The word, nasturtium, comes from nasus and tortus, roughly translating as 'nose twister' due to the plant's spicy scent and peppery taste. Nasturtium flowers, leaves and seeds are edible. Seeds can pickled and used as a substitute for capers or dried and used as a substitute for peppercorns. If you were wondering how to grow nasturtiums from seed, you've come to the right place!
GENERAL SOWING
When to Sow Outside: RECOMMENDED. 1 to 2 weeks after your average last frost date. Mild Climates: Sow in fall for winter bloom. Ideal soil temperature for germination is 55°���65°F.
When to Start Inside: Not recommended. 2 to 4 weeks before your average last frost date. Roots sensitive to transplant disturbance; sow in biodegradable pots that can be directly planted in the ground.
INDOOR SOWING
Soak seed in water for 12 to 24 hours before sowing. Use a lightweight seed starting mix/medium (sterile, and lighter than potting mix), and sow seeds ½"- 1" deep. Sow 3 seeds per pot, thinning to the strongest plant once leaves appear (clip extra plants at the soil level using scissors). The strongest plant may not be the tallest; look for thick, strong stems and deep color. By thinning early, you minimize the negative impact of crowding, like stretching for light. Read about more indoor sowing tips.
Containers
Containers should be clean, sanitized, and have drainage holes. If you choose to sow in cell packs, you may need to up-pot seedlings once into larger containers before transplanting outside
Transplanting
After hardening off, transplant seedlings 8"-12" apart.
OUTDOOR SOWING
Sowing preparation and spacing
Choose an area in full to part sun. Nasturtiums grow well in poor to average well-drained soil. If drainage needs to be improved, add organic material or grow on mounds.
Thinning
When plants are 2" tall thin to 1 plant every 8"-12".
Water
Though nasturtium is fairly drought tolerant once established, it does best with regular waterings.
Fertilization
Fertilizer usually is not necessary; too much nitrogen produces excess foliage and fewer flowers; add a phosphorous-rich, liquid fertilizer to encourage flowers if needed.
Weeding
Keep plants well weeded. Weeds compete with crops for light, nutrients, and water, and can harbor insects and diseases.
Special care
Deadhead (remove spent blossoms) for optimum number of blooms and to prevent seed formation. Nasturtium may self-sow.
HARVESTING
Harvest leaves and flowers in the morning, if possible, when they are more hydrated and cooler, rather than later in the day.
COMMON PESTS AND DISEASES
Nasturtiums can attract aphids which makes them an excellent trap crop, pulling the pest away from your other plants. Simply spray aphids off with a strong stream of water.