Growing degree day - AbsoluteAstronomy.com

Growing degree days also called growing degree units (GDUs), are a heuristic

Heuristic

Heuristic refers to experience-based techniques for problem solving, learning, and discovery. Heuristic methods are used to speed up the process of finding a satisfactory solution, where an exhaustive search is impractical...

tool in phenology

Phenology

Phenology is the study of periodic plant and animal life cycle events and how these are influenced by seasonal and interannual variations in climate...

. GDD are a measure of heat accumulation used by horticulturists

Horticulture

Horticulture is the industry and science of plant cultivation including the process of preparing soil for the planting of seeds, tubers, or cuttings. Horticulturists work and conduct research in the disciplines of plant propagation and cultivation, crop production, plant breeding and genetic...

, gardeners, and farmer

Farmer

A farmer is a person engaged in agriculture, who raises living organisms for food or raw materials, generally including livestock husbandry and growing crops, such as produce and grain...

s to predict plant and pest development rates such as the date that a flower

Flower

A flower, sometimes known as a bloom or blossom, is the reproductive structure found in flowering plants . The biological function of a flower is to effect reproduction, usually by providing a mechanism for the union of sperm with eggs...

will bloom or a crop

Crop

Crop may refer to:* Crop, a plant grown and harvested for agricultural use* Crop , part of the alimentary tract of some animals* Crop , a modified whip used in horseback riding or disciplining humans...

reach maturity.

Introduction

In the absence of extreme conditions such as unseasonal drought

Drought

A drought is an extended period of months or years when a region notes a deficiency in its water supply. Generally, this occurs when a region receives consistently below average precipitation. It can have a substantial impact on the ecosystem and agriculture of the affected region...

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

Weather

Weather is the state of the atmosphere, to the degree that it is hot or cold, wet or dry, calm or stormy, clear or cloudy. Most weather phenomena occur in the troposphere, just below the stratosphere. Weather refers, generally, to day-to-day temperature and precipitation activity, whereas climate...

into account and allow gardeners to predict (or, in greenhouse

Greenhouse

A greenhouse is a building in which plants are grown. These structures range in size from small sheds to very large buildings...

s, even to control) the plants’ pace toward maturity.

Unless stressed by other environmental factors like moisture, the development rate from emergence to maturity for many plants depends upon the daily air temperature. Because many developmental events of plants and insects depend on the accumulation of specific quantities of heat, it is possible to predict when these events should occur during a growing season regardless of differences in temperatures from year to year. Growing degrees (GDs) is defined as the number of temperature degrees above a certain threshold base temperature, which varies among crop species. The base temperature is that temperature below which plant growth is zero. GDs are calculated each day as maximum temperature plus the minimum temperature divided by 2 (or the mean temperature), minus the base temperature. GDUs are accumulated by adding each day’s GDs contribution as the season progresses.

GDUs can be used to: assess the suitability of a region for production of a particular crop; estimate the growth-stages of crops, weeds or even life stages of insects; predict maturity and cutting dates of forage crops; predict best timing of fertilizer or pesticide application; estimate the heat stress on crops; plan spacing of planting dates to produce separate harvest dates. Crop specific indices that employ separate equations for the influence of the daily minimum (nighttime) and the maximum (daytime) temperatures on growth are called crop heat units (CHUs).

GDD calculation

GDD are calculated by taking the average of the daily maximum and minimum temperatures compared to a base temperature, T_base, (usually 10 °C). As an equation:

GDDs are typically measured from the winter low. Any temperature below T_base is set to T_base before calculating the average. 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.

For example, a day with a high of 23 °C and a low of 12 °C (and a base of 10 °C) would contribute 7.5 GDDs.

A day with a high of 13 °C and a low of 10 °C (and a base of 10 °C) would contribute 1.5 GDDs.

