Annuals are plants that last through one growing season. Seeds are planted in the spring, grow, and bloom. After maturing their seeds, every part of them dies.
They have completed their entire life in one growing season; if they are true annuals, those same plants will not appear again in the spring. However, if there are plants the following spring, they will come from fallen seeds.
Biennials are plants that complete a life cycle in two years. A low rosette or crown is grown the first year with a fleshy root system.
In the second year, the plants send up bloom stalks, ripen seeds, and then die root and branch just as the annuals did the first year. Volunteer plants from the fallen seeds may appear, but the bloomed plants will not grow again.
Perennials live 3, 5, 10, and 20 years—some live indefinitely. Woody plants, such as trees and shrubs, are perennials inhabit.
When the term perennial is used in reference books and nursery catalogs, it almost always refers to herbaceous plants without persistent woody top growth.
Except for evergreen kinds, these perennials die down to the ground each year, but the roots live on. As a result, they can make new feeding roots and produce new top growth each spring.
Classifying Plants
There would be no confusion about classifying plants in these three categories if each that bloomed, made seeds, and died the first year could be classed as annual; if every biennial bloomed, made seeds, and died the second year; and if every perennial lived on and on.
The truth is they sometimes follow a different pattern than we expect. This is because too many outside conditions affect their behavior—the region in which they are planted—the time of planting—rainfall —temperature, and other factors.
Perennial Plants
Most perennial plants bloom in the second year, and occasionally it takes three years or longer. Among the perennial plants that have more of the general characteristics of an annual than a perennial when planted in northern gardens are snapdragons, Salvia farinacea varieties such as ‘Blue Bedder’ and four-o’clock.
They bloom the first year, mature seeds, and are killed by cold temperatures, not because they have completed a normal life cycle. Farther south, the roots live over winter, new top growth is made in the spring, and the plants bloom again.
During mild winter, snapdragons and the blue salvia occasionally live in northern gardens. Four o’clock can be dug and given winter storage, such as we give dahlias.
Biennials and Annuals
Seeds of such biennials as canter-bury bells and foxgloves may be planted in a greenhouse or warm window in January or early February.
If the plants are hardened off and set out in the garden when the danger of frost is over, they will bloom in late summer and fall. Thus they bloom and die the first year, performing as an annual rather than a biennial.
If the seeds are sown in May or June, the plants will make their crown growth and bloom in the second year.
Usually, the blossoms are more profuse if the plant has the extra year to make the crown grow and a good root system. Several short-lived perennials appear biennial in behavior.
Certain kinds of penstemons are examples. They make a low plant the first year, send up blossom stalks the second year, and then die.
Varieties Of Forms
Some varieties of plants have both annual and biennial, or perennial forms. For example, you may find annual canter-bury bells listed. These bloom the first year and then die.
The biennial forms usually bloom in the second season and then die. However, there are lovely annual and perennial varieties of candytuft (iberis).
Even though there is a similarity in characteristics among the three groups, and the differences are only sometimes clear-cut and distinct, we need not become confused.
If a plant is listed among the annuals, we can be sure it will bloom the first year from seeds and die either because it is a true annual or a perennial that blooms the first year but is not winter hardy.
Suppose a plant is listed as a biennial and does not bloom in the second year. In that case, it may be because something prevented it from making enough growth the first year (a drouth or too late planting), and it will likely live through a second winter and complete its life cycle the third year.
Some perennials are very long-lived without extra care. Others need attention to be perennial, such as dividing the plant in the third or fourth year.
44659 by Olga Rolf Tiemann