Nasturtium and Soil Temperature

Annual Nasturtium Germination

• Sow annual nasturtiums from seed after risk of frost or in early spring. Seeds will germinate at 55 to 65 F. At 68 degrees, they will germinate in about two weeks. Plant directly outdoors or start in a greenhouse or indoors up to two weeks before last frost. Space seeds 10 to 36 inches apart.

  Sow perennial nasturtiums as early as two weeks before last frost. They will germinate at a temperature of 55 F. To speed up germination, mix in with moist soil, place in a plastic bag, and refrigerate for three months. Space seeds 2 inches to 1 1/2 feet apart.

Heat

• Nasturtiums are native to temperate, high elevation areas of South America and grow well in both hot and cool weather. They will often flourish and grow vigorous foliage in hot summer months, but flowering tends to be reduced during such times. In hot climates, plant the seeds in February or fall, before the temperature gets really hot. During the hot season, water three times a week to keep the plant healthy. Planting in partial shade also helps protect the flowers from summer scorching.

Frost

• Nasturtiums like it relatively cool, but they will not survive harsh frosts. The plant may die off when temperatures dip below 30 F. To protect nasturtiums from such freezes, plant directly in the ground or near a building. Nasturtiums can thrive in containers but their roots will be less protected from freezing because the soil in the ground warms up faster. Planting directly next to a house foundation provides heat radiation to keep the roots warm.

Planting Guide

• Plant nasturtiums as spreading borders or plant in groups in both sun or part shade. Use the trailing, climbing varieties to cover banks and fences. Grow for the cut flowers or use the edible leaves and blossoms in salads and other dishes. They have a pungent, spicy aroma and flavor. Overly rich soil may diminish flowering.