Why Dormant Oil Spray Is a Must for Fruit Trees and Roses

As the weather begins to warm and the garden slowly wakes from its winter slumber, there's a small but critical task that can make a big difference in the health of your fruit trees and roses: applying dormant oil spray. 

This early-season treatment is one of the easiest and most effective ways to prevent pests and diseases that commonly plague your trees and shrubs later in the year. But timing is everything — and your window to apply it is short. 

What Is Dormant Oil Spray? 

Dormant oil spray is an organic combination of horticultural oil (insecticide) and lime sulphur (fungicide). It’s designed to target overwintering insects, eggs, and fungal spores that have taken shelter in the bark and buds over the cold months. 

By applying it now, before buds open, you’re stopping those hidden threats in their tracks — before they can cause damage to your plant’s new growth, fruit, and flowers. 

Why Timing Matters 

Dormant oil spray must be applied before the buds leaf out. Once you start to see leaves or flowers emerging, it’s too late — applying the treatment at that stage can actually damage tender new growth. 

We typically recommend applying dormant spray sometime in late March or early April, depending on your the weather conditions. Keep an eye on your trees and the forecast to make sure you don’t miss your opportunity. 

How to Apply Dormant Oil Spray 

To get the best results, follow these guidelines: 

✅ Wait for a dry day with no rain in the forecast 

✅ Apply when temperatures are above 5°C, ideally with 24–48 hours of above-zero weather before and after 

✅ Spray in the morning so the product has time to dry during the day 

✅ Mix only what you need — it’s best to apply a fresh batch each time 

Make sure to cover all branches and trunk surfaces thoroughly. This is where overwintering pests tend to hide! 

We’ve Got You Covered 

At Robert Plante Greenhouses, we carry Dormant Oil Spray Kits that include everything you need to get started. We also have a range of garden sprayers available if you need one for application. Our team is always here to answer questions and walk you through the process.