I don't think I realized how difficult it is for other people to can stuff.  I really am constantly surprised by people who say,"Oh, my jam came out like cranberry jelly and I could hardly get it to spread" or "Mine became pancake syrup." I used to make canning errors, but over the years, I've gotten very good at fudging it. I made a triple berry jam, like my mother used to make from blackberries, blueberries and strawberries.  (She used raspberries.) The recipe on the little sheet in the pectin box basically had blackberries and blueberries in equal parts to sugar for jam, but strawberries were their own category with measures that weren't easy to ration to blackberries.  I made an executive decision, however.

I didn't have a lot of strawberries, so I just used the recipe for the blackberries and blueberries because it was a double batch and there was no way it that pint of strawberries was going to really adversely affect the outcome.  I think the recipe for strawberry jam called for about half the strawberries and sugar that the blackberries/blueberries did, so I used the more dominant amounts of berries to sugar ratio to determine my recipe.

It came out perfectly. The strawberry flavor was just enough to soften some of the seed bitterness of the blackberries.  My mother typically used raspberries, but she also has a HUGE patch.  I literally wait with baited breath for my mother to bring me a jar of her raspberry jam.  It doesn't matter that it's the full sugar stuff.  You can taste the freshness of the berries.  She literally goes out, picks, and then cans it.  You can't beat that!

I also recommend canning the same day, but if you can't,  you can wait until the next day only usually with wild berries.  I don't recommend it, though.  Plan on a long day.  Pick in the morning and can in the evening. Strawberries you pick at a place in summer usually HAVE to be canned that day or they start to go.  Blackberries and blueberries are a bit more hardy, depending on how squished they get in picking or storage containers.  I typically try to put blackberries in a container that is wide, but not deep, to avoid squishing them too much.

Also, when a recipe tells you to hand crush the berries, feel free to ignore that and run them through the food processor.  It gives a better consistency to your jam and really can save your hands and wrist.  If you've already spent the day getting attacked by brambles, you will thank me because crushing them by hand with a pastry cutter sucks, as does a potato masher.

Almost any fruit can be combined with other fruit.  There are likely any assortment of recipes on the Internet.  The best recipe I ever found was plum-pear jam.  It seemed like it would be weird, but it was delicious.  It tasted like autumn, in the best sense.  It tasted like something that would go well with a bit of sharp cheddar on a good cracker.  It was that awesome.

I recently made nectarine, strawberry, blueberry jam.  It sounds weird, but it was really good.  The berries accented the nectarines beautifully.  The thing with nectarines and peaches is that you usually have to add some acidity to the mix, so I had about 2/3 of my jam mix from nectarines, so I used 2/3 of 2 tablespoons of lemon juice or 4 teaspoons to add enough acid to the mix. It came out beautifully.

My husband was mad as hell it had nectarines in it AFTER he ate it.  I had to use up the fruit, so I did and just didn't mention it to him.  He was mad that I'd tricked him into eating it. I just laughed and said, "Suckah!"  My daughter thinks it's pretty darned good, though she also loves the mixed berry I made, too.

I'm going to try to pick more berries between storms today or tomorrow.  I noticed the patch we hit has a ton of fruit again, this morning.  YUM!

Remember, you have to use the pectin for jam AS INSTRUCTED.  If you want a low sugar jam, you need to use a low sugar pectin.  Freezer jam maintains more of the freshness of the fruit and uses less sugar than regular jam, and there are also low/no sugar pectins for freezer jams. Not everyone has the freezer space for such frivolity, I realize.  If you want to make jarred jam low in sugar, you must by the low/no sugar pectin.  What sweetener you use is up to you.  You must also use low/no sugar pectin to use agave or honey, or it won't come out.

I hope this helps. :)