Our summers are getting hotter, and this can be challenging for young fruit trees in the city trying to establish and spread their roots.
Studies have shown that it is common for 30% of planted urban trees to die in the first year after planting. The figure can sometimes reach 70%. Lack of water and poor soils are usually to blame.
Trees grown in a nursery have a smaller area of roots than a tree grown naturally from seed in the ground. For this reason it is difficult for the roots of planted trees to get enough water, until they have had a chance to spread. But it can be hard for roots to spread when soil is dry, compacted or poor.
Roots can only grow where there is sufficient moisture – they can’t grow through dry soil towards a water source. And urban soils are often poor — a shallow layer of soil on top of rubble – limiting how deep the roots can go in search of water.
For this reason watering is very important in the first few years (more on that later). There are some other things you can do too to help the roots spread through poor, compacted or dry soils:
Mulch
A mulch of woodchip slows down water evaporation from the soil. It also helps keep soil cool in hot weather. As the mulch rots down it provides organic matter, improving the structure of the soil and making it more water-retentive. It also increases populations of soil fauna such as worms, which also improve structure. Read much more about the importance of mulching here.
Cool, moist and full of fungal mycellial: a thick layer of mulch doing it’s job after weeks of no rain
Mycorrhizae
Mycorrhizae are a type of fungus that have a beneficial relationship with tree roots. They may exist already in the soil, or you can add them in the form of a powder or a paste to your tree roots when planting. This helps to speed up the process of root establishment. The fungal hyphae (thread-like structures) spread far and wide, penetrating the soil and transporting water back to the tree.
Comfrey
Growing deep-rooted plants such as comfrey can also help to break up compacted soils. The roots create new channels through the soil helping to break it up. They also attract micro-organisms, which in turn attract larger organisms such as worms.
A Good Soak
So now we come back to watering. This is all too often neglected, as moving around large volumes can be hard work in the summer. 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 of these, two people could water a whole orchard in a short time.
The handy ‘H2go’ in action on a parched cherry
Drip Zone
If you planted your trees last winter you should be watering every two weeks. We recommend a good 20 litre soaking per tree every fortnight. 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. Pour the water slowly to allow penetration, and focus where most of the roots can be found. Fruit trees tend to distribute their roots in a wide circle with the ‘feeder’ roots occupying a ‘drip zone’. This is an area beyond the leaf canopy on which rain drips from the foliage above. Focus water and feed here. Watering in the cooler evenings will ensure optimum uptake.
Mulch and drip line
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