Produce Storage & Shelf Life: Post-Harvest Physiology

Overview

Every vegetable harvested from a garden is, physiologically speaking, still alive. It respires, loses water, responds to hormonal cues, and continues metabolic processes that will ultimately lead to senescence and decay — unless storage conditions intervene. For the home grower, understanding the underlying physiology transforms storage from a guessing game into a precise science. This guide draws on post-harvest physiology research to explain exactly why specific crops need specific conditions, how curing works at the cellular level, and how the invisible chemistry of ethylene gas can either help or devastate your stored harvest.

Part I: The Foundational Science of Post-Harvest Physiology

Respiration: The Metabolic Clock

After harvest, living plant tissue continues to respire aerobically, consuming stored carbohydrates (sugars, starches, and organic acids) in the presence of oxygen to produce CO₂, water, and heat. This catabolic process drives the progressive deterioration of color, texture, flavor, and nutritional value. The fundamental equation is:

The rate of this deterioration is governed by temperature, and the relationship is described quantitatively by the Q₁₀ temperature coefficient — the factor by which the reaction rate increases with every 10°C (18°F) rise in temperature. For most produce, the Q₁₀ value is approximately 2–3 in the 0–30°C range, meaning every 10°C rise in storage temperature roughly doubles or triples the rate of metabolic deterioration. This is the most critical single concept in post-harvest management: cold slows the biological clock.

Practical consequence: sweet potatoes stored at 25°C (77°F) respire at 27–35 mL CO₂/kg·hr, compared to only 10–12 mL CO₂/kg·hr at 15°C (59°F) — a reduction of 60–70% simply by lowering temperature. For the home grower without mechanical refrigeration, even moving produce from a 75°F kitchen to a 55°F basement represents a substantial metabolic slowdown.

Climacteric vs. Non-Climacteric Physiology

One of the most practically important distinctions in post-harvest science is whether a crop is climacteric or non-climacteric.

Climacteric crops undergo a dramatic, ethylene-triggered surge in respiration rate — called the climacteric rise — at the onset of ripening. This surge is autocatalytic: once ethylene production begins, it stimulates further ethylene synthesis in a positive feedback loop (hence the old adage "one bad apple spoils the whole bunch"). Climacteric produce includes apples, bananas, tomatoes, avocados, peaches, mangoes, and pears. These crops can be harvested at a physiologically mature but unripe stage and will continue to ripen post-harvest.

Non-climacteric crops do not exhibit this ethylene-driven respiratory peak. They must be harvested ripe because they will not continue ripening after separation from the plant. Citrus, strawberries, grapes, pineapples, cucumbers, and all root crops and alliums fall into this category. While they don't self-ripen, they remain sensitive to externally produced ethylene (more on this below).

For home storage of root crops, tubers, and alliums — the focus of this guide — understanding that these are non-climacteric is key: their decline is not driven by a programmed ripening surge, but by slow catabolic breakdown and pathogen intrusion, both of which are manageable with correct temperature and humidity.

Transpiration and the Water Vapor Pressure Deficit

Beyond respiration, produce loses moisture continuously through transpiration — the passive diffusion of water vapor through the skin, stomata, and lenticels. A loss of as little as 3–8% of fresh weight can trigger visible wilting, loss of crispness, and unmarketability. The driving force behind transpiration is the vapor pressure deficit (VPD): the difference in water vapor pressure between the interior of the tissue and the surrounding air. The higher the VPD, the faster moisture escapes.

Temperature and relative humidity (RH) together determine the VPD. Lowering the storage temperature reduces the water vapor carrying capacity of air, shrinking the VPD and slowing transpiration even at the same relative humidity. This is why cold-and-moist environments are ideal for most root vegetables: temperature suppresses both respiration and water loss simultaneously.

Maintaining proper RH requires vigilance. If RH is too low, shrivel and weight loss accelerate; if it is too high for certain crops (particularly alliums), condensation promotes mold and fungal decay. For each crop below, the RH targets are narrow and consequential.

Part II: The Science and Mechanics of Curing

What Curing Actually Does

Curing is a controlled environmental treatment applied immediately after harvest to crops that have thin, fragile skins prone to damage during digging and handling. The physiological goal is to stimulate the wound-healing response — a cascade of cellular and biochemical events that produce a new, protective layer of cells over abrasions, cuts, and pressure wounds before long-term cold storage begins.

