The best sweet potatoes for Colorado are the quick ones: orange-fleshed varieties bred for short seasons, ideally with compact vines, planted as slips once the soil has warmed. Slow, long-vine types that expect a Southern summer rarely finish before frost. The full method is in Growing Sweet Potatoes in Colorado. What follows sorts out which varieties earn the bed space.
The short answer for Colorado
Choose by type, and choose the earliest type. The Denver reference station, at 5,280 feet on the plains, has a mean last spring frost between May 1 and May 11 and a mean first fall frost between September 30 and October 12. Those dates mark the band where the odds of a 32F freeze fall between 30 and 70 percent. They describe chance, and any given year can land on either side. Sweet potato slips can’t go out on the last-frost date anyway, because cold soil holds them back, so the usable season starts later than the first date suggests and ends at the second.
Summer heat is the part that works in your favor. The same station averages 39.6 days a year at or above 90F, which is plenty of warmth for a crop that loves it. The limit is the length of the season, so you are shopping for speed.
| Type | Fit on the Colorado plains | What to know |
|---|---|---|
| Early orange-fleshed, shorter days to maturity | Best bet | Beauregard and Georgia Jet are commonly sold examples. Pick the lowest day count you can find. |
| Bush or compact-vine types | Good for small beds and large containers | Vardaman is a familiar one. Compact vines are easier to warm with plastic or a low tunnel. |
| Purple, white and heirloom types | Worth a few plants, not a whole bed | Okinawan and Murasaki types often want a longer warm season. Give them the hottest spot you have. |
| Long-season Southern types | Skip | The season ends before the roots size up. |
How do you read days to maturity on a sweet potato slip?
Sweet potatoes are transplanted, so the number counts from the day the slip goes into the ground. It also assumes decent warmth the whole way. Count forward from your real planting date, after the soil has warmed, and check that the harvest lands before the early end of the fall frost band. If it lands inside that band, pick a faster variety or plan on covering the vines.
What will not work here
Slow varieties fail first. A slip planted after the May 11 end of the spring band has until somewhere between September 30 and October 12 to fill out roots, and that is a short runway for a type that needs a long, steady summer. Frost blackens the vines, and roots left in cold ground deteriorate. A big, handsome vine in August means little if the roots under it are pencil-thin by October.
Do long-season sweet potatoes finish in Colorado?
Rarely, and the plains are the best case. Mountain towns run far shorter seasons and can frost in July, so a long-season type there has no real chance without serious protection. Even on the Front Range, a heirloom variety that does well in the Southeast tends to make a lot of vine and little to eat. Try one as an experiment, and keep your main planting on the quick types.
Does weekly watering work for sweet potatoes in Colorado?
Often it doesn’t. Summer rain at the reference station adds up to about 5.7 inches across June, July and August (June 1.94, July 2.14, August 1.58), out of 14.5 inches for the whole year. With roughly 40 days a year at 90F or above, the soil dries fast. A single thunderstorm tends to run off rather than soak in, so it counts for less than its number suggests.
Soil changes the picture. On sandy ground, one weekly soak drains below the shallow roots within the day, and the young plants go thirsty between waterings. On heavy clay the same soak lingers, but clay has its own problem: roots can’t swell freely in packed soil. Loose, well-drained soil, or a raised ridge of it, suits the crop. Keep the bed evenly moist while slips establish, then ease off as the roots bulk up.
Two more plans fail here. One is putting slips out on the first frost-free date because the calendar says so. The other is pulling no roots until the vines die back. In a year when frost arrives at the early end of the band, the digging has to happen first.
What changes across Colorado
Colorado spans USDA hardiness zones 3b to 7b, which makes one statewide recommendation impossible. The USDA system rests on a single variable, the average annual extreme minimum temperature. That tells you how cold winters get. Sweet potatoes are grown as a one-summer crop, so the winter low matters less than how many warm, frost-free weeks you have. Still, a zone at the cold end of the spread is a good hint that the summer is short too.
The Denver plains give a reasonable middle case, which is why the dates above come from there. Mountain valleys and higher towns run well below it, with shorter seasons and cooler nights. The western slope differs again, and lower, warmer valleys there can behave very differently from the plains. Look up your own location on the USDA Plant Hardiness Zone Map rather than guessing from a neighbor’s garden or a nearby town’s reputation.
If you’re in the north or at altitude, shift everything toward speed and warmth:
- Use only the earliest orange-fleshed or bush types.
- Start slips indoors, or buy them late, so they go out strong rather than leggy.
- Warm the bed ahead of planting with black plastic.
- Grow in large containers set against a south-facing wall.
Planting dates shift as well, and later is not always safer at altitude, where the fall comes early. The timing is laid out in When to Plant Sweet Potatoes in Colorado. Read it with your own frost pattern in mind.
Where to check this for your own county
Your county’s Colorado State University extension office is the next stop. Colorado State University Extension keeps local offices across the state, staffed by people who know the soil, the elevation and the frost pockets of your valley. They answer for your county rather than for an average of the whole state.
Two things are worth finding there. The first is a local planting calendar, with transplant and harvest windows set for your elevation instead of for Denver. The second is a list of varieties that have been trialled in your county, since a variety that performs on the plains can fail in a mountain valley, and the reverse is true too. If the office has no sweet potato trials nearby, ask what the nearest similar climate has produced. Master Gardener volunteers attached to many county offices often know which local growers get a harvest and which varieties they use.
A county recommendation beats a state one. Everything above is the statewide view, built on Denver-area normals, and it sets a sensible starting point. It can’t see your slope, your windbreak or the cold air that pools in your low corner. When the county office and this article disagree, go with the county office.
Checking this against your own garden
Dates give you a window. What your garden is doing tells you when to act inside it, and three things are worth watching.
The first is soil warmth by feel. On a morning, push your hand a few inches into the bed. If the soil feels cool and damp against your skin, wait. If it feels neutral or mildly warm, and the nights have stopped dipping low, slips can go in. Compare a bed against a south wall with one in the open, and you’ll see how much a few feet of exposure can change when the soil is ready.
The second is the new leaf growth on your slips. A slip that is rooting well puts out fresh leaves within a couple of weeks of planting. If it sits with its original leaves yellowing, the soil is probably still too cold or too dry. That is your cue to add plastic or a tunnel, or to check your watering against what the weather has actually delivered. A straight-sided can set out as a rain gauge will tell you what rain really fell, which beats guessing after a storm that ran off.
The third is the vines in midsummer. Vines that run and cover the bed say the spot has enough heat. Slow, stunted vines point to a cool corner, shade or soil that stays wet. In September, watch for the first frost on windshields and rooftops, and note which parts of your yard whiten first. Those low spots frost early, so harvest from them first.
Common questions
What is the best sweet potato variety for Colorado?
An early orange-fleshed variety with a short days-to-maturity count is the safest choice. Check the label and compare counts, remembering that they run from transplanting.
Can you grow sweet potatoes in the Colorado mountains?
It’s a long shot. Mountain towns have much shorter seasons and can frost in July. Compact types in containers, black plastic and a low tunnel give the best odds, and your county extension office can tell you whether anyone nearby has had a harvest.
Do sweet potatoes need a lot of water in Colorado?
They need steady moisture while the slips establish, then less as roots bulk up. With about 5.7 inches of rain over the summer, and roughly 40 days a year at 90F or above, rain alone won’t cover it. Sandy soil needs more frequent watering than clay.
Can I grow purple sweet potatoes in Colorado?
You can try a few plants. Many purple and heirloom types want a longer warm season than the plains give, so put them in the hottest spot you have and keep your main planting on the early orange types.