Hyssop · Evanston, Illinois, United States
When to plant hyssop in Evanston
Main outdoor window
18 Apr - 16 May
A climate estimate. Check your soil, forecast and cultivar.
Timed from last spring frost
4 April
In Evanston, on your chosen risk.
Ready to pick
1 Jun - 30 Sep
If you plant at the start of the window.
The average last frost. Half of all years are later than this.
Step by step in Evanston
Download these planting dates (.ics)
Import into Apple Calendar, Google Calendar or Outlook. Dates use the selected risk level and are planning estimates, not frost alerts.
Each window is a planning range. Check the forecast, soil and cultivar before planting; a later date is not automatically safer in hot or wet conditions.
Start indoors
7 Feb - 7 Mar
Eight weeks before your last frost, under cover or on a windowsill.
Plant out
18 Apr - 16 May
Two weeks after your last frost.
Harvest
1 Jun - 30 Sep
Hyssop through the year
Against the frost risk in Evanston
Seasonal context
Rainfall and the growing season in Evanston
May has the highest average precipitation (119 mm); January has the lowest (47 mm). Compare this pattern with the planting windows and your water supply.
During wetter months, check that beds and containers drain after heavy rain. During drier months, plan how you will keep seeds and new transplants watered. Monthly averages can hide long dry spells and intense storms; they do not show soil moisture, humidity or this week's weather.
Source: NASA POWER, corrected MERRA-2 precipitation, 2001–2020. Values are approximate monthly totals, including the water equivalent of snow, from the nearest 0.5° × 0.625° grid cell. This reference period differs from the temperature record. Rainfall provides context and does not change the calculated planting dates. Method and limitations.
Monthly growing conditions in Evanston
Compare the planting window with the local temperature pattern. These are historical monthly averages, not this year's forecast or measured soil temperatures. Average frost days do not tell you whether a particular night will freeze.
| Month | Average low | Average high | Frost days |
|---|---|---|---|
| January | -4.9°C (23.2°F)23.2°F (-4.9°C) | -0.2°C (31.7°F)31.7°F (-0.2°C) | 25.7 |
| February | -4.5°C (24°F)24°F (-4.5°C) | 0.8°C (33.5°F)33.5°F (0.8°C) | 23.6 |
| March | -0.5°C (31°F)31°F (-0.5°C) | 5.1°C (41.2°F)41.2°F (5.1°C) | 16.9 |
| April | 3.8°C (38.8°F)38.8°F (3.8°C) | 10°C (50°F)50°F (10°C) | 2.7 |
| May | 8.8°C (47.8°F)47.8°F (8.8°C) | 15.2°C (59.3°F)59.3°F (15.2°C) | 0.0 |
| June | 15.1°C (59.1°F)59.1°F (15.1°C) | 21.1°C (70°F)70°F (21.1°C) | 0.0 |
| July | 19.6°C (67.3°F)67.3°F (19.6°C) | 24.9°C (76.8°F)76.8°F (24.9°C) | 0.0 |
| August | 20°C (68.1°F)68.1°F (20°C) | 25.1°C (77.1°F)77.1°F (25.1°C) | 0.0 |
| September | 16.4°C (61.5°F)61.5°F (16.4°C) | 22°C (71.6°F)71.6°F (22°C) | 0.0 |
| October | 9.9°C (49.7°F)49.7°F (9.9°C) | 15.6°C (60°F)60°F (15.6°C) | 0.0 |
| November | 3.4°C (38.2°F)38.2°F (3.4°C) | 8.5°C (47.3°F)47.3°F (8.5°C) | 5.5 |
| December | -1.8°C (28.9°F)28.9°F (-1.8°C) | 2.7°C (36.8°F)36.8°F (2.7°C) | 18.4 |
For hyssop, also check drainage, sunlight and cultivar requirements. See the rainfall context above; humidity, irrigation and local pest pressure are not calculated.
Local growing check
Before choosing hyssop for Evanston
- May is the wettest month in the rainfall grid, averaging about 119 mm. Check how your own bed drains and plan watering around actual soil moisture; monthly rain totals are not an irrigation schedule.
The temperature and rainfall tables on this page show the underlying climate estimates. How these suitability checks work · Record what happens in your garden.
Before you plant hyssop
Use the calendar to plan ahead, then check the conditions in your own garden.
- Frost tolerance does not make saturated or frozen soil suitable for planting. Wait until the bed can be worked without smearing or compacting it.
- Harden off plants raised indoors: gradually expose them to outdoor light, wind and temperature before their final move into the bed.
- Check mature size, drainage and cultivar suitability before choosing a permanent position. A suitable planting window does not guarantee long-term survival or fruiting.
Build a small branching shrub rather than a crowded herb patch
Use drained soil and suitable light; some shelter from intense afternoon sun can help in hot conditions. Allow for its mature spread so neighbouring plants do not keep the base shaded and damp.
Trim living growth to encourage a bushier shape and remove damaged stems. Seed, cuttings or division can establish replacements, but retain the species label because similar common names cover different plants. Leave part of the plant uncut when flowers are the priority.
What to record this season
Did trimming create a sturdier shape without sacrificing the flowering display you wanted? Add the cultivar, sowing date and conditions to your growing record so you can compare next season.
Further reading: NC State Extension: Hyssopus officinalis . General crop guidance; local dates on this site are calculated separately. Source checked 19 September 2026 by Safe to Plant; this is not an expert review.
The reference describes plant identity and cultivation. Its regional calendar months and hardiness observations do not validate the calculated dates for another location.
How the dates are calculated and their limits · Keep a growing record · Report a local discrepancy
Why these dates
Use drained soil and suitable light; some shelter from intense afternoon sun can help in hot conditions. Allow for its mature spread so neighbouring plants do not keep the base shaded and damp.
Check the named variety and local forecast before exposing young growth. The catalog cold-damage figure is a reference, not a guarantee: plant age, acclimatisation, wind and the duration of a freeze affect damage.
This calendar uses frost-relative offsets as a starting point. Hyssop are timed from 8 weeks before that frost for an indoor start, with planting out 2 weeks after it, and this page simply resolves those offsets against the frost date computed for Evanston.
Evanston is zone 7a, within the crop's general range. This is an initial cold-hardiness check; cultivar, exposure, drainage and unusual winters can still change the outcome.
The general establishment guide is around year 1, under suitable conditions. This is not a prediction for this location; cultivar, winter conditions and care determine whether it crops reliably.
Growing hyssop in Evanston
Can I grow hyssop in Evanston?
The calendar estimates a planting window, not a guarantee of success. May is the wettest month in the rainfall grid, averaging about 119 mm. Check how your own bed drains and plan watering around actual soil moisture; monthly rain totals are not an irrigation schedule.
When should I plant hyssop in Evanston?
Aim for 18 Apr - 16 May in an average year. If you would rather not gamble on the weather, wait until 1-29 May - by then frost has finished in nine years out of ten.
When might hyssop be ready to harvest in Evanston?
The estimated period is 1 Jun - 30 Sep, based on 90 to 110 days from the modeled planting date. Cultivar, planting material and growing conditions can change this interval; check the plant as well as the calendar.
How much frost will hyssop tolerate?
Check the named variety and local forecast before exposing young growth. The catalog cold-damage figure is a reference, not a guarantee: plant age, acclimatisation, wind and the duration of a freeze affect damage.