Does anyone know what’s wrong with my snowball viburnum (Viburnum oculus)? And if so, is there anything I can do to prevent it from happening next year?
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It just looks like heat and lack of water. You could try covering during heatwaves and watering like mad.
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Thank you to the Master Gardener volunteers from Gardening Advice Line, a partnership between Milner Gardens & Woodland and the Vancouver Island Master Gardeners Association for the following information:
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Hello,
Your snowball viburnum (Viburnum oculus) is suffering from heat stress, probably due to a long spell of dry weather we have had this year, If it is in a location where it receives the hot afternoon sun, consider moving it to a location where it can have shade during the afternoon heat. If moving it isn’t practical, here are some tips for next year to help it get through a long hot summer.
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Water plants deeply so that the root zone is well hydrated. Roots always follow the water so shallow watering means shallow roots which are going to be much more affected by heat stress. Water less often but for a longer time so there is enough water to penetrate deeply. A soaker hose (as opposed to overhead watering) will help to get the water deeper into the soil so that the whole root zone is irrigated.
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Spread 3-4" deep layer of mulch around plants to help keep in moisture. Plant-based materials, such as arborist wood chips, straw or even grass clippings mixed with straw, are best for the health of your plants since they allow water and air to move freely into the soil, suppress weeds, moderate soil temperatures, and feed the soil as they decompose. Avoid gravel or black-plastic mulches, which raise soil temperatures and can damage plants.
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Avoid applying fertilizer prior to a heat event. This will just stress the plant further.
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Use a temporary shade structure. You can buy horticultural shade cloth (products that provide 30%-50% shade are ideal) or use lace curtain material. Even bed sheets can be used to keep the sun off plant foliage. It is be best to cover your plants in late morning and uncover them in late afternoon so they have some photosynthesis time in the cooler parts of the day.
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Right plant, right place. Choose plants well suited for the amount of sunlight and moisture received. Often the most severely damaged plants in heat waves are those planted in areas that receive more sunlight than they are adapted to. As our summers get hotter and drier, this will become even more important.
Also, the stress your viburnum experienced can attract pests such as spider mites, which are often become problematic in the dry heat of summer. Watch for these tiny pests that can cause bronzed or yellowed leaves and webbing. They can be sprayed off with a steady stream of water.
Regards
Diane and Gerry
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