The Best Time to Plant Nasturtium Seeds for Lush, Fast-Growing Flowers

After a long winter, many gardeners are itching for some spring color. Nasturtium is a beautiful example—its yellow, red, and orange blooms are a welcome sign that the weather is warming, and that gardening season is back in full swing.

However, like any plant, these lovely flowers need to be planted at the right time to grow and thrive. Starting them too early or too late can lead to issues down the line. Here, we spoke to gardening experts about when they recommend planting nasturtium seeds.

When to Plant

Wait until the danger of frost has passed before planting nasturtiums outside; the soil temperature should be above 55 degrees Fahrenheit.

"In most places, that means planting from late spring into early summer," says Ankit Singh, assistant professor and ornamental horticulture educator at the University of Maine Extension. "If you're in a cooler climate, wait until nights are no longer dipping near freezing."

Why is it so important to get the timing right? These flowers are tender annuals, and don't like frost, so if you plant them too early, chilly temperatures can slow their growth—or even kill young seedlings. However, a springtime planting window ensures "better germination, faster early growth, less risk of frost damage, and stronger summer flowering," adds Singh.

How to Plant

You can directly seed nasturtiums in the garden, or transplant seedlings from indoors. Niki Jabbour, founder of Savvy Gardening, says you can start seedlings indoors "in cell packs, 4-inch pots, or soil blocks—a month before your frost date." Place the seedlings in a sunny window for optimal growth, and harden them off before transplanting.

If you would rather direct sow, then plant the "large, wrinkly seeds in garden beds or pots after the last frost date," she says. "Plant them a half inch deep, spacing mounding nasturtiums 6 inches apart and climbing varieties 12 inches apart."

Regardless of how you start your seeds, you can always soak them in water for two to four hours prior to planting to help speed up the germination process.

Singh recommends direct sowing over transplanting, noting nasturtiums don't always transplant well. However, if you're itching to get going on your spring garden, then starting these flowers indoors is still a viable option.

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Where to Plant

Picking the right place in your garden will set your nasturtiums up for success. "Choose a spot with full sun to light shade, since they flower best with good light," says Singh. He recommends planting them in lean soil rather than very rich soil—the latter may lead to many leaves but fewer flowers.

You can plant them in containers on a patio or porch as well. Timing is the same in this case—wait until temperatures have warmed and the danger of frost has passed—but there are a few caveats. "Containers tend to warm up faster than garden soil, which can help seeds and seedlings get off to a quicker start," he says. However, the soil will also dry out faster.

Care Instructions

Nasturtiums need consistent moisture during the seedling stage, notes Jabbour. "Water them regularly at first while they establish, then water as needed when the soil starts to dry out, especially if they are growing in containers," adds Singh.

Later, when they've blossomed, remove any spent blooms to keep your nasturtiums flowering for longer. To get the most blooms, make sure you don't over-fertilize: Too much can lead to leafy growth, rather than flowers, according to Singh.