Planting calendar
March Planting Guide for Denver, CO: Raised Beds, Containers & In-Ground
In March, Denver gardeners can start planting cold-hardy vegetables and early flowers in raised beds, containers, and in-ground gardens. Focus on cool-season crops and begin indoor seed starting for warm-season plants to prepare for transplanting after the last frost.
Plant now (quick list)
spinach, kale, lettuce, peas, radishes, carrots, onions (sets or transplants), broccoli (transplants)
Plant now
- spinach
- kale
- lettuce
- peas
- radishes
- carrots
- onions (sets or transplants)
- broccoli (transplants)
- cauliflower (transplants)
- potatoes
Start indoors
- tomatoes
- peppers
- eggplants
- basil
- cucumbers
- melons
- pumpkins
- zucchini
- celery
- herbs like parsley and dill
Avoid
- beans (direct sowing)
- corn
- sweet potatoes
- warm-season flowers like marigolds
- tender tropical plants
- cucumbers (direct sowing)
- squash (direct sowing)
- tomatoes (outdoor planting)
- peppers (outdoor planting)
- eggplants (outdoor planting)
Next 2 weeks
- monitor soil temperature for planting warm-season crops
- harden off indoor seedlings before transplanting
- continue planting cold-hardy crops outdoors
- apply mulch to protect young plants from late frosts
- prepare garden beds by adding compost
- thin seedlings to prevent overcrowding
- start trellises for peas and vining crops
- check for pests and diseases regularly
- water newly planted seeds gently
- plan succession planting for continuous harvest
FAQs
When is the last frost date for Denver, CO?
The last frost typically occurs in late April to early May, so be cautious planting warm-season crops outdoors before then.
Can I plant tomatoes directly in March?
No, start tomatoes indoors in March and transplant them outdoors after the last frost to avoid cold damage.
What vegetables grow best in raised beds in March?
Cold-hardy vegetables like spinach, kale, lettuce, and peas thrive in raised beds during March.
How do I protect seedlings from late frosts?
Use row covers, cloches, or mulch to insulate seedlings and remove protections during the day for sunlight.
Is it okay to plant seeds directly in containers in March?
Yes, cold-tolerant seeds like radishes and lettuce can be sown directly in containers, but avoid warm-season seeds until temperatures rise.
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