These dates are drawn from 30-year averages for Story County, verified against the NOAA National Centers for Environmental Information. Plant outside this window, and the frost takes the seed. Plant inside, and the soil yields.
+
+
+
+
+
Winter turnip (Brassica rapa subsp. rapa) — the first green to break the crust.
+
+
+
Spring Sowing
+
+
+
Turnip (White Globe)
+
Sow IndoorsMar 1–15
+
Transplant OutApr 26 – May 5
+
ThinMay 12
+
HarvestJul 20 – Aug 10
+
Notes: Roots require loose soil. Compact clay = forked taproots. Cover with row fabric until June 15.
I built the cellar under the north root of the house in 2003, when the old Johnson place flooded out for the third year running. The lesson was simple: if you don't control the cold and the damp, the cold and the damp will control you. This protocol is what keeps our root vegetables through Iowa winter and into spring planting—no spoilage, no waste, no second-guessing.
+
+
A root cellar is an underground or partially underground cool store. The principle is old as the hills but the specifics matter. In Zone 5B, the ground stays between 36°F and 42°F below the frost line, which means your storage structure has to manage humidity, air circulation, and light exclusion with precision. Food preservation in this environment relies on inhibiting microbial growth through controlled temperature and moisture—not magic, just physics.
+
+
+
+ CELLAR INTERIOR — STONE WALLS, WOODEN RACKS, ZONE 5B STORAGE
+
+
+
I. ENVIRONMENTAL PARAMETERS
+
+
+
+
+
PARAMETER
+
TARGET
+
ACCEPTABLE RANGE
+
FAILURE MODE
+
+
+
+
+
Temperature
+
38°F (3.3°C)
+
32–45°F (0–7°C)
+
Freeze damage below 32°F; sprouting and rot above 45°F
The Freeze-Thaw Loop: In late fall (November) and early spring (March-April), our region swings through 32°F multiple times in a single week. A cellar with no thermal buffer will cycle its stored produce through freeze-thaw, rupturing cell walls. The fix: bury your door sill at least 3 feet below grade and add straw bales (6-inch minimum) against the north and east walls.
+
+
+
II. STORAGE ASSIGNMENTS
+
+
Not everything goes in the same bin. Here's how I sort, based on ethylene sensitivity, moisture needs, and seasonal decay rates:
Never store with apples—ethylene accelerates sprouting
+
+
+
Carrots (Danvers Half Long, Scarlet Nantes)
+
4–5 months
+
32–36°F
+
Buried in damp sand in wooden bins
+
Remove tops within 24 hours of harvest; they draw moisture from roots
+
+
+
Beets (Detroit Dark Red, Chioggia)
+
3–4 months
+
32–36°F
+
Damp sand or peat moss
+
Same bin as carrots works fine
+
+
+
Onions (walla walla type, storage yellow)
+
4–6 months
+
35–40°F
+
Hung in mesh bags or braided; 65-75% humidity
+
Lower humidity than roots. Separate shelving. High humidity causes rot.
+
+
+
Apples (Honeycrisp, Northern Spy, Arkansas Black)
+
5–8 months
+
30–32°F
+
Single layer on wax paper between boards
+
Arkansas Black is the keeper—lasts until May in our climate. Ethylene producer: isolate from other crops.
+
+
+
Squash (butternut, delicata, acorn)
+
2–5 months
+
50–55°F
+
Upper shelf, away from cold zone
+
Requires curing at 80°F for 10 days before storage. Too cold causes rot.
+
+
+
Turnips, Rutabaga
+
3–4 months
+
32–40°F
+
Damp sand, lower rack
+
Rutabaga outlasts turnips by a month in our cellar
+
+
+
Cabbage (Savoy, Red Russian)
+
2–3 months
+
32–36°F
+
Hung by roots or wrapped in kraft paper
+
Check weekly for slugs—they hide between the layers
+
+
+
Pumpkins (pie varieties: Libby's II, Betty Crocker)
+
1–2 months
+
50–55°F
+
Upper shelf, spaced apart
+
Like squash, needs curing. Don't stack.
