Hargreaves Plants is running trials on asparagus crown size to determine the optimum size for maximum yield.

Jamie Petchell, product manager for asparagus said: “The vast majority of growers now do prefer crowns, but the division is to be found when it comes to what size. The industry is currently supplied with large A crowns (normally graded at 70g+) and the smaller B crowns (often 40-70g). Individual growers certainly have their own very strong opinions about which are better.”

Hargreaves Plants estimates that preference is split approximately 50:50 in the UK, but in the recent past this would have been as strong as 90:10 in favour of the smaller size, Petchell estimated.

Although a large number of growers have already switched to bigger crowns, roughly half of growers are still not convinced. “One common thought is ‘I will plant B crowns because they are cheaper to purchase and they will soon catch up with the As’,” said Petchell. “A further remark is ‘large crowns stay larger for longer’, when in fact a B crown may well eventually catch up with an A, but this might take five years.”

Hargreaves Plants decided to put size to the test during the spring of 2004 and planted a trial to evaluate the differences between a range of crown sizes. In total, four carefully selected grades were planted: 30-40g, 50-60g, 70-80g and 90-100g.

The first test was carried out in December 2006 by Marie-Laure Bayard, asparagus technician for Hargreaves. Samples were lifted from each batch to check how the crowns had developed in the time since planting. “The results were stark with the two largest batches still almost twice the size of the smaller batch (1.135kg vs 0.64kg),” she said. “Full and detailed analysis is available to regular Hargreaves Plants’ customers. Most people now know that the density of the asparagus root system equates to the size of the fuel tank for the spear harvest.”

The trial will go on for a minimum of three years and each winter, crown samples will be lifted and weighed. “In addition, each spring the crops will be harvested to check for marketable yield,” said Bayard.

Other trials are being carried out by Hargreaves to measure optimum planting density, nutritional inputs, and the harvest of over 200 new and existing varieties.

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