Without curing, every harvest wound becomes a portal for fungal and bacterial pathogens (particularly Fusarium, Rhizopus, Botrytis, and bacterial soft rots), and an avenue for uncontrolled water loss that leads to rapid shriveling. Curing also allows enzymatic conversion of surface starches to sugars, which significantly improves flavor after storage.

The Cellular Biology: Suberization and Periderm Formation

The wound response unfolds in two biochemical stages:

Stage 1 — Closing Layer (Days 1–7): Within hours of wounding, damaged cells undergo programmed cell death. Adjacent parenchyma cells begin depositing suberin — a complex lipid-polyester polymer — into their cell walls. Solid-state ¹³C NMR studies on potato wound healing have shown that suberin deposition begins at the outermost intact cell wall surface within the first 4 days. This suberized closing layer acts as an immediate physical and chemical barrier against microbial penetration and desiccation. Initially, the suberin matrix contains a high proportion of aromatic groups (from the phenylpropanoid pathway) alongside relatively short aliphatic chains.

Stage 2 — Wound Periderm (Days 7–14): Deeper tissue cells begin dividing mitotically to produce a wound periderm — a multi-layered cork tissue functionally analogous to the bark of a tree. This meristematic activity (controlled by genes including StPAL-1, StPrx, StFHT, and StKCS6 in potato) generates long-chain fatty acid suberin aliphatics (≥C28) that create a progressively more robust water-vapor barrier. By day 14, the wound periderm offers durable protection against both moisture loss and secondary pathogen entry.

The critical insight is this: elevated temperature and high humidity are not optional preferences — they are the biochemical prerequisites for suberization to occur. Temperature activates the enzymes of the phenylpropanoid and aliphatic suberin biosynthesis pathways. High humidity prevents the wound surface from drying and dying before cellular reorganization can proceed.

Part III: Crop-Specific Curing Protocols

The following protocols reflect research-validated conditions. Deviations from these parameters — even by 10°F or 10% RH — produce measurable reductions in wound healing completeness and subsequent storage life.

Winter Squash (Cucurbita maxima, C. moschata, C. pepo)

Curing Conditions: 80–85°F (27–29°C) | 75–80% RH | 10–14 days | Good airflow required

The curing phase for winter squash is driven by the same suberization cascade described above. Small harvest cuts and pressure abrasions callous over as the outer rind hardens perceptibly. Curing also allows surface moisture to evaporate and immature flesh to continue starch-to-sugar conversion, improving sweetness.

Air circulation is not optional. Stagnant humid air at 80–85°F is a fungal incubation environment. Stacking squash against one another without airflow promotes skin-to-skin moisture accumulation and mold initiation. Ideal curing is accomplished on open wooden slats, wire mesh shelves, or elevated racks that allow air movement across all surfaces.

Important variety-specific exceptions: Acorn squash (C. pepo 'Table Queen' type) should not be cured — research from Alabama Cooperative Extension confirms that curing is detrimental to acorn types, reducing rather than extending storage life. Hubbard, Butternut, Buttercup, and Spaghetti squash all benefit from curing; acorn squash should go directly to cold storage.

Long-term storage: 50–55°F (10–13°C) | 50–70% RH | Variety-dependent duration

Do not store squash directly on concrete floors — moisture wicking and temperature fluctuations accelerate rot from the contact point. Elevate on pallets, cardboard, or shelving.

Sweet Potatoes (Ipomoea batatas)

Curing Conditions: 85°F (29°C) | 90–95% RH | 4–7 days

Sweet potatoes are arguably the most physiologically demanding crop to cure correctly. Their thin periderm is extremely fragile at harvest — the skin bruises and tears easily during digging, and every injury is a potential site for Rhizopus soft rot or Fusarium root rot, the two most economically significant pathogens of stored sweet potatoes.

The UC Davis Postharvest Research Center specifies wound healing conditions of 25–32°C (77–90°F) under relative humidity of >90 to 100% for several days to one week. At these conditions, the wounded periderm cells are physiologically competent to undergo suberization. A practical field trick: harvest into warm bins, wheel them directly into the storage room, and do not turn on the evaporative cooling fans for the first 5–7 days — this passively creates a warm, humid curing chamber within the room itself.

The starch-to-sugar conversion: During curing, amylase activity increases substantially, converting starches to maltose, sucrose, and other sugars. This biochemical transformation is responsible for the characteristic sweetness that distinguishes properly cured from uncured sweet potatoes — and it is why home-grown cured sweet potatoes taste markedly better than supermarket equivalents stored without proper curing.

