Observations When Summer Watering

Heat and water are the themes of this time of year! As we enter the heartlands of summer, watering requirements get a little wonky. Water drives a few things within a tree’s system.

1. Cooling – this function makes up a bulk of the necessity for the movement of water.
2. Metabolic function – Water is used in many ways metabolically. Moving water allows the tree to metabolise both during the processes of photosynthesis and respiration.
3. Evaporation

During spring the bulk of water use is for reason #2, metabolic function. In Spring, a tree is focused on growth and creating new leaf mass and flowers in some cases. This is an important time to get watering right, and the room for error can be small as trees move water, transpiring heavily to produce growth.

When the heat of summer truly arrives, and growth is hardened, leaf mass production takes a backstage. Water usage can actually be much less on milder days in summer than may have been observed on equivalently mild days earlier in the spring season when the tree is busy producing leaf mass. Water is being used less for metabolic functions and more for simply cooling functions, and so if the day is mild, water usage will be too. It is important to note here the third reason why water may leave the tree and require watering. Evaporation, when spoken of here, is less within the tree’s system but rather from the soil surface directly. Evaporation can be the culprit for a tree’s water loss on very hot, dry days, particularly when wind is involved. This dry-out effect can often be quicker on newly repotted trees due to the very open quality of the particles during this stage in the substrate’s life cycle.

There are so many variables that go into why a tree needs water at any given time of year. Just to name a few:=

• Species-specific needs
• Foliage % compared to pot size
• Proximity to having been repotted
• Substrate type
• Health
• Weather
• Exposure
• The season

Thinking about each individual tree’s needs and circumstances is always best. All in all, this time of year can be a gentler time of year for watering when the days are mild and simply pleasantly warm, the trees soaking it all in. On the other hand, watering needs can jack up in an instant if the sun blisters and the wind howls.

Happy watering!