The common garden nasturtium, Tropaeolum majus, is grown as an annual in most of the world. It completes its life cycle in a single growing season and dies at the first hard frost. That said, the answer depends on which nasturtium you mean and where you live. In mild, frost-free climates, the same plant can survive winter and bloom again the following year, functioning as a tender perennial. And several lesser-known species within the Tropaeolum genus are true perennials with underground tubers that return reliably year after year.
Why Garden Nasturtiums Are Treated as Annuals
Tropaeolum majus is native to the highlands of South America, where it evolved in a climate with cool but not freezing temperatures. The plant has no tolerance for hard frost. Once soil temperatures drop below freezing, the stems, leaves, and roots all die. In most of North America, Europe, and anywhere else with a real winter, that means the plant lives for one season: you sow seeds in spring, enjoy flowers and foliage from early summer through fall, and the first frost ends the show.
This frost sensitivity is the single reason most gardeners call nasturtiums annuals. The plant itself is not genetically programmed to die after one season the way a true annual like a sunflower is. It is what botanists call a “tender perennial treated as an annual,” a distinction that matters if you happen to garden somewhere warm. In USDA hardiness zones 9 through 11, or equivalent climates around the world, garden nasturtiums can survive winter and regrow. In parts of coastal California, southern Florida, Hawaii, and frost-free Mediterranean regions, nasturtiums sometimes naturalize and sprawl year-round, becoming almost weedy in their persistence.
Self-Seeding and Why It Looks Perennial
Even in cold climates, nasturtiums have a trick that makes them seem perennial: they self-seed aggressively. A healthy nasturtium plant produces large, wrinkled seeds that drop to the ground in late summer and fall. Those seeds are surprisingly tough. They can survive winter in the soil and germinate the following spring when conditions improve. The result is a new crop of nasturtiums appearing in roughly the same spot, which makes it look like the original plant came back. It did not. The parent plant died. Its offspring just took its place.
Research on nasturtium seed germination shows that watering conditions strongly influence how well those seeds sprout. In a study examining untreated nasturtium seeds, optimal germination reached about 90% when moisture levels were adequate, but germination dropped sharply under near-drought conditions.1Nature Publishing Group. Influence of irrigation conditions in the germination of plasma treated Nasturtium seeds This means self-seeded nasturtiums are most likely to “return” in gardens with reliable spring rainfall or regular watering. If your climate is dry in spring, fewer volunteers will show up, and you may need to resow intentionally.
The seeds themselves are easy to collect. They are about the size of a dried pea and turn from green to tan as they ripen. Many gardeners harvest them in fall, store them dry over winter, and plant them directly outdoors after the last frost. Since nasturtiums dislike having their roots disturbed, direct sowing outdoors tends to work better than starting them in pots and transplanting.
True Perennial Nasturtiums in the Tropaeolum Genus
The word “nasturtium” in everyday gardening almost always refers to Tropaeolum majus or its close relatives like Tropaeolum minus (a more compact species also grown as an annual). But the genus Tropaeolum includes roughly 80 species, and several are genuine perennials that survive winter by retreating to underground tubers or rhizomes.
The most economically important of these is Tropaeolum tuberosum, known in the Andes as mashua. Quechua farmers have cultivated mashua as a tuber crop for thousands of years, growing it alongside potatoes and other Andean staples at high elevations in Peru and Bolivia.2HortScience. Tropaeolum Mosaic Potyvirus (TropMV) Reduces Yield of Andean Mashua (Tropaeolum tuberosum) Accessions Mashua forms underground tubers that look somewhat like small, elongated potatoes with colorful skin ranging from yellow to deep purple. The tubers are edible, though they have a peppery, slightly bitter flavor that is more acquired taste than crowd-pleaser. Unlike garden nasturtiums, mashua dies back to the ground each year and then regrows from its tubers when conditions warm up, making it a true herbaceous perennial.
Other perennial Tropaeolum species are grown ornamentally in mild climates:
- Tropaeolum speciosum: Called the flame nasturtium or Scottish flame flower, this climbing species produces vivid scarlet flowers and thrives in cool, moist conditions. It is hardy to about USDA zone 7 and grows from fleshy rhizomes. It is famously difficult to establish but spectacular when happy, scrambling through hedges and shrubs.
- Tropaeolum polyphyllum: A creeping, ground-hugging species with silvery-blue foliage and bright yellow flowers. It grows from deep, fleshy roots and is hardy to roughly zone 7. It goes dormant after flowering in early summer and reappears the following spring.
- Tropaeolum tricolor: A delicate climber from Chile with small red, purple, and yellow flowers that look almost like tiny lanterns. It grows from a small tuber and is suited to cool greenhouse culture or mild outdoor climates.
These perennial species are far less common in garden centers than Tropaeolum majus. Most are specialty plants sold through bulb catalogs or plant societies. They also look quite different from the big, round-leaved, brightly flowered nasturtium most people picture. If you are specifically looking for a nasturtium that comes back every year in a temperate climate, Tropaeolum speciosum or Tropaeolum polyphyllum are the most realistic options for gardens in zones 7 through 9.
Extending the Season for Garden Nasturtiums
If you grow the common garden nasturtium and want to push it as close to perennial behavior as possible, a few strategies help. In borderline climates where frosts are light and infrequent, a thick layer of mulch over the root zone can sometimes get plants through winter. Container-grown nasturtiums can be brought indoors to a bright, cool spot before the first frost. They will not thrive the way they do outdoors in summer, but they can survive through winter and be moved back outside in spring.
