Native Range and Climate

Japanese honeyberries (Lonicera caerulea var emphyllocalyx) are native to Hokkaido (northern Japan) and the Kuril islands.  Rainfall varies between 2" to 6" per month during the grow season.  The average peak temperature of the year is ~79F (26.1C) on most of Hokkaido, but it can be as low as 60F (15.6C) on the Kuril islands.  'Haskap' is a term used to specifically refer to the Japanese honeyberry.^[1]

Russian honeyberries (Lonicera caerulea var kamtschatica) are native to Kamchatka and other nearby federal subjects of Russia.  Rainfall varies between 1" to 3.5" per month during the grow season.  The average peak temperature of the year resides between 63F (17.2C) and 73F (22.8C). 

Honeyberry flowers can survive temperatures between 17F (-8.3C)^[1] and 19F (-7.2C).  Early blooming varieties (e.g.  kamtschatica) cannot be grown in regions that regularly experience above freezing temperatures for roughly a week or more during the winter.  That is warm enough to wake them up from dormancy.

Pests

There does not appear to be any significant pests (other than birds) in the United States.  There may be a stem borer that can kill branches, but there is very little information about it.  I believe it is the species Oberea pupillata, which is native to Europe, but I have seen no mention of it in the United States.  While there are other longhorned beetle species native to the US, I do not know of any that feed on honeyberry or other honeysuckle plants.  There is, however, a very brief report of honeyberry borers in Ontario by their ministry of agriculture.

Disease

Powdery mildew is the most common disease to affect honeyberries, but sunburn can also be an issue.^[2] Mildew may exacerbate the problem by causing the leaves to curl, thus exposing their sensitive underside to the sun^[2].  Since honeyberries are one of the first fruit to ripen, the worst of it usually happens after harvest, but too much damage to the leaves may affect productivity the following year.

Mildew and sunburn have been observed, to varying degrees, in the cold summer, semi-arid climate (BSk) of Saskatoon, Canada^[2] at an elevation of ~1500ft.  In Ohio, where it is warmer and rather humid – but at a much lower elevation – varieties that demonstrated a high level of resistance in Saskatoon were troubled by both afflictions,^[2] but it does not mention which were tested.  This is important since Russian varieties are known for being more susceptible than Japanese varieties, and Japanese varieties developed in the United States are said to have additional resistance.

In Lexington, Kentucky, 6 plots were planted with 10 different Japanese honeyberry (haskap) selections, in addition to the hybrid variety 'Borealis', during the spring of 2014.  From 2016 to 2018, data was recorded.^[3][4][5] During this time, mildew was not present and "leaf bronzing" was implied to be low for many.  Unfortunately, most selections had a fairly high mortality rate by the end of the 5th year, and every dead bush was diagnosed with phytophthora root rot.  However, there were two selections with few or no deaths (one death was reported in 2017, but it was apparently retracted in 2018).  They were released under the names of 'Sunrise' and 'Early Blue'.^[5]

Fruit Maturity

Honeyberries may turn blue and look ripe 2-3 weeks before they are ready to harvest.^[1] Some varieties will turn dark purple inside when they are fully ripe, while others will remain green.  Mature berries can hang on the bush for 1 to 2 months in cool summer climates before they become overripe.  Smaller berries may dehydrate before then.

Flavor

Plants within the genus Lonicera are referred to as honeysuckle, where the name 'honeyberry' is derived.  It also doubles as a highly convenient gimmick to sell product that struggles to develop even a smidge of sweetness, that is, when it comes to every variety that was available back when the name was coined a few decades ago.  Intriguingly, some of these varieties still happen to be described by major nurseries as "sweet".  Sometimes, they even completely avoid any reference to their consistently high level of acidity.  Other times, they'll add cute words like "tangy".  However, some of the newer varieties, such as 'Aurora', can be quite good since they have an easier time developing sweetness and flavor to help balance their tart nature.

Honeyberries can have a fairly complex flavor consisting of tones reminiscent of other berries – such as strawberry, blueberry, or raspberry – that complement their own unique flavor.  Conversely, some varieties, particularly when it comes to those released before 2014, will regularly produce berries that develop a weak flavor that is easily overwhelmed by their acidity and, in some cases, bitterness or astringency.

Nutritional Values

Honeyberries provide a moderate to high amount of ascorbic acid, ranging from roughly 10 to 100 mg/100g.^{[6][7][8][9][10][11][12][13]} However, a measurement between 20 to 35 mg/100g was rather common.  The first honeyberries harvested from the bush will have more ascorbic acid than those that are harvested later in the season.^[6][8][12]

The total phenolic content of honeyberries ranged between 125 to 1154 GAE mg/100g FW, with the mean low and high being 359 and 620 mg/100g.^{[14][6][15][8][16][17][10][11][12]} Anthocyanins generally consisted of roughly 10-40% of the amount.  For context, other fruit often have a phenolic content in the lower range, while the content of the most phenolic-rich species appear to regularly be over 1000 mg/100g FW.

In colder climates, citric acid is the primary acid in multiple culinary berries.  This is often true for honeyberries, but malic acid can occasionally be the most dominate.^[17] Regardless, honeyberries regularly have a citric acid content rivaling that of citrus.  Overall, their total acid content is often measured between 1 to 4 g/100g FW.^{[6][7][8][9][17][18][13]}.

Their total sugar content generally ranged between 1.56 to 9.5 g/100g FW.^{[9][17][12][13]} In a study that tested 17 selections, the mean was 6.15 g/100g.^[9] Brix levels were not given in these studies.  Elsewhere, brix ranged between 9.3 to 19.9, but the majority of the measurements were below 15.^{[6][7][8][18][19]}

In one study, the variety 'Indigo Treat' was found to have a sugar content of 13.8 g/100g FW and a brix of 16.4 in 2015.^[19] This is a very high amount of sugar for a honeyberry, and it's from a variety that is currently known for being inferior to Aurora.  However, results were much lower during the other two years it was tested.  In 2014, Indigo Treat had a sugar content of 5.9g (14.3 brix), and in 2016, it was 5.6g (11.3 brix).^[19]

There were six other varieties that were tested in this study, and in 2015, they had a spike in sugar as well.  'Indigo Gem' had the second highest amount in 2015 (11.3g with a brix of 16.1), but it had the highest amount in 2014 (10.3g with a brix of 18.3) and 2016 (6.1g with a brix of 11.5).^[19] 'Tundra' was also tested.  It had a sugar content of 3.9g (11.5 brix) in 2014, 6.2g (11.7 brix) in 2015, and 3.9g (9.8 brix) in 2016.^[19]