Dormant Oil

Rose

January.  The month of wishful thinking for those of us in the garden centre industry.  Christmas is over and now we just want to get on with spring.  Unfortunately, Mother Nature might still have some winter in store for us and that means we can only dream of warmer seasons. Wait a minute, we live on the wet coast, not back east, so there IS something we can be doing in the garden!  It’s time to spray dormant oil!

If you haven’t tackled it already, and even if you have, now is the time to do a dormant oil spray on your deciduous trees.  It’s a very important task which will help combat overwintering pests and disease in the garden, especially on fruit trees and rose bushes.  Done correctly it will cut down immensely on problems in the summertime.

Largely organic, horticultural oil and sulphur is a twoDormant Oil Kit part liquid that comes in a kit that you mix with water and spray on trees and shrubs that are susceptible to disease and pests.  It must be done in the dormant season, thus the name, before the buds break and the bees fly or it will damage the tender new growth of the plant and smother the bees.

If you’ve already done a dormant oil/sulphur spray this winter, that’s great.  Get out there and do it again.  Once is ok, twice is better and three times ensures that you’ve penetrated most of the cracks and crevices.  Spray fruit trees, other small fruits, roses, hawthorn trees, hydrangeas, dogwood trees,basically anything deciduous, paying particular attention to ones you’ve had problems with last year.  Maple (Acer), beech (Fagus), redbud (Cercis), smokebush (Cotinus) and walnut (Juglans) trees don’t care for dormant oil so they can get a pass.

You need a good couple of days of clear weather, no rain and above freezing temperatures to be effective.  Make sure it isn’t windy because the last thing you want is to spray into the wind and end up wearing most of the oil mix.  So don an attractive disposable outfit, wear safety goggles, gloves and a mask and prepare to be the talk of the neighbourhood.  You can pretend that your family has come down with an infectious flu and then they’ll leave you alone.

Oil stains so if you’re spraying a bush planted next to the house make sure you slip something between the shrub and the siding such as a piece of plastic or plywood.  Same goes with pavement, benches, fences, stone walls, etc.

Read the instructions on the label carefully as different brands may have different measurements and always apply what is recommended.  Using a pressure sprayer is best (hand held or tank) or a hose end sprayer as this will force the mix into the cracks of the bark.

Prune first if needed (no use spraying what you won’t be keeping) then start from the top and work down, spraying until run off (dripping).  Spray the soil around the base of rose bushes as disease spores like to overwinter there and you might have missed a few leaves in your fall clean up.

Once the water dries there will be a thin coating of oil and sulphur left behind.  The oil coats insects and their eggs tucked in the bark such as mites, aphids, whitefly and eggs of various moths and leaf rollers.  The sulphur helps control the fungal spores that can spread disease like black spot and powdery mildew to other plants in the garden.

Being proactive by doing a spray now will cut down on pesticide products needed in the spring and summer months. Get out there and do the gardening chores now and then send pictures to your friends back east or in the Prairies.

Shirley Eppler

January 2014