Inflorescence

An inflorescence is a group or cluster of 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 mediate the union of male sperm with female ovum in order to produce seeds...

s arranged on a stem

Plant stem

A stem is one of two main structural axes of a vascular plant. The stem is normally divided into nodes and internodes, the nodes hold buds which grow into one or more leaves, inflorescence , cones or other stems etc. The internodes act as spaces that distance one node from another...

 that is composed of a main branch

Branch

A branch or tree branch is a woody structural member connected to but not part of the central trunk of a tree...

 or a complicated arrangement of branches. Strictly, it is the part of the shoot

Shoot

Shoots are new plant growth, they can include stems, flowering stems with flower buds, leaves. The new growth from seed germination that grows upward is a shoot where leaves will develop...

 of seed plants where 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 mediate the union of male sperm with female ovum in order to produce seeds...

s are formed and which is accordingly modified. The modifications can involve the length and the nature of the internodes and the phyllotaxis

Phyllotaxis

In botany, phyllotaxis or phyllotaxy is the arrangement of the leaves on the stem of a plant .- Pattern structure :...

, as well as variations in the proportions, compressions, swellings, adnation

Adnation

Adnation in plants is the developmental fusion of different organs, for example, a leaf to a stem, or the filament of a stamen to a corolla. This is in contrast to connation, the fusion of similar organs....

s, connation

Connation

Connation in plants is the developmental fusion of organs of the same type, for example, petals to one another to form a tubular corolla. This is in contrast to adnation, the fusion of dissimilar organs.-Terms for connation of flower parts:...

s and reduction of main and secondary axes.

The stem holding the whole inflorescence is called a peduncle

Peduncle (botany)

In botany, a peduncle is a stalk supporting an inflorescence, or after fecundation a fruit.The peduncle has the structure of a stem. It is usually green, and without leaves. It can however sometimes support small leaves, or be colored...

and the main stem holding the flowers or more branches within the inflorescence is called the rachis

Rachis

The rachis is the main axis of the inflorescence, or spike, of wheat and other cereals, to which the spikelets are attached. It is also the part of the axis that the pinnae are attached to in ferns, the main stem of a compound leaf , or the main axis in compound inflorescences in other...

. The stalk of each single flower is called a pedicel

Pedicel (botany)

A pedicel is a stem that attaches single flowers to the main stem of the inflorescence. It is the branches or stalks that hold each flower in an inflorescence that contains more than one flower....

.

The fruit

Fruit

The term fruit has different meanings dependent on context, and the term is not synonymous in food preparation and biology. Fruits are the means by which flowering plants disseminate seeds, and the presence of seeds indicates that a structure is most likely a fruit, though not all seeds come from...

ing stage of an inflorescence is known as an infructescence.

A flower that is not part of an inflorescence is called a solitary flower and its stalk is also referred to as a peduncle.

General characteristics

Inflorescences are described by many different characteristics including how the flowers are arranged on the peduncle, the blooming order of the flowers and how different clusters of flowers are grouped within it. These terms are general representations as plants in nature can have a combination of types.

Bracts

Inflorescences usually have modified foliage different from the vegetative

Vegetative

Things commonly known as Vegetative include:*Vegetative community*Vegetative reproduction*Related to Vegetation*Vegetative state...

 part of the plant. Considering the broadest meaning of the term, any leaf associated with an inflorescence is called a bract

Bract

In botany, a bract is a modified or specialized leaf, especially one associated with a reproductive structure such as a flower, inflorescence axis, or cone scale...

. A bract is usually located at the node where the main stem of the inflorescence forms, joined to the main stem of the plant, but other bracts can exist within the inflorescence itself. They serve a variety of functions which include attracting pollinators and protecting young flowers. According to the presence or absence of bracts and their characteristics we can distinguish:

• Ebracteate inflorescences: No bracts in the inflorescence.
• Bracteate inflorescences: The bracts in the inflorescence are very specialised, sometimes reduced to small scales, divided or dissected.
• Leafy inflorescences: Though often reduced in size, the bracts are unspecialised and look like the typical leaves of the plant, so that the term flowering stem is usually applied instead of inflorescence. This use is not technically correct, as, despite their 'normal' appearance, these leaves are considered, in fact, bracts, so that 'leafy inflorescence' is preferable.
• Leafy-bracted inflorescences: Intermediate between bracteate and leafy inflorescence.

If many bracts are present and they are strictly connected to the stem, like in the family Asteraceae

Asteraceae

The family Asteraceae or Compositae is the second largest family of flowering plants, in terms of number of species....