Plant development

Common name	Latin name	Number of growing degree days baseline 10 °C
Witch-hazel Witch-hazel Witch-hazel is a genus of flowering plants in the family Hamamelidaceae, with three species in North America , and one each in Japan and China...	Hamamelis spp.	begins flowering at <1 GDD
Red maple Red Maple Acer rubrum , is one of the most common and widespread deciduous trees of eastern North America. It ranges from the Lake of the Woods on the border between Ontario and Minnesota, east to Newfoundland, south to near Miami, Florida, and southwest to east Texas...	Acer rubrum	begins flowering at 1-27 GDD
Forsythia Forsythia Forsythia is a genus of flowering plants in the family Oleaceae . There are about 11 species, mostly native to eastern Asia, but one native to southeastern Europe. The common name is also Forsythia; the genus is named after William Forsyth.-Growth:They are deciduous shrubs typically growing to a...	Forsythia spp.	begin flowering at 1-27 GDD
Sugar maple Sugar Maple Acer saccharum is a species of maple native to the hardwood forests of northeastern North America, from Nova Scotia west to southern Ontario, and south to Georgia and Texas...	Acer saccharum	begin flowering at 1-27 GDD
Norway maple Norway Maple Acer platanoides is a species of maple native to eastern and central Europe and southwest Asia, from France east to Russia, north to southern Scandinavia and southeast to northern Iran....	Acer platanoides	begins flowering at 30-50 GDD
White ash White Ash For another species referred to as white ash, see Eucalyptus fraxinoides.Fraxinus americana is a species of Fraxinus native to eastern North America found in mesophytic hardwood forests from Nova Scotia west to Minnesota, south to northern Florida, and southwest to eastern...	Fraxinus americana	begins flowering at 30-50 GDD
Crabapple Crabapple Crabapple is a term used for several species of Malus in the family Rosaceae, which are characterized by small sour fruit resembling familiar table apples . They are usually small trees or shrubs....	Malus spp.	begins flowering at 50-80 GDD
Common Broom	Cytisus scoparius	begins flowering at 50-80 GDD
Horsechestnut Aesculus The genus Aesculus comprises 13-19 species of woody trees and shrubs native to the temperate northern hemisphere, with 6 species native to North America and 7-13 species native to Eurasia; there are also several hybrids. Species are deciduous or evergreen...	Aesculus hippocastanum	begin flowering at 80-110 GDD
Common lilac Lilac Syringa is a genus of about 20–25 species of flowering woody plants in the olive family , native to woodland and scrub from southeastern Europe to eastern Asia, and widely and commonly cultivated in temperate areas elsewhere....	Syringa vulgaris	begin flowering at 80-110 GDD
Beach plum Plum A plum or gage is a stone fruit tree in the genus Prunus, subgenus Prunus. The subgenus is distinguished from other subgenera in the shoots having a terminal bud and solitary side buds , the flowers in groups of one to five together on short stems, and the fruit having a groove running down one...	Prunus maritima	full bloom at 80-110 GDD
Black locust Black locust Robinia pseudoacacia, commonly known as the Black Locust, is a tree in the subfamily Faboideae of the pea family Fabaceae. It is native to the southeastern United States, but has been widely planted and naturalized elsewhere in temperate North America, Europe, Southern Africa and Asia and is...	Robinia pseudoacacia	begins flowering at 140-160 GDD
Catalpa Catalpa Catalpa, commonly called catalpa or catawba, is a genus of flowering plants in the trumpet vine family, Bignoniaceae, native to warm temperate regions of North America, the Caribbean, and East Asia....	Catalpa speciosa	begins flowering at 250-330 GDD
Privet Privet Privet was originally the name for the European semi-evergreen shrub Ligustrum vulgare, and later also for the more reliably evergreen Ligustrum ovalifolium , used extensively for privacy hedging. It is often suggested that the name privet is related to private, but the OED states that there is no...	Ligustrum spp.	begins flowering at 330-400 GDD
Elderberry Elderberry Sambucus is a genus of between 5 and 30 species of shrubs or small trees in the moschatel family, Adoxaceae. It was formerly placed in the honeysuckle family, Caprifoliaceae, but was reclassified due to genetic evidence...	Sambucus canadensis	begins flowering at 330-400 GDD
Purple loosestrife Purple loosestrife Lythrum salicaria is a flowering plant belonging to the family Lythraceae, native to Europe, Asia, northwest Africa, and southeastern Australia. It should not be confused with other plants sharing the name loosestrife that are members of the family Primulaceae...	Lythrum salicaria	begins flowering at 400-450 GDD
Sumac Sumac Sumac is any one of approximately 250 species of flowering plants in the genus Rhus and related genera, in the family Anacardiaceae. Sumacs grow in subtropical and temperate regions throughout the world, especially in Africa and North America....	Rhus typhina	begins flowering at 450-500 GDD
Butterfly bush	Buddleia davidii	begins flowering at 550-650 GDD
Corn (maize) Maize Maize known in many English-speaking countries as corn or mielie/mealie, is a grain domesticated by indigenous peoples in Mesoamerica in prehistoric times. The leafy stalk produces ears which contain seeds called kernels. Though technically a grain, maize kernels are used in cooking as a vegetable...	Zea mays	2700 GDD to crop maturity
Dry bean Bean Bean is a common name for large plant seeds of several genera of the family Fabaceae used for human food or animal feed.... s	Phaseolus vulgaris	1100-1300 GDD to maturity depending on cultivar Cultivar A cultivar'Cultivar has two meanings as explained under Formal definition. When used in reference to a taxon, the word does not apply to an individual plant but to all those plants sharing the unique characteristics that define the cultivar. is a plant or group of plants selected for desirable... and soil conditions
Sugar Beet Sugar beet Sugar beet, a cultivated plant of Beta vulgaris, is a plant whose tuber contains a high concentration of sucrose. It is grown commercially for sugar production. Sugar beets and other B...	Beta vulgaris	130 GDD to emergence and 1400-1500 GDD to maturity
Barley Barley Barley is a major cereal grain, a member of the grass family. It serves as a major animal fodder, as a base malt for beer and certain distilled beverages, and as a component of various health foods...	Hordeum vulgare	125-162 GDD to emergence and 1290-1540 GDD to maturity
Wheat Wheat Wheat is a cereal grain, originally from the Levant region of the Near East, but now cultivated worldwide. In 2007 world production of wheat was 607 million tons, making it the third most-produced cereal after maize and rice... (Hard Red)	Triticum aestivum	143-178 GDD to emergence and 1550-1680 GDD to maturity
Oat Oat The common oat is a species of cereal grain grown for its seed, which is known by the same name . While oats are suitable for human consumption as oatmeal and rolled oats, one of the most common uses is as livestock feed... s	Avena sativa	1500-1750 GDD to maturity
European Corn Borer European Corn Borer The European corn borer , also known as the European high-flyer, is a pest of grain, particularly maize. The insect is native to Europe, originally infesting varieties of millet, including broom corn. The European corn borer was first reported in North America in 1917 in Massachusetts, but was...	Ostrinia nubilalis	207 - Emergence of first spring moths

