GREEN & BLUE INFRASTRUCTURE
HOW TO COMBAT THE EFFECTS OF DROUGHT ON TREES
Different planting mediums at Cobham Services
This appears to happen most often in tree planted in poor water holding mediums in the early establishment years .
We are noticing that trees are turning colour this year before the end of July ! Isn ’ t it a bit early for autumn colours ? Why is this happening this year ?
There are several influencing factors why and when leaves turn yellow and fall from the trees : generally , it is when the temperature falls , the daylight hour shortens , or the autumnal winds blow .
But this doesn ’ t apply right now so what is going on ?
Tree leaf vitality is affected by several factors , and at this time of the year , the greatest of these is water availability . As trees take up water from the soil , this water , bringing hormones , minerals , and nutrients ( known as xylem sap ) is carried by the vascular system to the canopy , where the principle of evapotranspiration can take place , climatic conditions allowing .
This process helps create a cooler micro-climate around the canopy of the tree ( or plant – all green plants carry out evapotranspiration to some extent ) and prevents desiccation of the leaf , and damage to the tree .
This year so far has seen low rainfall overall – some areas experiencing unprecedented dry months , which is impacting on tree canopies . In areas where trees are planted in good soils , with a decent depth of soil , enough moisture is retained to keep the trees green . However , where soil depth or quality is compromised , we see these trees turning brown , and dropping leaves .
This is how a tree reacts to a lack of moisture : to protect itself from drying up , the first emergency measure is to close the leaf stomata – the minute openings in the leaf surface which allow evapotranspiration to take place .
Worryingly , in some cases this can be fatal to the tree – embolism or cavitation can occur where an “ air lock ” forms in the xylem of the tree , which blocks flow permanently to the canopy , and one side or the whole tree can die .
Whilst species choice can significantly affect how trees will cope in our increasingly hot and dry summers , correct planting specification is even more important .
GreenBlue Urban have 30 years ’ experience in getting trees to thrive in challenging environments and in all climates across the world and are uniquely placed to assist you with your planting questions . It is noticeable in many urban locations that whilst trees in GreenBlue Urban soil cell systems are healthy and green , trees planted in other mediums are struggling , and having to be given supplementary irrigation via watering bags .
Accurate soil specification and testing is probably the most critical part of any tree planting specification , and then maintaining that soil in a healthy state , with a good balance of aggregates , silts and clays , organic elements , water , and air to assist the micro-biological and fungal activity to help the tree and planting to flourish .
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