A selected article from the Aquaponics Journal.
by Tim Carpenter
Hydroponics and controlled environment agriculture have the potential to change the way strawberries are produced now and in the future. Strawberries are available almost year-round at present but the quality suffers greatly as the shipping distance increases. Strawberries do not ship or store well. This makes the strawberry a good crop for greenhouse production and in outdoor areas where the climatic conditions allow economic production of strawberries. In addition to research and commercial production in hydroponic systems, there is some research going on growing strawberries in aquaponics as well. Since strawberry plants are relatively small, they do well in vertical growing systems, such as VertiGro, that take advantage of vertical growing space that might not otherwise be used in a greenhouse.
One of the most difficult crops to write about is the strawberry because it is such a complex plant species. For instance, a two hundred page book has been written about the Chandler which is a popular variety in the southeast. Each variety has its peculiarities which include day length, temperature, humidity, diseases, shelf life, color, size and taste. Not only are there many varieties but many varieties within a type or class of strawberry. These include everbearer, Junebearer, day neutral and short day varieties, all of which were bred to fit particular climates and markets.
In order to grow strawberries with success either commercially or at home the grower must know the difference between the different types of strawberry plants. The flowering cycle of the strawberry is effected by day length and the name describes the variety type pretty well.
The following is a short strawberry variety review:
Short-day (SD)- These are winter varieties for outdoors (in FL and CA) or in greenhouses with good light conditions. The current varieties being grown are Sweet Charlie, Treasure, Camarosa, Gemstar, Festival, Gaviotta, Earlibrite and Chandler. These varieties are normally planted in late September or early October. They're available in plugs, green top and frigo plants.
Day-neutral (DN)- These are spring and fall varieties for field or greenhouse. Plant in late August, early September or in February or March. These are types of everbearers but are not true everbearing. They do not produce well during the winter and tend to cycle. However, they produce early. The varieties include Seascape, Everrest, Eversweet, Tristar, Tribute, Diamante, and Aromas. These plants are also good for hanging baskets after being used for commercial production or they can be sold to home gardeners or nurseries. Seascape is the most popular, especially in the west, but Tristar and Tribute are also favored in the east and Midwest. They are also good for baskets and home sales.
Everbearers (EB)- These are spring or summer varieties with some fall production. They are not really ever bearing but in some areas may cycle off and on throughout the year. They are not recommended for the Verti-Gro (vertical hydroponics) system. The varieties include Quinalt, Ft. Laramie and others. They are okay for home garden sales and hanging baskets.
Junebearers (JB)- They bear late May through June and sometimes into July, just as the name implies. They are not recommended for the Verti-Gro system or for greenhouse production. However, very little research has been done on these varieties as an "over-winter" crop in vertical towers. Production would be 4-6 week earlier in the vertical towers, especially if wrapped with a crop cover. June bearers produce very heavy over a short period of time that lasts for approximately 4-5 weeks. The varieties include Honeoye, Jewel, Cardinal Earliglo and others.
NOTE: The key to a successful crop is how the plants are handled in shipment and how fast they are planted when they arrive at their destination.
Unlike most produce or fruits, the strawberry is not often grown from seed, even though each strawberry contains hundreds of seeds. It is not that the strawberry can't be grown from seed but, rather, because it is not practical or economical. New, more mature plants called "daughters" are produced from a mother plant in an area where the climate is conducive to growing strawberry plants during the summer and early fall. These "daughters" start as runners. The commercial industry refers to them as tips. The runners are harvested from certified disease-free stock. The runners develop into plants in about eight weeks. If they are allowed to root in the soil where its mother plant is grown a rooted strawberry plant is produced. From the time this plant is replanted to production is 7-9 weeks, depending on the variety and age when the plant is dug.
On the other hand some "daughters" are not allowed to root into the soil and instead are cut and rooted in a potting soil containing a high percentage of peat moss or coconut coir. These tips become plugs or fully rooted plants. Some plants are also started from tissue culture and micro-propagation. However, it is not as important how the plant is started but where the plant is grown and how to get the plant you need.
To make things more difficult there are three types of plants sold to commercial growers. These include bare root plants with green tops (fresh dug) that have been harvested in late September or early October. These plants are alive and have to be planted immediately when received. These plants deteriorate very rapidly, particularly in hot weather. In order to survive this type of plant must be misted up to 10 days immediately after planting to give it time to develop a new root system. These plants are primarily grown in Eastern Canada but, recently, more are being grown in or near the mountains of NC. These are areas where there are disease-free soils as well as the right type of soils for strawberry plant production. These areas also cool off quickly as fall arrives. This helps the plants mature quickly and develop flowers early. The reason for a plug is rather simple: ease of planting and earlier production. There are also fewer losses after planting. The plug costs 2-3 times as much as a bare root plant but early production may justify this extra expense. The major advantage of the plug is that it can be grown in a greenhouse or outdoors on benches in many areas where the soil may not be suitable for plant production. This opens up many more potential markets, especially for greenhouse production and for "U-pick" farms. Plugs can be shipped without refrigeration and in smaller quantities than bare root plants.
Bare root plants are shipped in refrigerated trucks in very large quantities with up to a million plants per truckload. A truckload of boxed plugs would be only 100,000 plants. It is easy to see why it is so difficult for the small grower or home gardener to obtain a small quantity of quality grown plants. Unless you are near a large strawberry production area you may not find good commercial varieties. Small commercial growers combine their orders to get a volume shipment at a reasonable price. The minimum order for a commercial variety is 1,000 plants. However, some California growers now supply some commercial varieties in boxes of 100 for testing purposes or for the home gardener. Some garden clubs, such as Master Gardeners, order large quantities and divide them up among their members. You may be able to locate some of these commercial varieties through commercial catalogs, particularly day-neutral varieties. The cost per plant may be rather high for 25-50 plants and the quality may not be the same as the commercial grower would get. Plant availability and plant quality are the most important factors when establishing a small farm. The development of the "day-neutral" plant will have a major impact on the development of small farms with direct sales. Since this type of plant is not effected by day length it can be grown in many areas as long as there is sufficient sunlight. Day neutral plants are available 8-9 months out of the year, from December to late August. They are shipped primarily from northern California. These plants have been stored at about 0.5 degrees below freezing since shortly after harvest. They are shipped frozen; hence, they are called "frigo" plants. They have to be shipped by air freight or no more than 2nd day air in order to arrive before they start to deteriorate. These types of plants need to be soaked in cool water and preferably in a rooting solution and a biofungicide as soon as they arrive. They can then be stored at about 38-40 degrees for a few days until the time is right for planting.
About the Author: Tim Carpenter is president of VertiGro, Inc. He owns patents on his high-density vertical growing systems and is well-know for his contributions and research in hydroponic fertilizers , strawberries and other crops. Tim can be reached by e-mail at: Tim@vertigro.com
Reprinted with permission from the Aquaponics Journal, copyright 2003.
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