Determining an ideal harvest duration can be a difficult decision in asparagus. Yield targets are often based on:
- the age of the plantation,
- calendar date,
- market price,
- number of picks, and
- overall spear quality.
2015 has been an interesting year for asparagus. After a long wait, it started with a bang. Many growers reported record yields in the first weeks of picking. Then it slowed down, followed by unusually dry soil conditions.
For the most part, we were expecting good crown health heading into this season. 2014 was cooler and wetter than average, but foliar diseases were well managed and there was a good gradual senescence before freeze up.
That being said, over the past few weeks there has been a noticeable decline in spear quality, with a high proportion of pencil-thin whips in the fields. Understandably, growers are concerned and looking for possible causes.
Questions have come up regarding the impact of the severe winter temperatures over past two years. Asparagus is a very hardy perennial. Most of the research indicates that rapidly changing temperatures at freeze-up and thaw are more significant than the absolute lows during dormancy. However, I don’t think we can assume that prolonged low temperatures have no effect at all. Reduced carbohydrates, damaged buds, dry soil conditions will all affect the overall health of the crown.
With a perennial crop, there is a need to consistently balance yearly income versus the long term productivity of the plantation. An asparagus field during peak production usually supports 20-24 picks per year. However, exceptionally high daily yields at any point in the season, may actually reduce the total number of picks that the crown can support for the season.
A high proportion of whips in the field are a clear indication from the crop that it is running out of carbohydrate reserves and becoming stressed. Diseases like fusarium thrive under stress conditions.
If there was indeed winter injury in the crop, it will require extra care and optimized growing conditions to replenish the crown’s carbohydrates and avoid infection from soil diseases. A long, healthy fern producing season is the best guarantee for future yields and long-term productivity.
As fields are retired for the year, begin a scouting program immediately to manage rust, purple spot and asparagus beetles. Keep an extra close eye on young 2-4 year old fields, as foliar diseases generally become established in these fields first.