When to Plant Lobelia in Clark County, NV
Your July game plan for Clark County, Nevada
Here's what deserves your attention in Clark County, Nevada this month. Everything below is tailored to Zone 9b and timed around your local frost dates.
Lobelia (Lobelia erinus) is a cool-season annual prized for the intense cobalt blue that is rare among bedding flowers. It blooms most prolifically in spring and early summer but stalls or dies back during heat peaks above 90°F. In zones 3–7 it delivers a long display; in zones 8–9 it is best treated as a spring annual that fades by midsummer. Trailing types cascade beautifully from containers and window boxes.
Clark County, Nevada is in USDA Zone 9b. The average last spring frost is February 28 and the first fall frost is November 23, giving you a growing season of approximately 268 days.
At an elevation of 2,811 feet, Clark County receives approximately 9.3 inches of rainfall annually with predominantly sandy loam soil. Summer highs average 111°F, so Lobelia may need afternoon shade and extra watering during peak heat. Sandy soil warms quickly in spring — great for early planting — but Lobelia will need more frequent watering and organic matter to retain nutrients. With low rainfall, drip irrigation is essential for growing Lobelia successfully. Mulch heavily to conserve soil moisture.
Clark County Soil Profile
Soil Type
Sandy Loam
Soil pH
7.3-8.4
Drainage
Well Drained
Lobelia 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.
Soil Compatibility in Clark County
How your county's soil matches Lobelia's growing requirements.
Soil pH
Your soil pH (7.3–8.4) is more alkaline than Lobelia prefers (6.0–7.0). Add sulfur or peat moss to lower pH.
Soil Texture
Sandy soil in Clark County warms quickly in spring but drains fast. Lobelia will need more frequent watering and regular compost additions to retain nutrients.
Drainage
Drainage is adequate for Lobelia.
Organic Matter
Organic matter is low (0.8%). Add 2-3 inches of compost before planting Lobelia.
How to Plant Lobelia
Succession Planting Lobelia
Sow every 8 weeks. Last sowing by Sep 04 to harvest before frost.
Lobelia Water Budget
Water stress score is 10/10 — consider drought-tolerant varieties and mulching
Monthly Watering Guide for Lobelia
Lobelia needs approximately 1 inches of water per week (4.3" per month). Here's how your county's rainfall compares month by month.
| Month | Lobelia Needs | Rainfall | You Supplement | Action |
|---|---|---|---|---|
| Jan | — | 0.7" | 0" | ❄️ Dormant |
| Feb | 4.3" | 0.6" | 3.7" | 🚿 Regular watering |
| Mar | 4.3" | 0.6" | 3.7" | 🚿 Regular watering |
| Apr | 4.3" | 0.3" | 4" | 🚿 Regular watering |
| May | 4.3" | 0.2" | 4.1" | 🚿 Regular watering |
| Jun | 4.3" | 0.3" | 4" | 🚿 Regular watering |
| Jul | 4.3" | 1.5" | 2.8" | 🚿 Regular watering |
| Aug | 4.3" | 1.9" | 2.4" | 🚿 Regular watering |
| Sep | 4.3" | 1.2" | 3.1" | 🚿 Regular watering |
| Oct | 4.3" | 0.9" | 3.4" | 🚿 Regular watering |
| Nov | 4.3" | 0.5" | 3.8" | 🚿 Regular watering |
| Dec | — | 0.7" | 0" | ❄️ Dormant |
Water needs are for active growing months only (Feb–Nov in Clark County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.
Lobelia 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.
Lobelia Planting Timeline — Clark County, NV
Lobelia Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | January 3 | Jan 3 – Jan 17 |
| Transplant Outdoors | December 27 | Dec 27 – Jan 10 |
| Bloom | February 21 | Feb 21 – Mar 21 |
· 6" apart · Rows 8" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | Start Indoors Transplant Outdoors |
| February | Bloom |
| March | Bloom |
| April | — |
| May | — |
| June | — |
| July | — |
| August | — |
| September | — |
| October | — |
| November | — |
| December | Transplant Outdoors |
Growing Conditions
☀️ Sun
Partial Shade (3-6 hours)
💧 Water
1"/week · 2-3 times/week
📅 Days to Maturity
70–80 days
🧪 Soil pH
Needs 6–7 · Your soil: too_alkaline
🗺️ USDA Zone
Zone 9b
📆 Growing Season
268 days in Clark County
Growing Tips for Lobelia in Clark County
Direct sow Lobelia outdoors after February 28 in Clark County when soil has warmed and frost danger has passed.
Sandy soil in Clark County dries quickly — mulch Lobelia with 2-3 inches of straw and water deeply 2-3 times per week rather than lightly every day.
With summer highs reaching 111°F in Clark County, provide afternoon shade for Lobelia and water deeply in the morning.
Clark County receives only 9" of rain annually. Lobelia needs consistent moisture — install drip irrigation or water deeply 2-3 times per week.
General growing tips
Start seeds indoors 10–12 weeks before last frost — seed is dust-fine and requires light to germinate; surface-sow and press gently. Keep at 65–70°F. Not reliably direct-sown. Transplant in cool weather, 2–4 weeks before last frost date is acceptable in zones 5+. Shear plants by one-third after the first bloom flush to encourage a second flush in fall. Provide afternoon shade in zones 7+ to extend bloom into summer.
Companion Planting
Good Companions
Check more plant combinations with our Companion Planting Checker →
Lobelia in Other Locations
Frequently Asked Questions
When should I plant Lobelia in Clark County, NV?
Clark County is in Zone 9b with an average last frost of February 28. Plan your Lobelia planting based on this frost date — see the calendar above for exact timing.
What planting zone is Clark County, NV?
Clark County, Nevada is in USDA Hardiness Zone 9b. The average last spring frost is February 28 and first fall frost is November 23.
Your Clark County Garden Planner — Free
A 22-page printable planner built for Clark County (Zone 9b). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.