Colorado’s high altitude means sweet potatoes need protection from cold nights even into June. Finding the best time to plant sweet potato in colorado is the single most important step for a successful harvest in this challenging climate. Get the timing right, and you can enjoy a bumper crop of these warm-weather vegetables.
Sweet potatoes are not like regular potatoes. They are tropical plants that require warm soil and consistent heat. In Colorado, our short growing season and cool nights make timing everything. Plant too early, and your slips will rot. Plant too late, and the tubers won’t mature before the first frost.
Understanding Colorado’s Growing Season
Colorado’s climate is unique. We have over 300 days of sunshine a year, but our elevation means temperatures drop sharply at night. Even in June, overnight lows can dip into the 40s. Sweet potatoes need soil temperatures above 60°F to grow, and ideally above 70°F.
The average last frost date in Colorado varies by region. In Denver and the Front Range, it’s around May 5 to May 15. In the mountains, it can be as late as June 15. But frost is not the only concern. Cold soil is just as damaging.
Why Soil Temperature Matters
Sweet potato slips are sensitive. They are young plants grown from a mature sweet potato. If you put them in cold ground, they will not root. They may rot or stay stunted all season. Use a soil thermometer to check the temperature at a depth of 4 inches. Wait until it reads 65°F consistently.
In most of Colorado, this happens between late May and mid-June. That is the sweet spot for planting.
Best Time To Plant Sweet Potato In Colorado
The best time to plant sweet potato in colorado is from May 25 to June 15, depending on your specific location. This window gives the soil enough time to warm up while still leaving 100 to 120 frost-free days for the tubers to develop.
For the Front Range, aim for the first week of June. For warmer areas like Pueblo or Grand Junction, you can plant as early as May 20. In the mountains or high plains, wait until June 10 or later.
Using Black Plastic To Warm Soil
If you want to plant earlier, use black plastic mulch. Lay it over your garden bed two weeks before planting. The plastic absorbs heat and warms the soil by 5 to 10 degrees. This trick can let you plant by mid-May in many areas.
Cut slits in the plastic for each slip. The plastic also suppresses weeds and retains moisture. Just be sure to remove it in late summer if the soil gets too hot.
Checking Your Local Frost Dates
Every Colorado garden is different. Check your local extension office for exact frost dates. A good rule is to plant sweet potatoes two weeks after your average last frost date. This extra time ensures the soil is warm enough.
You can also use a soil thermometer. Measure the temperature at 4 inches deep each morning for a week. When it stays above 65°F, you are safe to plant.
Preparing Your Garden For Sweet Potatoes
Sweet potatoes need loose, well-draining soil. Colorado’s clay soil can be a problem. It holds water and stays cold longer. Amend your soil with compost or aged manure to improve drainage and warmth.
Raised beds are ideal. They warm up faster in spring and drain better. Build a bed at least 8 inches high. Fill it with a mix of garden soil, compost, and sand or perlite.
Choosing The Right Variety
Not all sweet potatoes grow well in Colorado. Look for short-season varieties that mature in 90 to 100 days. Good choices include:
- Beauregard – 90 days, reliable
- Georgia Jet – 90 days, good for cool climates
- Centennial – 100 days, classic flavor
- Vardaman – 100 days, compact bush type
Avoid long-season varieties that need 120 days or more. They will not have time to mature before the first frost in October.
Starting Slips Indoors
You can buy sweet potato slips from nurseries or start your own. To start slips, place a sweet potato in a jar of water, half submerged. Keep it in a warm spot with indirect light. In 4 to 6 weeks, sprouts will appear. When they are 6 inches long, twist them off and plant them.
Start this process 8 weeks before your planned planting date. For a June 1 planting, start slips in early April.
Step-By-Step Planting Guide
Follow these steps for the best results:
- Prepare your soil. Mix in compost and ensure it is loose to 12 inches deep.
- Warm the soil with black plastic for two weeks if needed.
- Check soil temperature. It should be at least 65°F.
- Plant slips on a cloudy day or in the evening to reduce shock.
- Dig holes 4 inches deep and 12 inches apart. Space rows 3 feet apart.
- Place each slip in a hole, burying the stem up to the leaves.
- Water thoroughly after planting.
- Cover with row cover if a cold night is forecast.
Watering And Care
Sweet potatoes need consistent moisture, especially in the first few weeks. Water deeply once a week, or more often in sandy soil. Do not overwater. Soggy soil causes rot.
