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Garden with Insight v1.0 Help: Plant next day functions: if perennial, check to see if should be dormant

One of the ways perennial plants stay alive during periods of bad weather (cold and/or dry seasons) is to become dormant. Actually, some animals become dormant (hibernating bears in cold weather, aestivating frogs in dry weather) and most bacteria enter a dormant "spore stage" when conditions are dangerous.

If the simulated climate contains at least one month whose long-term average minimum (night) temperature is below 5 degrees C (41 degrees F), perennial plants go into a dormant phase. The length of the dormant period is determined by day length. Dormancy begins when the day length falls below the minimum day length for the year plus some amount. That amount is set to a constant of one hour in this version.

Dormancy is simulated here by not calculating the daily growth equations. Above-ground biomass can still be reduced due to frost, short day lengths, and water stress, but root biomass remains intact. On the 15th day of the coldest month of the year the accumulated heat units of all perennial plants are reset to zero (and their heat unit index is reset as well). When the dormant period is over and the temperature warms up, perennials are ready to begin rapid new growth, because all of the processes that depend on heat unit index (allocation to shoots, vegetative growth, increasing leaf area index) are reset.

Note that the simulation does not model any type of dryness-induced dormancy. This is not usually an issue for gardens because adequate water is provided by irrigation.

calculation of potential biomass increase, damage from frost and short day length, damage from water stress, allocation to shoots
EPIC Winter Dormancy
Model contents

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Updated: May 4, 1998. Questions/comments on site to
Copyright © 1998 Paul D. Fernhout & Cynthia F. Kurtz.