Nasturtiums are among the easiest annuals to grow, so when the plants produce nothing but a mound of round, lily-pad-like leaves and zero flowers, it usually signals one of a handful of fixable problems. The most common culprit is soil that is too rich in nitrogen, which pushes the plant to keep making foliage instead of blooms. But light, water, temperature, and even how you started the seeds can all play a role, and understanding which factor is at work in your garden tells you exactly what to change.
Too Much Nitrogen Is the Number-One Cause
Nasturtiums are native to the rocky, nutrient-poor soils of South America, and they evolved to flower prolifically even in ground that would starve most garden plants. When you put them in rich, well-amended garden beds or feed them with a balanced fertilizer, the extra nitrogen tells the plant that conditions are ideal for vegetative growth. It responds by pumping out large, lush leaves on long stems while delaying or skipping flower production entirely.
This is the single most frequent reason gardeners end up with a beautiful nasturtium hedge and no blooms. If your soil has been recently enriched with compost, manure, or a general-purpose fertilizer, nitrogen is almost certainly the issue. Nasturtiums actually perform best in lean, even sandy soil. The stress of low fertility is what triggers them to shift energy from leaf production into reproduction, which means flowers and seeds.
The fix is straightforward: stop fertilizing. If you planted nasturtiums in a bed that was already amended for other crops, you may need to wait until the plants have used up some of that excess nitrogen before blooms appear. In containers, you can flush some nutrients out by watering deeply and letting it drain several times. Going forward, avoid planting nasturtiums in the same bed as heavy feeders you are side-dressing with nitrogen throughout the season. A spot with average-to-poor soil, or a container filled with a basic potting mix and no added fertilizer, is ideal.
Not Enough Sunlight
Nasturtiums need a solid six hours of direct sun each day to flower well. They will survive in partial shade, growing leggy stems and big leaves as they reach for light, but blooming drops off sharply once sunlight falls below that threshold. If your plants are tucked under a tree canopy, on the north side of a building, or in a spot that only gets morning light, that lack of direct sun could be suppressing flowers.
The tricky part is that nasturtiums in shade often look healthy. They are not wilting or yellowing, so you might not suspect a light problem. But flowering is metabolically expensive for any plant, and without enough photosynthetic energy coming in, nasturtiums will prioritize leaf growth. Move containers to a sunnier spot, or plan to relocate garden-planted nasturtiums next season. In hot climates, there is a sweet spot: nasturtiums appreciate some afternoon shade to escape scorching temperatures, but they still need strong morning and midday sun.
Overwatering and Soil Drainage
Consistent moisture is not what nasturtiums want. They are drought-tolerant plants that flower more generously when the soil dries out somewhat between waterings. Overwatering, especially in heavy clay or poorly drained containers, keeps the root zone soggy and mimics the “everything is fine, keep growing leaves” signal that rich soil sends. The plant has no reason to rush into flowering because it is not experiencing any stress at all.
Research on nasturtium responses to drought and salt stress confirms that moderate stress conditions can actually influence the plant’s reproductive chemistry, including changes in ethylene production and sugar accumulation in flowers. In practical gardening terms, this means a nasturtium that has to work a little for its water is more likely to bloom than one sitting in constantly moist soil.
Check your watering habits. If you are giving nasturtiums the same deep, regular watering schedule as your tomatoes or squash, cut back. Let the top inch or two of soil dry before watering again. In containers, make sure there are drainage holes and that the pot is not sitting in a saucer of standing water. In-ground plants in clay soil benefit from raised beds or from being planted on a slight slope where water naturally drains away.
Temperature Problems
Nasturtiums are cool-season plants at heart. They germinate and grow best when daytime temperatures sit between roughly 55°F and 75°F (13–24°C). When summer heat pushes consistently above 85°F (29°C), most nasturtium varieties slow down dramatically. Flowering stalls, existing blooms drop quickly, and the plant may look wilted and stressed during the hottest part of the day even with adequate water.
