|Air temperature dependent days|
|not uniformly defined:||Cold day|
|Weather- dependent days|
|Cloud cover||Bright day|
|Cloud cover||Cloudy day|
|Cloud cover||Foggy day|
|Humidity / temperature||Sultry day|
|Precipitation||Snow (cover) day|
The vegetation period , vegetation phase or vegetation time is the rhythmically repeating part of the year in which a plant actively grows and develops. The rest of the year is the period of dormancy , the exchange of the two is the vegetative cycle .
English oak ( Quercus robur ) in the growing season
To the subject
The growing season is enough
- in annual plants from germination to death,
- in the case of biennial and perennial plants and perennial herbaceous plants from budding to penetration into the perennial organs,
- with perennial woody plants from sprouting to leaf fall ,
- in evergreen plants from the beginning to the cessation of active growth.
The remaining part of the year in which a perennial plant does not grow is called dormancy , dormant period or dormant period and corresponds to hibernation in animals , but also in summer or dry sleep in some species. Finally, the totality of the annually recurring growth phases of a plant is known as its vegetation cycle . Notwithstanding this term is z. B. in viticulture sometimes only used as a synonym for the terms vegetation period or vegetation period, i.e. including the growth and maturity phase of the plant, in this case the vine , but not its (winter) resting phase.
Temperature and growing season
A sustained threshold temperature of +5 ° C is often used as a technical guideline for the delimitation of periods of vegetation and rest, below which plants normally grow. H. The division set. A day with a daily mean temperature above 5 ° C is called a vegetation day . The number of these days is then the growing season . It is typically around 200 in mid-latitudes .
This guideline is vague because it does not take into account the different heat requirements of different species. While maize only thrives at +6 ° C, winter cereals can grow from +2.5 ° C and typical early spring flowers can even start to sprout when the temperature is below zero.
In England it is customary to measure the growing season on the basis of five consecutive days> 5 ° C (because there is often a brief thaw), in the USA and Canada the 0 ° limit is more likely to be chosen.
For the temperate latitudes , an average temperature of over +10 ° C is given for the main vegetation period in which a large part of the plants assimilate.
In addition, the growing season can of course also be interrupted by heat and drought. In the Mediterranean region, for example, the growing season is largely year-round, but in the dry zones of Spain, for example, it is limited to the winter half-year. In the tropics, the vegetation period is no longer tied to the four seasons, which are missing there, but fluctuates in the rhythm of the rainy and dry seasons , so that there can be several vegetation seasons per year.
A more precise measure of the vegetation period is then the degree of growth days, i.e. the total heat of the vegetation days, which then provides information about the intensity of the growth period.
Ecological factors and climates
The change between vegetation and rest periods is significantly influenced by seasonal fluctuations in rainfall and the seasonal fluctuations, for the metabolism suitable more or less temperature conditions. In particular, high temperatures lead to increased evaporation and low temperatures to freezing of the water available for the metabolism of the plants and thus to the need to reduce growth in these situations.
In polar areas , where the water is permanently frozen on land, no higher plants can develop, and so there is only a vegetation period over the polar summer for some marine algae . There is also no vegetation period in the true sense of the word in desert areas where, at most, enough rain falls at very irregular intervals for the vegetation to develop. Conversely, in the always - humid tropics, which are characterized by the time - of- day climate, there is vegetation time all year round, so that the term "vegetation period " is actually meaningless here.
In all other areas of the world, depending on the degree of latitude , a more or less pronounced regular change between vegetation and rest periods can be observed. The different levels of solar radiation and the winds that follow the seasons, especially the trade winds and monsoon winds , result in very different temperatures and amounts of precipitation to which the plants have to adapt. In the temperate and subpolar climatic zones , the vegetation period is mainly determined by the temperature , whereas in the tropics it is mainly precipitation in the form of rain , dew or fog that is decisive. In the humid and dry tropics, for example, the vegetation period essentially coincides with the rainy season , while in the climatically temperate and subpolar regions it corresponds to summer or the time from spring through summer to autumn . Finally, in the subtropics , both factors can play a role at the same time.
Within a region, climatic factors such as ocean currents and different altitudes can also be decisive for the course of vegetation and rest periods. One example is South Africa , where through the influence of Benguela , a winter rainfall area almost immediately to a summer rain area borders. In the dry forests of Africa, a division of the vegetation period can be observed due to the two annual precipitation maxima .
Most plants usually follow the locally prescribed rhythm, but there are also opportunists who, through special adaptations, are capable of an opposing rhythm. In this way, plants with very long tap roots can still get to groundwater even in the hot and dry season and use the opportunity not to be shaded and overgrown by the neighboring plants that are at rest for their own growth. On the other hand, some plants with a very shallow root system or special suction hairs are able to absorb condensed mist and thus extend or shift their growing season.
The link between vegetation and rest periods and the length of the day can be genetically determined to different degrees depending on the species. Many plant species from the southern hemisphere adapt easily to the reversed rhythm of the seasons in the northern hemisphere , while other species, e.g. B. many orchids from the southern hemisphere , especially during the short days of our winter, have their growing season and thus their highest light requirement.
For the successful care of a plant species, both as an ornamental plant on the window sill and in general in horticulture , knowledge of the vegetation and rest periods preferred by the respective plant is of decisive importance. The generally practiced method of watering a plant regularly over the year and thus keeping it evenly moist is only tolerated well by relatively few species. If, on the other hand, the special needs of the species are catered for and more or less heavily watered seasonally, significantly better cultivation successes can be achieved. Most succulent plants even depend on a drastic change between damp and wet during the growing season and (almost) complete dryness during the rest period in order not to wither and ultimately rot away. The same applies to orchids, in which some genera (e.g. Phalaenopsis ) show quasi-continuous growth, while others (e.g. Dendrobium ) require a more or less pronounced alternation of vegetation and rest periods, often exactly the opposite our seasons.
List of measured values: Vegetation days (T med ≥ 5 ° C) per year on a long-term mean
|place||Country||Height ∗||there||Averaging period ∗∗|
|Mainz ( Marienborn )||Germany||153||276.7||1991-2017|
- SME Groten & R.Ocatre: Monitoring the length of the growing season with NOAA , International Journal of Remote Sensing 23 (14): 2797 - 2815, 2002
- Grassland temperature sum
- Phenology - geobotanical branch of meteorology
- ↑ Note: In contrast to the color markings for the temperature thresholds, the 0 ° C line on the graphic is on the border between turquoise and blue. → Annual cycle of the graphic (animated)
- ↑ a b c d e f g h i j k l m n o Climatological knowledge days in the weather dictionary of the German Weather Service
- ↑ Germany : 15 ° C according to VDI 2067 ; Austria , Switzerland , Liechtenstein : 12 ° C according to Usance
- ↑ also T med ≥ 10 ° C: day of the main vegetation period
- ↑ Bayerische Landesanstalt für Landwirtschaft ( Memento from March 18, 2013 in the Internet Archive ): Maize maturity prognosis model, according to Association générale des producteurs de maïs ( AGPM ) based on specifically defined heat sums ; there also +30 ° C as the upper limit of the growth period
- ↑ Klaus Waloszczyka: Influence of air temperature and crop density on the growth of winter wheat from emergence to the beginning of vegetation in spring. In: Archives of Agronomy and Soil Science , Volume 39, Issue 5, 1995, pp. 379-387, doi : 10.1080 / 03650349509365916 .
- ^ Sieghard Winkler: Introduction to Plant Ecology. Gustav Fischer Verlag, Stuttgart a. New York 1980. p. 103.