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Is it an Annual, Biennial or a Perennial?
Local climatic conditions, development of new
cultivars, and new uses for specific garden flowers
have blurred the distinctions among annuals, biennials,
and perennials. Annuals have traditionally been
referred to as plants that complete their life
cycle in one growing season. Some perennials that
bloom quickly (verbena, Jerusalem cherry) are
grown as annuals and discarded at the end of one
season. Some of our so-called annuals (begonias,
impatiens, snapdragons) are actually perennials
in warmer climates or mild winters.
New cultivars of plants traditionally referred
to as biennials are being developed that produce
flowers the first season. Foxy is a cultivar of
foxglove that will bloom the first year. Annual
cultivars of sweet williams and hollyhock have
been developed.
The distinction between perennials, flowering
bulbs, and wildflowers is also blurred. Some garden
books and magazines list flowering bulbs as perennials.
Many of our wildflowers are commonly grown in
perennial gardens, some are grown from bulbs.
Most annuals are planted in the spring, flower
through the summer and fall, and then die with
the first killing frost. Winter-flowering annuals,
such as pansies, violas, and flowering cabbage,
are planted in the fall, flower in the winter
and early spring and die during the summer.
Types of Annuals
Annual flowers differ in their tolerance to cold
weather and frost. Hardy annuals are the most
cold tolerant; they will take light frost and
some freezing weather without being killed. In
most cases, hardy annuals can be planted in the
fall or in the spring before the last frost date.
Hardy annuals include calendula, cornflower, foxglove,
larkspur, pansy, sweet alyssum, stocks, viola,
and many dianthus cultivars. Most hardy annuals
are not heat tolerant and usually decline and
die with the onset of hot summer temperatures.
Half-hardy annuals will tolerate periods of cold
damp weather, but will be damaged by frost. Most
half-hardy annuals can be seeded outdoors in early
spring since they do not require warm soil temperatures
to germinate. Seeds or plants are normally planted
after the last spring frost. Examples of half-hardy
annuals include baby’s breath, bells of Ireland,
blue sage, candytuft, celome, forget-me-nots,
love-in-a-mist, snow-on-the-mountain, strawflower,
and torenia. Many half-hardy annuals decline in
the midsummer heat but may rebloom in late summer
or fall.
Because most tender annuals are native to warm
tropical regions of the world, they are sensitive
to cold soil temperatures and are easily damaged
by frost. Most seeds will not germinate well when
soil temperatures are below 60°F. If the soil
is cold, seeds will rot instead of germinating.
Wait two to three weeks after the last spring
frost to sow seeds or transplant outdoors. Tender
annuals include ageratum, balsam, begonia, celosia,
coleus, globe amaranth, impatiens, marigold, morning
glory, nasturtium, nicotiana, petunia, scarlet
sage, verbena, vinca, and zinnia.
Annuals are sometimes categorized as cool- or
warm-season. Cool-season annuals, such as geranium,
petunia, and snapdragon, grow best when the temperatures
are in the 70’s and 80’s during the
day. Best flower production is in the spring and
fall; flower production declines in the middle
of a hot summer. Warm-season annuals, such as
blue daze, four-o’clocks, and pentas perform
well when the day time temperatures are in the
80’s and 90’s and the night time temperatures
are in the 60’s and 70’s.
Biennial flowers
The life cycle of biennial plants is completed
over two growing seasons. During the first season
they produce only leaves—usually in a rosette.
Following a winter cold period, they flower in
the second growing season, produce seeds, and
then die. Popular biennials include foxglove,
hollyhock, stocks, and sweet williams. Cultural
practices are basically the same as for annuals,
except that the plants are alive for two growing
seasons.
Biennials present the obvious disadvantage of
producing only foliage the first year. One solution
is to sow biennial seeds in mid-summer so that
the plants will develop during the summer and
fall. After exposure to the winter cold, they
will develop flowers in the spring.
Definition: A true annual is a plant that
completes its life cycle in one year. This means
it goes from seed to seed and then dies off, during
the course of one growing season. The whole mission
of an annual is to produce seed and propagate.
That's why deadheading or removing spent flowers
before the seed matures, produces more flowers
and therefore more potential seed.
Also see: Daisies,
Begonias
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