Planting calendar
May Planting Guide for Denver, CO: Raised Beds, Containers & In-Ground
May is an ideal month to plant warm-season vegetables and flowers in Denver, CO. You can safely transplant tomatoes, peppers, and herbs outdoors while continuing to direct sow beans and squash in raised beds, containers, or in-ground gardens. Be mindful of late frosts early in the month and choose well-draining soil for containers.
Plant now (quick list)
Tomatoes, Peppers, Basil, Green beans, Zucchini, Cucumbers, Marigolds, Lettuce
Plant now
- Tomatoes
- Peppers
- Basil
- Green beans
- Zucchini
- Cucumbers
- Marigolds
- Lettuce
- Carrots
- Radishes
Start indoors
- Eggplants
- Melons
- Pumpkins
- Winter squash
- Herbs like dill and cilantro
- Broccoli (for late summer transplant)
- Cauliflower (for late summer transplant)
- Celery
- Parsley
- Chives
Avoid
- Frost-sensitive plants before mid-May
- Potatoes (best planted earlier in spring)
- Corn (wait for warmer soil)
- Beets (may bolt in heat)
- Peas (prefer cooler weather)
- Spinach (bolts quickly in heat)
- Brussels sprouts (best started earlier)
- Kale (better in cooler months)
- Cabbage (better earlier or later in season)
- Asparagus (harvest only, avoid planting)
Next 2 weeks
- Harden off indoor seedlings before transplanting
- Mulch around plants to retain moisture
- Monitor soil moisture closely in containers
- Start succession planting of beans and squash
- Watch for pests like aphids and caterpillars
- Fertilize tomatoes and peppers after transplant
- Thin seedlings of carrots and lettuce
- Stake tall plants like tomatoes early
- Water early in the day to reduce disease risk
- Remove any frost-damaged leaves promptly
FAQs
When is the last frost date for Denver, CO?
The average last frost date in Denver is around mid-May, but it can vary year to year, so monitor local forecasts closely.
Can I plant tomatoes directly in the ground in May?
Yes, after the risk of frost has passed, typically mid-May, tomatoes can be transplanted outdoors safely.
How often should I water container plants in May?
Containers usually need daily watering in May due to warmer temperatures and quicker soil drying.
What vegetables are best for raised beds in May?
Warm-season crops like beans, cucumbers, zucchini, and peppers do well in raised beds during May.
Should I fertilize my garden in May?
Yes, applying a balanced fertilizer when transplanting and again mid-season supports healthy growth.
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