What are those brown marks on my apples?

We had a great question from one of our Grow Great Fruit members recently about what causes russet on apples, which describes both the yellow marks (as you can see on the side of this Cox’s Orange Pippin apple), and the rough brown marks around the stem end of the apple.

Russet is one of those curious conditions that occurs naturally – in fact several heritage apple varieties include it in their name, like Brownlees Russet, Egremont Russet and Old Somerset Russet. It’s also commonly seen on pear varieties such as Beurre Bosc.

These days, russet is not considered an attractive trait on apples (have you even seen a russeted apple in the supermarket?), and it’s just one of the reasons many of these beautiful old varieties have gone out of favour (which is one of the reasons we’ve planted a new heritage apple orchard to preserve many of these old varieties).

Russet can also be an injury caused by environmental conditions like frost, sunburn, or hail, or by spraying your apples at the wrong time – even using sulphur (which is an organic fungicide we use occasionally) at the wrong time can cause russeting on some apples (as can a lot of the chemicals used by chemical farmers).

This damage-type russet – think of it like scar tissue – usually happens in the three weeks after petal fall, when the trees are flowering, or when the environmental challenge happens. It is often not a problem in itself, but it can make the apples much more vulnerable to other diseases, like various fungal rots, cracking, or even sunburn.

Heritage varieties that were bred in the UK, such as the divine Cox’s Orange Pippin apples (above) or the much-loved Bramley (below), are really not suited to the harsh and hot conditions in Australia, and so it’s very common to see this type of damage on your apples.

Of course once you realise that, you can set about creating micro-climates that these trees will prefer, and you may find that much of the damage is preventable.

You can find out more about creating micro-climates in your garden in Permaculture in Action.

Sunburn strikes again

If you live in a hot climate (like we do) sunburn is an inevitable part of fruit growing, but it can also happen in temperate fruit growing areas during heat waves, which unfortunately are becoming more common due to climate change.

There are three types of sunburn damage you may see:

1. Sunburn necrosis

sunburn-necrosis

2. Sunburn browning

sunburn-spots

3. Photo-oxidative sunburn

sunburn-cooked

This week Ant (who leases our orchard) had his first experience of sunburn, when the Pizzaz plums were not quite ripe enough to pick last week, then the heatwave hit—a blistering day of 44C!

You can see the spots and shrivelling on the skin – that’s a version of sunburn browning. Most of the plums are still perfectly usable for jam, or cooking, or even for eating, but it definitely downgrades them.

Is it preventable? It can be incredibly difficult in cases like this, where there was probably only a very brief window of a day or two when the plums were ripe enough to pick (with the confidence that they would continue to ripen off the tree) before the heat wave hit.

In a home garden, if you were paying careful attention to both your trees and the weather forecast, it may be possible to harvest the fruit (or at least some of it) in time. In Ant’s situation, where he’s managing the competing needs of 5,000 trees it’s much harder.

If you live in an area that experiences heatwaves there’s a number of other things you can do to prevent sunburn damage, including irrigation practices, pruning practices, and careful monitoring—we list 10 different ways to minimise sunburn in “What’s that spot? Common diseases of deciduous fruit trees” (even though sunburn is not actually a disease, but an environmental impact).

The main thing to do when a heat wave is predicted is to make sure your trees are getting enough water, which may mean watering every day. The best time to water is either overnight or in the morning, to reduce evaporation.

When should you pick your fruit?

Fruit tastes better when allowed to ripen on the tree – don’t you agree? It can be tricky to get the timing of your picking quite right though, because it’s also a good idea not to let it get too ripe.

It’s apricot season at the moment, and they’re a good case in point, because if they’re a bit ripe when you pick them, it’s really easy to damage them.

Ideally when you pick your apricots they’ll come away with the stem, like this…

Or no stem, but a neat little scar where the fruit has pulled off the stem, like this…

One of the risks of letting fruit get too ripe is that you’ll get a picking injury at the stem end, as you can see in the following photo. The fruit has pulled away from the stem when it’s been picked, and made a little tear in the fruit.

Unfortunately this may make the fruit continue to ripen too quickly off the tree as it is likely to soften quickly at the scar site, and it can quickly go mushy.

The injury can also make the fruit vulnerable to brown rot, particularly if you’re growing organically (and we hope you are!).  Brown rot is much more likely to start if the fruit is injured, particularly if you’ve had a rainy season before the fruit was picked (because there’s likely to be more brown rot spores on the fruit).

If your fruit is a bit overripe when you pick, use it as quickly as possible, or get it into the fridge to keep it in good condition. But mainly, try to avoid picking injuries when you harvest!

It can be complicated getting the details right, so we’ve developed Fruit to be Proud Of to help home growers know how to choose the perfect time to pick fruit, learn great technique and proper storage practices to make the most of their precious fruit.