Colorado’s short growing season and cool nights require careful planning for amaranth to reach maturity. The best time to plant amaranth in Colorado is late spring, after the last frost has passed and soil temperatures have warmed to at least 60°F. This timing gives your amaranth the longest possible window to grow before the first fall frost arrives.
Amaranth is a warm-season crop that thrives in heat. In Colorado, the growing season can be as short as 90 days in some areas, but amaranth needs about 100 to 120 days to fully mature. That’s why nailing the planting window is so important.
In this guide, you’ll learn exactly when to plant, how to prepare your soil, and what to do if you’re running late in the season. We’ll cover everything from seed starting indoors to direct sowing in the garden.
Best Time To Plant Amaranth In Colorado
The ideal window for planting amaranth in Colorado is from mid-May to early June. This varies slightly depending on your specific location and elevation. Lower elevations like Denver and the Front Range can plant earlier, while mountain communities need to wait longer.
Here are the key factors that determine the perfect planting time:
- Last frost date: Wait until all danger of frost has passed
- Soil temperature: Must be at least 60°F at 2 inches deep
- Day length: Amaranth needs long days for best growth
- First fall frost: You need 100+ days before this date
For most of Colorado, the last frost falls between May 5 and May 20. In warmer areas like Pueblo, it can be as early as late April. In the mountains, it may not come until June.
Checking Your Local Frost Dates
You can find your area’s average last frost date online through the Colorado State University Extension website. Use this date as your starting point. Add about two weeks to be safe, then check the soil temperature.
To measure soil temperature, use a simple soil thermometer. Insert it 2 inches deep in the morning. If it reads 60°F or higher for three consecutive days, you’re good to go.
Why Timing Matters So Much
Amaranth is not frost-tolerant. A single late spring frost can kill young plants. On the other end, an early fall frost can ruin your harvest before the seeds fully mature. Colorado’s weather is unpredictable, so you need to plan carefully.
If you plant too early, your seeds may rot in cold soil. If you plant too late, you risk losing the crop to frost in autumn. The sweet spot is narrow but achievable.
Understanding Colorado’s Growing Zones
Colorado spans USDA hardiness zones 3 through 7. This means growing conditions vary widely across the state. Your planting time depends on which zone you’re in.
Here’s a quick breakdown by region:
- Denver and Front Range (Zone 5-6): Plant mid-May to early June
- Western Slope (Zone 6-7): Plant mid-May to late May
- Mountains and high valleys (Zone 3-4): Plant late May to mid-June
- Southeastern plains (Zone 6): Plant early to mid-May
If you live in a microclimate, like a warm south-facing slope, you can push these dates slightly earlier. Cold pockets near rivers or north-facing slopes need later planting.
Elevation Effects On Planting Time
Higher elevations mean cooler temperatures and shorter growing seasons. At 5,000 feet, you might have 120 frost-free days. At 8,000 feet, that drops to 90 days or less.
For amaranth, which needs 100+ days, high-elevation growers should consider starting seeds indoors. This gives you a head start of 4 to 6 weeks.
Starting Amaranth Seeds Indoors
Starting seeds indoors is a smart strategy for Colorado gardeners. It extends your growing season and protects young plants from late frosts. This is especially useful if you live in a short-season area.
Here’s how to do it step by step:
- Start seeds 4 to 6 weeks before your last frost date
- Use seed-starting mix in small pots or trays
- Plant seeds 1/4 inch deep, lightly covered
- Keep soil moist but not waterlogged
- Provide bright light, 14-16 hours per day
- Maintain temperatures around 70-75°F
Transplant seedlings outdoors after the last frost and when soil is warm. Harden them off by exposing them to outdoor conditions gradually over a week.
Hardening Off Your Seedlings
Hardening off is critical in Colorado’s dry, windy climate. Start by placing seedlings outside in a sheltered spot for a few hours each day. Increase time over 7 to 10 days. Protect them from strong wind and direct sun at first.
After hardening, transplant on a cloudy day or in the evening to reduce shock. Water well after planting.
Direct Sowing Amaranth Seeds
If you prefer to direct sow, wait until the soil is warm. In Colorado, this is usually late May or early June. Direct sowing is simpler but requires patience.
Steps for direct sowing:
- Prepare the soil by removing weeds and adding compost
- Sow seeds 1/4 inch deep, spacing them 6 inches apart
- Cover lightly with soil and water gently
- Thin seedlings to 12-18 inches apart once they are 4 inches tall
- Keep soil consistently moist until germination (7-14 days)
Direct-sown amaranth often grows stronger because it doesn’t suffer transplant shock. But it needs more time to mature, so timing is even more critical.
Using Row Covers For Early Planting
If you want to plant a bit earlier, use row covers or cloches. These protect young plants from light frost and help warm the soil. Remove them once temperatures are consistently warm.
Row covers can extend your season by 2 to 3 weeks. Just make sure to vent them on hot days to prevent overheating.
Soil Preparation For Amaranth
Amaranth grows best in well-drained soil with a pH between 6.0 and 7.5. Colorado soil is often alkaline, so you may need to amend it. Adding organic matter like compost helps balance pH and improve drainage.
Before planting, work 2 to 3 inches of compost into the top 6 inches of soil. This provides nutrients and improves water retention. Amaranth is not heavy feeder, but it benefits from rich soil.
If your soil is heavy clay, consider raised beds. They warm up faster in spring and drain better, which is ideal for amaranth.
