Over the years, growers have asked me if it is safe to harvest asparagus in the summer, to gain a market at a time where there is no local asparagus on the market, and to bring them a higher price. To help answer this question, I conducted a three-year study in North Carolina.

The study, conducted in Oxford, NC, tried to evaluate harvesting asparagus later in the year as compared to traditional spring harvest. Over three years, asparagus spears were harvested for two, four and six weeks, respectively, throughout the spring and summer. Harvest times were evaluated to determine if later harvests were detrimental to the plant as well as being profitable for the grower. With the exception of the first two-week harvest treatment the first year, the highest yields were obtained in the first four-week harvest treatment in the second year and the first six-week harvest treatment in the third year.

One-year-old crowns of “Jersey Giant” asparagus were planted in April. Harvest treatments were replicated five times with 12 plants per plot. Plants were spaced 12 inches apart in the row, with five feet between rows. The following year, spears were harvested every two weeks from April 1 – July 30. The next year, spears were harvested every four weeks from April 1 – Aug. 31. In the final year, spears were harvested every six weeks from April 1 – Sept. 2. In a commercial field, asparagus is usually harvested every two weeks during the second year, four weeks during the third year and six weeks during the fourth year. The plots were not irrigated, which is a common practice when growing asparagus, due to its extensive deep root system. Before each harvest treatment, the ferns were cut down and harvest started when new spears started to grow.

First Year Yields

Yields in two-week harvests were as follows:

April 1 – 15: 617 lbs./acre

April 15 – 30: 384

May 1 – 15: 408

May 15 – 30: 145

June 1 – 15: 405

June 15 – 30: 588

July 1 – 15: 546

July 15 – 30: 1,031

 Second Year Yields

Yields in four-week harvests were as follows:

April 1 – 30: 5,146 lbs./acre

May 1 – 31: 1,734

June 1 – 30: 932

July 1 – 31: 1,211

Aug. 1 – 31: 1,208

Third Year Yields

Yields in six-week harvests were as follows:

April 1 – May 13: 5,222 lbs./acre

April 15 – May 27: 3,235

May 13 – June 24: 586

May 27 – July 8: 473

June 10 – July 22: 1,282

June 24 – Aug. 5: 3,026

July 8 – Aug. 19: 1,911

July 22 – Sept. 2: 1,922

In North Carolina and states farther north, there is not sufficient time for the fern to regenerate between July and August to replace the carbohydrates that were removed when harvesting spears. As a result, even if yields decrease after the traditional spring harvest time and then increase in July and August, the highest yields generally occur when harvesting during April and May. Also, in North Carolina, harvesting asparagus during the hot summer months forces the spear tips to “fern out” or open up at a short spear height (between two and four inches tall), causing it to be tough and fibrous. These spears are of poor quality and cannot be sold to the consumer.