Once the vines spread, they shade the ground and reduce evaporation. You can water less often as the season goes on. Stop watering completely two weeks before harvest. This helps the tubers cure in the ground.
Fertilizing
Sweet potatoes are light feeders. Too much nitrogen makes big leaves but small tubers. Use a low-nitrogen fertilizer like 5-10-10. Apply it at planting time and again when the vines start to run.
Compost tea or fish emulsion are good organic options. Avoid fresh manure, which is high in nitrogen.
Dealing With Colorado’s Challenges
Colorado’s dry air and intense sun can stress sweet potatoes. Use mulch to keep the soil cool and moist. Straw or grass clippings work well. Apply a 2-inch layer around the plants.
Wind can damage young slips. Plant in a sheltered spot or use a windbreak. Row covers also protect against wind and cold.
Pests And Diseases
Sweet potatoes have few pests in Colorado. Watch for deer and rabbits, which love the leaves. Use fencing or repellent. Wireworms can sometimes damage tubers. Rotate your crops each year to reduce risk.
Fungal diseases are rare in our dry climate. Avoid overhead watering to prevent leaf spot. Water at the base of the plants.
Harvesting And Curing
Harvest sweet potatoes before the first frost. In Colorado, this is usually late September or early October. The leaves will start to yellow when the tubers are ready. Dig carefully with a garden fork to avoid bruising.
Curing is essential for sweetness and storage. Place the tubers in a warm, humid spot for 10 to 14 days. Ideal conditions are 85°F and 85% humidity. A spare room with a heater and a humidifier works. After curing, store them in a cool, dark place at 55°F to 60°F.
Signs Your Sweet Potatoes Are Ready
Look for these signs before harvesting:
- Vines start to yellow and die back
- Soil cracks near the base of the plant
- Tubers are at least 2 inches in diameter
- 100 days have passed since planting
Do not wait too long. A hard frost can ruin the crop. If frost is forecast, harvest immediately, even if the tubers are small.
Extending The Season
You can push the limits of Colorado’s growing season with a few tricks. Use a cold frame or hoop house to protect plants in spring and fall. These structures trap heat and keep the soil warm.
Plant in containers that you can move indoors if needed. Large pots with drainage holes work well. Use a light potting mix and water regularly.
Using Row Covers
Row covers are lightweight fabric that lets light and water through. They add a few degrees of warmth. Use them in spring to plant earlier. Remove them when the weather is consistently warm.
In fall, row covers can protect against light frosts. This gives you extra time for the tubers to grow.
Common Mistakes To Avoid
Many Colorado gardeners make these errors. Avoid them for a better harvest:
- Planting too early – Cold soil kills slips
- Using too much nitrogen – Big vines, small tubers
- Overwatering – Causes rot and disease
- Harvesting too late – Frost damage ruins the crop
- Skipping curing – Sweet potatoes will not store well
Learn from these mistakes. Your first season may not be perfect, but each year you will improve.
Frequently Asked Questions
Can I plant sweet potatoes in Colorado in July?
It is possible but risky. July planting gives the tubers less time to mature. You may get small sweet potatoes. Stick to the late May to mid-June window for best results.
What is the best sweet potato variety for Colorado?
Beauregard and Georgia Jet are top choices. They mature in 90 days and tolerate cool soil. Both produce good yields in our climate.
Do I need to water sweet potatoes every day?
No. Water deeply once a week. Daily watering can lead to rot. Check the soil moisture with your finger. If it is dry 2 inches down, it is time to water.
Can I grow sweet potatoes in pots in Colorado?
Yes. Use a large pot with drainage holes. Fill it with loose potting mix. Place it in a sunny spot. Water regularly and fertilize lightly. Harvest when the vines die back.
How do I store sweet potatoes after harvest?
Cure them first for 10 to 14 days at 85°F and high humidity. Then store them in a cool, dark place at 55°F to 60°F. Do not refrigerate. Properly cured sweet potatoes last for months.
Final Thoughts
Growing sweet potatoes in Colorado is rewarding. The key is timing. Plant too early and you lose them. Plant too late and they do not mature. Stick to the late May to mid-June window. Use black plastic to warm the soil. Choose short-season varieties. With care, you can enjoy homegrown sweet potatoes from your Colorado garden.
Remember, the best time to plant sweet potato in colorado is when the soil is warm and the nights are mild. Check your local conditions and be patient. Your effort will pay off with a tasty harvest in the fall.