Fertilizing For Best Growth
Amaranth doesn’t need much fertilizer. Too much nitrogen can cause lush leaves but poor seed production. Use a balanced fertilizer like 10-10-10 at planting time. Side-dress with compost mid-season if needed.
For organic growers, fish emulsion or seaweed extract works well. Apply every 3 to 4 weeks during the growing season.
Watering Amaranth In Colorado
Colorado is dry, so consistent watering is key. Amaranth is somewhat drought-tolerant once established, but young plants need regular moisture. Water deeply once or twice a week, depending on rainfall and temperature.
Drip irrigation is ideal because it delivers water to the roots without wetting the leaves. This reduces disease risk. Mulch around plants with straw or wood chips to conserve moisture and suppress weeds.
During hot spells, you may need to water more often. Check soil moisture by sticking your finger 2 inches into the soil. If it feels dry, it’s time to water.
Signs Of Overwatering
Yellowing leaves and wilting can indicate too much water. Amaranth doesn’t like soggy roots. If your soil stays wet, improve drainage or reduce watering frequency.
Companion Planting With Amaranth
Amaranth grows well with many vegetables. Good companions include corn, beans, squash, and peppers. It attracts beneficial insects and provides shade for tender plants.
Avoid planting amaranth near potatoes or fennel, as they may compete for nutrients. Also, keep it away from plants that need full sun if amaranth shades them.
In Colorado, amaranth can also serve as a windbreak for more delicate crops. Its tall stalks handle wind well.
Harvesting Amaranth
Amaranth is ready to harvest when the flower heads are full and the seeds start to fall off easily. This usually happens 100 to 120 days after planting. In Colorado, that means harvest time is late August to October.
To harvest, cut the flower heads and place them in a paper bag. Let them dry for a week or two. Then shake the bag to release the seeds. Winnow away the chaff by blowing gently or using a fan.
You can also harvest young leaves for salads or cooking. Pick them when they are tender, about 4 to 6 weeks after planting.
Storing Amaranth Seeds
Store dried seeds in an airtight container in a cool, dark place. They will keep for several years. For best quality, use within one year.
Common Problems And Solutions
Colorado gardeners face a few challenges with amaranth. Here are the most common issues and how to handle them:
- Frost damage: Use row covers or plant later
- Poor germination: Check soil temperature and moisture
- Stunted growth: Ensure adequate sunlight (6+ hours daily)
- Pests: Aphids and leaf miners can be controlled with neem oil
- Weeds: Mulch heavily to suppress competition
If you see yellow leaves, it could be a nitrogen deficiency. Apply a light dose of fertilizer. If leaves are brown at the edges, it might be wind burn or salt buildup from hard water.
Dealing With Colorado’s Wind
Wind can damage young amaranth plants. Use windbreaks like fences, shrubs, or tall crops. You can also stake individual plants if they get tall and top-heavy.
Varieties Of Amaranth For Colorado
Not all amaranth varieties are equal in Colorado’s climate. Choose ones that mature quickly and tolerate cooler nights. Here are some good options:
- Burgundy: 100 days, beautiful red heads
- Hopi Red Dye: 110 days, traditional variety
- Golden Giant: 120 days, high yields
- Love Lies Bleeding: 110 days, ornamental and edible
For short-season areas, stick with varieties that mature in 100 days or less. Check seed packets for days to maturity and choose accordingly.
Extending Your Growing Season
If you’re in a high-elevation area, you can extend the season with a few tricks. Use cold frames or hoop houses to protect plants in spring and fall. These structures trap heat and keep frost away.
Another option is to plant in containers that you can move indoors if frost threatens. This works well for a few plants but not for large crops.
You can also use black plastic mulch to warm the soil faster in spring. This can give you an extra week or two at the start of the season.
Succession Planting
For a continuous harvest, plant amaranth in two or three batches, spaced 2 weeks apart. This ensures you have fresh leaves all summer and seeds in fall. Just make sure the last batch has enough time to mature before frost.
Frequently Asked Questions
Can I plant amaranth in July in Colorado?
It’s risky. July planting gives you only 60-80 days before frost in most areas. Only try this with very fast-maturing varieties or if you have a protected location.
What is the soil temperature for amaranth germination?
Amaranth seeds germinate best when soil is between 65°F and 75°F. At 60°F, germination is slow. Below 55°F, seeds may rot.
Should I soak amaranth seeds before planting?
Soaking is not necessary. Amaranth seeds are small and germinate quickly in warm soil. Soaking can cause them to clump together.
How deep do I plant amaranth seeds?
Plant seeds 1/4 inch deep. They need light to germinate, so don’t bury them too deep. Just a light covering of soil is enough.
Can amaranth survive Colorado’s hail?
Young plants are vulnerable to hail. Use row covers or shade cloth if hail is forecast. Mature plants can recover from minor damage.
Final Tips For Success
Planting amaranth in Colorado is all about timing. Start indoors if you can, or wait for warm soil. Keep an eye on the weather and be ready to protect your plants from frost and wind.
With careful planning, you can enjoy a bountiful harvest of nutritious seeds and leaves. Amaranth is a rewarding crop that thrives with a little attention. Follow these guidelines, and you’ll be eating homegrown amaranth by late summer.
Remember to check your local extension office for specific advice for your area. They can provide frost dates and soil temperature data tailored to your location.
Good luck with your amaranth planting this season. With the right timing, you’ll have a successful crop even in Colorado’s challenging climate.