Are Nasturtiums Toxic to Humans?
In short, no, nasturtiums (Tropaeolum majus) are not toxic to humans when consumed in typical culinary quantities. The leaves, vibrant flowers, and even the unripe seed pods are all edible and commonly used in salads, garnishes, and other dishes. They are well-regarded for their peppery, radish-like flavor, which comes from compounds known as glucosinolates.
Potential Side Effects of Overconsumption
While not toxic, consuming excessively large amounts of nasturtiums can lead to some minor side effects. These are typically related to the high concentration of mustard oils present in the plant, especially in the leaves and stems.
- Gastrointestinal Upset: The most common side effect is stomach upset, which can include nausea, vomiting, or diarrhea. This is usually a result of overindulging and the body's reaction to the pungent compounds.
- Kidney or Stomach Irritation: For individuals with pre-existing conditions like kidney disease or stomach and intestinal ulcers, large doses of nasturtium are not recommended. The mustard oils can cause irritation and exacerbate these conditions.
Who Should Exercise Caution?
While most people can enjoy nasturtiums without issue, certain groups should be more cautious:
- Pregnant or Breastfeeding Women: Due to limited research on the effects of nasturtium on pregnancy and lactation, it is recommended to avoid consumption to be safe.
- Individuals with Kidney Disease or Ulcers: As mentioned, the irritating mustard oils can worsen these conditions, so nasturtium should be avoided.
- Young Children: While not highly toxic, nasturtium is labeled as 'likely unsafe' for children when taken orally in medicinal amounts. The risk of overconsumption and potential for upset stomachs is higher with smaller body weights.
Are Nasturtiums Toxic to Pets and Livestock?
The American Society for the Prevention of Cruelty to Animals (ASPCA) officially lists Tropaeolum majus as non-toxic to dogs, cats, and horses. However, this does not mean pets can consume unlimited amounts without consequence.
Potential for Mild Gastrointestinal Upset in Pets
If a dog or cat ingests a significant quantity of nasturtium, particularly the seeds, it can still lead to mild gastrointestinal irritation. Symptoms to watch for include vomiting, diarrhea, drooling, or lethargy. In most cases, these issues resolve on their own, but monitoring your pet is important. If symptoms persist or worsen, contact a veterinarian.
Livestock and Other Animals
- Chickens: Nasturtiums are generally considered safe and beneficial for chickens. The plant has been shown to have natural antibiotic and anti-bacterial properties that can benefit a flock's health.
- Rabbits: Nasturtiums are listed as a safe plant for rabbits to eat, along with dandelions and clover.
- Horses: The ASPCA explicitly lists nasturtiums as non-toxic to horses.
A Note on Watercress
It's crucial not to confuse garden nasturtium (Tropaeolum majus) with watercress (Nasturtium officinale). While watercress is also edible, foraging for it in the wild is extremely risky. Watercress can grow alongside highly toxic plants like water hemlock and can absorb toxins from polluted water. The safety of garden nasturtium does not extend to wild-foraged watercress.
Benefits of Nasturtiums
Beyond their culinary use, nasturtiums are valued in the garden and have several health-promoting properties.
- Rich in Nutrients: They are an excellent source of vitamin C, iron, and manganese.
- Natural Pest Control: Nasturtiums act as a 'trap crop' to attract pests like aphids away from other vegetables, and they also repel certain pests.
- Attract Pollinators: The vibrant flowers are a magnet for beneficial insects like bees and butterflies, promoting a healthy garden ecosystem.
- Antimicrobial Properties: The isothiocyanate compounds that give nasturtiums their peppery flavor also possess antimicrobial and antiviral properties.
Nasturtium vs. Watercress: A Comparison
To avoid any confusion, here is a comparison of common garden nasturtium and watercress.
| Feature | Garden Nasturtium (Tropaeolum majus) | Watercress (Nasturtium officinale) |
|---|---|---|
| Appearance | Round, shield-shaped leaves; bright, trumpet-shaped flowers. | Small, rounded, oval leaves; small, white, four-petaled flowers. |
| Growth Habit | Trailing or bushy annual that thrives in well-drained, average soil. | Aquatic or semi-aquatic perennial that grows in or near fresh water. |
| Toxicity Risk | Non-toxic, but excessive consumption may cause mild stomach upset in humans and pets. | Edible when commercially grown; wild-foraged watercress is highly risky due to potential for contamination or misidentification with poisonous plants. |
| Culinary Use | Leaves, flowers, and seeds used in salads, as garnish, or pickled like capers. | Peppery salad green often used in sandwiches, salads, and soups. |
| Location | Grown in gardens, containers, or beds. | Found naturally in streams and rivers; cultivated in clean aquatic environments. |
The Verdict: The Safety of Nasturtiums
For the vast majority of people and pets, nasturtiums are not toxic but are instead a safe and flavorful edible plant. The mild risks are limited to overconsumption, which can cause temporary digestive upset, and specific health conditions that warrant avoiding the plant altogether. By understanding the difference between common garden nasturtium and wild watercress, and by consuming nasturtiums in moderation, you can enjoy this versatile and attractive plant with confidence. If ever in doubt about a plant's safety for human or pet consumption, it's always best to consult with a medical or veterinary professional.
Conclusion
In conclusion, the common garden nasturtium (Tropaeolum majus) is a safe, edible plant for humans and is considered non-toxic to most common pets, including dogs, cats, and horses. While minor digestive upset is possible from overindulgence, severe toxicity is not a concern under normal circumstances. Individuals with kidney disease, stomach ulcers, or who are pregnant or breastfeeding should avoid consumption. For everyone else, this colorful and zesty plant offers nutritional benefits and acts as a beneficial garden companion, attracting pollinators and deterring pests. When sourced from a reputable, clean garden, nasturtiums can be a wonderful and worry-free addition to your culinary and ornamental plants.
