Plants 4 Bees :: Rosaceae :: photo_Pyrus_communis

Pyrus communis

Scientific name	:	Pyrus communis
Origin	:	Europe and western Asia
Description	:	Most commercial pear cultivars, often referred to as European or French types, have been derived from Pyrus communis. The exception to this are cultivars such as ‘Kiefer’ and ‘LeConte’ which are hybrids of P. communis and P. pyrifolia and are referred to in the botanical literature as Pyrus x Lecontei. P. communis is a long-lived pyramidal shaped tree that when not pruned can reach 50 ft in height, but in commercial orchards is greatly restrained by pruning. The leaves are leathery and without “fuzz” (glabrous), and range in length from 0.8 to 3, and occasionally up to 4 inches in length. The flowers emerge along with the first leaves and are about one inch across. As in apple, there are five petals and many stamens. There are also five styles, but unlike apple, the styles are not fused at their base. The flowers are generally white, but relatively rarely, can also assume a pinkish cast. When the flowers open, the stamens are bent inward and do not reach the height of the stigmas. The stigmas become receptive before the anthers release their pollen, and as the stamens mature they straighten, placing the anthers at the same height as the stigma. At this point, the anthers release their pollen. The nectary area is limited to 5 small slits between the stamens and the petals.
Distribution	:	The top pear producing states in the U. S. in descending order of production are Washington, California, Oregon, New York and Michigan. The major Canadian pear producing provinces in descending order of production are Ontario, British Columbia and Nova Scotia. The species frequently escapes culture and then most often can be found in thickets, clearings, and borders of woods. The species is frequently considered a zone 5 plant, but Dirr[7] rates it as a zone 4 to 8 (9) species , which he apparently feels under some limited circumstances can be grown in zone 9.
Blooming period	:	The blooming period of pear is about the same time as, but often a little ahead of apple. In Michigan that is usually late April or early May. Dirr[7] describes the blooming date in Athens, Georgia as generally during the first half of March, but sometimes as early as late February.
Importance	:	The sugar concentration of the nectar is low (4-25%)[McGregor] and as a honey producer, the common pear is considered inferior to apple. Because of its low nectar sugar concentration, the species sometimes fails to attract nectar collecting honey bees.
Honey potential	:	Crane[2] places common pear in her class 1 (lowest) honey potential category (0-22.3 lbs/acre). She also reports a sugar value range of 0.09 to 0.30 mg sugar per floret/24 hrs.
Honey	:	no data
Pollen	:	The Pollen is quite attractive to bees and is said to have a high protein content[15]. Howes[9] provides the information that the pollen is pale yellow, with perhaps a hint of green.
Additional information	:	Pollination considerations: The common pear produces many flowers and there is general agreement that a full fruit set would be highly undesirable. The estimates of the number of flowers that are needed to set fruit for an acceptable crop vary between 2 to 7% [12]. Over the years there has been some confusion in the literature about the pollination requirements for pear. Part of this confusion appears to this writer to result from differences in what is accepted as self-fertile by different authors when they report their findings in the literature. There are two issues here. The first is parthenocarpy where fruit will develop without any pollen transfer. In this case there is no pollination, and there also will be no seed development. The second issue is what I will call true self-compatibility where fruit is set when pollen is transferred from the anthers to the stigma of the same flower or at least flowers from the same cultivar. To meet the requirement of the definition I am using, viable seed would need to be produced. If no seed is produced, by this set of definitions, the fruit development would be considered parthenocarpic. Frequently, authors haven’t made these distinctions, and only rarely have they tested the seeds for viability. In North America, historically much confusion arose over the cultivar ‘Bartlett’, which at the time the confusion was arising, was the major pear cultivar of the U.S. It now seems that under good conditions, in well managed orchards, ‘Bartlett’ can become parthenocarpic, but under poorer conditions parthenocarpy doesn’t occur, and a pollinator variety is needed to set fruit. To place the subject of self-sterility in perspective, self-sterility is more typical in pear than in apple, but historically has been considered to be less common than in sweet cherries[13]. There has, however, has been a push relatively recently to develop self-compatible varieties of sweet cherry. The diploid pear cultivars are almost entirely self