Nasturtium plants are loved for their rich, saturated, jewel-toned colors. Planted in the spring after the threat of frost has passed, they are fast and easy to grow. In fact, they do best with a little neglect. In general, nasturtium flowers tend to the hot end of the color spectrum. The rounded leaves look like miniature lotus leaves.
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.
Nasturtium is started either from seed as an annual, or purchased as a start at nurseries, where you may find them alongside other vegetable companions. The seeds germinate quickly and the plant starts blooming soon after. Once planted, nasturtium generally takes care of itself, requiring the same amount of water as you would give surrounding plants. Deadheading (removing spent blooms) is usually not necessary, however, pulling ripe flowers for use in salads and to place on top of summer desserts is always recommended.
Nasturtium spills beautifully over walls and onto pavers when used as edging. It also holds up well in containers. Bushy, ground-hugging nasturtium will fill bloom gaps in a sunny perennial garden and works well planted among daylilies or roses.
Nasturtium grows and blooms 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.
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.
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 the warm conditions will dry the soil quickly. Nasturtium will survive moderate droughts, but blooms will likely diminish and the foliage will begin to look spindly.
Temperature & 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. Nasturtium 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. Nasturtium can struggle, however, in extremely dry or extremely humid conditions.
Using chemical fertilizers on nasturtium 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 something more fertile. Just remember, robust soil properties can cause nasturtium to put out more foliage and fewer flowers, so the balance needs to be just right.
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.
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.
Potting & Repotting
Sowing seeds directly into pots is the best method for growing nasturtium 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 to assure more blooms. Nasturtium grows 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 & Diseases
Nasturtium is prone to aphid infestation, consequently making it a good companion to, and deterrent for, vegetables that can also suffer from this infliction. If your plant’s foliage looks crinkled, or otherwise unhealthy, aphids might be the problem. To control the bugs, lessen the population by using 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 nasturtium 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
Nasturtium begins 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 its flowers under its leaves.
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 it’s growing in is water logged. This plant prefers almost sandy soil, so make sure there is ample drainage in the location you select.
What bugs does nasturtium repel?
When used as a companion in a vegetable garden, nasturtium repels whiteflies, squash bugs, aphids, several beetles species and cabbage loopers. It protects itself, as well as other plants, by emitting an airborne chemical that deters these bugs.
How long do nasturtium plants live?
In most climates, nasturtium is considered an annual and only lasts for one growing season. That said, healthy plants can reseed themselves without intervention and come back year after year.
Are there any any health benefits to eating nasturtium flowers?
Nasturtium flowers are packed full of antioxidants like Vitamin C, as well as magnesium, iron, flavonoids and beta carotene. For this reason, nasturtium is considered a plant that has antimicrobial, antifungal, hypotensive, expectorant, and anticancer effects.
Information courtesy of TheSpruce.com