The plums got us on the way back from something else entirely. Late August, hot, my son riding in the back with a sunhat he’d already thrown twice, and I pulled over because I saw a color in a draw off the county road that I’ve learned to notice — that dusty orange-red that doesn’t belong to anything else out here in the last week of summer.
Wild plums. A whole thicket of them, low and tangled and loaded.
I’d like to tell you I had a plan. What I actually had was a canvas grocery bag in the truck bed and a two-year-old who was thrilled to be handed fruit and deeply uninterested in the concept of “in the bag.” We picked for maybe forty minutes. He ate three, made a face at the first one, went back for the other two anyway, and got juice from his chin to his elbow. I got scratched up reaching into the middle of the thicket, which is where the good ones always are. We came home with about six pounds and I spent that evening pulling out leaves and stems at the sink while Kimi asked, reasonably, what exactly I intended to do with all of them.
What I intended to do was this. Wild plum jam is the companion piece to chokecherry jelly — same instinct, same season, a few weeks later, and honestly a little more forgiving. Chokecherry makes you strain juice through a bag and wait. Plums just want to be cooked.
Wild Plums in Wyoming
The fruit we’re talking about is the American plum, Prunus americana, and it is genuinely native to Wyoming — not an escaped orchard tree. University of Wyoming Extension lists it among the state’s native fruits, and describes exactly where to find it: drainage areas. Draws, ravines, the canyons of the plains and foothills. Anywhere water collects and runs, plus the fencerows and shelterbelts people planted for the same reason.
It grows as a thicket-forming shrub or small tree, spreading by root suckers, which is why you rarely find one plum — you find forty of them knitted together. The fruit runs up to about three-quarters of an inch across and hangs individually along the branches rather than in clusters. UW Extension notes the green fruit “develops an orange to a pink or reddish blush as it ripens,” which matches what I’ve seen: they go from hard and green to a blushed red-orange, and the ripe ones come off with almost no pull. Statewide the window is roughly August into September, running earlier at lower elevation and later as you climb. Native fruit season here can stretch a month or more depending on where you look.
Identify before you pick
I’m not going to tell you Wyoming’s draws are full of things that will hurt you. But plum and chokecherry are the same genus and look genuinely similar, so know which one you’ve got. Plum leaves taper more gradually to the tip; chokecherry stems are reddish-brown with distinct raised white lenticels, while plum stems are brown going gray with much less obvious bumps. The clearest tell is the fruit itself — chokecherries hang in long clusters, plums hang singly and are much bigger.
Two real rules. First, the pits, leaves, and stems of both plants contain compounds that release cyanide — use only the flesh, never crack and eat the kernels, and get the leaves out before you cook. Second, know whose land you’re on. Public land, road right-of-way, or a landowner who’s said yes. Ask. Wyoming people will usually say yes if you ask, and will absolutely notice if you don’t.
About the Recipe (and Why the Altitude Matters)
This is the USDA / National Center for Home Food Preservation Plum Jam without Pectin recipe. I’m using their tested formula and their processing table, not a version I made up, because canning is the one place on this blog where I won’t improvise. Wild plums are ideal for it: NCHFP notes that some plums carry enough natural pectin to gel on their own, and wild plums are tart and firm, which is precisely what a no-added-pectin jam wants.
Two things change at Casper’s roughly 5,150 feet, and both matter:
- Processing time. NCHFP’s plum jam table gives 5 minutes at 0–1,000 ft, 10 minutes at 1,001–6,000 ft, and 15 minutes above 6,000 ft, for half-pints or pints. Nearly all of Wyoming falls in that middle band. Use the jam table — not the general fruit-canning chart, which is a different set of numbers for a different product.
- Gel point. Jam sets at 8°F above your boiling point, not a fixed 220°F. NCHFP’s table lists about 211°F at 5,000 feet and 209°F at 6,000. The dead-reliable method: stick your thermometer in plain boiling water, read it, add 8°F, and use that number. A clip-on candy/jelly thermometer is the single best five dollars you’ll spend on preserving up here.
Wild Plum Jam
Yield: about 8 half-pint jars
Ingredients
- 2 quarts (8 cups) chopped, pitted tart plums — about 4 pounds whole fruit
- 6 cups granulated sugar
- 1½ cups water
- ¼ cup bottled lemon juice
Use bottled lemon juice, not fresh — its acidity is standardized. Don’t reduce the sugar; in a no-pectin jam it’s doing structural and preservative work, not just sweetening.
Method
- Clean the fruit. Pull every stem and leaf. Wash in cold water, floating off the debris. Discard anything soft, split, or wormy. NCHFP suggests about a quarter of your fruit be slightly underripe for a no-pectin gel — easy with wild plums, since a thicket never ripens all at once.
- Deal with the pits. Wild plums are small clingstone fruit and will not halve neatly. Put the washed plums in a pot with a little of the water, cover, and simmer 5–10 minutes until the skins split and the flesh loosens. Then either pick the pits out by hand as the fruit cools enough to handle, or run everything through a food mill, which strains pits and coarse skin in one pass. Measure the prepared fruit back to 8 cups before going on — that measurement is what keeps you inside the tested recipe.
- Sterilize your jars. Right side up on the canner rack, covered by an inch of water. Boil 10 minutes at under 1,000 feet, plus 1 minute per additional 1,000 feet — so about 15 minutes in Casper. Keep them hot until you fill them. A jar lifter and wide-mouth funnel make this stop being a burn hazard.
- Cook the jam. Combine plums, sugar, remaining water, and lemon juice. Bring up slowly, stirring until the sugar fully dissolves, then boil hard. Stir constantly — this scorches fast once it thickens.
- Test the set. Cook to your altitude-adjusted gel temperature (around 210–211°F in Casper). Thermometer vertical, bulb covered but off the pan bottom. Back it up with the sheet test: dip a cold metal spoon, lift it sideways, and watch for the drips to merge and sheet off instead of running.
- Fill and process. Ladle hot jam into the hot sterile jars, ¼-inch headspace. Wipe the rims with a damp clean towel, set the lids, apply bands fingertip tight. Process in a boiling-water canner: 10 minutes at 1,001–6,000 feet, 15 minutes above 6,000. Start timing at a full boil with jars covered by an inch of water.
- Cool. Lift the jars out, set them on a towel with space between, and leave them alone 12–24 hours. Check every seal. Anything that didn’t seal goes in the fridge and gets eaten first.
Storage and Shelf Life
Store sealed jars somewhere cool, dark, and dry — NCHFP recommends between 50°F and 70°F, bands removed so you’d notice a failed seal. For best quality, use home-canned jam within one year. It doesn’t become dangerous at 13 months, but color and flavor drift, and a bright plum jam is the whole point.
Opened jars live in the refrigerator. And skip the old scrape-the-mold-off trick — current research found mycotoxins in jelly with surface mold, so a molded jar gets thrown out whole. Not worth it.
How We Actually Eat It
On sourdough toast with too much butter, mostly. But wild plum has a tartness and a faint bitterness off the skins that makes it better than store jam at things store jam is bad at: whisked into a pan sauce for pork chops or venison, spooned over a wedge of sharp cheddar or something soft and local on a board, folded into thumbprint cookies, or warmed and poured over vanilla ice cream. It’s also the best jar you can hand somebody in December, especially if you tell them where it came from.
If you make a batch, tag @wyofood — I want to see your color. Every thicket in this state gives you a slightly different red.
— Sean