Colorful and versatile, it is easy to see why the nasturtium is such a popular addition to the garden. Not only does its bright, bold flowers attract scores of pollinators to the garden, the nasturtium is also a useful trap or companion plant. This means that, when planted in close proximity, it lures destructive pests such as aphids away from other, more precious, flowers and vegetables.
But the benefits of adding some nasturtium plants to your garden don’t end there. They are also fully edible and easy to grow. If you want to add something that is more than just a pretty ornamental flower to your garden, the nasturtium is the plant for you. Here is your complete growing guide.
Bright and colorful, this versatile, low maintenance plant can benefit your garden enormously.
Different Varieties of Nasturtium
There are over 50 different varieties commonly available. These enjoy a range of growth habits, while some can be bushy plants covered with flowers others are elegant, climbing specimens. The sprawling growth habit of the climbing cultivars can also be encouraged to cascade over the sides of pots and planters. There are also dwarf and variegated cultivars available.
One of the most common annual nasturtium (Trapaeolum) plants is Alaska. This variety produces flowers in shades of yellow, orange and red against green and cream marbled foliage. A bushy plant, it rarely exceeds 12 inches in height.
Empress of India is grown for its rich, crimson red flowers and dark red foliage. It grows to around 9 inches tall. Similarly, Tip Top Velvet also produces rich, dark red flowers. Slightly taller than Empress of India, it achieves a final height of roughly 12 inches. Salmon Baby is a great option if you want something a little different. It produces masses of salmon pink flowers and reaches a height of 12 inches.
Milkmaid Cream White is a trailing or climbing variety. Its white flowered covered stems can reach up to 70 inches in length. Other popular trailing varieties include Trailing Mixed and Tall Mixed. These produce masses of red, yellow and orange flowers on long stems, reaching up to 70 inches.
These attractive flowers come in a range of different shapes and shades. Planting a combination of different colors around your garden can look really effective.
If space is at a premium, the dwarf cultivar Tom Thumb is an ideal choice. It produces attractive, single color flowers in a range of shades. Whirlybird is a low growing plant which produces colorful, semi-double flowers.
Perennial varieties include Hermine Grashoff, a trailing perennial with double orange-scarlet blooms. Flame Flower is a climbing variety which produces vermilion red flowers amidst masses of dark green foliage.
Easy to grow, packets of seeds can be purchased from garden stores and plant nurseries. You don’t have to use all the seeds in the first year. If stored correctly, in an airtight tin in a cool dry place, seeds can keep for two to three years. However, the older the seeds are the less likely they are to germinate. If you don’t have the time or space to grow from seed many garden stores also sell a range of young, usually annual, varieties.
Growing from Seed
Nasturtium plants are easy to start from seed. However, they can suffer from transplant shock. This means that directly sowing into their final position is recommended. Sow the seeds in a full sun position. Ideally, sow your seeds in a position that has some shade from the hot afternoon sun.
Try not to plant in soil that is overly rich. This can encourage too much foliage to emerge, often at the expense of flowers. Pleasingly these are hardy flowers that thrive in moderate and poor soils. This means that you don’t need to work in any soil amendments before planting.
Your chosen position should also have some shelter from the wind.
Wait until the last frost date has passed and the soil has started to warm up before sowing your seeds.
The night before sowing, place the seeds in a saucer or shallow dish filled with warm water. Soaking the seeds overnight helps to soften the hard shells, speeding up the germination process.
Weed the soil and work it over before sowing. Sow each seed about an inch deep. Space the seeds 10 to 12 inches apart. If you struggle to space out the seeds, you can also thin them out after germination, once they have developed several sets of leaves.
After sowing the seeds, cover with a thin layer of soil and water well. Mark the site with a label to prevent accidental damage when weeding.
These attractive flowers are easy to grow from seed.
Starting Seeds Undercover
In cooler climates, if you have only a short growing period, it is better to start the seeds off undercover in biodegradable peat pots, such as MT Products Peat Seed Starter Pots. Following germination the plants can be planted out, still in their pots, negating the risk of transplant shock. Starting seeds undercover also enables you to maximise your growing time, meaning that you can cultivate larger plants and earlier flowers.
Sow two seeds per 3 or 4 inch pot. Nasturtium seeds are large, so they need a larger pot. Fill the pots with a general purpose potting soil. Sow the seeds about 1 inch deep and water gently. Place in a bright location, such as on a south facing windowsill. If you struggle to find a naturally light position you can also place the pots under grow lights.
Germination takes about 12 days. If both seeds germinate, pinch out the weaker of the two and allow the stronger seedling to grow on.
Allow the seedlings to grow on in their light position. Remember to regularly water the seedlings, don’t allow the soil to dry out.
When nighttime temperatures are consistently at or above 50 ℉ harden the seedlings off before transplanting into their final position.
Before transplanting dig over the planting area and work in organic matter such as leaf mould or compost if the soil is heavy. Place the pot containing the plant in the hole. The crown of the foliage should sit at or slightly above soil level. Backfill with a combination of soil and organic matter. Evenly spread a granular potash feed around the plant and water well.
Growing in Pots
Nasturtium plants do just as well in pots, planters and baskets as they do in the ground.
