Heat Stress in Plants

Design and InstallationGarden Caregarden TriviaIndoor plantsLighting and IrrigationPlant Health Care
Written By Peter Morris

Heat Stress

 Wilting in plants is a response to insufficient water in the leaf. It can be caused by many things, lack of being watered, high ventilation or in this case extreme temperatures of air or soil. When that happens, the excessive heat causes the metabolism to stop the photosynthesis processes and switch to an all out effort to cool down. 

Wilted plant from heat  - not lack of water

 In some cool loving plants, the entire metabolism stops working altogether. When plants are not adapted to this heat and are unable to cool down, they begin to “kill off its parts” to “save the whole”. Many times leaves, twigs and small branches are sacrificed. 

Talk about unhappy – heat stressed maple tree

 Continuous cycles of heat stress cause stunted growth, poor flowering, leaf drop, pale or yellowish leaves. It will propel the plant into a state of stress stasis. This process is worsened if the summer nights are unusually warm.Leaves damaged by cycles of wilting and re hydrating are also unable to produce sugar very well and as a result many times they are just dropped. This is most apparent in plants that evolved in cool, damp, or shady places - like Japanese maple or Pansies ! 

cycles of wilting and re hydrating damage the photosynthesis process

In some plants that evolved to deal with extreme summer heat, a heat wave may trigger a summer estivation or dormancy.  These plants drop all their leaves and basically go to sleep until it gets cooler.  A good example is Osteospermum – loves spring and fall but looks all shriveled in summer!

Happy in Spring this Osteospermum will soon stop blooming !

Leaf Scorch

 Thin leaf plants show the most obvious heat damage - leaf scorch - a marginal necrosis all the way around the leaf. This happens because the cells on the edges loose water faster than it is replenished and they die first. Sometimes the die back will move inward as well. 

Marginal necrosis

Plants with thick leathery leaves like Rhododendron will not wilt, but instead turn a dull gray-green and sometimes with dark blotches. 

             Rhododendron showing heat stress black blotches.

 The biggest issue that arises from heat is the temperature of the soil - root hairs begin to die at 95*F and above. Unfortunately, because they absorb 90% of the plants water needs, in a heat wave, they are perishing when they are most needed. 

super fine thin walled root hairs get damaged easily in high temperatures

 Planters that are above ground and in the sun are the first ones affected.  In these, the soil temperature can be many times higher than that of the air. A planter can also heat up due to its materials, location, or color - not just exposure.  Dark colored metal planters absorb the most heat fastest. 

appropriately planted heat loving succulents in large black bowl !

Solutions

 Plant Specialists designers are well aware of all these issues and have methods to deal with them including planter placement, insulation of soil, soil composition, plant selection, irrigation systems, and materials and colors of planters. 

by placing both furniture in front of planters the soil is shaded - plus the vines help too !

Plant Specialists has measured soil temperatures of 134*F in dark metal planters that are facing south. 

YIKES !!!!!

For the best heat solutions to your garden  -

Call Plant Specialists TODAY !

Don't delay – the sooner the better !

GREENING NEW YORK FOR OVER 53 YEARS !

  Article written by our Staff Horticulturist, Peter B Morris, BSc, MSc, MBAAll photographs used with permission from @SHUTTERSTOCK  

Peter Morris

Peter was born and raised on a beautiful green island in the midst of a tropical rainforest. He was introduced into the world of plants at the age of six when his grandmother, an avid Spanish gardener herself, asked him to help her grow seeds for her pepper garden. He was hooked! By the time he was a teen, he had his own rose and orchid collection numbering in the hundreds. Botany was in his blood, and that is what he set out to study.

His passion brought him to NY in the late seventies to further his education. His tenacity allowed him to work full time at Plant Specialists while he completed a MS in Plant Biology. As a manager at the time he felt unsatisfied with his knowledge of business and business processes. Peter felt compelled to learn, so he then pursued and completed an MBA in Quality Management within a few short years.

Peter’s other passion is teaching. His natural ability is quickly consumed by our staff in all subjects in Botany, Horticulture, and Landscaping. He created an immense reference library of more than 3,500 plants providing an invaluable resource for our staff.

Peter’s breadth of knowledge and wisdom allows him to effectively diagnose the needs of plants. Sometimes just by walking into a garden he can create a prescription that fixes even the hardest issue. He is our Staff Botanist, Diagnostician, and all around Mentor. Recently, he has put his immense knowledge and skills into developing a new department that focuses on Plant Healthcare. As he puts it, “Magic through Science”. The PHC staff that surround him have avidly consumed his teachings. Substantially developing their own plant wisdom, many have taken on difficult plant health issues with spectacular results.

Plant Healthcare has been an instant success with customers! The proper treatment of insects and diseases including Organic methods has made pest control a necessity for every plant. Correcting hormonal imbalances caused by planting in containers or refurbishing soils leached of nutrients by irrigation systems are big challenges PHC has become quite comfortable addressing. The scientific approach to the complex demands of keeping plants healthy in our harsh city environment has made many a customer say WOW!

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