When to Plant Lobelia in Franklin County, TX
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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.
Franklin County, Texas is in USDA Zone 8b. The average last spring frost is March 18 and the first fall frost is November 11, giving you a growing season of approximately 238 days.
At an elevation of 324 feet, Franklin County receives approximately 60 inches of rainfall annually with predominantly sandy loam soil. Summer highs average 97°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. Ample rainfall means less supplemental watering, but ensure good drainage to prevent Lobelia root diseases.
Franklin County Soil Profile
Soil Type
Sandy Loam
Soil pH
5.4-6.3
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 Franklin County
How your county's soil matches Lobelia's growing requirements.
Soil pH
Your soil pH (5.4–6.3) is more acidic than Lobelia prefers (6.0–7.0). Add garden lime to raise pH.
Soil Texture
Sandy soil in Franklin 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 moderate (2.0%). Annual compost additions will help Lobelia.
How to Plant Lobelia
Succession Planting Lobelia
Sow every 8 weeks. Last sowing by Aug 23 to harvest before frost.
Lobelia Water Budget
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 | — | 1.5" | 0" | ❄️ Dormant |
| Feb | — | 1.9" | 0" | ❄️ Dormant |
| Mar | 4.3" | 4.1" | 0.2" | 💧 Light watering |
| Apr | 4.3" | 5.6" | 0" | ✅ Rainfall sufficient |
| May | 4.3" | 7.9" | 0" | ✅ Rainfall sufficient |
| Jun | 4.3" | 9.9" | 0" | ✅ Rainfall sufficient |
| Jul | 4.3" | 8.3" | 0" | ✅ Rainfall sufficient |
| Aug | 4.3" | 7.1" | 0" | ✅ Rainfall sufficient |
| Sep | 4.3" | 6" | 0" | ✅ Rainfall sufficient |
| Oct | 4.3" | 3.9" | 0.4" | 💧 Light watering |
| Nov | 4.3" | 2.3" | 2" | 💧 Light watering |
| Dec | — | 1.6" | 0" | ❄️ Dormant |
Water needs are for active growing months only (Mar–Nov in Franklin 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 — Franklin County, TX
Lobelia Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | January 21 | Jan 21 – Feb 4 |
| Transplant Outdoors | February 4 | Feb 4 – Feb 18 |
| Bloom | April 1 | Apr 1 – May 13 |
· 6" apart · Rows 8" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | Start Indoors |
| February | Start Indoors Transplant Outdoors |
| March | — |
| April | Bloom |
| May | Bloom |
| June | — |
| July | — |
| August | — |
| September | — |
| October | — |
| November | — |
| December | — |
Growing Conditions
☀️ Sun
Partial Shade (3-6 hours)
💧 Water
1"/week · Only during dry spells
📅 Days to Maturity
70–80 days
🧪 Soil pH
Needs 6–7 · Your soil: too_acidic
🗺️ USDA Zone
Zone 8b
📆 Growing Season
238 days in Franklin County
Growing Tips for Lobelia in Franklin County
Direct sow Lobelia outdoors after March 18 in Franklin County when soil has warmed and frost danger has passed.
Sandy soil in Franklin 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 97°F in Franklin County, provide afternoon shade for Lobelia and water deeply in the morning.
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 Franklin County, TX?
Franklin County is in Zone 8b with an average last frost of March 18. Plan your Lobelia planting based on this frost date — see the calendar above for exact timing.
What planting zone is Franklin County, TX?
Franklin County, Texas is in USDA Hardiness Zone 8b. The average last spring frost is March 18 and first fall frost is November 11.
Your Franklin County Garden Planner — Free
A 22-page printable planner built for Franklin County (Zone 8b). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.