Blink and you’ll miss them. Sour cherries are a fleeting pleasure; their season lasts but a week or two, and then they disappear, leaving only the haunting memory of fragrant, sweet-sour pies.

I am late to this party. I only learned about pie cherries last year, in their last week. I bought enough for a cherry crumble, and then foolishly fed it to friends, without hoarding it and stabbing greedy hands away with fork tines.

I am not making that mistake again.

Sour cherries have been on offer for the past two weeks at the farmer’s markets, and I have spent all my money on them. I buy them by the quart — two or three quarts at a time. I have to restrain myself from buying more, reminding myself that I also need to buy yogurt. And lettuce. Which is so much less glamorous then sour cherry pie.

There’s probably one more weekend left of them, if I’m lucky. The Virginia farms have no more of the bright red orbs that feed my addiction. I’m hoping that next week, I’ll get the last few quarts from Maryland and Pennsylvania. I suggest you do the same (though I will be there early, and I’ll threaten you if you get in my way).

What makes them so great? What is it that beguiles me into spending all my money on them, tempting me into forsaking the healthy pleasures of skim yogurt and organic mesclun mix?

OK, well, since they are sour, these cherries are the perfect foil for cutting through the sweetness of dessert. The best foods are based on contrasting flavors; our palates demand salty with sour, bitter with sweet.

The pleasure of eating comes from the unexpected sharpness of goat cheese against sweet tomato. The crack of sea salt in lemon shortbread. The crunch of potato chip in a tuna sandwich. Sinking one’s teeth into a pie that is sweet and sour at once is a great summertime pleasure.

Dark red Bings are perfect for snacking on, their plump flesh bursting through thin skin, alive with sweetness. But for cooking, grab those sour cherries and hold on for dear life, while they last.

This year, I’m steeling myself for their departure. This year, I’m preserving them for the colder days of the fall and winter by making sour cherry preserves. They are remarkably easy to make, and so good they capture summertime in a glass jar. Like a firefly or a sunbeam, but so much better than either drizzled over vanilla ice cream.

Sour Cherry Preserves

Many people fear jam. I was one of them. It took a lot of coaxing, advice and reassurance from both my grandmother and my boyfriend’s mother. After the first couple of batches, though, you start to realize that jam is just fruit cooked with sugar!

After that, you can relax and have fun. If your jam doesn’t set, it’s OK! It will still taste delicious, will work in a pinch in a PB and J, and may be even better for drizzling into plain yogurt, over ice cream or onto a wedge of brie cheese. Or spooned directly from the jar into your mouth, which is my preferred method of delivery.

This time around, I didn’t sterilize my jars or seal them, so I’m keeping them in the fridge, where they should last several months before they start sprouting whiskers.

If you do want to can and seal your jam, be sure your jars are sterile by putting them in a 200-degree oven for 20 minutes, or submerging them in boiling water. To seal them, I simply invert the jars of hot jam so that the lid faces down for about five minutes, and then right them again.

As the jam cools, you’ll hear a loud thwack; it’s the sound of the lid sealing. Store them in the cupboard for up to a year, but if you find the seal broken, I’m afraid you should toss the jam out, for safety’s sake.

Now relax. Breathe. Can.

Gently wash as many sour cherries as you feel like pitting. I myself don’t have a cherry pitter, so I split them with a knife and remove the pit by hand. This means I only have the patience to do about three quarts at a time.

Roughly chop the pitted cherries. You want them big enough to impress your friends that you started with real cherries, but small enough that the pieces won’t roll off your toast.

In a large sauce pan, combine your chopped cherries with some lemon juice, about one lemon for each quart. Between the acid and the sugar you’ll add later, your preserves will be both delicious and will last longer. Bring the cherries and lemon juice up to a boil, and then lower the heat until they’re gently simmering for about 15 minutes. Turn off the heat.

Measure how much cherry mash you have, juice included. Then, add 3/4 that amount of white sugar. It seems like a lot, so you’ll have to trust me.

Bring the cherries and sugar back up to a rolling boil, stirring constantly so the mixture doesn’t burn at the bottom, heat the mixture to 224 degrees Fahrenheit. This will take longer than you think, and you’ll break a sweat stirring over a hot stove. Don’t worry! You’re almost there, and it’s worth it.

When the mixture reaches 224 degrees, the sugar-to-fruit ratio has hit the magical number at which it will gel. Though like I said, even if it doesn’t (mine didn’t this time), it’s still really, really delicious.

But don’t sample it yet, because at this stage it is 224 degrees of molten sugar and you will burn your tongue!

Ladle your jam into sterile jars, and seal as needed. Otherwise, allow them to return to room temperature, and then store them in the fridge.

Homemade jam makes a great, thoughtful gift come holiday time. But come on — you’ll want to keep this stuff for yourself.