Harvest and Handling
Cucurbit yields vary widely depending on plant spacing, production methods (plastics, row covers, irrigation system), and variety. Cucumbers and summer squash often yield 250-300 cwt/acre. Yield for winter squash and pumpkins average around 350- 400 cwt/acre. Higher yields are possible in intensively managed systems. Harvest and handling procedures vary with the type of crop grown and possibly with the intended market. Growers need to carefully supervise and train picking crews to prevent damage or losses from improper harvesting and poor crop handling techniques.
Pickling cucumbers require 4-5 days after pollination to reach harvestable size (cultivar and temperature dependent) while slicing cucumbers require 15- 20 days. Maturity characteristics vary by variety so having an experienced harvester is critical for quality cucumbers. Pickling cucumbers are ready for harvest within days of fruit set and fruit sizes vary depending on market requirements. The indicators of slicing cucumber maturity are glossy green rind sheen, smooth fruits, and no discoloration. Cucumbers should show the characteristic color for the variety, be well formed, fresh and firm, and free from decay and damage. Fruits should be “pushed” or twisted from the vine to avoid vine injury. Pulling fruits often damages or breaks the vines or pulls up the plant. Fields are often harvested for 2-3 weeks and may be picked 3-4 times per week.
The harvest of summer squash (zucchini, patty pans, crooknecks, ball types) is very labor intensive. For optimum quality, fruits should be tender and have a shiny or glossy appearance. Low quality fruits have a dull color. Fruit size depends on the market, but fruits should never have seed with hard seed coats. Ideally, the crop should be harvested every other day and sometimes every day when temperatures are very warm. When harvesting summer squash, leave a short piece of the stem attached to the fruit. If possible, use cotton gloves when harvesting to avoid scratching and puncturing the fruit and cut the squash from the vine rather than twisting them off. The first flush of fruit (first week) to be harvested is usually the best quality. Plan to harvest a given planting only 2 to 3 weeks and then start harvesting another planting. This will keep quality at its best, allows for a longer marketing season, and minimizes low production due to older plants and disease. Harvest crookneck and straight neck cultivars when fruits are 1¼ to 2 inches in diameter. Zucchini fruits should be 6-8 inches long while scallop or ball types are harvested when they are 3-4 inches in diameter. Plant production drops off significantly if fruits are allowed to grow to larger sizes.
For optimum quality, harvest the fruits of winter squash and pumpkins only after the shell (or rind) has hardened completely. If you can scratch the rind with a finger nail, the fruit is still not mature. Care should be taken during harvest not to damage or break off the stem. Most winter squash and pumpkins are cut off the vine and stacked 2-4 fruits deep, depending on their size. When loading out of the field, trucks and trailers should be padded and fruit should not be bumped or bruised. Winter squash intended for long-term storage should be washed or dipped in a 10% chlorine bleach solution (1 part chlorine bleach to 9 parts water), then dried before storing in a dry, cool place. Storage in the open sun causes excessive spoilage and sunburn.
Pumpkins are mature when fruits have achieved normal size, are fully colored, and when the rind is hard. Stop watering 7-10 days before harvest to help dry out the vine and soil. Fruits should be cut from the vine at maturity leaving a 3-5-inch-long stem. Generally, growers wait at least 2-3 days after harvest to allow time for the stem to cure. When moving, windrowing, or loading the fruits, do not grasp the stem to avoid breaking it off. Fruits can be windrowed and stacked like the winter squash before loading out of the field. Avoid storage in the open to minimize sunburn damage and fruit softening.
Watermelons mature5-6 weeks after pollination (cultivar and temperature dependent). The indicators of watermelon maturity are rind sheen, strong color differentiation between the stripes, creamy yellow color of the ground spot, and drying of the tendril nearest the fruit. Thumping is less effective, but a dull or muffled sound can indicate over-maturity. Ideally, it is best to cut a few melons in various parts of the field and compare these to other maturity indicators. A refractometer can help determine fruit sugar content and the BRIX values measured should be above 10. Harvesting and marketing under or over-mature fruits can hurt consumer interest and demand. Fruit sugar content does not increase after harvest but red color does continue to develop after picking. Fields are often harvested over a period of 2 to 3 weeks and may be picked once or twice a week.
To harvest watermelons, cut fruit from the vine, leaving some stem on the fruit. Watermelons should not be stood on end as flesh separation (hollow heart) can occur. Also, do not expose the ground spot to the sun to reduce sunburn. Over-stacking fruit piles can lead to bruising and compression injury both in the field and in storage. It is common to create small stacks of fruit in the field at harvest then to come later and load these into bins, trailers, or trucks. Typically, fruit are bulk loaded into 1000-pound cardboard boxes as these are easier to handle during loading, transport, and unloading. Few watermelons are graded here in Utah, though specific markets may request some fruit sizing for their customers.
