There are nasturtium varieties for almost every gardening purpose: bushy plants for borders and edges, trailing plants for walls and containers, and climbers that add dramatic height. The leaves and flowers are edible, with a peppery tang, so you’ll often find this plant in vegetable gardens planted alongside broccoli, cabbage, and cauliflower, where it keeps pests away. Nasturtiums spill beautifully over walls and onto pavers when used as edging. They also hold up well in containers. Bushy, ground-hugging nasturtiums will fill bloom gaps in a sunny perennial garden and work well planted among daylilies or roses.
Light
Nasturtiums grow and bloom best when planted in an area of full sun that receives six to eight hours of direct sunlight daily. This plant can tolerate some shade (three to six hours of sunlight), but might not bloom as profusely. When planted in a warm climate, some shade is actually preferred, as hot temperatures may end up browning leaves.
Soil
Surprisingly, nasturtium flowers do well in relatively infertile soil with good drainage. Soil that’s too rich will result in abundant greenery, but few flowers. This plant grows best in soil with a neutral pH (6 to 8) and can tolerate dry conditions, although a moderate amount of moisture is appreciated.
Water
Nasturtiums typically prefer weekly watering, but can be watered more often when planted in a greenhouse or in a sunny vegetable plot. In these conditions, the water demand can be high from surrounding plants and will dry the soil quickly. Nasturtiums will survive moderate droughts, but blooms will likely diminish and the foliage will begin to look spindly.
Temperature and Humidity
Some varieties of nasturtium are planted as perennials in USDA growing zones 9 through 11. However, in most North American climates, this plant is treated as an annual, completing its life cycle in just one growing season. They prefers daytime temperatures in the 70s F and can survive a light frost, but not a cold freeze. Additionally, this plant prefers average humidity levels (between 30 and 50 percent), yet it’s not overly particular. Nasturtiums can struggle, however, in extremely dry or extremely humid conditions.
Fertilizer
Using synthetic fertilizers is usually not recommended, as many gardeners grow them to eat. Organic gardeners rarely need to amend the soil before planting, unless conditions are very poor or the surrounding vegetables need soil im[rpvements. Just remember, robust soil properties can cause nasturtiums to put out more foliage and fewer flowers, so a good balance is important.
Types of Nasturtium
Nasturtium plants grow full, with rounded leaves and colored blooms peeking out behind their greenery. The flowers of this plant are funnel-shaped and come in varying shades of yellow, orange, pink, and red. Certain varieties boast subdued shades of butter yellow and cream, and others have variegated leaves. Of the dozens of species of nasturtiums, favorites include:
The ‘Alaska’ Series’ is a colorful heirloom variety with variegated foliage that holds different colored blossoms above its leaves. This bushy dwarf plant thrives in poor soil conditions and reaches a compact spread of 8 to 10 inches.The ‘Jewel’ Series’ grows vigorously to a height of 16 inches and produces different colored flowers in yellow, red, orange, mahogany, and rose. This variety is a profuse bloomer, but the flowers tend to get lost under the foliage.The flowers of ‘Peach Melba’ taste like watercress and are two-toned—yellow with maroon spots near the center. This bushy dwarf plant works well in containers and has a mature height and spread of 10 to 12 inches.‘Canary Creeper’ is a trailing variety that is best planted near fences or trellises, giving it the opportunity to climb. This unique variety boasts yellow flowers that look different from more common varieties, as they spread out like canary wings.
Pruning
Trailing nasturtium varieties are prone to legginess and usually need pruning mid-summer, and then again in late summer, to stimulate new growth and blooms. Trim the longest stems back by 6 to 12 inches on trailing varieties and thin browning leaves and flowers by pinching them off at the base. For bushy varieties, trimming stems is not generally needed, but pinching off spent flowers and dried leaves will aid in the plant’s overall aesthetic.
Propagating Nasturtium
After pruning your nasturtium, it is possible, and easy, to propagate the cuttings. You may also want to grow a new plant from a cutting if a large portion breaks off or if you want to replant the same variety in another part of your garden. Here’s how to propagate nasturtium from cuttings:
How to Grow Nasturtium From Seed
Most gardeners choose to sow nasturtiums annually from seed. Seeds can be sown directly in the garden once the soil has warmed, or started indoors two to four weeks before the average last spring frost date. For outdoor planting, sow seeds directly into soil that is at least 55 to 65 F, and plant them 1/2 inch deep and 10 to 12 inches apart. Keep the soil continuously moist until seeds sprout, which should take about a week to 10 days. When planting in pots, sow seeds in peat or paper pots, as nasturtiums can be finicky about transplanting. This will reduce transplant shock.
Potting and Repotting Nasturtium
Sowing seeds directly into pots is the best method for growing nasturtiums in containers. You can also sow seeds in peat starter pots, and then move them into a larger vessel once the seedlings sprout. A good quality potting mix will do, but don’t opt for one with added fertilizer if you want more blooms. Nasturtiums grow best in natural stone or clay containers with ample drainage. You can also add a layer of stones or pebbles to the bottom of the pot, before adding soil, to increase the drainage capacity.
Common Pests and Diseases
Nasturtiums are prone to aphid infestation, consequently making them a good companion to, and deterrent for, vegetables also vulnerable to aphids. If your plant’s foliage looks crinkled, or otherwise unhealthy, aphids might be the problem. Reduce the population with a strong blast of water from your garden hose. You can also opt for a non-toxic spray made at home from diluted vinegar or essential oils like lavender and peppermint. Better yet, plant catnip alongside nasturtiums to deter the pests altogether. This plant can also contract bacterial leaf spot under improper conditions. Small brown or black spots will show on the leaves if this is the issue. You can minimize or prevent the problem by providing ample airflow between plants and watering with drip irrigation, as opposed to sprinklers, as this condition spreads by splashing water.
How to Get Nasturtium to Bloom
Nasturtiums begin to bloom when temperatures rise, so make sure your plant is in a sunny, warm location to assure maximum color. If your nasturtium hasn’t started blooming within four to six weeks after sprouting, then you may need to wait for the outdoor temperatures to rise, or for weather conditions to improve. Plants with abundant foliage but no blooms may be an indicator of rich soil conditions. While it’s usually not recommended to fertilize this plant, under these circumstances, a plant food high in phosphorous may help promote flowers. Opt for natural products, like bone meal or rock phosphate, especially if you plan on eating the flowers. Pruning your plant may also help if you planted a variety that holds flowers under its leaves.
Common Problems With Nasturtium
Some varieties of nasturtium actually obstruct flower production due to the plant’s physical structure. If you are growing nasturtium at ground level, as opposed to one that trails or vines, choose a variety that holds its flowers above its leaves, allowing the sun to get to the buds. Root rot can also affect nasturtium if the soil is water logged. This plant prefers almost sandy soil, so make sure there is ample drainage in the location you select.
