It turns out that Bernal Heights in San Francisco is covered with blackberries! Over the course of a couple of weeks in July of 2019 my friend Bryan and I picked about five gallons worth. We made 1 bach of jam and froze the remaining berries. We ended up making two more batches of jam over the course of the next year.


The end result.


A small fraction of our haul.

The first batch we made with fresh berries and we decided to use the whole fruit (seeds and all). This was a mistake. The result, while delicious was very crunchy and not in a good way. For batch two in August of 2019 we deseeded the berries. This was not an easy task! We crushed the berries by hand and then pushed them through a flour sifter. Going mostly seedless greatly improved the texture however we used a bit too much pectin. This made the jam a bit hard to spread but it had an amazing flavor. We made our third and final batch in May of 2020 and finally got everything just right! The following pictures are a mashup across all three batches.



Smashing and deseeding.

There are probably better and less messy ways, but this seemed to give us a pretty good result. In batches two and three we added a bit of the seed pulp back to the juice to give the jam some body.


Cooking


Filling jars!


Batch two.


Batch three.

Our third batch (the really good one):

  • 24 cups (1.5 gal) blackberries
  • 4.5 lbs sugar
  • 1/8 cup lemon juice
  • 2 packs of Sure-Jell pectin

Yields about 16 cup jars.

Steps:

  1. Wash berries.
  2. In a large pot, smash berries into a pulp (don’t be afraid to use your hands).
  3. Strain pulp through through flour sifter (retaining 1 cup of seed pulp). 24 cups of berries should yield 16 cups of juice.
  4. Boil juice, reducing to about 8 cups of liquid (We used an instant pot with the lid off and it worked really well).
  5. Add 1 cup of seed pulp to juice to give it a bit of body.
  6. Add sugar, stir until dissolved.
  7. Add pectin.
  8. Cook, stirring continuously until temperature reaches 223 °F.

Jar prep (Sterilizing can be done while jam is cooking):

For detailed instructions see here.

  1. Sterilize by boiling 16 1-cup jars with lids (in batches).
  2. Fill jars to within 1/2” of top with hot jam.
  3. Using a cloth or paper towel dipped in boiling water clean around each jar’s rim and then add a lid.
  4. Loosely add a ring to the lid.
  5. Process filled jars in boiling water for about 8 minutes (in batches).
  6. Tighten lids down.
  7. You should hear each jar pop as it cools and seals.

If any jars don’t seal, take off the lid, clean the rim, re-process.

Happy jamming!