Rhubarb isn't just a species cultivated for cooking: it's also a medicinal plant known since antiquity, not to mention that you can absolutely use it to make your own plant spray.
Completely natural and truly economical to use, rhubarb spray mainly serves to repel insects harmful to your plants, particularly aphids. You don't need to be an expert gardener to try it, as its preparation remains simple and accessible to all: you'll find all the information you need to succeed in this article.
How to make rhubarb spray?
Required materials
- Naturally, you'll need chopped rhubarb leaves to prepare your spray;
- Water, ideally untreated: you can safely use rainwater or, failing that, mineral water;
- A glass or plastic container with a capacity of about 10 litres. Avoid using metal to prevent any oxidation;
- A lid or large cloth;
- A stick;
- A fine sieve;
- Several bottles or containers for storage.
Making rhubarb spray
- To make about 10 litres of rhubarb spray, you'll need to pick 1.5 kilograms of leaves. Place them chopped in a pot or bucket, diluted in your water.
- Leave to steep for at least 72 hours in a plastic container.
- To speed up the process, use a perforated lid that allows some air to filter through (and prevents dirt from settling) or simply a large cloth placed over the bucket.
- After the three days of steeping, strain the spray through your sieve and keep only the liquid.
- Pour it into a sprayer; you can use the undiluted rhubarb spray directly. In other cases, a dilution of one litre of spray to 5 litres of water is sufficient.
Note that there's a quicker method to make rhubarb spray. We recommend the first method, but if you're in a hurry, you can steep your leaves in boiling water and let it cool for just 24 hours before moving on to the straining stage.
Harvesting and storing rhubarb spray
The rhubarb leaves you'll use to make your spray can be harvested at the same time as the stems, in spring. As a reminder, to give yourself the best chance of growing good rhubarb in your garden, you should plant it in well-drained, cool soil rich in humus.
Provided you store your rhubarb spray in suitable containers, you can easily keep it for several weeks or even months. For this purpose, be sure to choose opaque plastic containers, kept away from sunlight, heat and all temperature extremes (your rhubarb spray shouldn't be exposed to winter frost either).
How to use rhubarb spray?
The benefits of rhubarb spray against harmful insects
Rhubarb spray is effective against all the insects we fear in the garden, which can cause more or less significant damage to plants. You can use it both preventively and curatively against black aphids, leek moth, carrot fly, and even slugs.
Warning: depending on its intended use, rhubarb spray won't always be applied in the same way. In some cases, it's recommended to apply it undiluted, while in others, it's better to mix it with water, following precise measurements.
Always ensure you use rhubarb spray on plants that haven't recently been exposed to chemical treatments. Where possible, we even advise replacing all such solutions with natural alternatives, as there are many! For example, a treatment with rhubarb spray can sometimes be complemented by using nettle spray. This combination helps strengthen the defences of specimens weakened by various pests.
Applying the spray undiluted or diluted
Naturally containing oxalic acid, rhubarb spray is both a repellent and an insecticide. Spray it undiluted if you want to combat aphids, carrot fly, leek moth and leek worm. You can apply it directly to affected areas, but also to others as a preventive measure. Remember to repeat the operation every two weeks until the parasites are completely eliminated. You should also reapply after rainfall.
If you'd rather fight slugs, you don't need undiluted rhubarb spray. Here, simply dilute one part of undiluted spray with 5 parts of water. However, you'll need to water the plants after each rain to maintain protection.
Precautions for the gardener
Always use your rhubarb spray with gloves. Although this repellent is 100% natural and contains no added chemicals, it does contain a substance that's toxic in high doses: oxalic acid.
Many other natural ingredients can help you make your own insect spray: tansy infusion, lavender and nettle in long maceration, wormwood and chamomile in decoction, among others.
Remember that rhubarb is a seasonal plant available between April and July. If you want to use its spray throughout the year, you'll need to prepare as much as possible in spring, knowing that it can be stored for several months in suitable containers.
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