ulch comes into its own, dealing with these issues in multiple ways; as a regulator of fluctuations in soil moisture and temperature; by creating more water-holding humus through the addition of organic matter, and the associated action of increased populations of soil biota. When out and about visiting some London orchards last week, I stuck my fingers deep into a thick layer of mulch we’d applied last winter; it was cool and moist and riddled with fungal mycelium. I assumed that the group had recently watered, but when I asked them, they sheepishly admitted that they hadn’t watered for weeks! The mulch was clearly doing its job.
Root inoculation with mycorrhizal dips should also help to speed up the process of establishment as the network of fungal hyphae stretch far and wide, penetrating pore spaces too fine for the finest of root tips and transporting water back to the host tree (although the scientific literature is still unclear on the benefits of this myco-inoculation, small scale experiments seem to show clear results).
Planting deep rooted plants such as comfrey can also help to break up compacted soils by creating new channels and attracting microbial activity in the rhizosphere which in turn attract larger organisms such as worms which work on improving structure.
So, if your trees were planted last winter you should be watering weekly, we recommend a good 20 litre soaking per tree per week. If they’ve been in for longer and are established, it’s still important to help them through these dry times with a good soaking here and there. In order to get the maximum tree benefit for your effort, ensure you pour the water slowly to allow penetration, and focus where the most of the absorbing roots can be found. Forest, ornamental and fruit trees tend to distribute their roots in a wide circle with the ‘feeder’ roots occupying a ‘drip zone’ – an area beyond the leaf canopy to which rain is deposited from the foliage above. Focus water and feed here. Watering in the cooler evenings will ensure optimum uptake.
In the first two years aim to soak your whole mulch area to ensure the whole root system, reduced in size by the nursery, has access to the water as well as encouraging the outward growth of new absorbing roots towards the edge of the mulch ring (roots can only grow where there is sufficient moisture – they can’t grow through dry soil towards a water source). In subsequent years, focus any watering and feeding around the drip line as this is where the absorbing roots will lie; there’s little point in watering and feeding the woody ‘secondary’ growth around the base of the trunk.
All too often watering gets neglected as moving around large volumes can be hard, sweaty work in the sun and people don’t fully appreciate the needs of young trees. Finding ways to make this less of a slog can make all the difference.
One great little invention is the H2go; an 80l water bag designed to sit in a wheel barrow where it can be filled up and emptied through a spout by simply tilting the barrow forward. That’s up to four trees in one journey. Using a couple these, two people could water a whole orchard sufficiently in little time.
So, we’d love to hear how groups are tackling their watering. In particular, we’re keen to see successful rain water collection set ups in public spaces, and how park groups get water to their trees when they’re planted far from a tap. Please share your ideas on our Twitter and/or Facebook, or email firstname.lastname@example.org.