. Cyclopedia of farm crops. Farm produce; Agriculture. Longevity of the plant. In duration, plants are of extreme types. Some kinds live only a few weeks ; some of the trees live for many centuries. It is customary to classify all plants into three groups as respects duration: annuals, living not more than one year from seed to seed, as the cereal grains and most garden vegetables; biennials, living two years, usually perfecting seed the second year, as beets and parsnips, common mullein; perennials, living more than two years, as asparagus, alfalfa, bushes and trees. These divisions are not a
. Cyclopedia of farm crops. Farm produce; Agriculture. Longevity of the plant. In duration, plants are of extreme types. Some kinds live only a few weeks ; some of the trees live for many centuries. It is customary to classify all plants into three groups as respects duration: annuals, living not more than one year from seed to seed, as the cereal grains and most garden vegetables; biennials, living two years, usually perfecting seed the second year, as beets and parsnips, common mullein; perennials, living more than two years, as asparagus, alfalfa, bushes and trees. These divisions are not at all exact, however. Annuals are of longer or shorter life within the year, some maturing and dying very quickly from the seed, as the garden cress, and others requiring practically the twelvemonth. Some plants are annual because they are destroyed by frost, and others because they normally complete their growth : the latter, of course, are the true annuals. Those that would outgrow the year if they had oppor- tunity have been called plur-annuals: they are plants that have been taken into a shorter - season year, as tomato, castor bean. Plants that are annual in one region, therefore, may be biennial or perennial in another region. Some plants are appar- ently annual although they live from year to year, carrying themselves over by means of bulbs or tubers, as onions and potatoes: these have been called pseud- annuals (false annuals). The mullein, bull thistle and teasel are true biennials, part of the growth occurring one year and the completion of the life-cycle the second year. Certain perennials have been bred by man to be biennials, as the cabbage and probably some root crops. Some of the root crops are really annual, as they complete the full cycle in one season if started early, as the radish. Whether a plant is biennial is often determined by the region in which it grows. There is the widest range in the length of life of perennials. Red clover is a perennial, but very
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