In practice, most gardeners find it easier to simply resow each year. Nasturtium seeds are cheap, germination is fast (usually within 7 to 14 days in warm soil), and the plants grow quickly enough to flower within about 60 days of sowing. The effort of overwintering a leggy, underlit plant indoors rarely seems worth it when fresh seeds produce vigorous new plants so readily.
For gardeners in warm climates where nasturtiums do persist as perennials, the main maintenance task is keeping them in check. Nasturtiums grow fast, and trailing varieties can spread several feet in a season. Without frost to kill them back, they can become sprawling and overgrown. Hard pruning in late winter or early spring encourages fresh, compact growth and a new flush of flowers.
Nasturtiums as Edible Plants
One reason nasturtiums are so widely grown, beyond their cheerful flowers, is that every above-ground part of the plant is edible. The flowers, leaves, and unripe seed pods all have a peppery, watercress-like flavor. This is not a coincidence: garden nasturtiums and watercress (Nasturtium officinale) both produce similar sulfur-containing compounds, which is why the genus Tropaeolum inherited the common name “nasturtium” from the unrelated watercress centuries ago.
Nutritionally, nasturtium flowers and leaves are more than a garnish. The flowers are rich in lutein, a carotenoid pigment associated with eye health. Yellow nasturtium flowers contain roughly 450 micrograms of lutein per gram of fresh weight, making them one of the richest food sources of this compound.3Journal of Food Science. Flowers and Leaves of Tropaeolum majus L. as Rich Sources of Lutein The leaves are a good source of both lutein and beta-carotene, a precursor to vitamin A.3Journal of Food Science. Flowers and Leaves of Tropaeolum majus L. as Rich Sources of Lutein Nasturtium plants also contain anthocyanins, polyphenols, and vitamin C, which together contribute to the plant’s antioxidant profile.4PubMed. Garden nasturtium (Tropaeolum majus L.) – a source of mineral elements and bioactive compounds
The unripe green seed pods are sometimes pickled in vinegar and used as a caper substitute. They have the same peppery bite as the leaves, plus a pleasant crunch. This use has a long history in European cooking, particularly in English kitchen gardens of the 18th and 19th centuries.
Companion Planting and Natural Pest Defense
Nasturtiums have a long reputation as companion plants in vegetable gardens, and that reputation has some chemistry behind it. The leaves contain high concentrations of a compound called glucotropaeolin, a type of glucosinolate. When nasturtium leaves are damaged, whether by chewing insects or by a person biting into a salad, glucotropaeolin is broken down by an enzyme called myrosinase to produce mustard oils. These oils are what give nasturtium leaves their sharp, peppery kick.5PubMed. The glucosinolate-myrosinase system in nasturtium (Tropaeolum majus L.): variability of biochemical parameters and screening for clones feasible for pharmaceutical utilization
In gardening lore, nasturtiums are planted near vegetables for two overlapping reasons. First, some gardeners use them as trap crops: aphids are strongly attracted to nasturtiums and may preferentially colonize them instead of nearby beans, squash, or brassicas. The idea is to sacrifice the nasturtiums to protect the vegetable crop. Second, the mustard oils released by nasturtium foliage may deter certain pests like whiteflies and squash bugs. The evidence for these effects is mostly observational rather than rigorously tested, but the practice is widespread enough among organic growers to be worth noting.
The same glucosinolate compounds that repel insects also have antimicrobial properties. When nasturtium leaves are consumed, the resulting mustard oils are absorbed in the intestine and excreted through the urinary tract, where they exhibit antimicrobial activity.5PubMed. The glucosinolate-myrosinase system in nasturtium (Tropaeolum majus L.): variability of biochemical parameters and screening for clones feasible for pharmaceutical utilization In parts of Europe, particularly Germany, nasturtium-based herbal preparations have been used traditionally to treat urinary tract and respiratory infections. Pharmaceutical research has explored standardized nasturtium extracts for these applications, screening different plant clones for the most consistent glucosinolate content.5PubMed. The glucosinolate-myrosinase system in nasturtium (Tropaeolum majus L.): variability of biochemical parameters and screening for clones feasible for pharmaceutical utilization
Choosing Between Annual and Perennial Types
For most gardeners, the practical question is not really “annual or perennial” but “what do I want from this plant?” If you want a fast, easy, colorful flower that fills beds, spills over containers, and gives you something edible to toss in salads, the common garden nasturtium (Tropaeolum majus) is hard to beat. It comes in trailing varieties that cascade beautifully from hanging baskets and window boxes, bush varieties that stay compact and tidy, and climbing varieties that can scramble up trellises or through other plants. Flower colors range from pale cream through yellow, orange, and deep mahogany red, with some bicolor forms. You sow seeds in spring, enjoy the show all summer, and start over the next year.
If you want a perennial nasturtium that returns on its own each spring, your options are more limited and more demanding. Tropaeolum speciosum needs cool, moist, acidic soil and partial shade, which is almost the opposite of what the common nasturtium wants. Tropaeolum polyphyllum needs excellent drainage and full sun but goes dormant by midsummer, so it leaves a gap in the garden for months. Tropaeolum tuberosum is a conversation piece and a food crop in the Andes, but it needs a long growing season and frost protection in most temperate gardens. None of these are drop-in replacements for the cheerful, all-summer flower display of Tropaeolum majus.
For gardeners in frost-free areas who find that their garden nasturtiums persist year after year, the main thing to watch is whether the plants become less productive over time. Older nasturtium stems get woody and produce fewer flowers. Cutting plants back hard once a year, or simply pulling out tired plants and letting self-seeded volunteers replace them, keeps the display fresh. In this sense, even where nasturtiums technically behave as perennials, many gardeners treat them as annuals anyway, because fresh young plants simply look and perform better.