Growing The Saskatoon - A Prairie Heritage
Article by Richard G. St-Pierre, Ph.D.
(This article is a revised version of the article that was originally published in 2001 in The Cider Press 14(2): pp 19-24.)
Part 3
Nutrition
There are no well-defined recommendations for fertilizing saskatoons. Soil testing should be conducted prior to planting and soil nutrient levels should be adjusted as required for fruit crops in general. Annual soil and leaf testing and monitoring for deficiencies will provide additional information on nutritional needs within an orchard. The annual application of compost or well-composted manure may meet all nutritional requirements unless the soil is very sandy. Iron chlorosis may be a problem on heavy, excessively wet soils, or on soils with a high pH. Fertilization should not be necessary at the time of transplanting. It is widely held that a starter fertilizer high in phosphorus should be added to the soil prior to placing the plant, in the belief that this will stimulate root growth and promote rapid transplant establishment. However, studies have indicated that applications of high P fertilizers do not promote either root or shoot growth in woody plants except where substantial deficiencies exist. Excessive soil fertility may actually reduce root development and over-fertilization may cause a spurt of growth that the roots can't support. Concentrated fertilizer can burn roots and cause plant death.
Irrigation
Where rainfall may be inadequate, irrigation is essential for the successful establishment of a saskatoon orchard and is important to maximize yields, and to minimize plant stress and problems with diseases such as canker. New transplants should be monitored closely and irrigated every 1 to 2 days with small volumes of water, so as to ensure that the root plug does not dry out. It is very important to maintain even soil moisture levels. The root plug of young saskatoon transplants dehydrates at a similar rate to the soil near the top of the root plug, even if soil near the base of the plug is adequately moist. To prevent root damage from dehydration in newly-transplanted saskatoons, the moisture level of the soil near the top of the root plug must be monitored in order to determine if irrigation is necessary. Mature plants require a consistent supply of water, especially on sandy soils, but it is possible to water saskatoons too much. In regions where irrigation or rainfull is excessive, fruit cracking and an insipid flavour will be the result.
Pruning
Past practice has dictated that pruning at planting time will improve a transplant's chances of survival and enhance subsequent growth. It is usually thought that such a practice will reduce the transplant's requirements for water because of the reduction in actual and potential leaf area. However, studies with apple, pear, peach, linden, and birch, where pruned transplants have been compared to unpruned transplants, have indicated that a minimalist approach to pruning newly-transplanted plants is the best. These studies all have indicated that topping or severe pruning at transplanting is not beneficial to survival, establishment and subsequent growth, and in fact may have substantial negative effects on subsequent root and shoot growth. The additional moisture stress resulting from leaving the shoot intact (that is, not-pruning) is more than compensated for by the additional availability of carbohydrates stored in the shoot, and the capacity to produce carbohydrates by the leaves, both of which are important to root and shoot growth. Additionally, severe pruning of young fruit trees delays the onset of bearing because of delayed growth and consequent lengthening of the period of juvenility. For the first three years following orchard establishment, pruning should be primarily associated with the maintenance of plant health and the encouragement of vigour and growth. During this period, pruning primarily involves the removal of weak, diseased, damaged and dead shoots. Low, spreading branches should be removed and the centers of shrubs thinned to keep them open and thus allow good air circulation. Subsequently, depending on the rate of growth, older wood (stems greater than 2.5 cm in diameter at the base) are thinned to improve airflow and stimulate new shoot production. Removal of diseased or damaged wood may be carried out at anytime. Pruning a large planting of saskatoons is a time consuming process. Pneumatic pruning equipment will help reduce the time an effort required for this task. Hand saws, good quality loppers, and secateurs may be all that is needed to prune a small saskatoon orchard.
Pollination & Yield
The saskatoon is mainly self-fruitful and does not require pollinizer cultivars for fruit set. Yields vary with year, location, cultivars grown, plant age, plant density, and management practices. Yields may range from 1 to over 8 kg per plant.
Weed Control
Weeds may be controlled through mulching, cultivation and the herbicides linuron, dichlobenil and glyphosate, all of which are registered for use on established saskatoons.
Insect Pest & Disease Control
The primary insect pest of young saskatoons is the woolly elm root aphid, which can cause significant plant losses during the initial years of orchard establishment. A soil drench of the insecticide Orthene is used to control this pest. Cultural methods of control have not been successful. During fruiting years, insect and disease control practices are essential to insure consistent fruit quality and yield. The primary insect pests of the saskatoon include the saskatoon bud moth, leaf rolling caterpillars, saskatoon sawfly and the apple curculio. IPM techniques designed for apple orchards may be suitable for control of the some of these insects in saskatoons. The primary diseases include Entomosporium leaf and berry spot, saskatoon-juniper rust and Cytospora canker. Pruning to ensure adequate air circulation, and the use of the registered fungicides Kumulus, Topas, and Nova, will help control these diseases.
Harvest, Cleaning & Sorting
Harvesting the saskatoon crop is one of the most labour intensive parts of the orchard operation. Fruit may be harvested by hand or with the aid of mechanical harvesting equipment (hand operated, pull-type or self-propelled). The hand-operated BEI Model H Harvester, developed for the blueberry industry, simply shakes fruit from branches into catch frames and works very well for harvesting saskatoons. More advanced harvesters include various pull-type and self-propelled harvesters that travel overtop of the row shaking the fruit into a catching area where fruit are automatically transferred to containers via a conveyer system. After harvesting, fruit should be cooled, cleaned and sorted as soon as possible. Fresh saskatoon fruit are very perishable and don't have a shelf life much beyond 3 or 4 days unless they are cooled and stored using modified atmosphere packaging.
Economics & Marketing
Saskatoons may be sold fresh or frozen direct from the farm gate, at Farmer's Markets, to wholesalers, to restaurants, or to processors. Some growers are also in the business of processing their crop. These processors often also purchase fruit from other growers. The price received for saskatoon fruit varies from $3.00 to $8.00 per kg depending on the year, volume sold and the particulars of the market. Fruit processors typically pay at least $4.00 per kg for frozen fruit. Small quantities of fresh fruit sold direct to the consumer generally sell for $6.00 - $8.00 per kg. Since saskatoons typically take 6 to 8 years to reach full production, the cost of establishing an orchard may take 7 to 10 years to recover. Harvesting and cleaning the fruit are the most costly parts of the orchard operation. Mechanical fruit harvesting is more economical than hand picking if the capital cost of the harvester is spread over a large enough orchard.
More information on saskatoon production may be found in: Growing Saskatoons - A Manual For Orchardists.