Extend your selling season or personal enjoyment of storage crops with proper post-harvest handling and holding conditions.
4 Basic Temperature/Humidity Combinations for Classic Storage Crops
Classic storage crops are products that are held post-harvest in a semi-controlled or controlled environment, for use/sale over the ensuing weeks and months. Most are harvested in the fall, then held for winter storage under 4 main combinations of low-temperature/humidity:
- Cold & Dry
- Cold & Moist
- Cool & Dry
- Cool & Moist
Crops that fit into the classic storage-crop category include most — though not all — root vegetables and tuberous vegetables; hard-shell cucurbits, that is, winter squashes and pumpkins; and some head crops, typically those that are brassicaceous, such as cabbages.
Grains, beans, and dried flowers, too, can be considered types of storage crops, though they are handled differently.
Optimal storage conditions as well as holding times vary by crop and type — and in some cases by variety, environmental conditions, and season or timing of harvest. Here's a quick guide to post-harvest handling and storage of classic storage crops. First we cover some practical considerations, then provide basic, crop-by-crop specifics.
A lot of people shy away from storage because they think they have to maintain perfect conditions to keep the produce in storage as long as possible, but that's not necessarily the case. Here are some guidelines to keep in mind.
- We give the ideal temperature ranges for storage, but you can get a decent storage life out of most crops even if conditions are not perfect.
- For all the crops that should be stored at 32°F/0°C, you can expect to get half the storage life (2–3 months for some things may be quite reasonable) by storing them in temps up to 50°F/10°C, provided there is high humidity (except for onions, which like it a little drier).
- A lot of people live in climates where they have this type of situation in their garage, basement, or mud room. Older structures and foundations may even have an existing root cellar or the potential makings (or ruins) of one.
- If you can get as close as possible to the target temperature and humidity, and if the crop is prepared properly, it will keep for a good while.
- We also recommend storing carrots, beets, turnips, leeks, celeriac, and all brassicas in perforated bags. Most crops will be able to maintain high humidity better if they are somewhat enclosed, but the bags must breathe well enough for air exchange to prevent decay.
- Another thing to try to keep in mind is to eat what you store, and don't wait! Some people try to stretch the life of their storage crops as long as possible, and in doing so can be reluctant to eat them early on. This can really backfire if things start to rot for whatever reason. Even under ideal conditions, crops can go bad at any time. You are better off having enjoyed the last of your veggies in February than you are throwing out half your stash in April.
Root Crops & Tubers
Because most people think of root crops and tubers first when they think of storage crops, we provide information for them first, then alliums, brassicas, and curcurbits, including a few examples of our recommended favorites and top-performing varieties.
BEETS & CARROTS • Tips for Post-Harvest Handling
- It is ideal to harvest in dry conditions, when the soil will easily slough off of the roots.
- For beets and carrots, it is also important to trim the tops off close to the root — leave about
¼"of tops material there. Leaving any more than this will invite decay, but not leaving anything will hasten the drying out of the root.
- Some say to wash these root crops before storage. We do not agree, for two reasons: 1) getting them wet can encourage decay; and 2) washing them will remove much of the beneficial bacteria that occupy the thin film of soil on the roots. These bacteria actually help fight decay.
- Instead, we recommend gently removing soil clods from the roots, being careful not to use anything abrasive that may scratch the root surface.
- Wash them as you remove them from storage for eating throughout the winter.
- Harvest before the first hard freeze, at about
- Trim tops (stems and leaves) to
- The taproot should be cut off with a sharp knife prior to storage.
- To store, pack in perforated plastic bags or in sealed containers filled with damp sand.
- Beets of all varieties will keep for
3–5months when stored at 32°F/0°Cand 90–100%humidity.
- Harvest carrots for storage before the first hard freeze.
- Trim tops to
¼"length. To store, place in perforated bags, or pack in damp sand in sealed containers.
- Carrots are sensitive to ethylene gas emitted by certain fruits (such as apples), so be sure to keep them separate.
- Store at
Tip: 'Bolero' is the best variety for harvesting in late fall, and will hold for up to 6 months under the above-noted conditions.
- Harvest celeriac prior to the first hard freeze.