Fill your chosen container with a good quality potting soil mix. Alternatively, you can make your own mix. A combination that is two thirds peat free compost and one third fine gravel or grit is ideal. This combination is well draining but not overly fertile. Soils that are overly rich or fertile can discourage flowering.
You can either directly sow the seeds or start in biodegradable pots and transplant as described above.
Caring for Nasturtium Plants
Once planted nasturtiums are easy to care for, low maintenance plants. Keep the soil around the plants clear and weed free. If you struggle to keep your garden weed free, or don’t have the time to spend hours weeding, homemade weed killers can be both safe and effective.
An easy to care for plant, regularly weed or mulch around their base to prevent weeds from smothering young specimens.
When to Water
Water regularly, especially during dry spells. Don’t let soil dry out. Plants growing in pots or containers may require more regular watering, especially during dry periods. Planting in a self watering pot helps to cut down the amount of time you need to spend watering plants.
Do I Need to Fertilize?
While the nasturtium happily grows without fertilizer, a regular application can help to boost growth and flowering. A regular dose of liquid fertilizer which is rich in potash can be applied once every 2 to 3 weeks. A general purpose, balanced liquid fertilizer can also be applied if the plants appear weak.
Low maintenance plants, you need only deadhead spent blooms. This helps to prolong the flowering period. Deadheading also prevents seed pods from forming.
You can also cut back old stems and foliage in the fall, once flowering has finished.
A versatile plant that grows in a range of conditions, you may need to prune to prevent the plant from outgrowing its space.
Larger or sprawling varieties may also require pruning to prevent them from overgrowing their space and smothering other plants. Alternatively, planting in pots or planters prevents the plants from overgrowing a space.
Perennial varieties may require some winter protection, however most varieties can survive a light frost. To protect the plants, cut back in the fall before covering with a mulch such as bark chippings. This helps to protect the crown from frost. Remember to remove the mulch in the spring as new growth emerges.
To use as a trap plant, position your nasturtium plants near roses or other aphid prone plants. Aphids are particularly drawn to the bright yellow flowering varieties. As well as drawing aphids away from plants, these useful plants also attract hoverflies. A beneficial insect, hoverflies target aphids.
A popular trap plant, yellow flowering varieties are particularly effective.
Similarly the plants can also be used to draw cabbage moths away from brassicas such as broccoli and cabbage. They can also be used to repel cucumber beetles and squash bugs, protecting cucumbers, tomatoes and eggplants.
A good ground cover option, the plants can also be used to suppress weed growth. They also shade the soil if planted near tall plants like tomatoes and sunflowers.
Other good companion plants include:
For an attractive floral display plant in a pot or hanging basket with geraniums and nemesia.
Common Nasturtium Problems
If cared for correctly the nasturtium is unlikely to develop any significant problems. However, the cabbage white butterfly can lay its eggs on the underside of the plant’s foliage. Regularly inspect the foliage for signs of eggs. These can be picked or washed off the plant with a blast from a garden hose.
A popular trap plant, aphids and blackfly also target these plants. Again infestations can be treated with a blast with a hose or an application of homemade insecticidal soap.
How to Harvest Nasturtium Flowers and Seeds
Cut away flowers in the morning when they are full of moisture. Before using, remove the base of the flower which has a bitter taste.
Wait until late summer or early fall before harvesting plump seeds. Don’t harvest the seeds too early. Immature seeds struggle to germinate. Ripe seeds will be plump and tan or light brown in color. If possible, allow the pods to dry and fall naturally from the vine. However, if temperatures fall or the weather deteriorates, you may need to harvest the seeds before they fall.
You may need to search through the foliage to find the seed pods. The seed pods are usually about the size of a pea. They form in groups of 2 to 4 in the center of the spent flower.
Harvest by simply picking the seeds from the plant. If the seeds don’t come away easily, allow them to remain in place and mature further. Try harvesting again in a few days.
To save the harvested seeds, allow them to dry on a paper towel until they are fully brown. This can take a couple of days. They can then be stored in a paper envelope, in a cool, dry location until you are ready to sow.
You can also use the seeds for culinary purposes. Nasturtium seeds have a mustard like taste. They are ideal for pickling or as a caper substitute. They can also be used in pastas and salads. If you want to use the seeds for pickling, harvest when they are green.
The plant’s peppery foliage can also be used in salads. Harvest the foliage when it is green and fresh.
Popular with gardeners and pollinators, the nasturtium is a great addition to any garden.
The nasturtium is a colorful, easy going addition to the garden. Flowering from summer until the first harsh frosts of fall, these plants are a reliable way to bring color and interest to an outdoor space. The nasturtium’s versatility means that they are suitable for a range of different planting schemes and situations. Popular with pollinators and an ideal companion plant, the nasturtium is the ideal summer flower for any garden.
Jen is a master gardener, interior designer and home improvement expert. She has completed many home improvement, decor and remodeling projects with her family over the past 10 years on their 4,500 sf Victorian house. She is also a passionate farmer who keeps goats, chickens, turkeys cows and pigs on her farm, and an instructor for her community’s Organic and Sustainable Farming project.