Growing degree days (GDD) are a heuristic tool in phenology. GDD are used by horticulturists and gardeners to predict the date that a flower will bloom or a crop reach maturity. Heuristic is the art and science of discovery and invention. ... Phenology is the study of the times of recurring natural phenomena especially in relation to climate change. ... The Latin words hortus (garden plant) and cultura (culture) together form horticulture, classically defined as the culture or growing of garden plants. ... A gardener is any person involved in the growing and maintenance of plants, notably in a garden. ...

In the absence of extreme conditions such as unseasonal drought or disease, plants grow in a cumulative stepwise manner which is strongly influenced by the ambient temperature. Growing degree days take aspects of local weather into account and allow gardeners to predict (or, in greenhouses, even to control) the plants’ pace toward maturity. A drought usually refers to an extended period of below-normal rainfall. ... Weather is an all-encompassing term used to describe all of the many and varied phenomena that can occur in the atmosphere of a planet. ... A greenhouse in Saint Paul, Minnesota. ...

GDD calculation

GDD are calculated by taking the average of the daily high and low temperature each day compared to a baseline (usually 10 °C). As an equation; GDD=(((High+Low)/2)-Baseline) GDDs are typically measured from the winter low.

For example, a day with a high of 23 °C and a low of 12 °C would contribute 7.5 GDDs. Any temperature below the baseline is set to the baseline before calculating the average. For example, a day with a high of 13 °C and a low of 7 °C would still contribute 1.5 GDDs. Likewise, the maximum temperature is usually capped at 30 °C because most plants and insects do not grow any faster above that temperature. However, some warm temperate and tropical plants do have significant requirements for days above 30 °C to mature fruit or seeds.

Plant development

Selected example GDDs (all in °C base 10 °C):

• Witch-hazel (Hamamelis spp.) - begins flowering at <1 GDD
• Red maple (Acer rubrum), Forsythia spp., Sugar maple (Acer saccharum) - begin flowering at 1-27 GDD
• Norway maple (Acer platanoides), White ash (Fraxinus americana) - begins flowering at 30-50 GDD
• Crabapple (Malus spp.), Common Broom (Cytissus scoparius) - begins flowering at 50-80 GDD
• Horsechestnut (Aesculus hippocastanum), Common lilac (Syringa vulgaris) - begin flowering at 80-110 GDD
• Beach plum (Prunus maritima) - full bloom at 80-110 GDD
• Black locust (Robinia pseudoacacia) - begins flowering at 140-160 GDD
• Catalpa (Catalpa speciosa) - begins flowering at 250-330 GDD
• Privet (Ligustrum spp.), Elderberry (Sambucus canadensis) - begin flowering at 330-400 GDD
• Purple loosestrife (Lythrum salicaria) - begins flowering at 400-450 GDD
• Sumac (Rhus typhina) - begins flowering at 450-500 GDD
• Butterfly bush (Buddleia davidii) - begins flowering at 550-650 GDD
• Corn (maize) - 1360 GDD to crop maturity
• Dry beans - 1100-1300 GDD to maturity depending on cultivar and soil conditions
• Sugar Beets - 130 GDD to emergence and 1400-1500 GDD to maturity
• Barley - 125-162 GDD to emergence and 1290-1540 GDD to maturity
• Wheat (Hard Red) - 143-178 GDD to emergence and 1550-1680 GDD to maturity
• Oats - 1500-1750 GDD to maturity

