When to Plant Sweet Potatoes in Knox County, TX
Your May gardening checklist
If you only do a handful of things in the garden this May, make it these. They're sequenced around your zone's frost timing.
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Get sweet potatoes seeds going inside
A seed-starting mix and a sunny window (or a grow light) are all you need. Keep soil warm — around 70°F — for fast germination.
Sweet potatoes are a warm-season root crop that produces nutritious, sweet tubers in orange, white, and purple varieties. They need a long, hot growing season.
Knox County, Texas is in USDA Zone 8a. The average last spring frost is March 24 and the first fall frost is November 12, giving you a growing season of approximately 233 days.
At an elevation of 1,847 feet, Knox County receives approximately 51.2 inches of rainfall annually with predominantly loam soil. Summer highs average 93°F, providing good warmth for Sweet Potatoes during the growing season. Ample rainfall means less supplemental watering, but ensure good drainage to prevent Sweet Potatoes root diseases.
Knox County Soil Profile
Soil Type
Loam
Soil pH
6.4-7.2
Drainage
Well Drained
Plant 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 Knox County
How your county's soil matches Sweet Potatoes's growing requirements.
Soil pH
Your soil pH (6.4–7.2) is more alkaline than Sweet Potatoes prefers (5.5–6.5). Add sulfur or peat moss to lower pH.
Soil Texture
The loam soil in Knox County is excellent for Sweet Potatoes — good drainage, moisture retention, and nutrient holding capacity.
Organic Matter
Organic matter is low (1.9%). Add 2-3 inches of compost before planting Sweet Potatoes.
How to Plant Sweet Potatoes
Plant Water Budget
Monthly Watering Guide for Sweet Potatoes
Sweet Potatoes needs approximately 1 inches of water per week (4.3" per month). Here's how your county's rainfall compares month by month.
| Month | Sweet Potatoes Needs | Rainfall | You Supplement | Action |
|---|---|---|---|---|
| Jan | — | 1.3" | 0" | ❄️ Dormant |
| Feb | — | 2.1" | 0" | ❄️ Dormant |
| Mar | 4.3" | 3.2" | 1.1" | 💧 Light watering |
| Apr | 4.3" | 6.4" | 0" | ✅ Rainfall sufficient |
| May | 4.3" | 6.7" | 0" | ✅ Rainfall sufficient |
| Jun | 4.3" | 7.3" | 0" | ✅ Rainfall sufficient |
| Jul | 4.3" | 6.5" | 0" | ✅ Rainfall sufficient |
| Aug | 4.3" | 5.9" | 0" | ✅ Rainfall sufficient |
| Sep | 4.3" | 5.4" | 0" | ✅ Rainfall sufficient |
| Oct | 4.3" | 3.3" | 1" | 💧 Light watering |
| Nov | 4.3" | 1.8" | 2.5" | 🚿 Regular watering |
| Dec | — | 1.3" | 0" | ❄️ Dormant |
Water needs are for active growing months only (Mar–Nov in Knox County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.
Sweet Potatoes 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.
Sweet Potatoes Planting Timeline — Knox County, TX
Sweet Potatoes Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | February 3 | Feb 3 – Feb 17 |
| Transplant Outdoors | April 7 | Apr 7 – Apr 21 |
| Direct Sow | March 31 | Mar 31 – Apr 21 |
| Harvest | July 7 | Jul 7 – Aug 25 |
Plant 1" deep · 15" apart · Rows 24" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | Start Indoors |
| March | Direct Sow |
| April | Transplant Outdoors Direct Sow |
| May | — |
| June | — |
| July | Harvest |
| August | Harvest |
| September | — |
| October | — |
| November | — |
| December | — |
Growing Conditions
☀️ Sun
Full Sun (6-8+ hours)
💧 Water
1"/week · Only during dry spells
📅 Days to Maturity
90–120 days
🧪 Soil pH
Needs 5.5–6.5 · Your soil: too_alkaline
🗺️ USDA Zone
Zone 8a
📆 Growing Season
233 days in Knox County
Growing Tips for Sweet Potatoes in Knox County
Direct sow Sweet Potatoes outdoors after March 24 in Knox County when soil has warmed and frost danger has passed.
General growing tips
Plant slips (rooted sprouts) after soil is thoroughly warm. Build raised mounds for better root development. Cure harvested roots at 80-85F for 10 days to develop sweetness.
Companion Planting
Good Companions
Avoid Planting Near
Check more plant combinations with our Companion Planting Checker →
Sweet Potatoes in Other Locations
Frequently Asked Questions
When should I plant Sweet Potatoes in Knox County, TX?
Knox County is in Zone 8a with an average last frost of March 24. Plan your Sweet Potatoes planting based on this frost date — see the calendar above for exact timing.
What planting zone is Knox County, TX?
Knox County, Texas is in USDA Hardiness Zone 8a. The average last spring frost is March 24 and first fall frost is November 12.
Your Knox County Garden Planner — Free
A 24-page printable planner built for Knox County (Zone 8a). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.