, the bracts might collectively be called an involucre. If the inflorescence has a second unit of bracts further up the stem, they might be called an involucel.

Terminal flower

Plant organs can grow according to two different schemes, namely monopodial

Monopodial

Vascular plants with monopodial growth habits grow upward from a single point. They add leaves to the apex each year and the stem grows longer accordingly...

 and sympodial

Sympodial

Sympodial means "with conjoined feet", and in biology is often used to refer to the outward morphology or mode of growth of organisms.-In botany:...

. In inflorescences these two different growth patterns are called indeterminate or determinate, and indicate whether a terminal flower is formed and where flowering starts within the inflorescence.

• Indeterminate inflorescence: Monopodial
  Monopodial
  Vascular plants with monopodial growth habits grow upward from a single point. They add leaves to the apex each year and the stem grows longer accordingly...
  
   growth. The terminal bud keeps growing and forming lateral flowers. A terminal flower is never formed.
• Determinate inflorescence: Sympodial
  Sympodial
  Sympodial means "with conjoined feet", and in biology is often used to refer to the outward morphology or mode of growth of organisms.-In botany:...
  
   growth. The terminal bud forms a terminal flower and then dies out. Other flowers then grow from lateral buds.

Indeterminate and determinate inflorescences are sometimes referred to as open and closed inflorescences respectively.

In determinate inflorescences the terminal flower is usually the first to mature (precursive development), while the others tend to mature starting from the bottom of the stem. This pattern is called acropetal maturation. When flowers start to mature from the top of the stem , maturation is basipetal, while when the central mature first, divergent.
In indeterminate inflorescence there is no true terminal flower and the stem usually has a rudimentary end. In many cases the last true flower formed by the terminal bud (subterminal flower) straightens up, appearing to be a terminal flower. Often a vestige of the terminal bud may be noticed higher on the stem.

Phyllotaxis

As with leaves

Leaf

In botany, a leaf is an above-ground plant organ specialized for photosynthesis. For this purpose, a leaf is typically flat and thin. There is continued debate about whether the flatness of leaves evolved to expose the chloroplasts to more light or to increase the absorption of carbon dioxide. In...

, flowers can be arranged on the stem according to many different patterns. See 'Phyllotaxis

Phyllotaxis

In botany, phyllotaxis or phyllotaxy is the arrangement of the leaves on the stem of a plant .- Pattern structure :...

' for in-depth descriptions.

Metatopy

Metatopy is the placement of organs out of their normally expected position: typically metatopy occurs in inflorescences when unequal growth rates alter different areas of the axis and the organs attached to the axis.

When a single or a cluster of flower(s) is located at the axil of a bract, the location of the bract in relation to the stem holding the flower(s) is indicated by the use of different terms and may be a useful diagnostic indicator.

Typical placement of bracts include:

• Some plants have bracts that subtend the inflorescence, where the flowers are on branched stalks; the bracts are not connected to the stalks holding the flowers, but are adnate
  Adnation
  Adnation in plants is the developmental fusion of different organs, for example, a leaf to a stem, or the filament of a stamen to a corolla. This is in contrast to connation, the fusion of similar organs....
  
   or attached to the main stem (Adnate describes the fusing together of different unrelated parts. When the parts fused together are the same, they are connately joined)
• Other plants have the bracts subtend the pedicel or peduncle of single flowers.

Metatopic placement of bracts include:

• When the bract is attached to the stem holding the flower (the pedicel or peduncle), it is said to be recaulescent; sometimes these bracts or bracteoles are highly modified and appear to be appendages of the flower calyx. Recaulescences is the fusion of the subtending leaf with the stem holding the bud or the bud itself, thus the leaf or bract is adnate to the stem of flower.
• When the formation of the bud is shifted up the stem distinctly above the subtending leaf, it is described as concaulescent.

Organisation

There is no general consensus in defining the different inflorescences. The following is based on Focko Weberling's Morphologie der Blüten und der Blütenstände (Stuttgart, 1981).

The main groups of inflorescences are distinguished by branching. Within these groups, the most important characteristics are the intersection of the axes and different variations of the model.

Inflorescences can be simple or compound.

Indeterminate

Indeterminate simple inflorescences are generally called racemose. The main kind of racemose inflorescence is the raceme, the other kind of racemose inflorescences can all be derived from this one by dilation, compression, swelling or reduction of the different axes. Some passage forms between the obvious ones are commonly admitted.