Witch hazel is the name of: Witch-hazel: Hamamelis, a genus of decorative shrubs in North America and east Asia. ... Binomial name Acer rubrum L. Red Maple (Acer rubrum) is also known as Swamp Maple or Soft Maple. ... Binomial name Acer saccharum Marshall The Sugar Maple Acer saccharum is a prominent tree in the hardwood forests of eastern North America. ... Binomial name Acer platanoides The Norway Maple (Acer platanoides) is a maple native to eastern and central Europe and southwest Asia, from France east to Russia, north to southern Scandinavia and southeast to northern Iran. ... Binomial name Fraxinus americana L. The White Ash (Fraxinus americana) is one of the largest of the ash genus Fraxinus, growing to 35 m tall. ... Species - Southern Crab - Siberian Crabapple - Sweet Crabapple - Apple - Japanese Crabapple - Oregon Crab - Chinese Crabapple - Prairie Crab - Asian Wild Apple - European Wild Apple Malus, the apples, is a genus of about 30-35 species of small deciduous trees or shrubs in the family Rosaceae, including most importantly the domesticated Orchard or... Binomial name Cytisus scoparius (L.) Link Common Broom (Cytisus scoparius or Sarothamnus scoparius), also known as European Broom, Scots Broom, Irish Broom or English Broom is a perennial, leguminous shrub native to northwestern Europe, where it is found in sunny sites, usually on dry, sandy soils. ... Species Aesculus arguta: Texas Buckeye Aesculus californica: California Buckeye Aesculus chinensis: Chinese Horse-chestnut Aesculus flava (): Yellow Buckeye Aesculus glabra: Ohio Buckeye Aesculus hippocastanum: Common Horse-chestnut Aesculus indica: Indian Horse-chestnut Aesculus neglecta: Dwarf Buckeye Aesculus parviflora: Bottlebrush Buckeye Aesculus pavia: Red Buckeye Aesculus sylvatica: Painted Buckeye Aesculus turbinata... Species About 20 species; see text. ... Plum is also a nickname for British humorist P.G. Wodehouse. ... Binomial name Robinia pseudoacacia L. Black Locust (Robinia pseudoacacia) is a tree in the subfamily Faboideae of the pea family Fabaceae. ... Species 11 species, including: Catalpa bignonioides Catalpa bungei Catalpa fargesii Catalpa longissima Catalpa ovata Catalpa punctata Catalpa speciosa Catalpa tibetica Catalpa (Catalpa), also spelled Catawba, is a genus of mostly deciduous trees of the United States, West Indies, and east Asia, in the flowering plant family Bignoniaceae. ... Species See text Privet was originally the name for the European semi-evergreen shrub Ligustrum vulgare, and later also for the more reliably evergreen Ligustrum ovalifolium (Japanese privet), used extensively for privacy hedging (hence privet, private). ... Species See text. ... Binomial name Lythrum salicaria L. Purple loosestrife (Lythrum salicaria)—also known as Spiked loosestrife, Purple lythrum, Rainbow weed or Salicaire—is a semi-aquatic herbaceous plant belonging to the loosestrife family, Lythraceae. ... Species About 250 species; see text Rhus is a genus approximately 250 species of woody shrubs and small trees in the family Anacardiaceae. ... Species About 100 species, including: Buddleja albiflora Buddleja alternifolia Buddleja americana Buddleja asiatica Buddleja auriculata Buddleja australis Buddleja bhutanica Buddleja candida Buddleja colvilei Buddleja crispa Buddleja crotonoides Buddleja curviflora Buddleja davidii Buddleja delavayi Buddleja fallowiana Buddleja forrestii Buddleja globosa Buddleja indica Buddleja japonica Buddleja lindleyana Buddleja madagascariensis Buddleja marrubiifolia Buddleja... Binomial name Zea mays L. Maize (Zea mays ssp. ... Green beans Bean is a common name for large plant seeds of several genera of Fabaceae (formerly Leguminosae) used for food or feed. ... This Osteospermum Pink Whirls is a successful cultivar. ... Two sugar beets - the one on the left has been cultivated to be smoother than the traditional beet, so that it traps less soil. ... Binomial name Hordeum vulgare L. Barley (Hordeum vulgare) is a major food and animal feed crop, a member of the grass family Poaceae. ... Species T. boeoticum T. compactum T. dicoccoides T. dicoccon T. durum T. monococcum T. spelta T. sphaerococcum References:   ITIS 42236 2002-09-22 Wheat (Triticum spp. ... Binomial name Avena sativa Carolus Linnaeus (1753) The Oat (Avena sativa) is a species of cereal grain, and the seeds of this plant. ...

Insect development and pest control

Growing degree days are also used by some farmers to time their use of pest controls so they are applying the treatment at the point that the pest is most vulnerable. For example: Classes & Orders See taxonomy Insects are invertebrate animals of the Class Insecta, the largest and (on land) most widely-distributed taxon within the phylum Arthropoda. ... Pest control refers to the regulation or management of another species defined as a pest, usually because it is detrimental to a persons health, the ecology or the economy. ... Farmer spreading grasshopper bait in his alfalfa field. ...

