Growing Nasturtiums From Seed

Nasturtiums are fast-growing flowering plants valued for bright blooms, rounded leaves, trailing or bushy growth, and easy direct sowing. They generally perform best in well-drained soil with moderate fertility. Excessive fertilizer can produce abundant leaves with fewer flowers, so rich garden soil usually does not need heavy feeding.

Choose a type

Choose a Nasturtium Type

Varieties may be compact, mounding, trailing, or climbing, with different flower colors and mature sizes.

Use Fresh Seed

Healthy seed from a known variety helps produce more predictable growth and flower characteristics.

Sow seeds

Direct Sow When Conditions Are Mild

Nasturtiums are commonly seeded directly into prepared soil because the large seed is easy to handle.

Start in Containers if Needed

Where indoor starting is useful, individual containers can reduce root disturbance during transplanting.

Use a Well-Drained Starting Mix

A light medium helps provide moisture while preventing prolonged saturation around the seed.

Follow Packet Depth Guidance

Plant at the depth recommended for the variety rather than applying one rule to every garden seed.

Keep the Seed Zone Moist

Maintain consistent moisture during germination without leaving soil waterlogged.

Do Not Overwater

Wet soil with poor oxygen can encourage seed and root problems before seedlings become established.

Provide Strong Light After Emergence

Bright conditions help seedlings develop sturdy stems and compact growth.

Care for seedlings

Thin Crowded Seedlings

Give plants enough space for their mature habit, especially trailing varieties that spread widely.

Plant outdoors

Harden Off Indoor Starts

Gradually introduce seedlings to outdoor sun, wind, and temperature changes before permanent planting.

Choose Sun or Light Partial Shade

Nasturtiums generally flower well in strong light, though some afternoon protection can help during intense heat.

Use Well-Drained Soil

Plants perform poorly where roots remain continuously saturated.

Avoid Excessive Fertilizer

Heavy nitrogen can encourage lush foliage at the expense of flower production.

Do Not Over-Amend Rich Beds

Where soil already supports healthy growth, large fertilizer additions are usually unnecessary.

Care for plants

Space Plants by Growth Habit

Compact varieties can be planted more closely than long trailing or climbing types.

Provide Support for Climbing Types

Some nasturtiums can be guided onto trellises, fences, or other structures as stems lengthen.

Guide Trailing Growth Early

Redirect young stems before they become tangled so vines can cover the intended container edge, support, or garden area.

Water During Establishment

Young seedlings need dependable moisture while roots spread into surrounding soil.

Reduce Watering Once Established

Mature plants often tolerate moderate drying better than young seedlings, though severe drought can reduce flowering.

Use Mulch Lightly

A modest mulch layer can conserve moisture and reduce weeds without keeping the crown too wet.

Control Weeds Early

Remove weeds while nasturtium plants are small so they can establish without heavy competition.

Watch for Aphids

Aphids frequently gather on tender nasturtium growth. Check stems and the undersides of leaves regularly.

Inspect for Caterpillar Damage

Chewing insects may feed on leaves, especially where nasturtiums are grown near other susceptible crops.

Remove Badly Damaged Growth

Trim severely damaged stems or leaves when needed while leaving enough healthy foliage for continued growth.

Watch for problems

Watch for Heat Stress

Flowering may slow during very hot weather, particularly where nights remain warm and plants dry rapidly.

Watch for Prolonged Wet Conditions

Dense growth that stays wet for long periods can decline, especially where airflow is poor.

Deadhead to Encourage Flowering

Removing faded blooms can encourage additional flowering while weather remains favorable.

Leave Flowers for Seed

If saving seed, allow selected flowers to develop mature seed rather than deadheading every bloom.

Collect seed

Collect Mature Seed Promptly

Nasturtium seeds become large and easy to see as they mature. Collect them before too many drop onto the ground.

Finish Drying Seed Before Storage

Freshly collected seed may retain moisture, so allow it to dry thoroughly in a protected location before sealing it into storage.

Label Saved Seed

Record the variety or flower color, growth habit, and harvest year when possible.

Expect Self-Seeding

Seeds that fall onto suitable soil may produce volunteer plants when conditions become favorable.

Containers

Grow Nasturtiums in Containers

Compact and trailing types grow well in pots, window boxes, and hanging containers with adequate drainage.

Check Containers Frequently

Container soil can dry quickly during sunny, windy, or hot weather.

Avoid Letting Trailing Stems Become Crushed

Position pots so long stems are not repeatedly stepped on, pinched beneath containers, or damaged by doors and walkways.

Keep Seasonal Notes

Record which planting dates and varieties produce the longest flowering period in your climate.

Practical Takeaway

Grow nasturtiums from seed in well-drained soil with strong light and moderate fertility. Avoid overfeeding, give trailing types adequate room, monitor for aphids, and allow selected plants to mature seed if you want future sowings.