Long-term storage: 55–60°F (13–16°C) | 80–85% RH | 4–7 months

Critical chilling injury threshold: Sweet potatoes are a tropical root crop with a hard chilling sensitivity boundary at 55°F (12.5°C). Exposure to temperatures below this threshold causes irreversible membrane damage in the flesh cells. Symptoms include:

• Pitting and sunken lesions on the root surface
• Internal pulp browning and darkening
• "Hardcore" — areas of flesh that remain hard after cooking (undetectable until cooking)
• Greatly increased susceptibility to fungal decay post-chilling

Hardcore can develop in just one day of exposure at 35°F, and in as little as three days at 50°F. This makes sweet potato storage in standard root cellars (which often run 45–52°F) inadvisable without supplemental heating. A spare bedroom, enclosed porch, or heated garage kept at 55–60°F is far more appropriate. Do not store sweet potatoes in a refrigerator under any circumstances.

Onions (Allium cepa)

Curing Conditions: 85–90°F (29–32°C) | 65–70% RH | 14–21 days | Well-ventilated

Onion curing is biochemically distinct from root-crop suberization. The physiological goal is desiccation of the neck and outer papery scales rather than wound healing. The neck tissue (where the foliage meets the bulb) must dry and collapse completely — any moisture retained in the neck creates a microbial pathway directly into the bulb interior. Insufficiently dried necks are the primary cause of "neck rot" (Botrytis allii) during storage.

The outer scales act as a natural barrier against moisture loss and microbial invasion — they should be preserved intact throughout the process. Curing is complete when the outer scale tissues are papery and crisp, the neck is visibly pinched and dry, and the roots are desiccated to a thin, brittle mass.

The hormonal dimension: Onion bulb dormancy is regulated by a complex interplay of plant hormones, primarily abscisic acid (ABA), which suppresses sprouting. Research from Cranfield University demonstrated that ABA concentration in stored onion bulbs declines exponentially over the storage period, and sprouting initiates when ABA falls below a threshold of approximately 50–150 ng/g dry weight. Critically, ABA concentration decreases significantly during the curing process itself at high temperatures — meaning extended high-temperature curing paradoxically reduces the post-curing storage window by depleting the dormancy hormone. This finding supports the practice of curing onions for the minimum sufficient time (14–21 days) rather than indefinitely.

Long-term storage: 32–40°F (0–4°C) | 65–70% RH | 4–6+ months for good-keeping cultivars

Key storage notes:

• Hardneck vs. softneck: Softneck varieties (e.g., 'Copra', 'Stuttgarter') are bred for long storage (6+ months); hardneck varieties and sweet types (e.g., 'Walla Walla', 'Sweet Spanish') have inherently shorter storage life of only a few weeks regardless of conditions.
• Container type: Use mesh bags, open crates, or braided-and-hung bundles — never airtight plastic bags, which trap moisture and rapidly promote mold.
• Spacing matters: Never pack bulbs deeper than 4 inches without ventilation between layers.

Garlic (Allium sativum)

Curing Conditions: 85–90°F (29–32°C) | 65–70% RH | 14–21 days | Well-ventilated

Garlic shares the allium curing physiology of onions: the objective is complete desiccation of the neck and development of tight, papery wrapper scales around the bulb. However, garlic has slightly greater physiological tolerance for ambient conditions during curing than onions, because individual cloves are enclosed in their own husks.

The biochemical quality change during curing deserves attention: alliin (the principal flavor and bioactive precursor compound in garlic) concentrates and stabilizes as free moisture is removed. Properly cured garlic develops tighter, more persistent flavor than fresh-dug, undried bulbs. The outer wrapper scales should feel dry, crinkle-papery, and slightly translucent — not soft or pliable.

Long-term storage: 32–40°F (0–4°C) or 50–70°F (10–21°C) | 60–70% RH | 3–6+ months

The "forbidden zone" for garlic is the temperature range of 40–50°F (4–10°C) — coincidentally, the temperature of most standard refrigerators. Within this range, garlic reliably initiates premature sprouting. The practical implication is that garlic must either be stored truly cold (near 32°F) or at cool room temperature (~50–68°F), but never in between.