If you live in a region with hot summers, you have two practical options. First, time your planting so that nasturtiums bloom during the cooler bookends of the growing season: plant seeds early in spring for late-spring and early-summer flowers, or plant in late summer for a fall flush of blooms once temperatures drop. Second, give plants afternoon shade during heat waves, which moderates temperatures enough to keep flowers coming. Research on nasturtium flower physiology has explored how temperature interacts with the plant’s developmental triggers, and the takeaway for gardeners is that heat genuinely disrupts the flowering process rather than just making the plant look droopy.
On the cold end, nasturtiums are frost-tender annuals. A hard frost kills them outright, and even temperatures below about 40°F (4°C) slow growth to a crawl. If you started seeds too early in a cold spring and the plants are just sitting there doing nothing, they may simply be waiting for warmer conditions. Once soil and air temperatures climb into their preferred range, growth and flowering usually pick up.
Overcrowding and Airflow
Nasturtiums planted too close together compete for light, water, and root space. The result is often a tangled mass of foliage where individual plants stretch upward rather than producing the lateral branching that supports abundant flowers. Climbing and trailing varieties are especially prone to this: they grow vigorously in length but may not bloom well if they are all tangled together with no room to spread.
Space bush-type nasturtiums at least 10 to 12 inches apart, and give trailing varieties even more room. If you planted densely and are already deep into the season, thin the weakest plants rather than trying to move them. Nasturtiums resent root disturbance, and pulling one plant out carefully is better than attempting to transplant several. Better airflow around the remaining plants also reduces the humidity that encourages aphid colonies, which brings us to another flowering obstacle.
Aphids and Other Pest Pressures
Nasturtiums are famous as a trap crop for aphids, and there is real irony in that reputation: the very trait that makes nasturtiums useful for luring aphids away from your vegetables means the nasturtiums themselves can become heavily infested. A serious aphid infestation sucks sap from stems and developing flower buds, weakening the plant and causing buds to abort before they open. You might see curled leaves, sticky honeydew residue, and tiny green or black insects clustered on stems and the undersides of leaves.
A strong spray of water from a garden hose knocks aphids off and is often enough to control light infestations. For heavier problems, insecticidal soap or neem oil applied to the plant (including the undersides of leaves) works without harming beneficial insects like ladybugs, which are themselves voracious aphid predators. If you are deliberately using nasturtiums as a trap crop, accept that the plants will look rough and may not flower as heavily. Planting a separate batch of nasturtiums away from your vegetable garden, purely for their flowers, gives you the best of both worlds.
Caterpillars from cabbage white butterflies also feed on nasturtiums, since the plants belong to the same botanical order as brassicas. These pests chew leaves and can defoliate a plant quickly if populations are high. Hand-picking caterpillars or using Bt (Bacillus thuringiensis) keeps them in check without affecting pollinators.
Transplant Shock and Seed-Starting Mistakes
Nasturtiums have a taproot system that does not appreciate being disturbed. Seedlings started indoors in small cells or trays and then transplanted into the garden often sulk for weeks, producing minimal new growth and delaying flowering significantly. Some never recover well enough to bloom at their full potential. This is why most gardening advice insists on direct sowing nasturtium seeds where you want them to grow.
If you do start nasturtiums indoors, use biodegradable peat or coir pots that can go directly into the ground without removing the seedling. Handle the root ball as gently as possible and plant at the same depth. Even with these precautions, directly sown seeds typically catch up to and outperform transplants within a few weeks, because the taproot can grow straight down without hitting a pot wall or being bent during transplanting.
Seed depth matters too. Nasturtium seeds are large and wrinkled, and they need to be planted about half an inch to an inch deep. Seeds sown too shallowly may dry out before germinating, while seeds buried too deep may exhaust their energy reserves pushing through the soil. Soaking seeds in warm water for eight to twelve hours before planting softens the hard seed coat and speeds germination from roughly ten to fourteen days down to about a week.