+
+
+
+
+
III. WEEKLY INSPECTION PROTOCOL
+
+
Every Monday, before the office opens, I walk the cellar. This takes twelve minutes. Do not skip it.
+
+
+
Check the thermometer and hygrometer at eye level on the east wall. Record readings in the ledger.
+
Open the upper vent if humidity reads above 95%; open the lower vent if temperature reads above 45°F.
+
Run hands through every bin—feel for soft spots. One rotten potato takes three with it.
+
Check onion bags for sprouting or dry-rot. Remove any specimen showing gray discoloration immediately.
+
Inspect squash for white mold patches. Wipe with a cloth dampened in diluted vinegar (1:4 ratio), do not use water alone.
+
Check door seal. The gasket fails in winter and lets in the wind—this is the most common cause of unexpected freeze damage.
+
Look for rodents. The trap on the west corner checks itself; reset if triggered.
+
Rotate front-to-back in each bin so older stock comes forward first.
+
+
+
+ Barbara's rule: If you wouldn't serve it at a potluck, it doesn't belong in the cellar. Pull it, compost it, and note the failure in the ledger. Pride of place matters—our neighbors eat what we share.
+
+
+
IV. SEASONAL TRANSITIONS
+
+
October–November: Stocking Season
+
Bring produce down on dry days only. Wet produce carries field bacteria that accelerate spoilage. Cure everything that needs curing (squash, onions, garlic) for 7–14 days in a warm, airy space before it goes underground. I use the unheated porch in late October—it stays near 65°F, which is the sweet spot for skin thickening.
+
+
December–February: Hold
+
Minimum intervention. Check once every two weeks. The ground is stable. Keep the door gasket inspected. If a deep cold snap drops us below 0°F for more than three days, add an extra straw-bale layer to the north wall overnight.
+
+
March–April: Thinning Out
+
This is the danger period. The ground warms in fits and starts. Temperature swings of 10°F in a single day are common. Inspect weekly. Begin consuming the shortest-lived crops first (turnips, cabbage). By late April, the cellar should be clearing out.
+
+
May–September: Deep Clean
+
Strip the shelves. Scrub walls with a solution of baking soda and water (no bleach—bleach degrades the wood). Replace sand in root bins. Re-braid rope for onion hanging. Patch any cracks in the foundation with hydraulic cement. Air it out completely before next year's stock arrives.
+
+
V. COMMON FAILURE MODES
+
+
+
+
+
SYMPTOM
+
LIKELY CAUSE
+
CORRECTION
+
+
+
+
+
Potatoes turning green
+
Light exposure through cracks or door gap
+
Seal all light sources. Cover bins with black plastic sheeting. Remove green potatoes—solanine is toxic in quantity.
+
+
+
Rapid sprouting of carrots
+
Temperature above 40°F; tops not removed before storage
+
Lower temperature by opening lower vent. Always remove tops within 24 hours of harvest.
+
+
+
Mold on squash
+
Insufficient curing before storage; excess humidity
+
Improve curing protocol (80°F, 10 days). Wipe mold with vinegar solution. Move affected squash to a drier shelf.
+
+
+
Shriveling in roots
+
Humidity below 85%
+
Sprinkle water on the dirt floor. Add a bucket of water in the corner. Check that vent openings aren't too large.
+
+
+
Frozen produce
+
Temperature dropped below 32°F; likely door seal failure
+
Remove and thaw affected produce. Fix the door gasket. Add insulation. Note the event in the ledger.
+
+
+
Onion rot
+
Humidity too high for onions (they need 65–75%, not 90%)
+
Move onions to a separate, drier shelf zone. Hang in mesh bags for maximum airflow around each bulb.
+
+
+
+
+
+
⚠ THE ONE RULE
+
If the cellar gets above 50°F for more than 48 hours in the middle of winter, something is wrong. Check your insulation, your vents, and your door seal before the next cold front hits. The ground will not forgive a lazy spring.