Commercial garlic is commonly stored in the dark at approximately 32°F and 65% RH, where it can remain viable for six months or longer. At home, hanging braided bulbs in a cool, dry pantry or basement (maintaining 60–70% RH) approximates these conditions adequately for 3–4 months.

Part IV: The Ethylene Dimension — Producers, Sensitives, and Separation

Ethylene Biosynthesis: The SAM-ACC-Ethylene Pathway

Ethylene (C₂H₄) is a simple two-carbon gas molecule — the simplest known phytohormone — yet its effect on harvested produce is profoundly consequential. Even concentrations as low as 0.1 parts per million (ppm) can trigger physiological responses in sensitive tissues. Understanding its biosynthesis pathway clarifies how and why separation strategies work.

The biosynthetic route proceeds as follows:

1. ATP + Methionine → SAM (S-adenosylmethionine) — a universal methyl donor
2. SAM → ACC (1-aminocyclopropane-1-carboxylic acid) — catalyzed by ACC synthase, the rate-limiting enzyme. ACC synthase is cytosolic, encoded by a multi-gene family, and upregulated by fruit ripening, wounding, auxin (IAA), chilling injury, drought, flooding, and — critically — by ethylene itself (autocatalytic induction)
3. ACC → Ethylene (C₂H₄) — catalyzed by ACC oxidase (formerly called "ethylene forming enzyme"), which requires Fe²⁺ and ascorbate, is inhibited by anaerobic conditions, and is stimulated by ripening

The autocatalytic nature of step 2 — where ethylene stimulates its own production — is the mechanism behind the exponential ripening cascade observed in climacteric fruit. It is also the reason a single overripe apple or a cluster of rotting tomatoes can dramatically accelerate deterioration across an entire storage space.

Ethylene Producers: High-Output Sources

The following crops produce substantial quantities of ethylene and should never be co-stored with sensitive produce:

High-ethylene producers:

• Apples (especially Malus domestica — among the highest producers)
• Avocados (ripe)
• Bananas
• Cantaloupe and honeydew melons
• Peaches, nectarines, apricots
• Tomatoes (ripening)
• Kiwifruit
• Pears

Critical note on damaged/overripe produce: Wounding dramatically upregulates ACC synthase — the rate-limiting enzyme — so damaged, overripe, or decaying produce generates ethylene at far higher rates than sound fruit. A single soft apple in a bin initiates a localized ethylene plume that accelerates ripening in surrounding items. This is the physiological basis for the practice of culling storage regularly.

Ethylene-Sensitive Crops: High Risk of Damage

The following crops suffer accelerated deterioration when exposed to exogenous ethylene:

Highly ethylene-sensitive crops:

• Broccoli, cauliflower, cabbage (chlorophyll degradation, yellowing)
• Carrots (develop bitter flavor from isocoumarin accumulation)
• Cucumbers (accelerated yellowing and softening)
• Lettuce and leafy greens (russeting, rapid senescence)
• Onions (premature sprouting and softening)
• Sweet potatoes (increased respiration, phenolic metabolism disruption, adverse flavor and color changes in cooked roots)
• Winter squash (accelerated ripening)
• Eggplant

Sweet potatoes are particularly vulnerable: UC Davis research shows that ethylene exposure at 1–10 ppm increases respiration rates and phenolic metabolism, adversely affecting flavor and cooked color. Even the very low ethylene produced endogenously by sweet potatoes (~0.1 µL/kg·hr) increases dramatically after chilling or wounding — another reason to cure wounds before cold storage.

Crops That Are Neither Producers Nor Sensitive

Some crops occupy a metabolically quiet middle ground and can be stored near either group without significant effect:

• Potatoes (ethylene-resistant as stored tubers; ethylene promotes sprouting at high concentrations)
• Garlic (listed as non-sensitive in most storage classifications)
• Citrus fruits
• Pineapple
• Beets, turnips

Practical Ethylene Separation Strategies

Spatial segregation: The most important principle is physical separation of ethylene producers and sensitive crops. In a multi-room cellar or storage facility, dedicate one space to apples, tomatoes, and other climacteric fruit and a separate space to root vegetables, squash, and alliums. Even in a single-room root cellar, placing a fan between storage zones significantly reduces ethylene concentration gradients.

Ventilation: Adequate air exchange flushes accumulated ethylene from storage areas. Natural root cellars with vents on opposing walls provide passive ethylene dilution. A small exhaust fan running on a timer can maintain effective ventilation without excessive moisture loss.

