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Monday, April 25, 2011

What happened to my rhododendrons? Evergreens and winter burn.

If you went outside in the past few weeks and looked at your rhododendrons, mountain laurel, boxwood, or any other broad leaf evergreen (wide flat leaves as opposed to needles) and woundered why they looked "burned" you are not alone.
Cape Cod South Shore Winter Burn Damage


What happened?- Broadleaf evergreens that are planted on a site that is exposed to excessive winter winds or are facing the south or west are the ones most likely damaged.  In their natural habitat these plants would be found growing in the filtered shade of a decidious tree and rarely on a site exposed to the winds.  In the winter when the ground is frozen solid and the wind starts to blow or the sun shines brightly the plant and its leaves start to respire.  This process of respiration ends up desicatting the plants leaves because the plant can not replace the lost water with uptake by its roots because the ground is frozen.  This is why you are more likely to see this winter burn on the top of the plant because this is the area that is exposed to the sun and drying winds the most.
What to do?- Nothing at first.  It is many peoples first instict to chop the plant back or worse add a lot of chemical fertilizer.  Paitence is required at this point since vegetative buds may still be alive and new growth will occur later in the spring.  Often what will happen is by late spring those crispy leaves will fall off as new leaves come to take their place.  Sometimes you will have twig dieback and the top 6-24" of the bush may be dead.  In this case new growth will happen below the dead branches indicating where to cut off the deadwood.  But again wait until new growth happens.  You can speed up this process a bit by giving you plant water if it is a dry spring.
How to prevent?-  There are a few things you can do to reduce the chance this can happen again.  First to prevent the ground from freezing to solid you should always have 3 inches of mulch (NOT AGAINST THE TRUNK PLEASE!) under the canopy of the shrub.  This will also help the plant conserve moisture during times of drought.  And a thirsty plant is a stressed plant and a stressed plant is one that is more susceptable to diseases, insects and general weather extremes.  Shade is also a big factor.  If your plants are say... in the planting islands in the parking lot at Wendys your ability to give them shade is unlikley.  But if they are in a residental landscape and they can have a tree planted on the side facing the sun or winds they will greatly appreacaiated it.  Or if they are small and can be moved to a more protected site they will be better off.  Lastley do not juice them up with chemical fertilizer.  This causes execessive vegative growth which is more sustible to diseses, insects & (yes you guessed it) general weather extremes.  Although a little organic fertilizer for acid loving plants is ok and may help speed up the refoliating process.
Some people reccommend wrapping your plants up in burlap or spraying them with an anti-transpirant.  But my feeling is if a plant needs a sweater and a cocktail to survive the winter than that is a plant that is to finicky for me.


Jim McSweeney owns and operates Hilltown Tree and Garden, landscape design,installation and tree care for Northampton and Western Mass. You can also find (and please "Like" us) on Facebook.

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