Is your tree water stressed?

How do you know if your trees are moisture stressed? In spring it can be hard to tell, but it’s a crucial time to make sure your trees DON’T dry out, particularly if they’re still flowering.

Gala apple blossom
Gala apple blossom

Why is it a problem?

In spring while the fruit is forming it goes through cell division, and if it doesn’t have enough water, there won’t be enough cells formed in your fruit.

Once that has happened, then it doesn’t matter how much water your trees get later in the season – you can’t correct this problem because the cell division phase is well and truly over, and you’ll be sentenced to a year of small fruit.

We learned this the hard way during the millenial drought. In our district here in central Victoria, traditionally there’s enough winter rainfall that there’s plenty of water in the soil in spring, and fruit trees never get water stressed at this time.

Small Anzac peaches that didn't get enough water early in the season
Small Anzac peaches that didn’t get enough water early in the season

After one particularly dry winter during the drought we had to endure a year of tiny fruit (see the peaches above – urgh!) so we quickly learned that we had to start watering the trees much earlier than usual, and it’s now one of the conditions we keep an eye on as we come out of winter each year.

With much of Australia in drought and a hot summer predicted, it’s worth noting that heat waves are another time when it’s really important to monitor your fruit trees for water stress.

Here’s an extreme example of a really dry tree:

Apple trees that haven't been watered
Apple trees that haven’t been watered

We’ve always had heat waves here in Australia, but their frequency and severity seems to be increasing. There’s not much we can do about that (apart from trying to slow down climate change), but we can make sure our trees are adequately irrigated, particularly during a heat wave, to minimise the stress on the tree.

The easiest way to check whether your trees need water is the ‘boot test’ – kick the soil under the tree with your boot and if you see dust, the tree needs watering!

Going up one step in sophistication is to dig a hole a few cm deep near the trunk of the tree with a shovel; the soil should feel cool and moist. If it looks and feels hot and dry, and is very hard to dig into, it’s too dry. (There are also many more degrees of sophistication with moisture monitoring equipment, but in most cases it’s not necessary).

The most sustainable way to protect your trees from inadequate water is to continually improve your soil quality, which in turn increases the amount of water your soil can hold. Learn how to store water in your soil here, and how to improve the health of your soil without expensive additives here.

A tree with a blocked dripper
A tree with a blocked dripper

And finally, check your irrigation system regularly! A quick 5 minute check every couple of weeks can prevent this situation, where a blocked dripper was discovered because the leaves turned yellow and started to fall!

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