Ethylene scavenging: Potassium permanganate (KMnO₄)-impregnated sachets, available commercially, oxidize ethylene into CO₂ and water. They are non-toxic when enclosed, show a visible color change from purple to brown when exhausted, and provide effective local ethylene control in enclosed containers or bins. These are practical and inexpensive additions to any serious home storage setup.

Remove damaged produce immediately: Given ACC synthase upregulation by wounding, any bruised or softening item produces ethylene at elevated rates. Weekly inspection and immediate culling of borderline produce prevents cascade spoilage.

Part V: The Five Environmental Variables — An Integrated Framework

Every storage decision involves trade-offs among five interdependent variables:

1. Temperature

The dominant variable. Every 10°C reduction approximately halves metabolic rate (Q₁₀ ≈ 2). The caveat: chilling-sensitive crops have hard lower limits below which cold causes injury rather than preservation. Always know whether your crop is chilling-sensitive before placing it in a cold space.

2. Relative Humidity

Controls transpirational water loss and fungal risk simultaneously. Higher RH preserves turgidity in root crops but promotes mold in alliums.

3. Air Circulation

Serves two distinct functions: (a) heat dissipation — removing respiratory heat that would otherwise raise local temperature, and (b) ethylene dilution — preventing accumulation of ripening gases to damaging concentrations. For bulb crops, air circulation also prevents condensation from forming on surfaces during temperature cycling, which would promote mold.

4. Light Exclusion

Storage spaces should be dark or semi-dark for most crops. Light stimulates chlorophyll synthesis in potato tubers (greening, which produces the toxic alkaloid solanine) and can promote premature sprouting in alliums. Winter squash and sweet potatoes are less sensitive to light but still perform best in dim conditions.

5. Ethylene Management

As detailed above, spatial separation, regular culling, ventilation, and optional KMnO₄ scavenging constitute a complete home-scale ethylene management protocol.

Part VI: Harvest Timing and Pre-Storage Handling

The "Three C's" Framework

Before any curing or storage begins, post-harvest management starts with: Culling, Cleaning, and Curing.

• Culling: Sort every item before storage. Damaged, bruised, cut, or diseased produce will not store well regardless of conditions — it will produce elevated ethylene, attract fungi, and seed rot outward to neighboring items. The rule is absolute: store only perfect or near-perfect specimens.
• Cleaning: For most root crops and alliums, remove excess soil with a dry brush only — do not wash before storage or curing. Water on the skin surface dramatically increases fungal risk during storage. Sweet potatoes should never be washed before curing.
• Curing: Apply the crop-specific curing protocol before transitioning to long-term cold storage.

Harvest Maturity Indicators

Premature or delayed harvest significantly affects storage potential:

• Winter squash: Rind should resist nail penetration; skin should be dry and dull; stem should begin to dry and brown. Harvest before first frost — frost damages rind integrity and slashes storage life.
• Sweet potatoes: Harvest when roots have reached desirable size, typically before soil temperatures drop below 55°F. Avoid holding roots in waterlogged soil pre-harvest; anaerobic conditions predispose roots to rapid decay in storage.
• Onions: Harvest when 50–80% of tops have naturally fallen over and begun to dry. Do not force tops down to hasten harvest — premature harvesting shortens storage life.
• Garlic: Harvest when foliage begins to dry; typically 5–6 leaves remaining green indicates ~5–6 wrapper scales available. Overcured in-ground garlic loses its wrapper integrity and stores poorly.

Mechanical Damage: The Silent Storage Killer

Every bruise, cut, and compression injury does four things simultaneously: it activates ACC synthase (increasing ethylene production), compromises the periderm barrier (allowing pathogen entry), induces wound respiration (accelerating metabolic heat and CO₂ production), and initiates the suberization response (which is beneficial — but only if curing conditions are correct). The practical implication is that harvest and handling technique directly determine storage outcome. Dig root crops with care, use padded harvest containers, and minimize drops and impacts.

Part VII: Advanced Storage Concepts for the Serious Home Grower

Modified Atmosphere in Home Storage

Modified atmosphere (MA) storage — reducing O₂ and elevating CO₂ — suppresses both respiration and ethylene biosynthesis at the level of ACC oxidase (the final enzyme in the ethylene pathway, which is inhibited by anaerobic conditions). Commercial CA (controlled atmosphere) storage for apples, for example, typically maintains 2–3% O₂ and 5–15% CO₂ at low temperature.