• Black cutworm larvae have grown large enough to start causing economic damage at 165 GDD
• Azalea Lace Bug emerges at about 130 GDD
• Boxwood leaf miner emerges at about 250 GDD

Several beekeepers are now researching the correlation between GDD and the lifecycle of a honeybee colony. Beekeeping (or apiculture) is the maintenance of one or more hives of honeybees. ... Species Apis andreniformis Apis cerana, or eastern honey bee Apis dorsata, or giant honey bee Apis florea Apis koschevnikovi Apis laboriosa Apis mellifera, or western honey bee Apis nigrocincta Apis nuluensis Honey bees are a subset of bees which represent a far smaller fraction of bee diversity than most people...

Baselines

10 °C is the most common base for GDD calculations, however, the optimal base is often determined experimentally based on the lifecycle of the plant or insect in question.

• 5.5 °C wheat, barley, rye, oats, flaxseed, lettuce, asparagus
• 6 °C stalk borer moth
• 7 °C Corn Rootworm
• 8 °C sunflower, potato
• 9 °C Alfalfa weevil
• 10 °C maize (including sweet corn), sorghum, rice, soybeans, tomato, Black cutworm, European Corn Borer, standard baseline for insect and mite pests of woody plants
• 11 °C Green Cloverworm
• 12 °C many other crop calculations
• 30 °C the USDA measure heat zones in GDD above 30 °C; for many plants this is significant for seed maturation, e.g. reed (Phragmites) requires at least some days reaching this temperature to mature viable seeds

GDDs may be calculated using either Celsius or Fahrenheit, though they must be converted appropriately; 5 GDD^C = 9 GDD^F Species T. boeoticum T. compactum T. dicoccoides T. dicoccon T. durum T. monococcum T. spelta T. sphaerococcum References:   ITIS 42236 2002-09-22 Wheat (Triticum spp. ... Binomial name Hordeum vulgare L. Barley (Hordeum vulgare) is a major food and animal feed crop, a member of the grass family Poaceae. ... Binomial name Secale cereale M.Bieb. ... Binomial name Avena sativa Carolus Linnaeus (1753) The Oat (Avena sativa) is a species of cereal grain, and the seeds of this plant. ... Binomial name Linum usitatissimum L. Linnaeus, 17?? Common flax (also known as linseed) is a member of the Linaceae family, which includes about 150 plant species widely distributed around the world. ... Binomial name Lactuca sativa L. Percentages are relative to US RDI values for adults. ... Binomial name Asparagus officinalis L. Asparagus is a type of vegetable obtained from one species within the genus Asparagus, specifically the young shoots of Asparagus officinalis. ... Binomial name Helianthus annuus L. The sunflower (Helianthus annuus) is an annual plant in the Family Asteraceae, with a large flower head (inflorescence). ... Binomial name Solanum tuberosum L. The potato (Solanum tuberosum) is a perennial plant of the Solanaceae, or nightshade, family, commonly grown for its starchy tuber. ... Binomial name Zea mays L. Maize (Zea mays ssp. ... Species About 30 species, see text Sorghum is a genus of about 20 species of grasses, native to tropical and subtropical regions of Eastern Africa, with one species native to Mexico. ... Species Oryza glaberrima Oryza sativa Rice refers to two species (Oryza sativa and Oryza glaberrima) of grass, native to tropical and subtropical southern & southeastern Asia and to Africa, which together provide more than one fifth of the calories consumed by humans[1]. (The term wild rice can refer to wild... Binomial name Glycine max Soybeans (US) or soya beans (UK) (Glycine max) are a high-protein legume (Family Fabaceae) grown as food for both humans and livestock. ... Binomial name Solanum lycopersicum L. Percentages are relative to US RDI values for adults. ... The U.S. Department of Agriculture, also called the Agriculture Department, or USDA, is a Cabinet department of the United States Federal Government. ... species Pragmites australis Reed is a generic term used to describe numerous plants including: Common Reed (Phragmites australis Cav. ...

See also

• Heating degree day
• Weather derivatives

Heating degree day (HDD) and cooling degree day (CDD) are quantitative indices demonstrated to reflect demand for energy to heat or cool houses and businesses. ... Weather derivatives are financial instruments that can be used by organisations or individuals as part of a risk management strategy to reduce risk associated with adverse or unexpected weather conditions. ...

External links

• Growing Degree Days as a Method of Rating the Maturity of Corn Hybrids
• Current year-to-date GDDs for selected US cities
• a table of GDDs necessary for grapes
• GDDs to various stages of maturity for selected crops
• University of Massachusetts Amherst Extension, Integrated Pest management Tools, web site accessed Jan 2005