- Trim tops to ¼" in length.
- Store harvested celeriac with soil and roots intact.
- Can be placed in perforated bags or packed in damp sand in a sealed container for storage.
- Clean before selling.
Tip: 'Brilliant' is an excellent celery root choice for storing, with large, round, solid roots that will hold nearly as long as a carrot under the same conditions.
- Harvest storage kohlrabi while the tap root is still round, before it begins to elongate.
- Remove leaf stems and tops prior to storing.
- Can be placed in peforated bags for storage.
- Store at
Tip: 'Kossak' is a variety that maintains its dense white flesh — still sweet, delicious, and tender — with storage for 2–4 months.
- Mow tops then broadfork or undermine, or use root crop harvester.
- Parsnips require a full season of growth, and their sweet flavor is brought on by cold weather. Harvest in the fall or leave in the ground through the winter.
- When harvesting in early spring, dig before the tops begin to re-grow for the highest quality roots.
- Storage conditions are the same as carrots — hold unwashed (or washed) in perforated bags or bins at
32°F/0°Cand 95% relative humidity — but they should be handled with more care as they bruise more easily.
- Plants are mature when foliage naturally dies back. Late-maturing varieties may need to be flail-mowed to encourage maturity prior to frost.
- Tubers should remain in the ground for at least 2 weeks after foliage has died back to allow for skin set. Do not allow tubers to freeze, as they will become watery and unusable.
- Dig tubers and allow skins to air dry for a day if rainy weather is not expected.
- Do not wash tubers or put wet tubers directly into storage.
- Place in mesh bags, crates, or vented boxes.
- Store in a dark cooler at
40°F/4.4°Cand 95% relative humidity.
- Healthy tubers can store for 5 months or more under the proper conditions.
- Harvest rutabaga when roots reach the desired size, preferably after a couple of good frosts.
- Remove tops.
- Store at
- Clean roots may be waxed prior to delivery at market to prevent drying, but this step is not necessary.
- Sweet potatoes can be dug whenever they reach the desired size, but should always be harvested prior to frost as the plants and roots will be damaged otherwise.
- Clip vines at soil surface and dig tubers with fork.
- Handle tubers very carefully to avoid damaging skin; do not wash.
- Cure tubers in a warm
(85°F/29°C), dark place with good ventilation and 85% relative humidity for 5–7days.
- Place tubers in crates or vented boxes and store in dark at
60°F/16°Cand 85% relative humidity. Do not allow the storage temperature to drop below 50°F/10°C,as this will chill and injure the tubers.
- Once cured, store the tubers for 3–4 weeks before selling and/or consuming for better sugar content and eating quality.
- Properly handled tubers can be stored for 7 months or more.
- Harvest turnips when the roots have reached the desired size.
- A light frost can enhance flavor.
- May be waxed, but this is not necessary.
- Store at
Tip: 'Purple Top White Globe' can be kept up to 4–5 months under the above conditions.
- Leek varieties vary in the length of time they require to reach maturity ("days to maturity" or DTM), and the length of that period is directly related to their cold tolerance:
- Early leeks grow faster and are ready for harvest in late summer to early fall, but they are less cold-tolerant.
- Midseason leeks are ready in fall, and can be relatively cold tolerant.
- Late leeks are ready in late fall to early winter, and are the most cold tolerant. These late types can be held in the field and harvested as needed. In milder climates, plants may overwinter with some protection.
- Harvest early/summer leeks first, moving on to midseason/fall leeks, and then late/winter leeks.
- Lift plants with fork to harvest.
- Plants will store several weeks with either method below:
- Clean plants by trimming tops, roots, and peeling outer leaves. Store in boxes at near freezing
(32°F/0°C)and 95% relative humidity.
- Trim tops and peel any necrotic leaves. Trim roots, but leave an inch or two. Store in a root cellar, plants upright in a container with roots in a moist soil/sand/peat mix. Exposing to some light will keep tops green. Fully trim roots and peel outer leaves as necessary to clean up prior to selling/use.
- When necks are soft and tops are falling (about 50% of plot), pull plants and cure in field for
2–7 days,depending on weather. Cure in warm (80°F/27°C), dry area (barn or shaded greenhouse) if rainy weather is expected. Too much sun exposure can result in bulb sunscald.
