If you’ve recently noticed that your nasturtiums are being attacked by aphids, such as that they have yellow leaves or are experiencing abnormal growth, you might wonder why the pests are attracted to your plants.
Aphids are attracted to nasturtium plants because they have succulent, lush leaves. This is, interestingly, also why nasturtiums are used to deter aphids from other plants in the garden. However, there can be elements lacking in your plants’ care, causing aphids to become even more of a problem.
In this article, I’ll explore the most common reasons why nasturtiums experience aphid infestations and how to eliminate these pests from your garden forever.
Why Your Nasturtiums Get Aphids
There are various reasons why your nasturtiums can be attacked by aphids. The good news is you don’t have to let them suffer from these pests that steal their sap and feed on their leaves.
Here are some common reasons for aphids and how to eliminate them:
1. Your Nasturtiums Have Too Much Nitrogen Fertilizer
If you’ve been feeding your nasturtiums a nitrogen-rich fertilizer because you want to boost their growth, this could have backfired by making your plants more appealing to pests like aphids.
Large amounts of nitrogen overstimulate plant growth, which has the effect of making aphids reproduce at a faster rate.
How To Fix
Aphids are attracted to plants with higher levels of nutrition, so you want to stop giving your nasturtiums so much nitrogen. This will also enable your plants to deter other insects, such as mites, while preventing them from producing too much foliage.
Fertilize your flowering plants with compost instead of any liquid or granular fertilizer. Another solution for this problem is to choose an organic fertilizer. These products release moderate quantities of nutrients so that plants are not overwhelmed by having too much at once.
2. Your Nasturtiums Have Plant Debris Near Them
If your nasturtiums have been planted within close proximity to plant debris, it’s important to clear away the clutter, as this is where aphids like to lay their eggs. They will especially search for debris in the form of brown leaves and rotting foliage.
How To Fix
Clear away any debris within close proximity to your nasturtium plants. Clean up your flower beds, rake brown leaves, and uproot plants that have not survived the frost so that aphids don’t lay eggs on or under them, as this will make it easy for aphids to infest those plants before reaching your healthy nasturtiums.
Besides cleaning away organic clutter in the garden, a good tip is to use reflective mulch so that aphids won’t be able to find and settle on the plants they want to attack.
3. Your Garden Is Filled With Weeds
If you’ve noticed weeds growing in your garden, especially if they’re within close proximity to your nasturtiums, this is what’s making it easy for aphids to reach your plants. Insects infest the weeds and then spread to your nasturtiums and other flowers. Some types of weeds that are particularly appealing to aphids include mustard and sow thistle.
How To Fix
Make sure you de-weed your garden regularly. A great de-weeding tool I’d recommend is a stand-up weed puller with a long handle, so you don’t have to hurt your knees or back by bending down when using it.
You should also consider planting plants that repel aphids naturally within close proximity to your nasturtiums, such as garlic. Since it has a very strong scent, this deters a variety of common garden pests.
4. You Haven’t Pruned Your Nasturtiums
Since aphids are attracted to succulent, tender growth on plants, it can help to keep them at bay by lightly trimming or pruning your nasturtiums.
That said, be careful not to prune your nasturtiums at the wrong time as this can cause suckers, which is vertical growth on the plant that comes from its lower main stem or root system.
These are problematic for plants because they draw sap from other important components of it. They are particularly susceptible to attacks from aphids, as the University of Nevada, Reno reports, so you’ll want to remove them.
How To Fix
When lightly trimming your nasturtiums, focus on removing the following:
- Long, leggy stems.
- Sparse flowers.
- Small leaves on the plants.
To remove plant suckers, tear the shoot so most of the dormant basal buds are eliminated. This ensures that the suckers can’t grow again.
5. Your Nasturtiums Are Getting Too Much Water
Be careful not to overwater your nasturtiums, as this can cause your plants to grow too quickly and therefore attract aphids. Overwatering your nasturtium plants can cause their leaves to become yellow. The plants will be sitting in waterlogged soil, which could lead to root rot, a condition that can be fatal.
That said, if you’re not giving your nasturtiums enough water, this can also cause aphids to attack them. If your nasturtiums aren’t blooming or are looking scraggly, these are signs that they are becoming dry and need a top-up of water.
Both underwatering and overwatering your plants cause them to become stressed, which is what makes them more susceptible to pests such as aphids.
How To Fix
Your nasturtiums need to be watered when the top inch (2.54cm) of their soil is dry, so strive to water them once or twice a week. You should give the plants enough water so that the soil is moist up to six inches (15.24cm) in depth.
If you keep your nasturtiums in planter boxes, they should be the right depth to keep the soil moist without causing root rot. If you don’t know how deep your planter box should be, read my article for useful tips: How Deep Does a Planter Box Need to Be for Flowers?
If you’re growing nasturtiums indoors, use a watering can so that you can direct the water into the soil. Give the water a chance to seep deeply into the soil and check that it drains out of the pot. If no water comes out, this is a sign that you should add more.
6. Your Nasturtiums Are Overcrowded
Nasturtiums that are overcrowded usually show signs of stress, which makes them susceptible to aphids. When the plants are planted too close to each other, it causes poor air circulation, which leads to fungal diseases and pests. This is because the crowded plants make it easier for the aphids to move between them.
How To Fix
If you’re planting nasturtium seeds, you should place them approximately three inches (8cm) apart from each other so that they all have enough room to grow. As they grow, you should thin the seedlings so that there are 12 inches (30cm) all around each plant.
How you thin the seedlings depends on the nasturtium varieties. Make sure you thin seedlings so that they’re about 12 inches (30cm) apart if your nasturtium is a bush, but thin them to between 18 and 24 inches (46 – 61cm) if you have a trailing plant.
7. Your Nasturtiums Are in Hot, Dry Conditions
When nasturtium plants are placed in areas of the garden that experience high temperatures, this makes them more susceptible to insects. This is because insect development is accelerated in conditions of intense heat, so it takes less time for insects to complete their life cycles, as the University of Illinois reports.
Drought conditions are also more appealing to insects, so you want to keep your plants protected from heat and drought.
How To Fix
Nasturtiums want to be in full sun for between six and eight hours per day, but they also thrive in partial-shade conditions. Make sure you plant nasturtiums in temperatures that are approximately 70°F (21°C).
Since these plants battle to grow and thrive in very dry conditions and can become scorched or start to wither in very high temperatures, be wary of planting them in humid conditions. You can prevent too-high humidity levels by spacing your nasturtiums so they have more room to grow.
You can’t eliminate aphids if you don’t first know why they’re being attracted to your plants. There are many reasons why nasturtiums become more appealing to aphids and which should be prevented, such as:
- Feeding your plants too much nitrogen.
- Underwatering or overwatering your plants.
- Overcrowding your plants.
- Planting them in very dry or hot conditions.