CELLAR PROTOCOL

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.

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
Relative Humidity	90–95%	85–98%	Shriveling below 85%; mold proliferation above 98%
Light	Zero	Total darkness	Greening of potatoes (solanine production); accelerated sprouting
Air Exchange	2–4 changes/hour	1–6 changes/hour	Stagnant air breeds condensation and mold; too much exchange drops humidity
CO₂ Level	<0.1%	0.03–0.15%	Elevated CO₂ causes off-flavors in brassicas; above 0.3% risks anaerobic conditions

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:

CROP	SHELF LIFE	TEMP PREFERENCE	STORAGE METHOD	NOTES
Potatoes (storage varieties: Katahdin, Russet Burbank)	4–6 months	38–40°F	Perforated bins, loose in wood shavings	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.

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.