August 2013 Newsletter (vol.21)   >>   Late summer, Time to enjoy



Apple Orchard

After a long season of hard work and challenging weather, it is time to think about the harvest. The next few months farmers and growers will be preparing for the harvest, storing, and packaging of many fruits. Some of the most common, yet not necessarily the easiest, of these fruits are apples, grapes, and tomatoes, among many others. Professionals and amateurs alike learn how to judge the perfect time to pick, how to store, and better techniques for their harvest each year.

The key to a successful and profitable apple harvest is picking at the proper time and storing them correctly. Each year the ideal time for harvest may vary; cloudy days, cool conditions, and drought can all delay the fruit maturity. The first step is to determine when the fruit has reached maturity and is ready to be picked. There are a few options in doing this, one being a starch test. This is a visual test done by cutting the apple horizontally and spraying with a mild iodine solution. The iodine will turn cells containing starch a dark color. However the iodine solution will not color the cells containing sugar. When the core of the apple is clear of starch, uncolored, and the rest is dark, then the fruit is unripe and immature. Fruit good for storing should be about half or a little more clear of starch and uncolored by the iodine. Other options for testing ripeness are using a pressure tester, or the most precise way, is by using a refractometer. The refractometer is an instrument used to measure the percent of sugars in a liquid. Varieties differ however shoot for 10 percent of sugars at harvest time. For highly colored varieties this is an excellent option. Also, keep in mind that fruit on the edges of the trees and in direct sun may turn color more quickly than the ones hidden by branches and limbs, therefore you may need to conduct more than one harvest. To reach those fruits in large trees, try using an tripod orchard ladder. Pears also use simmilar practices and techniques like apples. Pears will look “green” when they are ready to be picked, if you wait until they have a “yellow” skin color they will be soft and not store long.

After you have picked your apples, you must be able to properly store them to preserve the quality. If you are planning on storing a large quantity for an extended period of time, be sure to choose the proper cultivar. Red Delicious and Golden Delicious are considered to be good storage apples. The storage life for many cultivars range from 2 weeks to 6 months, at roughly 32 degrees with 90 percent humidity, lower temperatures slows the respiration rate and preserves good quality. The relative humidity must be kept high to help keep the apples from dehydration. There are products designed to aid in the storage of apples with temperature and humidity in mind. Small quantities of apples are often kept and sold in perforated plastic bags. Then the bags can be stored in refrigerators to reduce the respiration rate and keep them firm and crisp. If using boxes or crates, try to avoid stacking fruits more than two high to keep ventilation and not bruise them. When the harvest is too abundant for consumption there are alternatives in such as, drying, freezing and canning. To ensure your hard work pays off, the key words to storage are cool and ventilated!

Another very popular fruit in harvest this time of year is grapes! It is hard to beat the birds, but make sure your grapes are ripe before you harvest. There are a few things to keep in mind when deciding to harvest, most grapes color up before they flavor up so don’t rush it. When they are ready, the whitish coating on the fruit will become more noticeable, and the seed will change from green to brown. It is a good idea to cut a few open to check before harvest. Another indicator of ripeness is the size and firmness of the grape. Be sure to know the cultivar’s characteristics, but most should be slightly less firm. Unlike other fruits, once you pick them they will not ripen any further, so be sure they are ready. Another helpful hint to harvesting grapes is to, harvest at night. It is good for the workers and the environment. There is less heat which leads to higher productivity, cooler temperatures that help the grapes stay firmer, no refrigeration is needed, and there are fewer trucks on the road at that time, win win! Techniques also vary, some prefer to hand-pick their grapes, others use more modern ways with machines, both options have their advantages. The obvious perks of the machine method are time and labor, however there is the issue of “MOG” (material other that grapes). By using shears, harvest knives, bushel baskets, and lugs, you have control over what actually ends up in the tanks and barrels. Picking the fruit perfectly ripe may mean 2, 3 or even 5 passes through the vineyard. After harvest, grapes can be stored up to eight weeks. As always, this is cultivar dependant, but ideally they should be stored at 32 degrees, with a relative humidity of 85 percent. If you have too many to store, jellies, jams, juice, and wine are excellent alternatives.

Quite possibly the most popular harvest from home owner to mass producer is the tomato. There are two basic types of tomatoes: determinate, a “bush” type with early fruit bearing and doesn’t need staking, and indeterminate, the type that are later to mature and typically need staking or cages. To be sure that your harvest contains the best flavor, provide them with fertile soil by using 5-10-10 formulas or bone meal. Keep in mind that tomatoes need warmth to ripen, not light. They will stop ripening when temperatures reach over 86 degrees. After about 60-85 days from planting, it is time to start the harvest. When the fruit is evenly colored, but still firm they are ready to pick. Be sure to keep checking your tomato plants often, for they will continue to produce until frost. After collecting your fruit, wash and dry the tomatoes, and remember not to pack them more than two deep. When storing ripe tomatoes keep the temperature between 45 and 50 degrees with relative humidity at 90-95 percent and they should last roughly 4-7 days. If you are storing green tomatoes, have the temperature at 55-70 degrees with humidity around 90-95 percent to keep for 1-3 weeks. And as always if you end up with more tomatoes than you can handle, canning, freezing, and drying are other great ways to enjoy your harvest!

It’s that time. You have worked hard all season; you know how to best harvest your apples, grapes, and tomatoes. Choose your methods of choice to pick, store, and enjoy the fruits of your harvest!


Iowa State University, University Extension

Purdue University Consumer Horticulture