Growing Nasturtiums in Pots: Fast Color, Edible With Care
Nasturtiums are among the easiest flowers to grow in a pot: they germinate quickly from large seeds, they flower hard in poor soil, and feeding them actually reduces the flowers. Bushy types suit pots and trailing types suit baskets and window boxes. They are also widely listed as an edible flower, but that is a separate decision with conditions attached, and growing a plant is not the same thing as establishing that it is safe to eat.
Growing nasturtiums in pots: what the plant wants
Tropaeolum majus is an annual herb, and NC State Extension describes it as a rapid, low-maintenance grower that performs in poor to average, well-drained soil and prefers full sun, six or more hours of direct sunlight a day, with afternoon shade useful in hot summers. In containers that translates into a short list.
A pot with working drainage. Well-drained is the one non-negotiable in that description, and in a container, drainage is a property of the holes and the mix rather than of the soil.
An unfertilized or low-fertility mix. This is the part that catches people who are used to pushing container plants. NC State's note is direct: fertilizing increases foliage but reduces flowering. A nasturtium in rich, well-fed mix produces a magnificent mound of round leaves and almost nothing to look at. If your other pots are on a feeding schedule, this one comes off it, which is the one case where the advice in feeding container flowers without burning them runs in the opposite direction.
Sun. Six hours or more for flowers. Fewer hours gives you leaves again. The general rule for which plants cope with a baking, fully exposed position is in the guide to flowers for full sun containers.
Water, but not standing water. Containers dry on their own clock, and a plant with large soft leaves in full sun goes through more than you expect. Hanging baskets in particular dry faster than anything else on a balcony, for the reasons set out in why hanging baskets dry out so fast.
Bushy or trailing: pick before you buy
Nasturtiums come in two very different habits and the seed packet does not always make it obvious which you are holding.
| Habit | Size per NC State | Suits |
|---|---|---|
| Dwarf, bushy | About 12 inches tall, 2 feet wide | A pot on the floor or a shelf, mixed containers |
| Climbing or trailing | Up to 10 feet | Window boxes, hanging baskets, a pot at height with something to spill over |
Two feet of spread from a twelve-inch plant is the number worth noticing. Even the compact types are wide, so a nasturtium in a mixed pot will sprawl across its neighbors by midsummer unless it has the rim to spill over. In a small space that is usually a feature rather than a problem, but it is a reason not to plant one in the middle of a carefully arranged container.
The climbing types are the ones that make a balcony look furnished, because ten feet of growth hanging from a window box covers a stretch of wall nothing else will. They need the height to do it and they are heavy when wet.
The things that go wrong
Nasturtiums fail in predictable ways, and almost all of them are kindness.
Too much feed, too few flowers. The most common one, and the fix is to stop feeding.
Too much shade. The plant will survive and sulk.
Aphids. NC State lists aphids, mealybugs and whiteflies as common pests, and nasturtiums are notorious aphid magnets in particular. On a balcony this is usually dealt with by a jet of water and by not planting them right up against something you were hoping to keep clean. If the plant is one you are considering eating from, anything you spray on it becomes part of that decision, which is covered in the next section.
Self-seeding. The same NC State entry notes that self-seeding can cause unwanted spreading. In a pot this is a minor nuisance and in some regions a more serious one. Whether a vigorous self-seeding annual is a problem where you live is a local question with a local answer, so your state or regional invasive-species list, and any rules that apply to your building or your tenancy, are the place to check rather than a general gardening page.
Frost. It is a warm-weather annual and it ends when the cold arrives.
Edible with care, and "with care" is the whole sentence
Nasturtiums are one of the most commonly listed edible flowers, and NC State's entry states that all parts except the roots are edible, with a spicy flavor, and that the seeds are sometimes used as a substitute for capers. Colorado State University Extension lists nasturtium among recommended edible flowers, describing the flavor as watercress and peppery and the usual use as fresh in salads.
That is what the sources say. Here is what the same sources attach to it, and it matters more than the flavor note.
