Nasturtiums: Annuals or Perennials?
The question of whether nasturtiums 'come back' each year is a common one among gardeners. In most temperate climates, nasturtiums (Tropaeolum majus) are treated as annuals because they are not hardy enough to survive freezing winter temperatures. They complete their life cycle within a single growing season, from seed to flower to seed production. However, this doesn't mean they cannot reappear in your garden.
- Nasturtiums typically die back in frost but can reseed themselves readily.
- In warmer climates, they may survive winter and act as perennials.
- Seed saving offers a reliable method for annual replanting.
- Specialised propagation methods can ensure continuity.
This means that while the original parent plant usually perishes with the first hard frost, its seeds often survive the winter in the soil, germinating to produce new plants the following spring. This self-seeding behaviour gives the impression that the nasturtiums have 'come back' from the previous year's plants, even though they are technically new plants grown from seed.
The key factor determining whether you see them return is the climate. In regions with mild winters, where the ground rarely freezes deeply, established nasturtium plants or their fallen seeds can overwinter successfully. These plants might then resume growth in the spring, behaving much like perennials. If you live in an area with harsh winters, relying on self-seeding or actively saving seeds and replanting them is the most dependable way to ensure you enjoy these vibrant, edible flowers and foliage season after season.
Understanding Nasturtium's Growth Habits
Nasturtiums are native to Central and South America, where they grow in warmer, often subtropical or tropical, conditions. Their natural habitat influences their hardiness. In their native regions, they can indeed behave as perennials, growing year-round. When cultivated in gardens across the UK and similar climates, they are susceptible to frost, which damages their tender stems and leaves, ultimately killing the plant. The seeds, however, are more resilient. They can remain dormant in the soil, protected by a hard outer shell, until conditions are favourable for germination in the spring. The warmth of the soil and sufficient moisture trigger this process. This natural reseeding is a common phenomenon for many popular annual garden plants, making them appear to return year after year without direct intervention.
The success of self-seeding depends on several factors: the abundance of seeds produced, how well they are dispersed, and the specific microclimate of your garden. Areas with well-drained soil and a sunny spot might encourage more successful germination of dropped seeds. Conversely, if you clear your garden beds thoroughly at the end of the season or use heavy mulches that prevent seeds from reaching the soil, you might find fewer volunteers appear the following year.
The fundamental answer is that while the original plant usually dies, nasturtiums have a strong tendency to re-establish themselves through self-seeding.
For many gardeners, this self-seeding is perfectly adequate. You might find new plants popping up in unexpected places, adding a charming, informal feel to your borders and containers. If you value a more controlled planting scheme, or if self-seeding has not been successful in your garden, then alternative methods for ensuring their return are available.
Encouraging Nasturtiums to Reappear
If you want to ensure your favourite nasturtium varieties grace your garden again next year, you have several reliable strategies beyond simply hoping for successful self-seeding. These methods involve either saving seeds from your current plants or actively protecting them through the winter.
Saving Nasturtium Seeds
This is perhaps the most straightforward and effective way to guarantee you have nasturtium seeds for the following season. Nasturtium seeds are relatively large and easy to harvest. Wait until the flowers have faded and you see seed pods forming. These pods are typically green and round, maturing to a yellowish-brown or tan colour and becoming somewhat dry and brittle when ready. It's important to collect them before they split open and scatter their contents, or before heavy rain can damage them.
Once harvested, lay the seed pods on a tray or paper in a dry, well-ventilated spot, away from direct sunlight. They will continue to dry out. You can tell they are fully mature and ready for storage when they are crisp and easily separate from the plant. You may need to gently rub the dried pods to release the seeds. Store the seeds in a paper envelope or a breathable cloth bag, clearly labelled with the variety and date, in a cool, dark, and dry place. They typically remain viable for several years when stored correctly.
To ensure good seed quality, let plants produce an abundance of flowers, as this usually correlates with ample seed development. Don't be tempted to harvest seed pods too early; wait until they have fully matured and dried on the plant or can be easily detached.
Overwintering Nasturtium Plants
In milder climates, or if you have a protected space like a conservatory or a frost-free greenhouse, you can attempt to overwinter nasturtium plants. This involves either bringing potted nasturtiums indoors before the first frost or taking cuttings from healthy plants to propagate new ones. Potted plants need to be kept in a cool, bright location and watered sparingly throughout the winter months. They may not grow much, but they should survive. Prune them back in late winter or early spring to encourage new growth.
Alternatively, taking cuttings is a more advanced method. In late summer, before the weather turns cold, take healthy stem cuttings (about 10-15 cm long) from your mature plants. Remove the lower leaves and insert the cuttings into pots filled with a well-draining compost or a mix of compost and perlite. Water them gently and keep them in a warm, humid environment, such as a propagator or under a plastic bag, until they root. Once rooted, they can be treated as young plants and overwintered in cooler, frost-free conditions.
The choice between saving seeds and overwintering plants depends on your climate and the effort you wish to invest.
While nasturtiums aren't typically considered hardy perennials for most of the UK, these methods allow you to maintain continuity. If you live in a region with very mild winters, such as parts of coastal Cornwall or the Scilly Isles, you might find that nasturtiums can indeed survive the winter outdoors and re-sprout vigorously in the spring, behaving much like a short-lived perennial. Always check local microclimates and plant hardiness zones.