Pest control

Insect

Insects are a class of living creatures within the arthropods that have a chitinous exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae...

development and growing degree days are also used by some farmer

Farmer

A farmer is a person engaged in agriculture, who raises living organisms for food or raw materials, generally including livestock husbandry and growing crops, such as produce and grain...

s and horticulturalists to time their use of organic or biological pest control

Biological pest control

Biological control of pests in agriculture is a method of controlling pests that relies on predation, parasitism, herbivory, or other natural mechanisms...

or other pest control

Pest control

Pest control refers to the regulation or management of a species defined as a pest, usually because it is perceived to be detrimental to a person's health, the ecology or the economy.-History:...

methods so they are applying the procedure or treatment at the point that the pest is most vulnerable. For example:

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

Honeybees

Several beekeeper

Beekeeper

A beekeeper is a person who keeps honey bees for the purposes of securing commodities such as honey, beeswax, pollen, royal jelly; pollinating fruits and vegetables; raising queens and bees for sale to other farmers; and/or for purposes satisfying natural scientific curiosity...

s are now researching the correlation between growing degree days-GDD and the lifecycle of a honeybee colony.

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
Wheat
Wheat is a cereal grain, originally from the Levant region of the Near East, but now cultivated worldwide. In 2007 world production of wheat was 607 million tons, making it the third most-produced cereal after maize and rice...

, barley
Barley
Barley is a major cereal grain, a member of the grass family. It serves as a major animal fodder, as a base malt for beer and certain distilled beverages, and as a component of various health foods...

