Given the fluky weather in so many places, it's hard to tell if plants have gone dormant and even harder to know if they'll stay dormant. So it's no wonder I've been getting questions about when it's safe to apply dormant oil.
Dormant oil used to refer a certain type of horticultural oil. The first dormant oils were so heavy you couldn't safely use them on actively growing plants or you could damage the foliage. Dormant oils have since been refined, to produce lighter-weight oils that can be applied during the growing season without harm to most plants. Now a days, when the term dormant oil is used, it generally refers to the application timing, during the dormant season, rather than a type of oil. Here's the lowdown on what actually counts as a horticultural oil and when and why to use them safely.
Photo: © Marie Iannotti