Plump blackberries are water balloons, not sweet
Unfortunately, most of the local farmer's market where I live are closing up for the season or I have a craving for produce when they are not open. Recently, I have noticed that the blackberries in the store are very plump with literally only 8-10 berries per pint, but are like water balloons - full of water with no hint of sweetness whatsoever. I know that in general a lot of people avoid store-bought, imported fruit, but I have had OK luck with apples, raspberries, strawberries, oranges, etc. Also, I have never encountered this problem with store-bought blackberries before and in general they have been flavorful, sweet and tart. Is it just time to admit that blackberry season is over even though they are imported (most seem to be from Guatemala by the way if that means anything, as in perhaps they have year round season) and move on to other fruits for the fall/winter?
Blackberry lover in distress
Well... we have had similar experiences and since we mostly buy in season fruit and vegetables at local farms I can't blame the supermarkets. These farms practice either organic growing methods or Integrated Pest Management so I'd expect the berries, especially, to be sweet and juicy. The strawberries and raspberries are, the blueberries were but the blackberries were horribly sour and very seedy. I have no idea why this is, but can only guess it's the variety of berry they are growing. I'll have to ask...
Most thornless blackberries are tarter than most thorny (normal) blackberies and mature later. You can pretty much count on the thornless type being sour but no more seedy than others. Blackberries are quite sensitive to soil moisture levels while approaching ripeness. Rainfall and irrigation practices are important so large berries for a particular variety are likely to be watery while small berries for the same variety are likely to have more concentrated flavor and a higher proportion of seeds to fruit volume. Unless you grow the berries yourself or have a good relationship with a farmer, you will not know what variety you are eating.
The drought and hot summer made for some very good blackberries in southwestern Michigan this year with the season starting and ending several weeks early. As usual the later berries were too tart to eat plain while the midseason berries were delightful to eat unadorned.
On my way to the local apple orchard yesterday, I stopped at one of our large markets for dried fruits and noticed the attached berry farm was still in operation for the end of season. I picked four lbs of blackberries and after enjoying a bowl this morning with soft goat cheese and honeycomb would be hard pressed to settle for the "water" filled orbs that pass for blackberries at the big box stores...no matter the price.
The sweet smell of fall was a bonus!
I had some very large, but flavorful blackberries from Monterey Market in Berkeley very early in the season. Generally, I have found that berries bought at grocery stores have nowhere near the flavor of farmers market berries. Best of all are wild berries, which I happen to have in my backyard but grow all over the Bay Area.
I gave them up many years ago when I no longer could go out in the woods and pick them from the fallen tree stumps they were winding themselves around.
There never was/never has been anything like them, sadly.
The ones friends have purchased at local farmer's markets taste like weird perfume.