{"id":79839,"date":"2022-08-05T10:03:59","date_gmt":"2022-08-05T09:03:59","guid":{"rendered":"https:\/\/greenblue.com\/?p=79839"},"modified":"2022-08-05T15:23:34","modified_gmt":"2022-08-05T14:23:34","slug":"how-to-combat-the-effects-of-drought-on-trees","status":"publish","type":"post","link":"https:\/\/greenblue.com\/gb\/how-to-combat-the-effects-of-drought-on-trees\/","title":{"rendered":"How to Combat the Effects of Drought on Trees"},"content":{"rendered":"
Am I the only one noticing that trees are turning colour this year before the end of July? Isn\u2019t it a bit early for autumn colours? Why is this happening this year?<\/p>\n
There are a number of 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\u2019t apply right now so what is going on?<\/p>\n
Tree leaf vitality is affected by a number of 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.\u00a0 This process helps create a cooler micro-climate around the canopy of the tree (or plant \u2013 all green plants carry out evapotranspiration to some extent) and prevents desiccation of the leaf, and damage to the tree. It is noticeable that trees adapted to hot climates have smaller glossy leaves which transpire less \u2013 coping with less rainfall and higher air temperatures. Therefore the higher the ambient temperature, the more water the tree requires to regulate the leaf condition.<\/p>\nTrees planted in soft vs trees planted in hard. Cobham Services<\/figcaption><\/figure>\n
This Year so far has seen low rainfall overall \u2013 some areas experiencing unprecedented dry months, which is impacting 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.<\/p>\n
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 \u2013 the minute openings in the leaf surface which allow evapotranspiration to take place. Some tree species such as the Silver Lime (Tilia Tomentosa) turn their leaves upside down to show a lighter and more sunlight-reflective side to the sunlight and therefore minimise water loss. Secondly, the tree will then resort to cutting off sap flow to the furthest leaves from the roots to minimise water travel and finally will drop all of its leaves to save the water resources for next year \u2013 in effect, go into a dormant state prematurely. Worryingly, in some cases this can be fatal to the tree \u2013 embolism or cavitation can occur where an \u201cair lock\u201d forms in the xylem of the tree, which blocks flow permanently to the canopy, and one side or the whole tree can die. This appears to happen most often in trees planted in poor water-holding mediums in the early establishment years.<\/p>\n
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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 of experience in getting trees to thrive in challenging environments and in all climates across the world and is uniquely placed to assist you with your planting questions. 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.<\/p>\n
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