An annual plant is a plant that completes its
life cycle, from
germination
Germination is the process by which an organism grows from a seed or spore. The term is applied to the sprouting of a seedling from a seed of an angiosperm or gymnosperm, the growth of a sporeling from a spore, such as the spores of fungi, fer ...
to the production of
seeds, within one
growing season
A season is a division of the year marked by changes in weather, ecology, and the amount of daylight. The growing season is that portion of the year in which local conditions (i.e. rainfall, temperature, daylight) permit normal plant growth. Whil ...
, and then dies. The length of growing seasons and period in which they take place vary according to geographical location, and may not correspond to the four traditional seasonal divisions of the year. With respect to the traditional seasons, annual plants are generally categorized into summer annuals and winter annuals. Summer annuals germinate during spring or early summer and mature by autumn of the same year. Winter annuals germinate during the autumn and mature during the spring or summer of the following calendar year.
One seed-to-seed life cycle for an annual plant can occur in as little as a month in some species, though most last several months.
Oilseed rapa can go from seed-to-seed in about five weeks under a bank of
fluorescent lamps. This style of growing is often used in classrooms for education. Many desert annuals are
therophytes,
because their seed-to-seed life cycle is only weeks and they spend most of the year as seeds to survive dry conditions.
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Cultivation
In cultivation, many food plants are, or are grown as, annuals, including virtually all domesticated
grain
A grain is a small, hard, dry fruit (caryopsis) – with or without an attached hull layer – harvested for human or animal consumption. A grain crop is a grain-producing plant. The two main types of commercial grain crops are cereals and legum ...
s. Some
perennials and
biennials
A biennial plant is a flowering plant that, generally in a temperate climate, takes two years to complete its biological life cycle.
Life cycle
In its first year, the biennal plant undergoes primary growth, during which its vegetative structures ...
are grown in gardens as annuals for convenience, particularly if they are not considered
cold hardy for the local climate.
Carrot
The carrot ('' Daucus carota'' subsp. ''sativus'') is a root vegetable, typically orange in color, though purple, black, red, white, and yellow cultivars exist, all of which are domesticated forms of the wild carrot, ''Daucus carota'', nat ...
,
celery and
parsley
Parsley, or garden parsley (''Petroselinum crispum'') is a species of flowering plant in the family Apiaceae that is native to the central and eastern Mediterranean region (Sardinia, Lebanon, Israel, Cyprus, Turkey, southern Italy, Greece, Por ...
are true biennials that are usually grown as annual crops for their edible roots, petioles and leaves, respectively.
Tomato,
sweet potato
The sweet potato or sweetpotato (''Ipomoea batatas'') is a dicotyledonous plant that belongs to the Convolvulus, bindweed or morning glory family (biology), family, Convolvulaceae. Its large, starchy, sweet-tasting tuberous roots are used as a r ...
and
bell pepper
The bell pepper (also known as paprika, sweet pepper, pepper, or capsicum ) is the fruit of plants in the Grossum Group of the species ''Capsicum annuum''. Cultivars of the plant produce fruits in different colors, including red, yellow, orange ...
are tender perennials usually grown as annuals. Ornamental perennials commonly grown as annuals are
impatiens
''Impatiens'' is a genus of more than 1,000 species of flowering plants, widely distributed throughout the Northern Hemisphere and the tropics. Together with the genus ''Hydrocera'' (one species), ''Impatiens'' make up the family Balsaminaceae. ...
,
mirabilis,
wax begonia,
snapdragon, ''
pelargonium
''Pelargonium'' () is a genus of flowering plants that includes about 280 species of perennials, succulents, and shrubs, commonly called geraniums, pelargoniums, or storksbills. '' Geranium'' is also the botanical name and common name of a separ ...
'',
coleus and
petunia. Examples of true annuals include
corn
Maize ( ; ''Zea mays'' subsp. ''mays'', from es, maíz after tnq, mahiz), also known as corn (North American and Australian English), is a cereal grain first domesticated by indigenous peoples in southern Mexico about 10,000 years ago. Th ...
,
wheat,
rice,
lettuce,
peas,
watermelon,
bean
A bean is the seed of several plants in the family Fabaceae, which are used as vegetables for human or animal food. They can be cooked in many different ways, including boiling, frying, and baking, and are used in many traditional dishes th ...
s,
zinnia and
marigold
Marigold may refer to:
* Marigold (color), a yellow-orange color
It may also refer to:
Plants
* In the genus ''Calendula'':
** Common marigold, '' Calendula officinalis'' (also called pot marigold, ruddles, or Scotch marigold)
* In the genus ' ...
.
Summer
Summer annuals sprout, flower, produce seed, and die, during the warmer months of the year.
The lawn weed
crabgrass is a summer annual.
Winter
Winter annuals germinate in autumn or winter, live through the winter, then bloom in winter or spring.
The plants grow and bloom during the cool season when most other plants are dormant or other annuals are in seed form waiting for warmer weather to germinate. Winter annuals die after flowering and setting seed. The seeds germinate in the autumn or winter when the soil temperature is cool.
Winter annuals typically grow low to the ground, where they are usually sheltered from the coldest nights by snow cover, and make use of warm periods in winter for growth when the snow melts. Some common winter annuals include
henbit,
deadnettle,
chickweed, and
winter cress.
Winter annuals are important ecologically, as they provide vegetative cover that prevents soil erosion during winter and early spring when no other cover exists and they provide fresh vegetation for animals and birds that feed on them. Although they are often considered to be weeds in gardens, this viewpoint is not always necessary, as most of them die when the soil temperature warms up again in early to late spring when other plants are still dormant and have not yet leafed out.
Even though they do not compete directly with cultivated plants, sometimes winter annuals are considered a pest in commercial agriculture, because they can be hosts for insect pests or fungal diseases (such as ovary smut, ''Microbotryum'' sp.) which attack crops being cultivated. The property that they prevent the soil from drying out can also be problematic for commercial agriculture.
Molecular genetics
In 2008, it was discovered that the inactivation of only two genes in one species of annual plant leads to its conversion into a
perennial plant.
Researchers deactivated the SOC1 and FUL genes (which control flowering time) of ''
Arabidopsis thaliana
''Arabidopsis thaliana'', the thale cress, mouse-ear cress or arabidopsis, is a small flowering plant native to Eurasia and Africa. ''A. thaliana'' is considered a weed; it is found along the shoulders of roads and in disturbed land.
A winter a ...
''. This switch established
phenotypes common in perennial plants, such as
wood formation.
See also
*
*
* - Plant that flowers & sets seeds once, then dies.
References
External links
{{Authority control
Garden plants