Nasturtiums, members of the genus Tropaeolum, are popular flowering plants grown both for their ornamental qualities and their culinary uses. These herbaceous plants are native to Central and South America and are typically cultivated as warm-season annuals in most regions. They are admired for their vibrant, warm-toned blossoms and unusual, shield-like foliage.
The Unique Foliage
The leaves of the Nasturtium plant are one of its most distinctive visual features, often resembling miniature lily pads. Their shape is described as peltate, meaning the leaf petiole, or stem, attaches near the center of the blade rather than at the edge, creating a shield-like appearance. Foliage color typically ranges from a deep, saturated green to a distinctive blue-green or gray-green, with some cultivars displaying attractive white or cream variegation.
The surface of the leaf exhibits a characteristic known as superhydrophobicity, often called the “Lotus effect”. This property causes water droplets to bead up almost perfectly into spheres that roll off the leaf with minimal friction. This self-cleaning mechanism is due to a microscopic structure of waxy nanotubules on the surface, which makes the foliage feel smooth to the touch while actively repelling moisture and dirt.
Flower Characteristics and Color Range
Nasturtium flowers are typically trumpet- or funnel-shaped, measuring between 2 and 3 inches wide. A defining structural detail is the presence of a nectar spur, a narrow, elongated tube extending from the back of the flower. This spur contains nectar and is a key feature that distinguishes the bloom.
The flowers usually have five petals, which can be single, semi-double, or fully double, and are often held on long stems above the foliage. Nasturtiums offer a wide color palette in warm hues, including pale creams, yellows, oranges, scarlet reds, and deep mahoganies. Many cultivars feature bicolored patterns, often with dark markings or contrasting throats that enhance the flower’s visual depth.
Growth Habit and Form
The growth habit of the Nasturtium plant varies depending on the cultivar, generally falling into one of two main categories. Vining or trailing types, often derived from Tropaeolum majus, produce long, sprawling stems that can climb or trail up to 10 feet in length. These varieties are frequently used to cascade over walls, hang from baskets, or grow along trellises.
In contrast, dwarf, bushy, or mounding types, often classified as Tropaeolum minus, maintain a compact and contained form. These plants typically reach a height of only 12 to 18 inches and are favored for container gardening or for use as edging in garden beds. The stems supporting both the leaves and flowers are soft and slightly succulent.
Seeds and Reproductive Structures
Following the fading of the flower, the Nasturtium produces a reproductive structure that develops into the plant’s seeds. The fruit is a three-segmented capsule, with each segment containing a single, large seed. When unripe, these pods are green and can be collected for pickling.
The mature seeds are large and roundish, often described as having a convoluted or bumpy texture, sometimes likened to a small, wrinkled pea. As they dry, they harden and change color from green to a light brown or tan. These easily handled seeds are often saved by gardeners for planting in the following season.