+
+
+
+
RELATED WORK IN THE TOWN
+
Aisha Henry's essay "The Ground Beneath the Foundation" explores the covenant between land and family in Georgia—different red clay, same principle: you steward what the ground gives you.
The frost date in Story County falls on October 15th, give or take three days depending on the chinook winds off the Missouri. This guide does not teach hope. It teaches timing.
-
Each section below names a root crop that survives the freeze, lists the exact window for sowing, and marks the depth at which the taproot finds shelter. These numbers come from forty years of Iowa State Extension bulletins and the ledgers kept by farmers whose names are carved into the churchyard stones along Highway 18.
+
+
PREFACE
+
This is not a suggestion. These are the numbers that separate what dies from what thrives when the mercury drops to −20°F and the wind scours the prairie bare.
-
-
WINTER TURNIP (Brassica rapa var. rapa)
-
-
+
+
+
The pergola stands through January. Its timber was seasoned for this.
+
-
-
PLANTING WINDOW
-
August 10 – September 5
-
-
SOIL TEMP AT SOW
-
14–18°C (57–64°F)
-
-
ROOT DEPTH
-
25–35 cm below surface
-
-
FROST TOLERANCE
-
−8°C crown survival
-
-
DAYS TO HARVEST
-
55–65 days
-
-
CROWD SPACING
-
15 cm between plants
+
+
CROP 01: TURNIP (Brassica rapa subsp. rapa)
+
Species authority: Wikidata Q3916957 | Natural product of Brassica rapa subsp. rapa
Lift before the first hard freeze (−12°C). Store in sand at 0°C with 95% humidity. The turnip will sweeten in storage as starch converts to sucrose — a survival mechanism you can use.
+
+
+
+ PLANTING WINDOW
+ AUG 15 – SEP 5
+
+
+ DAYS TO MATURITY
+ 56–62
+
+
+ HARVEST BEFORE
+ OCT 15
+
+
+ SOIL TEMP MINIMUM
+ 35°F
+
+
+ OVERWINTER DEPTH
+ 18"
+
+
+
+
+ SUCROSE ACCUMULATION
+ 18–22%
+
+
+ FROST TOLERANCE
+ −10°F (bare)
+
+
+ SNOW COVER REQ
+ ≥6"
+
+
+ SPRING RECOVERY
+ 21 days
+
+
+
+
+
+ CRITICAL FAILURE MODE: Planting after September 10 yields insufficient sucrose accumulation. Root dies at −5°F without protective mulch.
+
+
+
+ SURVIVABLE CONDITION: 18" soil burial + ≥6" snow cover maintains root viability at −20°F ambient. Sugar concentration reaches 22% by December 21.
+
+ CRITICAL FAILURE MODE: Clay soil causes forked roots. Frost before September 20 destroys beta-carotene synthesis. Loss rate: 94%.
+
-
-
HARVEST PROTOCOL
-
Leave in ground under heavy straw mulch. Harvest through January as needed. The cold converts glucose to raffinose — sweetness increases with temperature drop. Pull only what you will use within 48 hours.
Do not harvest before November 1. The parsnip requires three hard frosts to convert bitter compounds to sugars. Mark the row — you will dig in February.
+
+
+
+ PLANTING WINDOW
+ APR 15 – MAY 10
+
+
+ ESTABLISHMENT
+ 60 days
+
+
+ WINTER PROTECTION
+ Cold frame mandatory
+
+
+ MIN SOIL TEMP
+ 28°F
+
+
+ HARVEST CYCLE
+ Outer stems weekly
+
+
+
+
+ APIOLE CONTENT
+ ↑ 2.1x post-frost
+
+
+ FROST TOLERANCE
+ −8°F (protected)
+
+
+ COLD FRAME HEIGHT
+ 18"
+
+
+ LIFESPAN
+ Biennial (yr 2 = flower)
+
+
+
+
+
+ CRITICAL FAILURE MODE: Unprotected parsley dies at 20°F. Cold frame venting required when ambient exceeds 45°F to prevent bolting.
+
+
+ 
+ 
+ 
-
- 
+