- Bring in to a protected area (e.g., a barn or shaded greenhouse) and allow plants to finish drying. Ensure adequate circulation, using fans if needed. Laying the onions a foot or further away from walls will also help air circulation. Skins should be dry; necks should be dry and tight, and should not slip when pinched.
- Trim tops to about 1" from bulb, and trim roots.
- Place in mesh bags, crates, or vented boxes. (Lack of air circulation reduces shelf life.) Store in a dark cooler that is near freezing
(32°F/0°C)with 65–70%relative humidity.
- Avoid storing with potatoes or other root crops that emit moisture.
- Sweet/mild onions have much higher water content, and thus will not store longer than a few weeks. Pungent storage onions typically store 4–6 months or longer.
- Sort onions in storage on a regular basis to remove any soft or rotten bulbs.
Tip: Many onion varieties are suitable for storage, but some have greater storage potential than others. For specifics, refer to our Full-Size Onion Comparison Chart.
- When necks are soft and tops are falling over, pull and sun-cure at least 2–7 days, depending on weather. Move to a protected location to finish drying.
- When dry, clip off tops and roots, and store in onion bags or shallow boxes at near-freezing temperature
(32°F/0°C)and 65–70%relative humidity.
- Shallots can last in storage up to 6 months.
- Harvest when heads are about 1" in diameter.
- Once cut, they should be stored in perforated bags at 32°F/0°C and 90–100% humidity.
- Whole stalks can also be harvested and stored for up to 1½ months.
- Harvest when heads are compact and firm.
- Store with a few of the outside wrapper leaves at
- Clean before selling.
Tip: 'Storage No. 4' will keep until spring from a late fall harvest if held at the conditions noted above.
- Ornamental pumpkins are ready for harvest when color is fully developed.
- Fruits may be left in the field after reaching maturity, but overexposure to sun at this point will reduce fruit and stem (handle) color quality.
- Fruits can tolerate 1–2 light frosts prior to harvest.
- To harvest, clip handles close to vine. Avoid picking up pumpkins by handles, and take care to not damage skin/rind.
- Sun cure in the field for 5–7 days, or cure indoors by keeping fruits at 80–85°F/27–29°C with good air ventilation for 5–7 days.
- White varieties should be brought in out of direct sunlight once foliage starts to die back; cure inside and keep out of sun to avoid yellowing.
- Some growers prefer to wash fruits with a mild bleach solution after curing.
- Store at 50–60°F/10–15°C, with 50–70% relative humidity and good ventilation.
Tip: 'Long Island Cheese,' 'Musque de Provence,' and 'Baby Bear' are all renowned for their long storage as well as great eating qualities. These pumpkin varieties will keep up to 5 months after frost at the conditions noted above.
WINTER SQUASH & PIE PUMPKINS — Cool & Dry
- Winter squash and pie pumpkins are generally mature about
50–55days after fruit set, and should be harvested before hard frost.
- Cut fruits from vines and handle carefully.
- Sun cure in the field for
5–7days or cure indoors by keeping squash at 80–85°F/27–29°Cwith good air ventilation for 5–7days.
- Store at
50–60°F/10–15°C,with 50–70%relative humidity and good ventilation. Repeated exposure to temperatures below 50°F/10°Cmay cause chilling damage.
- Storage potential and timing of best eating quality vary by type.
Tip: A good rule of thumb is to sell and/or consume small-fruited varieties first, such as acorns, delicatas, mini kabochas, and mini butternuts. See our convenient Winter Squash Curing & Storage Chart for average curing times and storage potential. To learn more about the factors that govern eating quality in winter squash and edible pumpkins, read our article on Eating Quality in Winter Squash.
Remember, it is important to inspect produce and to cull anything showing signs of disease or decay before putting it into storage. Continue to monitor and cull while in storage (disease and decay spread fast). And enjoy!
More Resources from Johnny's
- Winter Squash Curing & Storage Times • Chart
- Guide to Winter Cucurbit Eating Quality & Storage
- The Winter Squash Eating Experience • Article
- Storage of Summer-Harvest Vegetables • Chart