Yield cost of strawberry runner growth

Strawberry plants operate a bit like a household budget, if photosynthates were the income. The mature leaves keep “earning” sugars by photosynthesis, and they have to divvy them up between the competing sinks for sugars. In a very basic sense, the more leaves the plant has, the more capable it is of supplying the needs of developing fruit.

The strongest demanders of sugar are the fruit, followed in the hierarchy by flowers, roots and new leaves. When the plant starts making runners, they’re very demanding, strongly competitive with flowers and fruits.

How much yield we stand to loose by leaving runners to grow is variable. Back in the 1980s work was done by Albregts and Howard on short day varieties grown in Florida, and they found that fortnightly runner removal increased yield by 17-30% in ‘Tufts,’ a short day variety that made a lot of runners. ‘Dover,’ on the other hand, naturally made fewer runners and runner removal didn’t make much difference to yield.

To frame this, “a lot” of runners in Tufts was in the order of 5 runners/plant, compared to Dover which made 2 runners/plant. Our experience with Monterey is that it makes a heck of a lot more runners than that!

So how often do you have to whack off those runners in order to avoid yield loss?

That study mentioned above compared monthly removal and fortnightly removal to no runner removal. Digging into the data, the year where fortnightly runner removal spurred 30% more berry yield, removing runners monthly would have been nearly as good, giving 25% more berry yield than leaving all the runners on. The year previous when fortnightly runner removal gave 17% yield increase, removing them monthly gave 10% yield increase over leaving all the runners on. So it’s variable, but those runners are competing and reducing yield by the time they’re 2-4 weeks old.

Does this work the same with day neutrals?

Yes. In more recent work with a day neutral (ever-bearing) variety, fortnightly runner removal gave a similar benefit in the first 3 months of fruiting, 15% yield increase over no runner removal. This will vary with variety and growing season, but the more runners your variety makes, the more beneficial removing those sinks will be to overall yield.

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