Harvest timing for blue honeysuckle (Lonicera caerulea L. ), a.k.a. ‘haskap’, has become a commonly discussed issue as production increases across the province.  When a number of new cultivars were introduced a few years ago, it was thought that the berries would ripen in late May under Ontario conditions, creating a niche opportunity for an early season berry crop.  Over the last 4 years we have learned that haskap are not ready for harvest in May and typically ripen between the middle of June and early July, depending on environmental conditions of the year.

Understanding the optimal harvest time for these berries is an important factor when developing the market of this new crop.  If haskaps are harvested too early, the bitter flavour could deter customers and negatively affect market development for the crop.  However, if harvested at the right time, the berry flavour is quite acceptable and may provide customers with a wider selection of fresh berries at farm markets.

Fruit colour typically starts changing at the beginning of May and continues through the month of June.  But don’t be fooled by purple fruit – fruit colour is not a good indicator of fruit ripeness in haskap!

Harvest timing trials using various methods to understand optimal time for picking have been completed on other fruit species.  A few of the parameters that have been studied in relation to fruit ripeness include: Total Soluble Solids (TSS) (of which sugar content is one component), pH and Titratable Acidity (a general measure of acidity).

Unfortunately there are no replicated studies outlining these parameters for haskap. However, measurements of TSS using a hand held refractometer, commonly known as a ‘Brix meter’, (Figure 1) have been performed on haskap fruit grown in Ontario during the 2013 and 2014 seasons. Values obtained from these readings may provide a general indication of when the haskap fruit is ready for harvest.

Figure 1: Hand held refractometer and distilled water for calibration.

Table 1 provides the TSS (Brix) reading of 5 haskap cultivars on two dates from bulk, homogenized fruit samples containing 5 or more berries.  Brix readings for 2013 were conducted on fruit that was frozen directly after harvest on June 26^th and thawed for analysis at a later date.  Interestingly, the fruit with the highest overall ranking in 2013 taste tests was ‘Indigo Treat’ followed by ‘Tundra’, ‘Indigo Gem’, ‘P.17’ and ‘Borealis’ which generally (but not completely) corresponds with the 2013 TSS values from highest to lowest.  The Brix readings for 2014 were completed on June 18th using marketable fruit which had been brushed or dropped from the plant (fruit was not removed directly from the plant in order to preserve research material for upcoming harvests).  The 2014 TSS values demonstrate variability across the 5 cultivars and may provide a general guide for fruit maturity when compared to the 2013 TSS values and taste test results.  From these estimates, it appears that haskap fruit with a reading above 13% TSS may have average to good flavour, which means the 2014 harvest is not far away for most cultivars.

Table 1: Total Soluble Solids (TSS) as determined by a hand held refractometer on juice extracted from 5 blue honeysuckle (haskap) cultivars over two dates grown at Simcoe, Ontario.

For reference, Table 2 shows comparative Brix values and corresponding indices for common small fruit species.  It should be noted that each fruit species has its own range and comparisons between species cannot be made.

Table 2: Adapted from International Ag Labs Inc. (Minnesota, USA), Index of crop juices calibrated in Brix.

It’s important to reiterate that the TSS values presented above for haskap have not been validated through a replicated harvest timing study.  However, these values may serve as a general guide for growers, independent of fruit colour, when trying to determine the ripeness of haskap fruit.