Planting nasturtiums: sowing, location & plant care
The flavourful nasturtium can thrive in many settings, whether in a raised bed, along the garden fence or climbing over a wall; it is an absolute must in herb and cottage gardens.
Nasturtiums (Tropaeolum) are native to South America and form a plant family of their own. Despite its exotic beginning, the garden nasturtium (Tropaeolum majus) has become a staple in gardens across the UK and all over the world. Read on to find out how to grow nasturtiums, including where to plant nasturtiums as well as how to care for them.
Location: where to plant nasturtiums
Nasturtiums feel most at home in fresh, moderately nutrient-rich, humus-rich, loamy soil in a sunny to semi-shady location. If the soil contains too many nutrients, the nasturtium plant will develop significantly more leaves than flowers. Avoid dry soil as well as waterlogging, as this visibly causes difficulties for nasturtiums. Mix sand into compacted heavy soils to improve it. If your soil is very sandy, work in some organic matter such as mature compost to increase nutrients and the soil’s ability to store water.
Do nasturtiums need climbing supports?
Not all nasturtiums need a climbing aid. The necessity depends largely on the variety: some are slow and limited in their growth, whereas others, like trailing nasturtiums, proliferate strongly and can form very long stems. These stems grow either by creeping along the ground or by hanging down from a balcony, a hanging basket, a raised bed or a wall. Planting a trailing nasturtium against the garden fence saves you the trouble of attaching an additional climbing aid while also beautifying the garden border.
Which soil is suitable for nasturtiums?
If you want to create perfect growing conditions for the spicy nasturtium plant, mix the dug-up soil with a high-quality potting compost. Our peat-free Plantura Organic Flower Compost is ideal for this, as it has a loose, permeable structure due to the coconut and wood fibres it contains. The plant’s basic nutrient requirements will be covered by the quality compost and fertiliser contained in our soil. Our compost provides particularly good support for flower formation and can also be used for planting nasturtium in pots. Find out more about what to look out for when growing nasturtiums in pots in our other article.
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Growing nasturtium from seed
Since they are very sensitive to cold temperatures, do not plant nasturtiums outdoors until after the last frosts have passed, roughly in mid-May. If you want to start nasturtiums inside, you can sow them indoors as early as mid-April. Nasturtiums need darkness to germinate, so cover the seeds with about 2cm of soil. Keep the soil moist. At a temperature of 20 to 25°C, the first sprouts can usually be seen after about 7 to 10 days. If you have planted several nasturtium seeds in one pot, prick out the seedlings at the cotyledon stage to allow them to develop to their full potential.
Tip: autumn is the perfect time to save seeds from your own nasturtium plants for the next gardening season. The germination capacity of the collected nasturtium seeds is about three years.
Nasturtium companion plants
When it comes to companion planting, the nasturtium can serve a purpose. In some cases, it can help repel or distract pests. For example, it can be planted near roses (Rosa) to keep aphids (Aphidoidea) away from the plants. It is also said to help against the cabbage butterfly (Pieris brassicae) when planted near cabbage plants (Brassicaceae), as the latter prefers to lay its eggs on the nasturtium.
Once nasturtiums have been pre-grown and planted in a suitable location, hardly any care is necessary. The following explains what can be done to support growth.
Watering, fertilising and pruning
Only fertilise the nasturtium in moderation and be sure to use fertiliser that does not contain too much nitrogen, otherwise the plant will produce more leaves than flowers. The most suitable option is an organic slow-release fertiliser that gently releases its nutrients to the nasturtium. Our Plantura Flower Food meets this criterion perfectly. In addition, the nutrient ratio of our fertiliser promotes the formation of flowers through the phosphorus content, while also giving the foliage a lush green thanks to the nitrogen. The potassium content enhances the overall vitality of your plants by strengthening their resistance. A single fertiliser application in spring when planting is sufficient in most cases.
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If the nasturtium is exposed to a lot of sun, support the plant with additional watering during dry periods and on hot days. If planted in a pot or balcony box, it may be necessary to water the nasturtium daily under these circumstances. Remember to water close to the base and not to get water on the leaves.
Nasturtium stems can be pruned if they get too long or become a nuisance. The plant itself does not need any pruning. However, removing wilted flowers regularly, if they are not harvested, will significantly promote flower formation. Find out which parts of the nasturtium you can harvest in our expert guide.
My nasturtium has yellow leaves: what can I do?
If you notice increasingly yellow leaves on your nasturtium that are not indicative of the normal ageing process, this could be due to one of several factors:
- Lack of water: if, in addition to the yellow colouring, the leaves droop and have partially curled edges, drought stress may be the cause. In sunny places, this can happen on particularly warm days or during longer periods without rain. Under these circumstances, make sure to support your nasturtium with additional watering.
- Waterlogging: in locations prone to waterlogging or if overwatered, it is likely that the nasturtium roots will rot. This may cause the leaves to turn yellow.
- Overfertilisation: as described above, the nasturtium only tolerates moderate fertilisation over a long period of time. Overfertilisation can occur quickly if the plant is treated a little too well. If this has happened, avoid fertiliser and water more often, but without causing waterlogging, so that the nutrients are no longer as concentrated in the soil.
- Deficiency symptoms: even if the nasturtium has a low nutrient requirement, this does not mean that it will thrive without nutrients. If the garden soil is poor in nutrients, yellowish discoloured leaves may indicate a lack of nourishment. In this case, fertilise the soil.
Nasturtium common pests
As mentioned above, nasturtiums attract certain pests. Here is a list of the pests that attack nasturtiums and what steps to take to get rid of them:
- Cabbage butterfly: the white butterfly lays its eggs on the nasturtium leaves. Usually only the feeding traces of the hatched caterpillars are noticeable. Remove the eggs or caterpillars as soon as they are discovered on the plants. There are various ways to prevent this pest. An infestation can be tackled with some methods of biological control.
- Aphids: simple household remedies, such as regular spraying with soapy water, often help against aphid infestations. Simply cut off heavily infested stems. As with all plants that will eventually end up on your plate, toxic sprays are not the remedy of choice. Controlling aphids can also be done by natural and biological means; read more about this in our article.
- Flea beetles (Psylliodes): flea beetles like munch on young leaves, leaving behind holes in the foliage. Dry weather in spring can lead to an increased infestation.