Tincture of iodine makes you think of treating hurt knees or disinfecting wounds. As it happens, it is also a great measure against pests. If you are fighting disease called by micro-organisms preying in your garden, you definitely must find out why iodine should be used there and how exactly it ought to be used. Its great advantage is price – iodine is dirt cheap!
Iodine in the garden
Iodine is an indispensable element not only for people, but also for plants. They need it for maintaining basic life functions as well as a means of protection against bacteria and fungus. Unfortunately, our soil is very often low in this element. The soil in areas near the sea look much better in this respect.
We can supply plants with iodine using its tincture, which is a 3% solution of iodine in 90% ethanol, plus some potassium iodide.
Another source of iodine is Lugol’s solution which is a water solution of iodine and potassium iodide. Unfortunately, iodine evaporates very quickly so most formulations have to be made as you go.
But… iodine always works. No bacterium or fungus is capable of growing immune to iodine. In fact, no micro-organisms can do it.
Applying iodine tincture you can protect the roots of plants against rotting and you will nourish their seedlings. Iodine helps increase the yield and get rid of powdery mildew. Additionally, iodine participates in photosynthesis, breathing and nitrogen exchange. That is why it is essential that plants never run out of this element. Its shortage can lead to impaired immunity resulting in rotting of leaves and roots eventually exposing the plants to a variety of diseases.
What kind of soil is rich in iodine?
Natural iodine is present in fertile black soils, usually close to the coast or on plains. If the soil is too acidic, then iodine accumulates in lower layers of the ground and therefore becomes inaccessible for plants. It is difficult to visually assess the iodine content, so it is recommended that plants receive some iodine fertilisation as a preventive measure.
How to use iodine in the garden?
To support growth and to strengthen plants
Iodine tincture can be added while watering seedlings, which will stimulate their growth and supply them with the additional support to endure unfavourable weather conditions and disease. Use iodine while planting tomatoes, peppers, cabbage, aubergines or cucumbers.
How to use iodine tincture
Dissolve 1 – 2 drops of iodine in 3.5 litres of water stirring it well. Use the solution to water plant. Be careful not to spill it over the leaves and stalks, because even a moderate dose of iodine can burn the delicate parts of plants.
Iodine against powdery mildew
Powdery mildew is a nightmare of thousands of gardeners. They look high and low for an effective way of getting rid of it. It attacks currants, tomatoes, gooseberry, cucumbers pumpkins as well as roses and peonies. To fight it, dissolve a millilitre of iodine tincture in 9 litres of water, with a bit of washing-up liquid and liquid soap, as well as a litre of skimmed milk. Then pour the mixture into a spray bottle and apply on affected plants.
Iodine vs other pests
If it is not powdery mildew that is the problem, then dissolve 20 ml of iodine tincture in 10 litres of water. Pour approximately a litre under each shrub. Remember to do it in the evening. If the plants (for example potatoes or tomatoes) were infected and you see brown stains on the leaves, while the fruits begin to rot, use 15 drops of iodine tincture and 10 litres of water with a litre of skimmed milk. Spray this mixture over your plants two or three times a month.
Iodine tincture as a fertiliser for potted plants
Dissolve 40 drops of iodine tincture in 10 litres of water. Pour it under the roots of cucumbers, tomatoes, cabbage or peppers. Water them with this mixture every three – four weeks.
Apart from its garden applications, iodine can be used for potted plants. If their roots are weak, pour down the pot wall a small amount of iodine tincture dissolved in water. Remember to use it only with humid soil.
Some gardeners shared a formula based on starch and iodine tincture which is even more effective in the fight against tomato blight.
Half a litre of water
A teaspoonful of potato starch
Rainwater (for appropriate pH)
3 ml of 10% vinegar
2 ml of iodine tincture
Dissolve a teaspoonful of potato starch in half a glass of water stirring it well. The rest, that is 1.5 glasses of water, needs to be boiled. After boiling it pour the starchy solution and keep stirring it while it’s boiling for about a minute.
Pour a quarter of litre of rainwater into a 1-litre bottle. Add 100 ml of boiled starch and add 5 ml of 6% vinegar or 3 ml of 10%vinegar. Mix the starch with the water and vinegar. Then add 2 ml of iodine tincture and rainwater to get a litre of the preparation. Mix it well. If it doesn’t spray well, add a few drops of washing-up liquid.