When to Plant Hyssop in Robertson County, TX
May to-do list for Robertson County, Texas
Here's what deserves your attention in Robertson County, Texas this month. Everything below is tailored to Zone 9a and timed around your local frost dates.
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Bring in the hyssop
Taste as you pick. The first ripe produce is the best feedback loop you'll get all season.
Looking ahead to June
- First harvests: hyssop
Hyssop is a semi-evergreen perennial herb with intense blue flower spikes that attract bees and butterflies. It has a minty, slightly bitter flavor used in liqueurs and teas.
Robertson County, Texas is in USDA Zone 9a. The average last spring frost is March 7 and the first fall frost is November 16, giving you a growing season of approximately 254 days.
At an elevation of 85 feet, Robertson County receives approximately 61.1 inches of rainfall annually with predominantly clay soil. Summer highs average 93°F, providing good warmth for Hyssop during the growing season. Clay soil retains moisture well for Hyssop, but amend with compost to improve drainage and prevent root rot. Ample rainfall means less supplemental watering, but ensure good drainage to prevent Hyssop root diseases.
Robertson County Soil Profile
Soil Type
Clay
Soil pH
6.8-8
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 Robertson County
How your county's soil matches Hyssop's growing requirements.
Soil pH
Your soil pH (6.8–8.0) is within Hyssop's preferred range (6.0–8.0).
Soil Texture
Heavy clay soil (45% clay) in Robertson County compacts easily and drains slowly. Amend with compost and avoid working soil when wet.
Organic Matter
Organic matter is moderate (3.4%). Annual compost additions will help Hyssop.
How to Plant Hyssop
Succession Planting Hyssop
Sow every 8 weeks. Last sowing by Aug 18 to harvest before frost.
Plant Water Budget
Water stress score is 6/10 — consider drought-tolerant varieties and mulching
Monthly Watering Guide for Hyssop
Hyssop 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 | Hyssop Needs | Rainfall | You Supplement | Action |
|---|---|---|---|---|
| Jan | — | 1.4" | 0" | ❄️ Dormant |
| Feb | — | 2.2" | 0" | ❄️ Dormant |
| Mar | 2.2" | 4.3" | 0" | ✅ Rainfall sufficient |
| Apr | 2.2" | 5.6" | 0" | ✅ Rainfall sufficient |
| May | 2.2" | 10" | 0" | ✅ Rainfall sufficient |
| Jun | 2.2" | 8.4" | 0" | ✅ Rainfall sufficient |
| Jul | 2.2" | 8.3" | 0" | ✅ Rainfall sufficient |
| Aug | 2.2" | 8.2" | 0" | ✅ Rainfall sufficient |
| Sep | 2.2" | 5.2" | 0" | ✅ Rainfall sufficient |
| Oct | 2.2" | 3.7" | 0" | ✅ Rainfall sufficient |
| Nov | 2.2" | 2.3" | 0" | ✅ Rainfall sufficient |
| Dec | — | 1.6" | 0" | ❄️ Dormant |
Water needs are for active growing months only (Mar–Nov in Robertson County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.
Hyssop 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.
Hyssop Planting Timeline — Robertson County, TX
Hyssop Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Transplant Outdoors | March 14 | Mar 14 – Mar 28 |
| Harvest | May 23 | May 23 – Jul 25 |
Plant 0.5" deep · 8" apart · Rows 12" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | Transplant Outdoors |
| April | — |
| May | Harvest |
| June | Harvest |
| July | Harvest |
| August | — |
| September | — |
| October | — |
| November | — |
| December | — |
Growing Conditions
☀️ Sun
Full Sun (6-8+ hours)
💧 Water
0.5"/week · Natural rainfall sufficient
📅 Days to Maturity
70–90 days
🧪 Soil pH
Needs 6–8 · Your soil: ideal
🗺️ USDA Zone
Zone 9a
📆 Growing Season
254 days in Robertson County
Growing Tips for Hyssop in Robertson County
Direct sow Hyssop outdoors after March 07 in Robertson County when soil has warmed and frost danger has passed.
With Robertson County's clay soil (45% clay), work in 3-4 inches of compost before planting Hyssop. Avoid tilling when soil is wet to prevent compaction.
General growing tips
Start seeds indoors or direct sow in spring. Prune back in early spring to encourage bushy growth. Hyssop is drought-tolerant once established and thrives in poor soil.
Companion Planting
Good Companions
Avoid Planting Near
Check more plant combinations with our Companion Planting Checker →
Hyssop in Other Locations
Frequently Asked Questions
When should I plant Hyssop in Robertson County, TX?
Robertson County is in Zone 9a with an average last frost of March 7. Plan your Hyssop planting based on this frost date — see the calendar above for exact timing.
What planting zone is Robertson County, TX?
Robertson County, Texas is in USDA Hardiness Zone 9a. The average last spring frost is March 7 and first fall frost is November 16.
Your Robertson County Garden Planner — Free
A 24-page printable planner built for Robertson County (Zone 9a). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.