This is my third season planting and tending nasturtiums so I figured I might share what I have learned. I always tells myself that I will “cool it” on the nasturtium planting, but every year I find myself with anywhere from 30-50 individual nasturtiums, from seed. (And yes, they are all in containers.)
I have a few planters devoted solely to nasturtiums, but I also tend to mix them in with other plants. Nasturtiums are good because they make great filler plants. You can literally poke a seed in any container, and if the weather and soil are okay (meaning, not too soggy, not too warm, not too dry…) you’ll end up with a lovely, leafy plant with beautiful blooms in about six weeks. Since Nasturtiums grow low and bushy and spill over, they are great with taller vegetable plants as well as anything that’s sort of “top heavy” (sunflowers, passiflora, etc.) They are also edible (slightly pepper-y- perfect for salads) and smell amazing.
But they can also be extremely finicky, especially in small spaces or containers. While they tend to do fine without much fuss, I find that if you really want your nasturtium plants to last a long time and not become moldy/crispy near the soil, it’s completely important to continually trim them.This is hard for me because there are very few things I hate more than cutting off healthy foliage with buds on it. But in order to keep the nasturtium compact and healthy close to the root line, it’s important to keep growth at bay. The longer/taller a nasturtium gets, the less growth at the base of the plant. So unless you are doing tall-hanging baskets, it’s better to just trim the tips and undersides of nasturtiums every few days even if it means trashing flowers that have yet to bloom (I hate that, but I hate dead nasturtiums even more, so…)
You can put multiple nasturtiums in one small area/container, but they do root profusely so plan on having to re-pot fairly regularly. But be careful, because nasturtiums HATE having their roots disturbed. It’s best to transfer the entire root ball with the soil packed around it than try and tranfer just a segment of the plant and roots.
Also, nasturtiums do grow wide, so if you are doing multiple plants in one small space, plan on trimming regularly to keep each Nasturtium in a “line” (narrow and longer as opposed to wide and bushy). If you don’t do that, usually there will be one or two stronger plants in each area that will overtake the others.
Nasturtiums are super-quick to seed. That’s great if you want to collect the seeds for next seasons planting- simply let the flowers wilt out completely and leave them be. Within a few weeks you will see tiny seed pods that look like little brains on the end of the stems. Once they grow big enough, give the stem a gentle shake- if they fall off or detach easily, they are ready to be placed in the sun to dry out. Once dried, they shrivel into little hard-shelled pods.
As far as planting nasturtiums from seed, I find it best to nick the seed pretty deeply (“gouge” would be a better description for what I do) and then plant them about an inch deep in moist (but not soggy!) soil that gets a ton of light and warmth. Some say to soak the seed, but I have never had success with that.
Then there’s the issue of fertilizer. I have fertilized Nasturtiums very successfully in the past, but this season I have decided NOT to fertilize because they just grow TOO well with fertilizer. They will leaf and bloom profusely, and if you are growing them in anywhere other than a field, fertilized nasturtiums will grow out of control within weeks and then die from lack of space. It’s better to not fertilize them, have slightly sparse plants with good blooms that last a season rather than a crazy, full knockout plant that will only last a few weeks, especially in a container garden.
I think nasturtiums are THE perfect container plant for someone who has recently started gardening. Don’t get me wrong- they DO require work, but it’s more of the “enjoyable tending to your garden” kind of work as opposed to grudge work. Nasturtiums are edible, they grow easily, they flower, they smell great, they grow in most climates, they don’t require much as far as soil chemistry, they don’t use a lot of water and once they are mature, they can tolerate a lot of difficult conditions (besides extreme heat and extreme moisture).
I wouldn’t recommend them as a very first plant, but if you’ve had a season or two in the garden, are comfortable with trimming and repotting, and don’t mind spending a few minutes a week tending to them (removing dead leaves, misting them for pests, checking for seeds, etc.), they are SO rewarding. Even though I want to try more exotic plants and devote more space to bigger bloomers (I’m also a bit obsessed with hibiscus at the moment…) I still find myself planting more nasturtium than anything else, season after season.