When to Plant Spinach in Colorado (2026 Guide)
Planting spinach in Colorado can lead to a rewarding garden experience, as this cool-season green thrives in the state's unique climate. With its quick growth cycle of 40–50 days, spinach is perfect for early spring planting or for a fall harvest. For gardeners in Zone 5b, it's important to note that the median last spring frost date is May 5, while gardeners in Zone 5a should keep in mind a later date of May 17.
In Colorado, especially in areas like Denver and Colorado Springs, proper timing is crucial for spinach cultivation. Spinach can withstand light frosts, allowing it to be among the first vegetables sown in chilly soil. A smart approach is to directly sow the seeds as soon as the soil reaches 40°F, leading to a fruitful harvest when temperatures remain between 35–75°F.
As the summer heat approaches, spinach is highly susceptible to bolting. Therefore, the key is to plant again every 2-3 weeks to ensure a continuous harvest until late spring. By practicing careful succession planting throughout early spring and considering a fall sowing for a second crop, Colorado gardeners can enjoy fresh spinach right through October.
Planting Schedule by USDA Zone in Colorado
| Zone | Indoor start | Transplant out | Direct sow | Harvest |
|---|---|---|---|---|
| Zone 5b | Start March 10 – March 24, ~6–8 weeks before May 5 | Transplant outdoors April 10 – April 24, after frost risk | Direct sow March 24 – April 10 | Harvest May 20 – July 1 |
| Zone 5a | Start March 20 – April 3, ~6–8 weeks before May 17 | Transplant outdoors April 24 – May 8, after frost risk | Direct sow April 3 – April 24 | Harvest June 10 – July 20 |
| Zone 6a | Start March 1 – March 15, ~6–8 weeks before April 25 | Transplant outdoors April 10 – April 25, after frost risk | Direct sow March 15 – April 10 | Harvest May 25 – July 10 |
Spinach Planting Windows in Colorado
- Indoor start: Start seeds indoors from March 1 – March 20 to get a head start on the growing season.
- Transplant outdoors: Transplant seedlings outdoors from April 10 – April 25 to ensure they thrive in the cooler soil.
- Harvest: You can expect to start harvesting spinach from May 20 – July 10, depending on your planting dates.
Common Mistakes Growing Spinach in Colorado
- One common mistake for Colorado gardeners is planting spinach too late in the season. With temperatures often rising rapidly in late spring, a May planting may lead to bolting before a harvest can be enjoyed.
- Overwatering can be an issue in Colorado's arid climate. Although spinach requires consistent moisture, gardeners must be careful not to let the soil become waterlogged, which can lead to root rot and poor plant health.
- Many inexperienced gardeners in Colorado forget about the danger of late spring frosts. It's important to wait until after the May 17 last frost date in Zone 5a before planting spinach outdoors to avoid damage.
- Choosing varieties without considering heat tolerance is another frequent mistake. In Colorado, gardens can experience abrupt temperature changes, making it crucial to select bolt-resistant spinach cultivars to prolong harvest times.
- Failure to practice succession planting is a missed opportunity for continuous spinach harvest throughout the growing season. Without staggering sowings, many may find their harvest peaking all at once, leaving them overwhelmed.
Frequently Asked Questions
What if I'm in a cold pocket of Colorado?
If you're in a cold pocket, consider starting seeds indoors earlier or using row covers for outdoor sowings to mitigate frost risks. Adjust your planting dates according to local conditions to ensure successful germination and growth.
Can I still plant spinach in May?
While you can plant spinach in May, it's best to do so as early as possible within the month to avoid the heat that prompts bolting. If planting after mid-month, make sure to choose bolt-resistant varieties for a better chance at a harvest.
How often should I water my spinach?
Spinach requires consistent moisture but be careful not to overwater. Water deeply once a week, allowing the soil to dry slightly between waterings. This will promote stronger roots and healthier growth.
What are the best varieties of spinach for Colorado?
In Colorado, look for bolt-resistant varieties like 'Bloomsdale Long Standing' and 'Space'. These varieties are well-suited to withstand the fluctuations in temperature common to the region while providing a productive yield.
Is it possible to overwinter spinach in Colorado?
Yes, you can overwinter spinach in Colorado. If you plant in late fall, using row covers can protect the plants through winter, allowing you to harvest fresh leaves as soon as the weather warms in spring.
Keep Learning
City guides in Colorado
Other crops in Colorado
Typical fall sowing window for Spinach in Colorado: August 5 – August 26.