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Watering Trees and Shrubs – Do's and Don'ts

In our experience more newly planted trees and shrubs are killed by overwatering than by under watering. This sounds a bold statement, but gardeners will often keep the soil around young trees and shrubs soggy and waterlogged causing root death and shoot die back. Plants will wilt if the roots are waterlogged as well as if dry. If the right selection of plants is made for your site and soil conditions, watering should generally not be necessary.

So let’s examine what to do in certain situations:

Planting pot or field grown dormant trees/shrubs during winter: Do not water.

Planting pot grown trees/shrubs whilst in growth: Stage 1 – Dig hole. If soil is dry, pour in a bucket of water and let the hole drain for an hour or two. If soil is moist, go to stage 2. Stage 2 – Soak the pot and allow to drain, then plant and backfill and then soak around the plant once the soil is firmed.

In the growing season following either of the above actions, it is vital to keep an area of at least 1 metre diameter around the new plant weed free, by spraying or mulching. If the plants are small they are unlikely to need further watering, unless the soil is very light and sandy, or if the summer is exceptionally hot and dry. The young roots will seek moisture down in the soil. A newly planted tree can put on over 60 cm of root growth in its first year in well structured soil. If you do need to water, totally soak the root run about twice during the summer, thereby encouraging the plant to root to depth.

If large specimens have been planted, then it is likely that watering will have to take place at least in the first summer after planting, even when kept weed free. This should take the form of flooding the root zone to depth at about three to four week intervals once the tree is in leaf, to encourage deep rooting. This is often best achieved by arranging a length of perforated drainage pipe in the planting hole around the roots and coming to the surface at one end. Starting in June water can be applied at monthly intervals. The quantity depends on the size of the plant, but up to 20—30 gallons at a time for very large trees.

Some Do’s and Don’ts

Don’t

Over water
Water little and often
Keep the ground soggy
Water a deciduous plant if it has no leaves
Water a newly planted dormant tree or shrub in winter

Do

Keep weed free
Mulch if possible
Water only if necessary
Soak soil to depth and allow to drain