sterile. Apparently for practical purposes, the same can be said of the triploid cultivars. The tetraploid varieties appear to be more self-fertile than either the diploid or triploid cultivars. The degree of parthenocarpy varies with cultivar and growing conditions [13], but even in cultivars that are partly self-fertile, fruit set is increased by cross pollination. McGregor [12] came to the following conclusion in his 1976 treatise on pollination, “Evidently insect cross pollination is essential for some cultivars in all areas and for all cultivars in some areas.” To play it safe, generally most cultivars are considered self-sterile and require a pollinator. Most cultivars of pear are cross-compatible, that is, the pollen of one cultivar can pollinate almost any other cultivar. One of the major exceptions to this rule is the ‘Bartlett’ ‘Seckle’ combination[18]. When these two cultivars are planted together, they must be accompanied by a third cultivar. While it may be stating the obvious, a pollinator variety should be chosen that blooms at the same time as its companion variety. The necessary information to make appropriate cultivar choices can usually be provided by reputable fruit tree vendors. For pear, pollination recommendations that appear in the literature generally range from one strong colony per two acres to two strong colonies per acre. It is usually considered best to scatter them throughout the orchard or at least to scatter them along the edge of the orchard. Be sure to read the pollination discussion that is presented in the accompanying sidebar that discusses pollination considerations that are generally applicable to the deciduous rosaceous tree fruits. Other considerations Despite its showy floral display in the spring and the attractive glossy leaves in summer, P. communis is generally not considered to be a good choice as an ornamental for the home landscape because of its extreme susceptibility to the disease, fireblight. It also is attractive to pear psylla that produces copious amounts of honeydew, which in addition to the possibility of contaminating a high quality honey crop, is a culture medium that produces a black sooty mold which can give any object covered with honeydew (the leaves, the fruit and your car, etc) an unsightly sooty black appearance.
Reference	:	1 Ayers, G. S. and J.R. Harman. 1992. Bee Forage of North America and the Potential for Planting for Bees. Inventory and Relative Importance of Nectar and Pollen Plants of North America. In The Hive and the Honey Bee, (J. M. Graham Editor). Dadant and Sons. Hamilton, IL. 2 Crane, E. The Flowers Honey Comes From. 1975. In: Honey A Comprehensive Survey (E. Crane Ed.). Crane, Russak and Company, Inc. New York, NY. 3 Crane, E., P. Walker and R. Day. 1984. Directory of Important World Honey Sources. International Bee Research Association. London. 4 DeGrandi-Hoffman, G., R. Hoopingarner and K. Baker. 1984. Pollen transfer in apple orchard:tree-to-tree or bee-to-bee? Bee World 65:126-133. 5 DeGrandi-Hoffman, G., R. Hoopingarner and K. Baker. 1985. The Influence of Honey Bee "Sideworking" Behavior on Cross-pollination and Fruit Set in Apples. HortScience 20(3):397-399. 6 Dennis, F. 2003. Flowering, Pollination and Fruit Set and Development. In: Apples Botany Production and Uses. (Ferree, D. C. and I. J. Warrington. Eds.) CABI Publishing. Cambridge, MA. 7 Dirr, M. A. 1998. Manual of Woody Landscape Plants. Their Identification, Ornamental Characteristics, Culture, Propagation and Uses (Fifth Edition). Stipes Publishing L.L.C. Champaign, IL. 8 Free, J. 1993. Insect Pollination of Crops. Academic Press Limited. London 9 Howes, E. N. 1979. Plants and Beekeeping. Faber and Faber. London. 10 Lovell, H. B. 1966. Honey Plants Manual. A Practical Field Handbook for Identifying honey Flora. A. I. Root Co. Medina, OH. 11 Luby, J. J. 2003. Taxonomic Classification and Brief History. In: Apples Botany Production and Uses. (Ferree, D. C. and I. J. Warrington. Eds.) CABI Publishing. Cambridge, MA. 12 McGregor, S. E. 1976. Insect Pollination of Cultivated Crop Plants. Agricultural Handbook No 496, Agricultural Research Service. United States Department of Agriculture. Washington DC. This publication is being updated and is available on the web at: gears.tucson.ars.ag.gov/book. 13 Nyéki, J. M. Soltész. 1996. Floral Biology of Temperate Zone Fruit Trees and Small Fruits. Akadémiai Kiadó, Budapest. 14 Pellett, F. C. 1978. American Honey Plants. Dadant and Sons, Hamilton, IL. 15 Ramsay, J. 1987. Plants for Beekeeping in Canada and the Northern USA: A Directory of Nectar and Pollen Sources Found in Canada and the Northern USA. International Bee Research Association. London. 16 Roberts, J. The Origins of Fruit and Vegetables. Universe Publishing. New York. 17 USDA, NRCS. The PLANTS Database, Version 3.5 (http://plants.usda.gov). National Plant Data Center, Baton Rouge, LA 70874-4490 USA 18 Wyman, D. 1997. Wyman's Gardening Encyclopedia. Scribner, New York, NY.