When Nasturtiums Act Like Perennials
The classification of a plant as annual or perennial is largely determined by its ability to survive a winter frost and resume growth. Nasturtiums, with their tropical origins, are tender plants. This means they are easily damaged or killed by freezing temperatures. However, the definition can become blurred, especially in specific geographical locations or with diligent garden management.
Climate's Role in Nasturtium Longevity
In their native South America, nasturtiums thrive in conditions where frost is rare or non-existent. They can grow and flower for extended periods, sometimes behaving as short-lived perennials or even hardy perennials in very specific niches. When gardeners in the UK, for example, ask if nasturtiums come back, they are typically asking if the same plant will survive the winter and regrow. The answer for most of the UK is no, the parent plant will not survive significant frost.
However, in coastal areas with very mild winters, such as the milder parts of the South West of England, or sheltered urban microclimates, it's possible for nasturtium plants to survive a mild winter. If the temperature does not drop significantly below freezing, and the plant is protected from harsh winds, it might resprout from its base in the spring. These plants may not be as vigorous as first-year plants, but they will offer an earlier show of flowers. For these fortunate few, nasturtiums might feel like perennials. It's crucial to observe your specific garden conditions; some plants might surprise you with their resilience.
Comparison to Other Garden Plants
It can be helpful to compare nasturtiums to other common garden plants regarding their perennial qualities. For instance, plants like primroses (Primula) are true perennials, reliably returning year after year from their root systems, even after harsh winters. Cosmos, often grown from seed, are generally treated as annuals, similar to nasturtiums, though they can also self-seed. Geraniums, specifically hardy geraniums (often called cranesbills), are robust perennials that definitely come back. However, Pelargoniums (often colloquially called 'geraniums' in the UK, especially bedding types) are tender and are treated as annuals or overwintered indoors, much like nasturtiums.
Begonia plants, depending on the variety, can be tender perennials or annuals; tuberous begonias are typically grown as annuals but their tubers can be overwintered. Zinnias, like cosmos and nasturtiums, are usually grown as annuals but are prolific self-seeders in warmer areas. Marigold seedlings, when planted out, grow as annuals, though some types have better self-seeding capabilities than others. Sweet peas are annuals, requiring replanting each year, though some gardeners do try to overwinter their plants in milder regions. Fuchsias, many varieties of which are tender, can be treated as annuals or overwintered indoors or as cuttings, similar to nasturtiums.
The key difference lies in how readily they survive a typical British winter without intervention.
For nasturtiums, the resilience comes more from their prolific seeding than the survival of the parent plant. If you are in a warmer zone, you might enjoy longer-lived plants, but for most, understanding their self-seeding nature or preparing for seed saving is the practical approach.
Alternatives for Continuous Bloom
While the primary question is about whether nasturtiums 'come back', gardeners often seek continuous bloom and vibrant displays throughout the growing season. If you're not relying solely on self-seeding or overwintering, there are proactive ways to ensure a steady supply of nasturtiums and complement them with other plants that offer reliable returns or extended flowering periods.
Succession Planting and Resowing
To ensure a prolonged display of nasturtiums, consider a strategy of succession sowing. Instead of planting all your seeds at once in spring, sow batches at intervals of two to three weeks. This means that as early blooms fade or plants begin to look tired, subsequent sowings will be coming into their prime, providing a continuous cascade of colour and foliage. Nasturtiums grow relatively quickly from seed, so this method is quite feasible and yields excellent results for a longer flowering season.
You can also use this technique to replace plants that may have succumbed to pests or diseases. If you notice aphid infestations or other issues affecting your initial planting, resowing seeds into fresh soil or a different part of the garden can help maintain the display without interruption. For those aiming for an exceptionally long flowering period, starting seeds indoors a few weeks before the last frost can give you an earlier start, followed by outdoor sowings.
Companion Planting for Garden Health
Nasturtiums are excellent companion plants themselves, known for deterring certain pests like aphids and whiteflies from more delicate vegetables. However, pairing them with other reliable performers can enhance your garden's overall appeal and resilience. Consider planting them near crops like brassicas (cabbage, broccoli) or tomatoes. Their cheerful, peppery flowers and leaves add visual interest and edible components to the garden.
Other plants that offer reliable returns and can complement nasturtiums include cosmos, which also self-seed readily and provide delicate, airy blooms. Growing cosmos in pots is a popular method, offering flexibility in placement. Where to plant sweet peas depends on their need for support and sun, but their fragrance and beauty make them a worthwhile annual. If you're looking for plants that genuinely come back, robust perennials like sunflowers (though annuals, many varieties produce abundant seeds that birds enjoy and can also self-seed) are great companions, and their large heads provide a different structural element. Considering plants like zinnias, which are generally annuals but can self-seed, or marigolds, known for their pest-repelling qualities and vibrant colours, can create a mixed planting that offers a succession of colour and benefit.
Choosing plants with complementary growth habits ensures continuous interest and robustness in your garden.
For example, if you find that your nasturtiums are struggling with specific pests, a companion planting strategy with plants like marigolds or certain herbs can offer natural protection. Understanding the needs of each plant, such as the best conditions for growing cosmos in pots or where to plant sweet peas for optimal support, allows for a more integrated and successful garden design. This approach moves beyond the simple question of 'do nasturtiums come back' to a more holistic view of garden planning and plant longevity.