Blackberry Jam Day

“In Seattle, blackberries are as likely to vex gardeners as delight them.” This KUOW story on the invasive blackberry gives you a sense of why that is. As a gardener, I might swear at the vines, but as a baker, I’m in love with this ubiquitous berry. I also love that this recipe is lower in sugar (bringing the flavor to the forefront) than other recipes you might see. This recipe and canning method applies to all berries. My neighbor just gave me a jar of a raspberry blackberry jam that I plan to try myself next season it was so good. Have fun with this!

Blackberry Jam

  • Servings: 10 pints or 20 half pints
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Blackberry Jam
This jam ratio is 5 parts blackberries to 2 parts sugar which speaks to my sweetness preference. If you prefer a sweeter jam, you can increase the sugar up to a 1/1 ratio (or beyond if you really like it sweet). It’s also possible to make jam with no sugar whatsoever. I also skip the pectin here because berries are naturally loaded with pectin. If you choose to add pectin, your cooking time will be dramatically shorter (follow guidelines on the pectin box).

At this sugar ratio, the yield is one half pint for every cup of blackberries.
20 cups of blackberries
8 cups granulated sugar
Juice from two lemons

Canning Equipment Needed: (available at your local hardware store and most groceries)
Canning jars
Jar Lifter
Canning Funnel

When blackberries are ripening on the vine in late August, I bring containers with me on my daily walks, often getting a quart or so at a gathering. Back in my kitchen, I lay them on parchment paper on a small sheet pan and pop them in the freezer for several hours. Once frozen, it’s easy to pick off the silly things that tend to stick to the fruit that you might not notice when picking. A full sheet pan does an admirable job of filling a one gallon Ziploc bag. I return these to the freezer until Jammin’ Day and then spread them out again to thaw.

After they’re picked, I lay them on sheet pans and freeze them, making them easier to transfer into large Ziploc bags.
When I’ve collected enough berries, I reverse the process and let the berries thaw on trays for half an hour or so.

30 minutes later (or once thawed)…
If you have a juice pitcher, they can be very useful as a measuring cup. The pitcher below holds 10 cups of blackberries (2.5 quarts). Whatever quantity you’re making, put the berries into a pot, and add the sugar on top.

Juice pitchers are a great way to measure!
Splitting the bounty between two pots.

Now bring them to a medium heat. It’s easy for the bottom to get overheated and scorch (you don’t want a burnt flavor here) so don’t go too high with the heat, and stir often, making sure to scrape the bottom well.

The left photo below shows two pots at the start of the process. Within an hour, it had reduced down to about 3/4 of one pot (I combined them at some point) and the bubbles were slow and thick–exactly what you want. You’re now ready to can them!

Starting point
Both pots cooked down and combined into one.

The Canning Part
There are several methods available to preserve your jam, but all require that you put them in sterile containers. I keep my jars from year to year and often can make the rings last too, but the inner lids must be new for this. They have a seal around the edge which will pressurize during it’s water bath and seal it safely to the jar.

To sterilize used jars, first clean off any old labels and remove any stubborn dust or dead spiders and then run them through a long dishwasher cycle. Meanwhile, fill a large pot with water, making sure the water level is at least one inch above the tallest jar you will be placing in it. I don’t bother with the metal jar racks if I have a lot of jars but if you have one, feel free to set it in the pot first. Bring the water to a boil and then let it simmer on the sidelines while you make your jam. If you don’t have enough room on your stove for two jam pots and the canning pot, set the canning pot on the counter, covered, after its boil. It will be easy to bring it back to a boil when you’re ready.

This monster canning pot held all 20 of my jars but any size will do as long as they don’t tip over during their water bath
Lids and rings, right out of the boiling water

Sterilizing the Lids and Rings
I used to throw the lids and rings into the same pot as the jars but now realize it’s much easier to boil them in a separate pot.

When you’re ready to fill your jam jars, use the jar lifter to lift them onto a clean counter, no more than one or two at a time. Use the canning funnel and ladle jam in 1/4″ from the top. Take a clean, damp paper towel and wipe any drippings off the rim. This is important! You want to make sure the seal is tight to prevent bacteria down the line.

Use a jar funnel to load your jars, rinsing it after each fill
Make sure you wipe off any jam drips with a clean paper towel

Once your rim is clean, place the lid on and screw the ring over the top. The jars will be hot, so I usually wait until all the jars are filled and lidded before tightening them (giving the jars a chance to cool a little).

Return the canning water to a boil and then use the jar lifter to lower them into their water bath for a ten minute spa treatment. Then remove them to a clean sheet pan. Over the next several minutes, you should hear loud pops as the lids suction on to the jars. The center bump on the lids will invert and look concave once they’ve popped and that’s a very good thing. If a jar lid doesn’t invert, the jam will still be fine in the fridge for a month or so.

Lid goes on!
As I had a request for some seedless blackberry jelly for a few of my jars, I used a food mill to strain out the seeds.

Once cooled, add some labels (and a date) and you’re good to go!!

Many thanks to all my jam teachers over the years, including my aunt Susan Nickum, who bought me my first canning pot and inspired me to respect this glorious tradition.

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