When the first beautiful spring days are announced, you often see posts about the importance of applying dormant oil to your plants. What is it? What is it used for?
Dormant oil, its mode of action, and its benefits
Dormant oil is, as its name suggests, an oil that is applied when woody plants like trees and shrubs are dormant, meaning without leaves. When dormant oil is applied, it suffocates insects and their eggs by coating them with a layer of oil that prevents them from breathing.
Pro tip: Dormant oil can be applied simultaneously with lime sulfur, which acts as a fungicide-acaricide (against fungal diseases and mites). Both products can be mixed together and applied in a single pass. It is very important to follow the supplier's instructions for the doses to use.
Necessary equipment
To successfully apply your dormant oil, visit your Passion Jardins retailer. You will find all the necessary equipment, with advice to boot!
- Sprayer
- Dormant oil
- Lime sulfur
- Personal protective equipment (gloves, goggles if needed, long clothing)
Ideal application conditions
This is where it gets tricky: optimal conditions are sometimes difficult to achieve. You need to be attentive and check the weather forecasts for your region. The application will be done earlier in the Montreal area than in the Bas St-Laurent. Usually, the treatment is carried out between the end of March and the end of April, depending on the region and temperatures. It is important to follow a few rules:
- No frost expected within 24 hours of application
- No rain expected within 24 hours of application
- Buds should not be open; they should still be closed
- Daytime temperature is 8-10℃ and does not exceed 21℃
- No strong winds (we want the product to reach the branches and not you).
How to apply it
Simply mix the dormant oil (and lime sulfur if needed) with water in a sprayer following the manufacturer's instructions and dosage. The oil solution will be sprayed on the branches and trunk of the plants. It has no effect on the soil. It is important to regularly shake the oil and water solution during application to keep it well mixed.
It is suggested to only make the amount needed for spraying since the diluted product does not keep until the following year.
It is important to always keep the original packaging to have the instructions at hand.
F.A.Q
Can I spray dormant oil on all my plants?
- No. Not all plants benefit from a dormant oil application. It will mainly be used on trees, shrubs, and fruit trees, especially those sensitive to insects and diseases (lime sulfur). Conifers with bluish foliage should not be treated as the oil discolors blue spruces. However, new shoots will be blue.
My products spent the winter in the shed and froze. Can I still use them?
- No. All liquid products that have frozen are no longer effective. They must be disposed of at your municipality's eco-center.
The buds on my fruit trees have started to open, is it too late to treat with dormant oil?
- Yes. It is too late to spray plants with buds that are starting to open. The spraying must be postponed to next year. It should be noted that the oil can also be used during the growing season at lower doses for certain insects such as scale insects, spider mites, and whiteflies. Caution! Some plants cannot receive oil during the growing season, such as sugar maples, Japanese maples, and beeches. For the complete list, follow the restrictions on the product sheet.
Tips and advice