Home-scale approximations include:

• Sealed polyethylene bags create a mild MA environment around individual items as respiration depletes O₂ and accumulates CO₂ — effective for potatoes and some root vegetables, though monitoring is required to avoid O₂ depletion below 3% (the anaerobic threshold where fermentative metabolism begins).
• Vacuum-sealed bags combined with cold storage can extend shelf life of certain produce significantly, though this is more suited to processed (blanched, dried) items than whole root crops.

Temperature Zoning in Multi-Use Storage Spaces

If a single storage room must accommodate crops with different requirements, prioritize the most temperature-sensitive crop (chilling-sensitive items) and use the following zoning strategy:

• Zone 1 (coldest, near floor and outer walls): 32–40°F for garlic, onions, root vegetables
• Zone 2 (moderate, interior): 50–60°F for sweet potatoes and winter squash
• Physical barriers (cardboard, foam board) between zones maintain gradients even in uninsulated spaces

Monitoring Tools for Precision Storage

Precise home storage requires at minimum:

• A calibrated min/max thermometer in each distinct storage zone
• A hygrometer (digital preferred) for RH monitoring
• A humidity source (damp sand, wet burlap bags, a water reservoir) for crops requiring ≥85% RH
• Optionally, a small electric fan on a timer for ethylene ventilation

The cost of these tools ($30–60 total) is negligible compared to the value of a well-managed home harvest.

Consolidated Quick-Reference Storage Parameters

*Sources: *

Conclusion

Post-harvest physiology is not complicated at its core — it is the science of slowing life without ending it. Produce harvested at physiological maturity continues to respire, transpire, respond to hormonal signals, and heal wounds if given the right conditions. The art of the home storage cellar is aligning those conditions precisely: warm enough for suberization during curing, cold enough to suppress respiration in long-term storage, humid enough to prevent desiccation, dry enough to prevent mold, airy enough to dilute ethylene, and above all, organized enough to keep ethylene producers well away from sensitive crops.

Mastery of these principles — Q₁₀-guided temperature management, the two-stage suberization cascade, the SAM-ACC-ethylene pathway, and hormone-regulated dormancy in alliums — transforms storage from a passive waiting game into an active extension of the harvest. Applied correctly, these techniques can stretch a summer's labor into a winter's sustenance, month after month.

References

Ordered by scientific authority and relevance — peer-reviewed studies first, postharvest-science institutions and university extension after.

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2. Ethylene and its crosstalk with hormonal pathways in fruit ripening. PMC. 2024. Accessed July 5, 2026. https://pmc.ncbi.nlm.nih.gov/articles/PMC11579711/

3. Following suberization in potato wound periderm by histochemical and solid-state 13C nuclear magnetic resonance methods. PMC. Accessed July 5, 2026. https://pmc.ncbi.nlm.nih.gov/articles/PMC159227/

4. Wound-induced suberization genes are differentially expressed with wound duration. Postharvest Biol Technol. 2013. Accessed July 5, 2026. https://www.sciencedirect.com/science/article/abs/pii/S0925521413003529

5. The contribution of transpiration and respiration in water loss of perishable agricultural products: the case of pears. Biosyst Eng. 2016. Accessed July 5, 2026. https://www.sciencedirect.com/science/article/abs/pii/S1537511016308145

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11. Auburn University Alabama Cooperative Extension System. Harvesting, curing, and post-harvest care of pumpkins and winter squash (ANR-1110). Accessed July 5, 2026. https://www.aces.edu/wp-content/uploads/2019/03/ANR-1110-Harvesting-Curing-Post-Harvedt-Care-of-Pumpkins-and-Winter-Squash_070319La.pdf

12. Washington State University Extension. Harvesting and storing winter squash and curing gourds. Accessed July 5, 2026. https://extension.wsu.edu/snohomish/2013/10/18/harvesting-and-storing-winter-squash-and-curing-gourds/

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14. Iowa State University Extension. Yard and garden: harvest, dry and store onions, garlic and shallots. Accessed July 5, 2026. https://www.extension.iastate.edu/news/yard-and-garden-harvest-dry-store-onions-garlic-shallots

15. College of Saint Benedict / Saint John's University. Ethylene [plant physiology]. Accessed July 5, 2026. https://employees.csbsju.edu/ssaupe/biol327/Lecture/ethylene.htm

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