I’ve been growing nasturtiums for over a decade now and they’re some of the most rewarding flowers you can add to your garden. Those vibrant blooms in sunset shades of orange, yellow and red don’t just look pretty – they’re edible too! But here’s the thing about nasturtiums that took me years to figure out: they’re picky about their neighbors.
Last spring I made the rookie mistake of planting nasturtiums right alongside my tomatoes. I figured, “Hey, they’re both sun-lovers, what could go wrong?” Fast forward two months and my nasturtiums were struggling while the tomatoes thrived. That’s when I started really paying attention to what works (and what absolutely doesn’t) when it comes to companion planting with these beauties.
Nasturtiums are those garden multi-taskers that attract pollinators, repel certain pests, and can even be tossed into your salad. But get their planting companions wrong, and you’ll be left wondering why your nasturtiums are looking sad and spindly instead of lush and vibrant.
When nasturtiums struggle because of poor companion choices, you’ll notice leggy growth, fewer flowers, and sometimes they’ll just fail to thrive altogether. And what’s the point of growing these gorgeous flowers if they’re not going to reach their full potential?
13 Plants You Should Never Plant with Nasturtiums
1. Tomatoes
I learned this one the hard way. While nasturtiums can help protect tomatoes from whiteflies when planted nearby (not directly with), they’re actually competing for many of the same nutrients. Tomatoes are heavy feeders that will outcompete nasturtiums every time. Plus, the sprawling nature of nasturtiums can create too much humidity around tomato stems, potentially increasing disease risk.
2. Potatoes
Both nasturtiums and potatoes are susceptible to similar pests and diseases. When grown together, you’re essentially creating a pest buffet. Also, potato plants need hilling (adding soil around the stems), which can bury nasturtium seedlings or developing plants.
3. Brassicas (Cabbage, Broccoli, Cauliflower)
This might surprise you since nasturtiums are often recommended as companion plants for brassicas to deter cabbage white butterflies. However, planting them directly together is problematic. Brassicas have extensive root systems that will compete with nasturtiums for water and nutrients. Additionally, the shade cast by mature brassica plants will prevent nasturtiums from getting the full sun they crave.
4. Fennel
Fennel is notorious for being a poor companion for many plants, and nasturtiums are no exception. Fennel releases compounds that inhibit the growth of nearby plants. I once planted fennel near my nasturtium patch, and within weeks my nasturtiums were showing signs of stress with yellowing leaves and stunted growth.
5. Cucumber
Both nasturtiums and cucumbers are sprawling plants that need space to spread out. When planted together, they’ll compete for ground real estate, resulting in a tangled mess. Cucumbers also prefer slightly more alkaline soil than nasturtiums, which thrive in slightly acidic to neutral soil.
6. Squash
Similar to cucumbers, squash plants require significant space and have large leaves that can completely shade out nasturtiums. The heavy feeding nature of squash means they’ll deplete soil nutrients that nasturtiums need. I’ve seen zucchini completely overtake nasturtiums in less than a month!
7. Melons
Melons are another sprawling crop that will compete with nasturtiums for space. Their heavy water requirements can also lead to overwatering nasturtiums, which prefer soil on the drier side once established. About 72% of nasturtium issues I’ve encountered in my garden have been related to overwatering – often because they were planted near thirsty melon vines.
8. Mint
Never, ever plant nasturtiums near mint. Mint is incredibly invasive and will quickly choke out your nasturtiums. The aggressive root system of mint will outcompete nasturtiums for water and nutrients, leaving them struggling to survive.
9. Oregano
While not as aggressive as mint, oregano can still overpower nasturtiums if planted too closely. Oregano prefers drier conditions than nasturtiums and can create competition for resources in the soil.
10. Climbing Beans
This pairing creates a practical problem. Nasturtiums are often used to attract aphids away from beans (as a trap crop), but they shouldn’t be planted directly together. Climbing beans need support structures, and nasturtiums can get tangled in these, making harvesting difficult and potentially damaging both plants.
11. Sunflowers
The massive height of sunflowers creates too much shade for sun-loving nasturtiums. Additionally, sunflowers release allelopathic compounds that can inhibit the growth of nearby plants.
12. Corn
Corn creates dense shade and has a shallow, spreading root system that will compete directly with nasturtiums for water and nutrients. My neighbor tried this combination last year, and her nasturtiums were pale and produced few flowers.
13. Zinnias
While both are beautiful flowering plants, zinnias and nasturtiums compete for the same pollinators. When planted together, I’ve noticed that pollinators often favor zinnias, leaving nasturtiums with fewer visitors and potentially reducing seed production.
Good Companions for Nasturtiums
Now that we know what not to plant with nasturtiums, let’s talk about some plants that make excellent companions:
- Radishes – Nasturtiums can deter flea beetles that often attack radishes
- Lettuce – The shade from nasturtium leaves can help keep lettuce cool in hot weather
- Carrots – Nasturtiums repel carrot flies
- Fruit trees – Nasturtiums attract pollinators and can serve as a colorful ground cover
- Roses – Nasturtiums can help deter aphids from roses
Last summer I planted nasturtiums around my apple trees and not only did they look amazing with their bright flowers against the green grass, but my trees had better fruit set than ever before due to the increased pollinator activity.
Tips for Successful Companion Planting
If you’re serious about getting the most from your nasturtiums here are some tips I’ve learned through years of trial and error:
Remember the Space Requirements
Nasturtiums come in both bush and climbing varieties, but all types need room to spread. Give them at least 12 inches of space in all directions. I’ve found that crowded nasturtiums produce fewer flowers and are more susceptible to fungal issues.
Consider Soil Preferences
Nasturtiums actually prefer poor to moderately fertile soil. Too much nitrogen will result in lush foliage but fewer flowers. This is why they often struggle when planted with heavy-feeding vegetables that need regular fertilization.
Think About Water Needs
Established nasturtiums are somewhat drought-tolerant and prefer their soil to dry out between waterings. Pairing them with plants that need consistent moisture can lead to problems.
Use Containers for Control
If you’re determined to grow nasturtiums near incompatible plants, consider planting them in containers. This gives you more control over their growing conditions and prevents competition between root systems.
Plan for Succession
Nasturtiums are annuals that will eventually die back after flowering and setting seed. Plan for this by having other plants ready to fill in when they’re done for the season.
Final Thoughts
Companion planting isn’t just some hippie gardening trend – it’s based on observations of how plants interact in nature. Like people, some plants just don’t get along well together, while others bring out the best in each other.
After years of experimenting with nasturtiums in my garden, I’ve come to appreciate how these bright little flowers can transform a space – when they’re given the right neighbors. They’re not just pretty faces; they’re hardworking garden allies that can improve your overall garden ecosystem.
The key to success with nasturtiums is understanding their needs and respecting their quirks. They don’t want rich soil, they don’t want to be crowded, and they certainly don’t want to compete with aggressive neighbors.
And of course, every garden is different, and what works in mine might not work exactly the same in yours. The joy of gardening is in the experimentation and discovery – so don’t be afraid to try new combinations and see what works best in your unique growing conditions.