Colorado State's edible flowers guidance sets out conditions, and three of them bear directly on a container grower:
- Identification comes first. Its wording is that proper identification of the plant is essential because some flowers are poisonous and should not be eaten, and that scientific names should be used because common names are shared between unrelated plants. A page like this one is not an identification. Nothing you read about a plant online establishes what is growing in your pot.
- Nursery and garden-center plants are not food. The guidance is explicit that flowers from florists, garden centers or nurseries should not be eaten, because those plants are not grown for consumption. A bedding plant bought in a tray was produced as an ornamental, and what was applied to it in production is not disclosed to you.
- Chemicals and manure rule a plant out. Flowers that have been sprayed with pesticides, or collected from plants fertilized with fresh or uncomposted manure, are excluded. In practice that means a decision made at the start of the season, not at the moment you pick, because a plant you treated for aphids in June does not become untreated in August.
On tolerance, the same guidance advises limiting initial consumption and increasing quantities only slowly, in order to find out whether a flower causes an allergic reaction or stomach upset. That is a caution about individual reactions, and it applies to a plant that is perfectly edible for most people.
This site does not tell you that anything in your pot is safe to eat. It cannot, because it cannot see your plant, your seed source or what has been sprayed on your balcony. If there is any doubt at all about what a plant is, the people who can answer are a qualified plant identifier, a local extension service or a botanic garden, and the answer is worth waiting for.
If someone has already eaten something and you are not sure what it was, the National Capital Poison Center's Poison Control service is reached on 1-800-222-1222 or through its online tool, webPOISONCONTROL. Its own instruction is to call 911 instead if the person collapses, has a seizure, has trouble breathing or cannot be woken.
Pets, and where that question goes
Nasturtium shows up on NC State's toolbox tagged as problematic for cats, dogs and horses, and household plant-safety lists are not unanimous about it. This site is not the place that resolves that, and it publishes nothing about symptoms, amounts or what to do after an animal has eaten something.
The useful version for a container grower is the before-you-buy version: if an animal shares the balcony and chews things, check the plant against the ASPCA's toxic and non-toxic plant list before it comes home, and take anything that has already happened straight to a veterinarian or an animal poison control service rather than to a gardening page.
Why they are worth the pot anyway
Set the edible question aside entirely and nasturtiums still earn their space. They go from a large, easy-to-handle seed to a flowering plant quickly, they are genuinely hard to kill, and they do their best work in exactly the thin, unimproved, under-fed conditions that make most container flowers sulk. For a beginner that combination is rare, and it is the same reason marigolds get recommended so often, as set out in the guide to growing marigolds in pots.
They also pull their weight ecologically on a small balcony. A pot of open, nectar-rich flowers is part of the mix that makes a pollinator pot on a balcony work, and the sprawling habit means one plant covers more rim than its root ball suggests.
FAQ
Are nasturtiums safe to eat?
NC State Extension states that all parts except the roots are edible and Colorado State University Extension lists nasturtium among recommended edible flowers. Both of those are statements about the species, not about a particular plant. Colorado State's conditions still apply: positive identification, no pesticide-treated or nursery-grown plants, and small initial quantities to check for an allergic reaction or stomach upset.
Why is my nasturtium all leaves and no flowers?
Almost always fertility. NC State's entry notes that fertilizing increases foliage and reduces flowering, so a plant in rich mix or on a feeding schedule produces leaves. Too little sun does the same thing.
How big a pot do nasturtiums need?
Enough for the habit you bought. Dwarf, bushy types reach about 12 inches tall and 2 feet wide, so they need width more than depth. Trailing types reaching up to 10 feet want height to fall from rather than a bigger pot.
Do nasturtiums come back every year?
No. The plant is an annual, though it self-seeds readily, which in some regions is welcome and in others is unwanted spreading. Your local invasive-species list is the place to check that.
Will nasturtiums keep aphids off my other plants?
They are frequently described as a trap crop, but what a balcony grower reliably gets is a nasturtium covered in aphids. Treat that as a reason to site the plant thoughtfully, and remember that anything you spray on it has to be weighed against ever eating from it.