If you want to bring their bold fire colors to your backyard, you’ll be wondering when to plant nasturtium seeds – or the bedding plants you could alternatively select.
Growing nasturtiums (Tropaeolum) is easy, and from mid-summer into fall, they brighten the yard. The annual forms have spurred flowers in hot shades of gold, orange, or red, amongst green leaves that resemble tiny waterlily pads. The word nasturtium comes from the Latin nasus tortus, which means twisted nose, because the whole plant has a strong (but not unpleasant) aroma that sometimes makes your nostrils sting and tingle.
Here, we’ve got the details you need about the optimum times for sowing and planting nasturtiums to enjoy their fabulous form and color.
When to plant nasturtium seeds
The answer to the question of when to plant nasturtium seeds is that the optimum time depends on the type of nasturtium you want to grow. Annuals can be sown in spring or early summer or planted as ready-grown bedding in early summer. While the perennial forms are best planted during their dormant period in fall or winter.
Since annual nasturtium seeds are big and easy to grow, they are a great choice for flower bed ideas when you want to get kids involved. And many varieties scramble and trail, creating cascades of orange and green that can be grown to clad obelisks or wigwams or tumble out of hanging baskets.
There are larger perennial nasturtiums available as well – such as the stunning scarlet T. speciosum (flame nasturtium) from Chile – and many of these also climb and trail, forming fiery waterfalls of flowers in summer and fall.
When to sow annual nasturtium seeds
In most areas, annual nasturtiums can be sown direct into soil outside in late spring.
‘Sow nasturtiums outside around the time of the last frost,’ advises Catherine Kaczor of Hudson Valley Seed Co, based in the northeast.
If you live in a mild climate, nasturtiums could be sown direct in early spring. But for those of us in cooler areas, it’s safest to sow nasturtiums under cover in March or April – for example, in a greenhouse or on a bright windowsill – if we want to give them an early start.
Once the weather warms in your area, nasturtiums can be sown straight into the soil outside – they flower into fall, so sowing in early summer is fine. ‘Sow nasturtiums indoors in March or April and plant out after last frosts, or sow direct between May and July,’ suggests UK supplier Sarah Raven.
Anyone who has slugs or rabbits in their backyard is strongly advised to start nasturtiums off under cover – otherwise, the emerging seedlings might be nibbled.
When to plant annual nasturtiums
As to when to plant nasturtiums if you buy them as ready-grown bedding plants? It is probably the easiest way to grow them, and they are widely available in nurseries in early summer and usually inexpensive.
Plant them outside in May or June in well-drained soil in sun. They like moist soil, but don’t over-water them or they won’t flower as well; and there is no need to feed them.
They can be grown as ground cover bedding to fill gaps in borders. The more impressive varieties – such as ‘Indian Chief’, which has blazing red flowers and dark blue-green leaves – are wonderful in hanging baskets.
Alternatively, since annual nasturtiums are edible, they can be used to liven up vegetable garden ideas, perhaps coaxing them up wigwams of hazel or birch sticks. The colorful flowers have a peppery taste and look beautiful added to summer salads.
When to plant perennial nasturtiums
Perennial nasturtiums are tuberous plants that are often only available to buy and plant during their dormant period in fall, winter, or early spring. This helps them to establish and is more reliable than attempting to raise them from seed.
Both orange T. tuberosum var. lineomaculatum ‘Ken Aslet’ and red T. speciosum (flame nasturtium) have a trailing habit, making them ideal for cladding a fence or a shrub that you don’t mind concealing. T. speciosum is particularly stunning, forming a cascade of vivid vermillion-red, and performs best in cool, moist climates (such as Scotland).
T. polyphyllum (yellow lark’s heels) is a very different perennial nasturtium that has lovely glaucous foliage and golden flowers. Only reaching 6in (15cm) high, but spreading to 4 to 5ft (1 to 1.5m), it is ideal at the front of a gravel border or the top of a wall.
What month do nasturtiums flower?
Nasturtiums flower from mid summer to fall until the frosts begin and make a spectacular display because of the masses of bold colored blooms.
How long does it take nasturtium seeds to sprout?
It takes up to two weeks for nasturtium seeds to sprout, although it can be quicker. When sowed direct, the seeds sprout best when soil is warm.
After experience in the fashion industry, Hazel became a beauty and wellbeing journalist, and worked for The Ecologist as Green Living Editor. During a period of injury, she studied horticulture and garden design, and went on to work as a gardener and write about gardening for national newspapers, including The Guardian. Today, she enjoys regularly contributing to print and online magazines, including Amateur Gardening and Homes & Gardens.
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