Flowers – Nasturtium – Heirloom Seeds

Preparation

Nasturtium plants commonly self-seed in the garden. Self-seeding plants drop seeds onto the soil at the end of the season that may germinate and grow without help the following season. Choose a position where new plants will be welcome. If you do not want nasturtiums to become established in your garden, deadhead plants before they can drop seed or grow them in containers.

Nasturtium plants are best grown in full sun or part shade. Choose a location that will receive at least 3 hours of full sun each day.

Nasturtium plants need a well drained soil enriched with plenty of organic matter. Prepare soil by weeding it thoroughly, digging it over to loosen it and adding aged animal manure or compost. Keep the area free of weeds until planting. 

Nasturtium plants can be grown in containers. If possible choose a variety that’s recommended for container growing. Use a good quality potting mix and make sure your container is large enough for mature plants; a minimum of 20 litres is recommended for nasturtiums. During the growing season, keep in mind that container grown plants may need additional fertiliser to encourage healthy growth.

How to Sow Nasturtium Seeds

Nasturtium seeds do not require any treatment (eg soaking, stratification) before sowing.

Nasturtium seeds can be sown directly into the garden OR seedlings can be raised in trays or other containers and transplanted to the garden once established.

Sow Direct

1. Sow seeds directly in the garden 15mm deep and 30-45cm apart.
2. Keep soil moist but never wet or dry.
3. Seeds should germinate in around 7-14 days at a soil temperature of 16-20°C.
4. Young seedlings will need protection from pests, pets and weather until they are established.

Raise Seedlings

1. Fill trays, punnets or jiffy pots with a good quality seed-raising mix, or use soil starter pellets.
2. Sow seeds 15mm deep.
3. Keep soil moist but never wet or dry.
4. Seeds should germinate in around 7-14 days at a soil temperature of 16-20°C.
5. Transplant seedlings to the garden once they have their first true leaves and are large enough to handle (usually 5-10cm tall).
6. Plant out, spacing plants 30-45cm apart.

How to Grow Nasturtium

Nasturtium plants may need watering during the growing season. Water when the soil is dry about 5cm below the surface (test this by scratching away a little soil with your finger). Water deeply in the early morning or late afternoon. Avoid watering the leaves of plants to avoid fungal diseases. 

If soil was well prepared no extra fertiliser should be necessary. In poor soil or to give your plants an extra boost, application of a high-potassium fertiliser or one formulated for flowering plants can be beneficial:

• Apply slow release fertiliser at the recommended rate when transplanting or when seedlings are 5-10cm tall.
• Apply liquid fertiliser at the recommended rate and frequency while plants are fruiting or flowering.

Plants can sprawl along the ground or be grown up a trellis, wire fence or tripod. If growing on a support, plants will support themselves but they can also be tied gently using twine or plant ties. Make sure you have the support in place when you sow seed or transplant seedlings to avoid disturbing the plant’s roots later.

Nasturtium plants should flower in approximately 70-80 days.

Deadhead nasturtium flowers regularly during the growing season. Using sharp secateurs or snips cut fading or dead flowers off just above a set of leaves. Removing old flowers regularly will encourage plants to produce more flowers.