Variety Selection and Expectations
Not all nasturtium varieties bloom equally. The classic garden nasturtium, Tropaeolum majus, comes in bush types that tend to flower earlier and more densely, and trailing or climbing types that put more energy into vine growth before blooming. If you planted a vigorous climbing variety like ‘Tall Trailing Mix’ and trained it up a trellis, the plant may focus on reaching the top of the structure before shifting into heavy flower production. Bush varieties like ‘Jewel Mix’ or ‘Whirlybird’ typically bloom sooner and more compactly.
Double-flowered varieties also exist but tend to produce fewer overall blooms than single-flowered types. If sheer flower count is your goal, stick with the single-petaled cultivars. Color range is wide, spanning pale yellow through orange, deep red, and even bicolored patterns, and there is no meaningful difference in ease of flowering among colors. Variegated-leaf varieties like ‘Alaska’ are popular for their marbled foliage, and they flower just as reliably as solid-green types.
A Practical Troubleshooting Approach
When you are standing in front of a flowerless nasturtium trying to figure out what went wrong, work through the likeliest causes in order. Start with nitrogen and soil richness, since that is the problem in the majority of cases. Then check sunlight exposure by actually timing how many hours of direct sun the spot receives over a full day. Assess your watering frequency. Look for aphid colonies. Consider the temperature pattern over the past few weeks.
Often it is a combination of two factors rather than a single dramatic one. A nasturtium in moderately rich soil that also gets only five hours of sun is being pushed toward foliage growth from two directions at once. Fixing just one of those factors may be enough to tip the balance toward flowering, and fixing both almost certainly will. The encouraging thing about nasturtiums is that once the conditions shift in their favor, they respond quickly. Plants that have been sitting in leaf-only mode for weeks can begin budding within ten to fourteen days after a change in fertilization, light, or watering.
Harvesting Flowers to Encourage More Blooms
Once your nasturtiums do start flowering, regular picking actually extends the bloom period. Like many annuals, nasturtiums put energy into developing seeds once a flower is pollinated. If you deadhead spent blooms or harvest open flowers for salads and garnishes, the plant redirects that energy into producing new buds. Nasturtium flowers, leaves, and even unripe seed pods are edible, with a peppery, watercress-like flavor that comes from the same glucosinolate compounds found in mustard and horseradish.
Pick flowers in the morning after the dew has dried for the best flavor and longest vase life. If you want to collect seeds for next year, let a few flowers mature and dry on the vine at the end of the season. The large, round seeds are easy to harvest and store, and they remain viable for several years if kept cool and dry. Self-sowing is also common in mild climates: nasturtiums that are allowed to drop seed in fall often produce volunteer seedlings the following spring, sometimes in slightly different spots than where you originally planted them.
Growing Nasturtiums in Containers
Containers are actually one of the best ways to grow nasturtiums, because you control soil quality and moisture precisely. Use a basic potting mix without added slow-release fertilizer, or cut a rich mix with perlite or coarse sand to reduce fertility. A pot at least 8 to 10 inches in diameter works for bush types; trailing varieties look dramatic spilling over the edges of hanging baskets or window boxes but need a bit more root volume to sustain long vines.
The biggest container mistake is overwatering, since potting mixes in plastic pots retain moisture longer than garden soil. Terra cotta pots dry out faster and suit nasturtiums well. If you notice lush foliage and no flowers in a container nasturtium, check whether the potting mix you used contains fertilizer. Many commercial mixes do, and that slow-release nitrogen will keep feeding your plant for months. Switching to a leaner mix next round, or simply top-dressing with sand, helps shift the balance toward blooms.
Containers also let you move plants to chase the sun or escape a heat wave. If your patio nasturtiums stop flowering during a mid-July scorcher, sliding them into a spot with morning sun and afternoon shade for a couple of weeks can restart bud production once temperatures ease. That kind of flexibility is harder to achieve with in-ground plantings, which is one reason container nasturtiums often end up being the most floriferous in a garden.