Plant spacing impacts both yield and fruit size

When running our Lincoln trial in the 2024/25 season, we had some plant losses in some of the plots of Valiant that left fewer productive plants in the plot.  Despite those losses, the production per plot was about the same.  This suggested that wider spacing might be the way to grow this variety.

To test this out, we received NZBP support to carry out a properly replicated and randomized trial looking at plant spacing for Valiant.  We know Valiant is a big plant and it made sense that wider spacing could work.

We tested out 4, 6 and 8 plants per linear meter in our tabletop covered system in Lincoln.  Plants were established in troughs with peat/coir media on 18^th September, 2025.  Fruiting went from late November 2025 through March 2026.

Wider spacings gave bigger fruit size but at a cost to overall yields.

Not surprisingly, the highest yield per plant was achieved at the widest spacing, which also gave us the biggest fruit.  Yield was a whopping 50% higher, on a yield per plant basis, when comparing 4 plants/linear meter with the 8 plants/linear meter spacing.

But CAUTION, while we’re used to quoting yields on a per plant basis to compare productivity in different systems, this is not a fair comparison when plant spacings differ!

While we often talk about yields on a per plant basis in strawberries, farm profitability will be more closely aligned with yields on a per area basis, because many farm costs are driven by costs like management, structures, equipment, irrigation and the like, which are experienced on a per area basis.

Does the advantage of bigger fruit in the widest spacing compensate for the lower per-linear meter production?

The biggest average fruit size was achieved with the widest plant spacing.  We have just established that bigger fruit are cheaper to harvest, and harvest labour is a huge contributor to strawberry growing costs (see Fruit size and harvest costs – Notes for NZ Berry Growers).

Picking costs are based on a $30/hour picking cost and a variable harvest rate based on size (see article on Fruit size and harvest costs for a full explanation).  To better compare profitability to the grower, we can take into account that plant costs are more for denser spacings (assume $1/plug plant as plant cost).

Despite larger fruit leading to cheaper harvest costs, the return to the grower is still better at the higher plant density.  In this model, there is no advantage, based on this trial, to space even a relatively large plant like Valiant at wider spacings than our standard 8 plants per meter.

Obviously there wasn’t much difference in the per plant yields until midway through the season.   The wider spaced plants didn’t start to have a higher per-plant productivity until around New Years in Lincoln, after about 400g/plant had already been harvested, which is probably equivalent to sometime in November in Auckland.  This is probably when inter-lant competition is starting to kick in.  This raises questions about options for starting at higher densities and then removing every second plant.  Another interesting cost/benefit question.

Further considerations:

Higher densities still?
The data even begs the question about whether we should be trialing plants at an even higher density than the standard 8 plants/linear meter.  This work didn’t find the “tipping point” where higher density leads to lower returns to the grower.

Price premium for large fruit?
We know there are some premium markets where extra is paid for big fruit.  The long stem chocolate dipping market has historically been one of those.  Obviously a premium price changes the calculations.   We don’t have good data on this, so haven’t included this potential price premium in our analysis, but it is an aspect worth thinking about.

Disease pressure:
We thought about pest and disease pressures and the good news is that we didn’t see any differences.  We thought the botrytis pressure might have been more of an issue, but this has been a very low botrytis pressure season for us, and with the plants under cover we don’t have the same botrytis pressure as we used to have in the outdoor trial.