When to Plant Portulaca in Calgary, AB
Portulaca (Portulaca grandiflora), commonly called moss rose, is a succulent- stemmed annual built for hot, dry, low-fertility conditions where other flowers fail. Its silky, rose-like blooms open in full sun and close at night or on cloudy days. Excellent for slopes, rock gardens, containers, and parking-strip plantings where irrigation is limited. One of the easiest annuals for neglect- proof summer color.
Calgary, Alberta is in USDA Zone 5a. The average last spring frost is May 7 and the first fall frost is October 14, giving you a growing season of approximately 160 days.
At an elevation of 3,428 feet, Calgary receives approximately 26.9 inches of rainfall annually with predominantly dark brown chernozem soil. Summer highs average 75°F, so choose short-season varieties of Portulaca to ensure they mature before fall.
Calgary Soil Profile
Soil Type
Dark Brown Chernozem
Soil pH
6.0-7.0
Drainage
Well Drained
Portulaca Planting Risk Windows
Percentages indicate frost risk at transplant. The 70% safe window means there is a 30% chance of frost after transplant — suitable for cold-hardy crops or gardeners with frost protection. The 90% safe window is best for tender plants.
How to Plant Portulaca
Portulaca Water Budget
Monthly Watering Guide for Portulaca
Portulaca needs approximately 0.5 inches of water per week (2.2" per month). Here's how your county's rainfall compares month by month.
| Month | Portulaca Needs | Rainfall | You Supplement | Action |
|---|---|---|---|---|
| Jan | — | 1.1" | 0" | ❄️ Dormant |
| Feb | — | 1.2" | 0" | ❄️ Dormant |
| Mar | — | 2.1" | 0" | ❄️ Dormant |
| Apr | — | 2.5" | 0" | ❄️ Dormant |
| May | 2.2" | 3.3" | 0" | ✅ Rainfall sufficient |
| Jun | 2.2" | 3.3" | 0" | ✅ Rainfall sufficient |
| Jul | 2.2" | 3.1" | 0" | ✅ Rainfall sufficient |
| Aug | 2.2" | 2.9" | 0" | ✅ Rainfall sufficient |
| Sep | 2.2" | 2.1" | 0.1" | 💧 Light watering |
| Oct | 2.2" | 2" | 0.2" | 💧 Light watering |
| Nov | — | 1.9" | 0" | ❄️ Dormant |
| Dec | — | 1.4" | 0" | ❄️ Dormant |
Water needs are for active growing months only (May–Oct in Calgary). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.
Portulaca Heat Requirements (GDD)
What are Growing Degree Days (GDD)?
Growing Degree Days measure the total warmth your plants receive during the growing season. Think of it as a "heat bank" — every day above 50°F deposits warmth that helps your plants grow.
Each plant needs a certain amount of accumulated heat to mature. If your county provides more GDD than the plant needs, it's a great fit. If it's close, you may want to choose faster-maturing varieties or start seeds indoors to get a head start.
Portulaca Planting Timeline — Calgary, AB
Portulaca Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | April 2 | Apr 2 – Apr 16 |
| Transplant Outdoors | May 21 | May 21 – Jun 4 |
| Direct Sow | May 21 | May 21 – Jun 11 |
| Bloom | July 9 | Jul 9 – Oct 8 |
· 8" apart · Rows 10" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | — |
| April | Start Indoors |
| May | Transplant Outdoors Direct Sow |
| June | Transplant Outdoors Direct Sow |
| July | Bloom |
| August | Bloom |
| September | Bloom |
| October | Bloom |
| November | — |
| December | — |
Growing Conditions
☀️ Sun
Full Sun (6-8+ hours)
💧 Water
0.5"/week · Natural rainfall sufficient
📅 Days to Maturity
50–70 days
🧪 Soil pH
Needs 5.5–7 · Your soil: N/A
🗺️ USDA Zone
Zone 5a
📆 Growing Season
160 days in Calgary
Growing Tips for Calgary
Direct-sow after last frost once soil warms to 65°F, or start indoors 4–6 weeks before last frost. Seed is tiny — surface sow and do not cover. Thin to proper spacing after germination. Thrives in poor, well-drained soil; rich or wet soil produces lush foliage but fewer blooms. No deadheading required — plants are self-cleaning. Double-flowered varieties hold blooms open longer in overcast conditions.
Companion Planting
Good Companions
Check more plant combinations with our Companion Planting Checker →
Portulaca in Other Locations
Frequently Asked Questions
When should I plant Portulaca in Calgary, AB?
Calgary is in Zone 5a with an average last frost of May 7. Plan your Portulaca planting based on this frost date — see the calendar above for exact timing.
What planting zone is Calgary, AB?
Calgary, Alberta is in USDA Hardiness Zone 5a. The average last spring frost is May 7 and first fall frost is October 14.
Your Calgary Garden Planner — Free
A 22-page printable planner built for Calgary (Zone 5a). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.