Agriculture Reference
In-Depth Information
•
seed production—energy directed toward production of seed. Uptake
of water and nutrients is slow and is directed mainly to flower, fruit,
and seed structures
•
maturity—little or no energy production or movement of water and
nutrients.
B.
LIFE CYCLES OF PLANTS
1.
Annuals
Plants with a one-year life cycle are annuals. They grow from seed, ma-
ture, and produce seed for the next generation in one year or less. They are
grasslike (crabgrass and foxtail) or broad-leaved (pigweed and cocklebur).
There are two types:
Summer annuals
are plants that grow from seeds which sprout in the
spring. They grow, mature, produce seed, and die before winter. Examples
include: crabgrass, foxtail, cocklebur, pigweed, and lambsquarters.
Winter annuals
are plants that grow from seeds which sprout in the fall.
They grow, mature produce seed, and die before summer. Examples include:
cheat, henbit, and annual bluegrass.
2.
Biennials
Plants with a two-year life cycle are biennials. They grow from seed and
develop a heavy root and compact cluster of leaves (called a rosette) the first
year. In the second year they mature, produce seed, and die. Examples in-
clude: mullein, burdock, and bull thistle.
Figures 3.11
and
3.12
show several
biennials.
3.
Perennials
Plants which live more than two years and may live indefinitely are per-
ennials. Perennial plants may mature and reproduce in the first year and then
repeat the vegetative, seed production, and maturity stages for several follow-
ing years. In other perennials, the seed maturity and production stages may be
delayed for several years. Some perennial plants die back each winter: others,
such as trees, may lose their leaves, but do not die back to the ground. Most
perennials grow from seed; many also produce tubers, bulbs rhizomes (below-
ground rootlike stems), or stolons (above-ground stems that produce roots).
Examples of perennials are johnsongrass, field bindweed, dandelion, and plan-
tain.
Figure 3.13
shows several pictures of the parts of the dandelion, and
Figure 3.14
shows the Trumpet-weed or Joepyeweed which is also a perennial.
