What to plant this week in Calgary, AB
Calgary gardeners are in a unique race against the clock this week, with the average last frost still lingering until May 12. While you can finally start your garlic indoors or outdoors, the window to harvest summer crops like beefsteak tomatoes and watermelons is closing fast before the Sep 25 frost hits.
The next 7 days
Calgary, ABGrowing in Calgary right now
- Protect young spring transplants from late April snow squalls with floating row covers, as Calgary's unpredictable weather often sends cold snaps well past the official May average.
- Take advantage of the dry prairie soil by planting your harvest-ready squash and cucumbers now; their deep roots need immediate moisture retention before summer heat sets in.
- Avoid heavy fertilizing on potatoes and beans this week to prevent rapid, tender growth that could be damaged by sudden temperature fluctuations common in Calgary's spring.
- Use the mild weather to finish harvesting basil and zinnias from your containers or greenhouse benches while they are still lush and green.
Sow this week
1 crops- Garlic
Transplant this week
Nothing is due to go out this week.
Harvest soon
46 crops- Basil
- Beefsteak Tomato
- Bell Pepper
- Borage
- Brussels Sprouts
- Bush Bean
- Cantaloupe
- Celery
- Cleome (Spider Flower)
- Cosmos
- Cowpea (Black-Eyed Pea)
- Cucumber
- Dahlia
- Edamame
- Fennel
- Flour Corn
- French Marigold
- Garden Verbena
- Garlic
- Habanero Pepper
- Honeydew Melon
- Jalapeño
- Leek
- Lima Bean
- Loofah (Luffa)
- Marconi Pepper
- Nasturtium
- Ornamental Sweet Potato Vine
- Parsnip
- Pole Bean
- Potato
- Pumpkin
- Rutabaga
- Scarlet Runner Bean
- Shiso (Japanese Basil)
- Summer Savory
- Sunflower
- Sweet Corn
- Thai Basil
- Tomatillo
- Vinca (Madagascar Periwinkle)
- Watermelon
- Winter Squash
- Yellow Summer Squash
- Zinnia
- Zucchini
Seasonal tips
- Mulch around potatoes and squash to retain moisture as summer heat peaks.
- Deadhead Cosmos and Zinnias regularly to encourage more blooms throughout the season.
- Space newly harvested Brassicas like Brussels Sprouts carefully to allow room for final growth.
Pest & disease watch
- Spider mites may appear on sunflowers and beans as the dry, warm winds pick up speed across the plains this week.
- Watch for aphids clustering on the new growth of nasturtiums and marigolds, especially if plants are crowded in sunny spots.
- Slugs can still be active late at night on tender leaves of shiso and petunias before the soil fully warms.
Watering this week
Water deeply at the base of large crops like pumpkins and squash in the early morning to reduce evaporation.
Now is an excellent time to start planning your garlic planting schedule for next fall, as it requires cool soil to establish roots before winter.
Calgary gardening questions
3Can I plant my zucchini seeds directly outside right now?
Yes, Calgary's warm days allow you to sow zucchini and summer squash directly after the last frost risk has passed for early-maturing varieties. Ensure the soil is workable and not waterlogged before digging.
How do I extend the harvest window for my basil before the first fall freeze?
Since our average first frost hits around September 25, cut your basil back twice during summer to encourage bushier growth that survives longer into October. You can also start a new batch indoors now if you want fresh leaves after the final frost.
Is this the right time to plant potatoes in Calgary?
Yes, potatoes are listed as harvest-soon, meaning established tubers are ready or nearly ready depending on your planting date. If you haven't planted them yet, start immediately with seed pieces that have 'eyes' facing up.
Other cities in zone 4a
2See the full zone 4a guide → · Plan your Calgary garden in SproutGuide →