• A raceme
  Raceme
  A raceme is a type of inflorescence that is unbranched and indeterminate and bears pedicellate flowers — flowers having short floral stalks called pedicels — along the axis. In botany, axis means a shoot, in this case one bearing the flowers. In a raceme, the oldest flowers are borne...
  
  is an unbranched, indeterminate
  Indeterminate growth
  In biology and especially botany, indeterminate growth refers to growth that is not terminated in contrast to determinate growth that stops once a genetically pre-determined structure has completely formed. Thus, a plant that grows and produces flowers and fruit until killed by frost or some other...
  
   inflorescence with pedicellate (having short floral stalks) flowers along the axis.
• A spike
  Raceme
  A raceme is a type of inflorescence that is unbranched and indeterminate and bears pedicellate flowers — flowers having short floral stalks called pedicels — along the axis. In botany, axis means a shoot, in this case one bearing the flowers. In a raceme, the oldest flowers are borne...
  
  is a type of raceme with flowers that do not have a pedicel.
• A racemose corymb is an unbranched, indeterminate inflorescence that is flat-topped or convex due to their outer pedicels which are progressively longer than inner ones.
• An umbel
  Umbel
  An umbel is an inflorescence which consists of a number of short flower stalks which are equal in length and spread from a common point, somewhat like umbrella ribs....
  
  is a type of raceme with a short axis and multiple floral pedicels of equal length that appear to arise from a common point.
• A spadix
  Spadix
  In botany, a spadix is a type of spike: an inflorescence with small flowers crowded on a thickened, fleshy axis. The term is applied to certain monocotyledons, especially members of the Family Araceae called arums or aroids...
  
  is a spike of flowers densely arranged around it, enclosed or accompanied by a highly specialised bract called a spathe
  Spadix
  In botany, a spadix is a type of spike: an inflorescence with small flowers crowded on a thickened, fleshy axis. The term is applied to certain monocotyledons, especially members of the Family Araceae called arums or aroids...
  
  . It is characteristic of the Araceae
  Araceae
  Araceae is a family of monocotyledonous flowering plants in which flowers are borne on a type of inflorescence called a spadix. The spadix is usually accompanied by, and sometimes partially enclosed in, a spathe or leaf-like hood. The group also goes by the name of Arum family and species in this...
  
   family.
• A flower head or capitulum is a very contracted raceme in which the single sessile flowers share are borne on an enlarged stem. It is characteristic of Dipsacaceae
  Dipsacaceae
  The Dipsacaceae, or teasel family, of the order Dipsacales contains 350 species of perennial or biennial herbs and shrubs in eleven genera. Native to most temperate climates, they are found in Europe, Asia and Africa...
  
  .
• A catkin
  Catkin
  A catkin or ament is a slim, cylindrical flower cluster, with inconspicuous or no petals, usually wind-pollinated but sometimes insect pollinated . They contain many, usually unisexual flowers, arranged closely along a central stem which is often drooping...
  
  or ament is a scaly, generally drooping spike or raceme. Cymose or other complex inflorescences that are superficially similar are also generally called thus.

Determinate

Determinate simple inflorescences are generally called cymose. The main kind of cymose inflorescence is the cyme. Cymes are further divided according to this scheme:

• Only one secondary axis: monochasium
  • Secondary buds always develop on the same side of the stem: helicoid cyme or bostryx
    • The successive pedicels are aligned on the same plane: drepanium
  • Secondary buds develop alternately on the stem : scorpioid cyme
    • The successive pedicels are arranged in a sort of spiral: cincinnus (characteristic of the Boraginaceae
      Boraginaceae
      Boraginaceae, the Borage or Forget-me-not family, includes a variety of shrubs, trees, and herbs, totaling about 2,000 species in 146 genera found worldwide.A number of familiar plants belong to this family....
      
       and Commelinaceae
      Commelinaceae
      Commelinaceae is a botanical name for a family of flowering plants, also known as the spiderwort family. The family has always been recognized by most taxonomists....
      
      )
    • The successive pedicels follow a zig-zag path on the same plane: rhipidium (many Iridaceae
      Iridaceae
      The Iris family or Iridaceae is a family of perennial, herbaceous and bulbous plants included in the monocot order Asparagales, taking its name from the genus Iris. Almost worldwide in distribution and one of the most important families in horticulture, it includes more than 2000 species...
      
      )
• Two secondary axes: dichasial cyme
  • Secondary axis still dichasial: dichasium (characteristic of Caryophyllaceae
    Caryophyllaceae
    The Caryophyllaceae, commonly called the pink family or carnation family, is a family of flowering plants. The species are dicotyledons included in the order Caryophyllales. It is a large family, with 88 genera and some 2,000 species....
    