, rye
Rye
Rye is a grass grown extensively as a grain and as a forage crop. It is a member of the wheat tribe and is closely related to barley and wheat. Rye grain is used for flour, rye bread, rye beer, some whiskeys, some vodkas, and animal fodder...

, oat
Oat
The common oat is a species of cereal grain grown for its seed, which is known by the same name . While oats are suitable for human consumption as oatmeal and rolled oats, one of the most common uses is as livestock feed...

s, flaxseed, lettuce
Lettuce
Lettuce is a temperate annual or biennial plant of the daisy family Asteraceae. It is most often grown as a leaf vegetable. It is eaten either raw, notably in salads, sandwiches, hamburgers, tacos, and many other dishes, or cooked, as in Chinese cuisine in which the stem becomes just as important...

, asparagus
Asparagus
Asparagus officinalis is a spring vegetable, a flowering perennialplant species in the genus Asparagus. It was once classified in the lily family, like its Allium cousins, onions and garlic, but the Liliaceae have been split and the onion-like plants are now in the family Amaryllidaceae and...
6 °C stalk borer moth
7 °C Corn rootworm
8 °C sunflower
Sunflower
Sunflower is an annual plant native to the Americas. It possesses a large inflorescence . The sunflower got its name from its huge, fiery blooms, whose shape and image is often used to depict the sun. The sunflower has a rough, hairy stem, broad, coarsely toothed, rough leaves and circular heads...

, potato
Potato
The potato is a starchy, tuberous crop from the perennial Solanum tuberosum of the Solanaceae family . The word potato may refer to the plant itself as well as the edible tuber. In the region of the Andes, there are some other closely related cultivated potato species...
9 °C Alfalfa weevil
10 °C maize
Maize
Maize known in many English-speaking countries as corn or mielie/mealie, is a grain domesticated by indigenous peoples in Mesoamerica in prehistoric times. The leafy stalk produces ears which contain seeds called kernels. Though technically a grain, maize kernels are used in cooking as a vegetable...

(including sweet corn), sorghum
Sorghum
Sorghum is a genus of numerous species of grasses, one of which is raised for grain and many of which are used as fodder plants either cultivated or as part of pasture. The plants are cultivated in warmer climates worldwide. Species are native to tropical and subtropical regions of all continents...

, rice
Rice
Rice is the seed of the monocot plants Oryza sativa or Oryza glaberrima . As a cereal grain, it is the most important staple food for a large part of the world's human population, especially in East Asia, Southeast Asia, South Asia, the Middle East, and the West Indies...

, soybeans, tomato
Tomato
The word "tomato" may refer to the plant or the edible, typically red, fruit which it bears. Originating in South America, the tomato was spread around the world following the Spanish colonization of the Americas, and its many varieties are now widely grown, often in greenhouses in cooler...

, Black cutworm, European Corn Borer
European Corn Borer
The European corn borer , also known as the European high-flyer, is a pest of grain, particularly maize. The insect is native to Europe, originally infesting varieties of millet, including broom corn. The European corn borer was first reported in North America in 1917 in Massachusetts, but was...

, Coffee
Coffee
Coffee is a brewed beverage with a dark,init brooo acidic flavor prepared from the roasted seeds of the coffee plant, colloquially called coffee beans. The beans are found in coffee cherries, which grow on trees cultivated in over 70 countries, primarily in equatorial Latin America, Southeast Asia,...

(Jaramillo-Robledo & Guzman-Martinez published by Cenicafé), standard baseline for insect and mite pests of woody plants
11 °C Green Cloverworm
12 °C many other crop calculations
30 °C the USDA
United States Department of Agriculture
The United States Department of Agriculture is the United States federal executive department responsible for developing and executing U.S. federal government policy on farming, agriculture, and food...

measure heat zones in GDD above 30 °C; for many plants this is significant for seed maturation, e.g. reed
Phragmites
Phragmites, the Common reed, is a large perennial grass found in wetlands throughout temperate and tropical regions of the world. Phragmites australis is sometimes regarded as the sole species of the genus Phragmites, though some botanists divide Phragmites australis into three or four species...

(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

Introduction

GDD calculation

Plant development

Pest control

Honeybees

Baselines

See also

External links