Celeriac · Mount Prospect, Illinois, United States
When to plant celeriac in Mount Prospect
Main outdoor window
10-31 May
A climate estimate. Check your soil, forecast and cultivar.
Timed from last spring frost
26 April
In Mount Prospect, on your chosen risk.
Ready to pick
28 Aug - 27 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 Mount Prospect
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
15 Feb - 8 Mar
Ten weeks before your last frost, under cover or on a windowsill.
Plant out
10-31 May
Two weeks after your last frost.
Harvest
28 Aug - 27 Sep
Celeriac through the year
Against the frost risk in Mount Prospect
Seasonal context
Rainfall and the growing season in Mount Prospect
May has the highest average precipitation (121 mm); January has the lowest (44 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 Mount Prospect
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 | -9.8°C (14.4°F)14.4°F (-9.8°C) | -1.5°C (29.3°F)29.3°F (-1.5°C) | 29.4 |
| February | -8.2°C (17.3°F)17.3°F (-8.2°C) | 1.1°C (33.9°F)33.9°F (1.1°C) | 26.6 |
| March | -2.4°C (27.6°F)27.6°F (-2.4°C) | 7.7°C (45.9°F)45.9°F (7.7°C) | 23.1 |
| April | 2.6°C (36.7°F)36.7°F (2.6°C) | 14.5°C (58.1°F)58.1°F (14.5°C) | 8.7 |
| May | 8.8°C (47.8°F)47.8°F (8.8°C) | 20.7°C (69.3°F)69.3°F (20.7°C) | 0.3 |
| June | 14.7°C (58.5°F)58.5°F (14.7°C) | 26.3°C (79.3°F)79.3°F (26.3°C) | 0.0 |
| July | 17.6°C (63.8°F)63.8°F (17.6°C) | 28.7°C (83.6°F)83.6°F (28.7°C) | 0.0 |
| August | 17.2°C (63°F)63°F (17.2°C) | 28.3°C (83°F)83°F (28.3°C) | 0.0 |
| September | 12.9°C (55.2°F)55.2°F (12.9°C) | 24.7°C (76.4°F)76.4°F (24.7°C) | 0.0 |
| October | 5.9°C (42.7°F)42.7°F (5.9°C) | 17°C (62.6°F)62.6°F (17°C) | 3.2 |
| November | -0.7°C (30.7°F)30.7°F (-0.7°C) | 8.4°C (47.2°F)47.2°F (8.4°C) | 18.0 |
| December | -6.3°C (20.6°F)20.6°F (-6.3°C) | 1.4°C (34.5°F)34.5°F (1.4°C) | 27.5 |
For celeriac, 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 celeriac for Mount Prospect
- May is the wettest month in the rainfall grid, averaging about 121 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 celeriac
Use the calendar to plan ahead, then check the conditions in your own garden.
- Measure the soil at sowing depth. Aim for at least 10°C (50°F); the calendar estimates soil warmth from air temperatures and cannot measure your bed.
- 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.
- Use the maturity range on your seed packet when choosing a variety. Cold, short days and transplant stress can make harvest later than the calendar estimate.
Keep the crown exposed and support uninterrupted swelling
Harden off transplants and delay moving them during unsuitable cold conditions. Plant with the crown at soil level rather than burying it, and keep moisture available through growth. Repeated drying can limit a useful crop.
Lift carefully with a fork when bases reach a usable size. Established plants can tolerate cool conditions, but frozen ground can make lifting difficult. Record actual size and kitchen quality rather than assuming the largest top growth means the largest base.
What to record this season
Did the exposed crown swell steadily, and were dry spells associated with smaller bases? Add the cultivar, sowing date and conditions to your growing record so you can compare next season.
Further reading: RHS celeriac growing guide . 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 RHS reference is written for UK growing conditions. Use its cultivation advice with local seasonal guidance; UK sowing months are not worldwide planting dates.
How the dates are calculated and their limits · Keep a growing record · Report a local discrepancy
Why these dates
Harden off transplants and delay moving them during unsuitable cold conditions. Plant with the crown at soil level rather than burying it, and keep moisture available through growth. Repeated drying can limit a useful crop.
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. Celeriac are timed from 10 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 Mount Prospect.
The median frost-free season here is 179 days, against 110 to 140 days to maturity for this crop counted from planting out. That margin is what decides whether a late sowing is worth attempting.
Nearby
Celeriac in places close by
Also in Mount Prospect
Other vegetables to time
Growing celeriac in Mount Prospect
Can I grow celeriac in Mount Prospect?
The calendar estimates a planting window, not a guarantee of success. May is the wettest month in the rainfall grid, averaging about 121 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 celeriac in Mount Prospect?
Aim for 10-31 May in an average year. If you would rather not gamble on the weather, wait until 26 May - 16 Jun - by then frost has finished in nine years out of ten.
When might celeriac be ready to harvest in Mount Prospect?
The estimated period is 28 Aug - 27 Sep, based on 110 to 140 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 celeriac 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.