    )
  • Secondary axis monochasia: double scorpioid cyme or double helicoid cyme
• More than two secondary axes: pleiochasium

A cyme can also be so compressed that it looks like an umbel. Strictly speaking this kind of inflorescence could be called umbelliform cyme, although it is normally called simply 'umbel'.

Another kind of definite simple inflorescence is the raceme-like cyme or botryoid; that is as a raceme with a terminal flower and is usually improperly called 'raceme'.
A reduced raceme or cyme that grows in the axil of a bract is called a fascicle. A verticillaster is a fascicle with the structure of a dichasium; it is common among the Lamiaceae

Lamiaceae

Lamiaceae or Labiatae, also known as the mint family, is a family of plants. It has been considered closely related to Verbenaceae but several recent phylogenetic studies have shown that numerous genera classified in Verbenaceae belong instead in Lamiaceae, whereas the core genera of Verbenaceae...

. Many verticillasters with reduced bracts can form a spicate (spike-like) inflorescence that is commonly called a spike.

Compound inflorescences

Simple inflorescences are the basis for compound inflorescences or synflorescences. The single flowers are there replaced by a simple inflorescence, which can be both a racemose or a cymose one. Compound inflorescences are composed of branched stems and can involve complicated arrangements that are difficult to trace back to the main branch.

A kind of compound inflorescence is the double inflorescence, in which the basic structure is repeated in the place of single florets. For example a double raceme is a raceme in which the single flowers are replaced by other simple racemes; the same structure can be repeated to form triple or more complex structures.

Compound raceme inflorescences can either end with a final raceme (homoeothetic), or not (heterothetic). A compound raceme is often called a panicle. Note that this definition is very different from that given by Weberling.

Compound umbels are umbels in which the single flowers are replaced by many smaller umbels called umbellets. The stem attaching the side umbellets to the main stem is called a ray.
The most common kind of definite compound inflorescence is the panicle (of Webeling, or 'panicle-like cyme'). A panicle is a definite inflorescence that is increasingly more strongly and irregularly branched from the top to the bottom and where each branching has a terminal flower.

The so called cymose corymb is similar to a racemose corymb but has a panicle-like structure. Another type of panicle is the anthela. An anthela is a cymose corymb with the lateral flowers higher than the central ones.
A raceme in which the single flowers are replaced by cymes is called a (indefinite) thyrse. The secondary cymes can of course be of any of the different types of dichasia and monochasia. A botryoid in which the single flowers are replaced by cymes is a definite thyrse or thyrsoid. Thyrses are often confusingly called panicles.
Other combinations are, of course, possible. For example, heads or umbels may be arranged in a corymb or a panicle.

Other

The family Asteraceae

Asteraceae

The family Asteraceae or Compositae is the second largest family of flowering plants, in terms of number of species....

 is characterised by a highly specialised head technically called a calathid (but usually referred to as 'capitulum' or 'head'). The family Poaceae

Poaceae

Poaceae or Gramineae is a family in the Class Liliopsida of the flowering plants. Plants of this family are usually called grasses, or, to distinguish them from other graminoids, true grasses; the shrub- or tree-like plants in this family are called bamboo...

 has a peculiar inflorescence of small spikes (spikelets) organised in panicles or spikes that are usually simply and improperly referred to as spike and panicle. The genus Ficus

Ficus

Ficus is a genus of about 850 species of woody trees, shrubs, vines, epiphytes, and hemiepiphyte in the family Moraceae. Collectively known as fig trees or figs, they are native throughout the tropics with a few species extending into the semi-warm temperate zone. The so-called Common Fig Ficus ...

(Moraceae

Moraceae

Moraceae — often called the mulberry family or fig family — is a family of flowering plants comprising about 40 genera and over 1000 species. Most are widespread in tropical and subtropical regions, less so in temperate climates...

) has an inflorescence called syconium

Syconium

A syconium is the type of fruit borne by figs , formed of an enlarged, fleshy, hollow receptacle with multiple ovaries on the inside surface. In essence, it is really a fleshy stem with a number of flowers, so it is considered both a multiple and accessory fruit. The name comes from the Greek word...

and the genus Euphorbia has cyathia

Cyathium

A cyathium is one of the specialised pseudanthia forming the inflorescence of plants in the genus Euphorbia . A cyathium consists of:...

(sing. cyathium), usually organised in umbels. For detailed descriptions, see the respective articles.