page_title: Deciduous
section_title: Botany
hierarchical_section_title: Deciduous / Botany
caption_attribution_description: Photo of a forsythia, taken around Turin (Italy). Thanks to GG!
context_page_description: In the fields of horticulture and botany, the term deciduous means "falling off at maturity" and "tending to fall off", in reference to trees and shrubs that seasonally shed leaves, usually in the autumn; to the shedding of petals, after flowering; and to the shedding of ripe fruit. The antonym of deciduous in the botanical sense is evergreen.
  Generally, the term deciduous means "the dropping of a part that is no longer needed or useful to the plant" and the "falling away [just a part] after its purpose is finished". In plants, it is the result of natural processes. "Deciduous" has a similar meaning when referring to animal parts, such as deciduous antlers in deer, deciduous teeth in some mammals; or decidua, the uterine lining that sheds off after birth.
context_section_description: In botany and horticulture, deciduous plants, including trees, shrubs and herbaceous perennials, are those that lose all of their leaves for part of the year. This process is called abscission. In some cases leaf loss coincides with winter—namely in temperate or polar climates. In other parts of the world, including tropical, subtropical, and arid regions, plants lose their leaves during the dry season or other seasons, depending on variations in rainfall.
  The converse of deciduous is evergreen, where foliage is shed on a different schedule from deciduous trees, therefore appearing to remain green year round. Plants that are intermediate may be called semi-deciduous; they lose old foliage as new growth begins. Other plants are semi-evergreen and lose their leaves before the next growing season, retaining some during winter or dry periods.
  Many deciduous plants flower during the period when they are leafless, as this increases the effectiveness of pollination. The absence of leaves improves wind transmission of pollen for wind-pollinated plants and increases the visibility of the flowers to insects in insect-pollinated plants. This strategy is not without risks, as the flowers can be damaged by frost or, in dry season regions, result in water stress on the plant. 
  The conditions that trigger leafout in spring can vary depending on the species or genera of plant. Most herbaceous perennials and some woody plants are triggered to leaf out by warming air or soil temperatures, for example birches (Betula) and willows (Salix) will attempt to send out flowers and/or leaves if there are a few days where ambient air temperatures exceed 50°F (10°C). This strategy is risky as a renewed burst of cold air may freeze off the new growth. Other woody plants such as oaks, walnuts, and hickories leaf out based on photoperiod, meaning they wait until the day length is long enough. These tend to be plants that have frost-intolerant foliage, so leafout is held off until late spring when the danger of frost has largely passed.
  Leaf drop in the fall months is based on photoperiod and varies by genera and species. Walnuts tend to drop their leaves early while some trees such as Norway Maple and willows have extremely late leaf drop, often in the middle of November.
  Leaf drop or abscission involves complex physiological signals and changes within plants. The process of photosynthesis steadily degrades the supply of chlorophylls in foliage; plants normally replenish chlorophylls during the summer months. When autumn arrives and the days are shorter or when plants are drought-stressed, deciduous trees decrease chlorophyll pigment production, allowing other pigments present in the leaf to become apparent, resulting in non-green colored foliage. The brightest leaf colors are produced when days grow short and nights are cool, but remain above freezing. These other pigments include carotenoids that are yellow, brown, and orange. Anthocyanin pigments produce red and purple colors, though they are not always present in the leaves. Rather, they are produced in the foliage in late summer, when sugars are trapped in the leaves after the process of abscission begins. Parts of the world that have showy displays of bright autumn colors are limited to locations where days become short and nights are cool. In other parts of the world, the leaves of deciduous trees simply fall off without turning the bright colors produced from the accumulation of anthocyanin pigments.
  The beginnings of leaf drop starts when an abscission layer is formed between the leaf petiole and the stem. This layer is formed in the spring during active new growth of the leaf; it consists of layers of cells that can separate from each other. The cells are sensitive to a plant hormone called auxin that is produced by the leaf and other parts of the plant. When auxin coming from the leaf is produced at a rate consistent with that from the body of the plant, the cells of the abscission layer remain connected; in autumn, or when under stress, the auxin flow from the leaf decreases or stops, trigg
caption: Like a number of other deciduous plants, Forsythia flowers during the leafless season.
exif: {"Image Make": "EASTMAN KODAK COMPANY", "Image Model": "KODAK Z740 ZOOM DIGITAL CAMERA", "Image Orientation": "Horizontal (normal)", "Image XResolution": "72", "Image YResolution": "72", "Image ResolutionUnit": "Pixels/Inch", "Image YCbCrPositioning": "Centered", "Image ExifOffset": "180", "Thumbnail Compression": "JPEG (old-style)", "Thumbnail Orientation": "Horizontal (normal)", "Thumbnail XResolution": "72", "Thumbnail YResolution": "72", "Thumbnail ResolutionUnit": "Pixels/Inch", "Thumbnail JPEGInterchangeFormat": "3290", "Thumbnail JPEGInterchangeFormatLength": "7759", "EXIF ExposureTime": "1/750", "EXIF FNumber": "16/5", "EXIF ExposureProgram": "Program Normal", "EXIF ISOSpeedRatings": "80", "EXIF ExifVersion": "0221", "EXIF DateTimeOriginal": "2006:03:14 14:54:11", "EXIF DateTimeDigitized": "2006:03:14 14:54:11", "EXIF ComponentsConfiguration": "YCbCr", "EXIF ShutterSpeedValue": "19/2", "EXIF ApertureValue": "17/5", "EXIF ExposureBiasValue": "0", "EXIF MaxApertureValue": "17/5", "EXIF MeteringMode": "Pattern", "EXIF LightSource": "Unknown", "EXIF Flash": "Flash did not fire, compulsory flash mode", "EXIF FocalLength": "173/5", "EXIF FlashPixVersion": "0100", "EXIF ColorSpace": "sRGB", "EXIF ExifImageWidth": "2576", "EXIF ExifImageLength": "1932", "Interoperability InteroperabilityIndex": "R98", "Interoperability InteroperabilityVersion": "[48, 49, 48, 48]", "EXIF InteroperabilityOffset": "3154", "EXIF ExposureIndex": "80", "EXIF SensingMethod": "One-chip color area", "EXIF FileSource": "Digital Camera", "EXIF SceneType": "Directly Photographed", "EXIF CustomRendered": "Normal", "EXIF ExposureMode": "Auto Exposure", "EXIF WhiteBalance": "Auto", "EXIF DigitalZoomRatio": "0", "EXIF FocalLengthIn35mmFilm": "209", "EXIF SceneCaptureType": "Standard", "EXIF GainControl": "None", "EXIF Contrast": "Normal", "EXIF Saturation": "Normal", "EXIF Sharpness": "Normal", "EXIF SubjectDistanceRange": "0"}