Cantaloupe Honeydew, and Others
Harvesting specialty melons like cantaloupe and honeydews is very labor intensive. Melons need to be picked every few days and fields may be harvested over a period of 2 to 3 weeks. Length of harvest depends on vine quality, number of fruits, variety, and market demands. Fruit maturity takes 4-6 weeks after pollination depending on type, temperature, and season.
Cantaloupe are ready for market when fruits are at “half-slip,” well-netted, and of appropriate color for the variety. Half-slip is when the abscission zone between the stem and the fruit is partially formed and it takes a slight pull to separate the fruit from the vine. Cantaloupe harvested at half-slip allows sufficient time from harvest to market so that fruits do not arrive overripe. Typically, fruit are loaded into 1000-pound cardboard boxes for transport to markets.
Honeydew melons are cut from the vine at maturity. Honeydews are ripe and ready for market when plants have achieved normal size, when the ground spot turns a creamy or a light yellow color, when a waxy “bloom” develops on the rind, when the blossom end softens slightly, and when small micro-cracks form near the blossom end. Honeydews do not form an abscission zone where the stem and fruit meet so other maturity indicators are necessary.
Casaba, Crenshaw, and other specialty melons are cut from the vine at maturity. These melons are ripe when the skin color changes slightly from green to yellow and the blossom end of the fruit is slightly soft when pressure is applied with your thumb (similar to honeydew). Use a refractometer to test fruits for sugar content. Cantaloupe and specialty melons with BRIX values above 12 have sufficient sugar to meet market requirements. With all melons, cooling prior to shipping extends marketability, increases the time for the melons to reach maturity, and extends shelf life.
Postharvest Care (Cucumber, Pumpkin, and Squash)
The optimal storage conditions for cucumbers is 50-55 °F and summer squash is 45-50 °F at 80-90% relative humidity . Cucumbers and summer squash stored at these conditions generally keep for 7-10 days before fruit shriveling, yellowing, or decay occurs. Storage or transit temperatures should be kept above 45° F to minimize chilling injury which takes as little as 2-3 days to occur. Chilling injury symptoms are watersoaked areas, fruit wall pitting, fruit color changes, and accelerated decay. Chilling injury may be initiated in the field prior to harvest, and then gets progressively worse during storage. Cucumber and summer squash varieties vary considerably in their susceptibility to chilling injury.
The optimal storage conditions for winter squash and pumpkins are 50-60 °F at 50-70% relative humidity. All cucurbits are sensitive to chilling injury when exposed to or stored at low temperatures (less than 45 °F). For long-term storage of winter squash, maintain temperatures near 55 °F and relative humidity of 60% with good ventilation. Green skinned winter squash types (acorns, buttercups, or kabocha) tend to loose rind color (de-green) when stored at warmer temperatures and higher relative humidity. If pumpkins are stored in a well ventilated, shaded area, fruits will hold for 3-5 weeks even under the colder temperatures experienced in early-mid October. For fruits intended for long-term storage into the winter, first warm the fruits to condition them, then store near the minimum for the type.
For more detail on storage, handling and ripening techniques of the different cucurbits, refer to the specific produce fact sheets available through the UC Davis Postharvest Technology website. These fact sheets are comprehensive guides to maintaining postharvest quality of the specific crop of interest.
For more detail on storage, handling and ripening techniques of the different cucurbits, refer to the specific produce fact sheets available through the UC Davis Postharvest Technology website: http:// postharvest.ucdavis.edu. These fact sheets are comprehensive guides to maintaining postharvest quality of the specific crop of interest.
Postharvest Care (Melons)
Most melons have a relatively short storage life. Larger growers may have refrigerated storage facilities but smaller producers will only hold fruits for a few days. Postharvest handling is as important as the growing of the crop. If possible, cool the fruits quickly after harvest or harvest is in the early morning when temperatures are cool and plants are well hydrated.
Watermelons stored at 55-60°F and 90% humidity will keep for 10-15 days. Do not store below 50°F, as fruits are sensitive to chilling injury and disease development. If kept at ambient temperatures, watermelon will hold for about 5-7 days. Cantaloupe are highly perishable and will maintain good quality for about 1 week. Full-slip cantaloupe can be stored at 40°F but those harvested at half-slip should not be stored below 45°F to ensure they ripen properly. Never store casaba and other specialty melons at temperatures less than 50°F as they are subject to chilling injury. For more detail on storage, handling and ripening techniques of the different melons, refer to the specific produce fact sheets for the different melons available through the UC Davis Postharvest Technology website: postharvest.ucdavis.edu.