What to plant this week in Calgary, AB
Calgary gardeners are in a critical push phase this week as the average last frost date of May 12 has passed, signaling it is finally safe to move heat-loving crops like basil and peppers into your raised beds. With night temperatures still dipping toward that -30°F winter low in early spring memories but currently warming up for a September 25th first frost window, you must maximize this short growing season by harvesting Brassicas and beans immediately before the chill returns. The local prairie wind is likely drying out soil fast, so prioritize mulching around your squash and melons to retain moisture while they race toward maturity.
The next 7 days
Calgary, ABGrowing in Calgary right now
- Apply a thick layer of straw or wood chip mulch immediately around watermelons, cantaloupes, and zucchini to combat the rapid evaporation caused by Calgary's dry prairie winds and hot afternoons.
- Take advantage of the current harvest window for garlic by planting cloves now in prepared soil to ensure they establish roots before any unexpected late spring snaps occur next year.
- Protect your Brussels sprouts and leeks from strong chinook winds this week, as the high-speed gusts common in the Calgary basin can strip foliage faster than pests can damage it.
- Avoid transplanting tender seedlings into cold, wet ground yet; instead, use this time to sow garlic or harden off any basil started indoors for that September 25th deadline.
Sow this week
1 crops- Garlic
Transplant this week
Nothing is due to go out this week.
Harvest soon
45 crops- Basil
- 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
- Ghost Pepper (Bhut Jolokia)
- Gourd (Ornamental/Bottle)
- Habanero Pepper
- Honeydew Melon
- Leek
- Lima Bean
- Lisianthus (Prairie Gentian)
- Loofah (Luffa)
- Nasturtium
- Ornamental Sweet Potato Vine
- Parsnip
- Pole Bean
- Potato
- Pumpkin
- 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
- Start planning succession planting schedules so that when your zucchini and squash are done, you can replant in their spots immediately.
- Prepare cold frames or row covers now to protect any tender seedlings from unexpected early frosts before May 12.
- Organize your transplanting tools and labels for the upcoming wave of peppers, beans, and melons that will be ready to move outdoors.
Pest & disease watch
- Watch closely for aphids on your newly transplanted peppers and tomatoes, as the warming Calgary air often triggers early outbreaks before natural predators fully emerge.
- Scout cucumber and squash plants for powdery mildew, a common fungal issue in our dry but humid nights that thrives when overhead watering wets the leaves during this late summer heat.
- Check the undersides of bean and pepper leaves for spider mites, which can explode in populations during the dry, windy spells typical of our September weather.
Watering this week
Water deeply in the morning to encourage deep root growth, especially for thirsty crops like cucumbers and pumpkins.
Garlic planted now will need consistent moisture during its establishment phase, so keep the soil evenly moist but not soggy.
Calgary gardening questions
3What is the latest I can plant garlic in Calgary to still get a harvest?
Since your average last frost date is May 12, this week is actually the ideal time to sow hardening-in garlic cloves so they establish roots before winter. Plant them about an inch deep and water well to ensure strong bulb development for next year's crop.
My zucchini and cantaloupe are growing fast but look dry; how do I keep them from cracking or rotting?
Calgary's intense sun and wind demand that you mulch heavily around the base of these heavy feeders to lock in soil moisture. Water deeply at the root zone rather than spraying foliage, as wet leaves combined with our windy nights invite powdery mildew.
Can I start harvesting Brussels sprouts now, or should I wait until after the first frost?
You can harvest smaller outer leaves from your Brussels sprouts right now, but the main heads will likely be too immature to eat well before that September 25th first frost date. For best flavor and size, plan to pull the mature heads just as temperatures drop, which actually sweetens them.
Other cities in zone 4a
2See the full zone 4a guide → · Plan your Calgary garden in SproutGuide →