"Periodically in Florida's environment, stormy weather fronts will settle over large parts of the state bringing cloudy weather. These situations foster the development of a physiological condition called edema in landscape plants. Under overcast weather, photosynthesis is reduced which reduces stomatal openings in the leaves. Air circulation is often reduced under cloudy weather which reduces evaporation of moisture from soil. A normally vigorous plant in the above situation is absorbing soil moisture through the root system but is transpiring a reduced amount from the leaves due to the closed stomata. Internal water pressure buildup results in the rupturing of water from the lower leaf surface creating small water-soaked blisters overnight. These minute wounds quickly callus into scab-like spots. The upper leaf surface may exhibit small chlorotic spots directly above the lower leaf edema. This disorder happens literally overnight and ends abruptly with the advent of higher light intensity and air circulation that re-establishes normal transpiration through the stomata."

We likely compounded the situation by covering our crops of Agave 'Joe Hoak' with frost protection cloth (Agryl fabric) the nights after the rain which because of frosts warning associated with the tail end of the storm. This would have trapped moisture around the plants and also limited transpiration the following day when the plants were left covered. Large unprotected plants of Agave Joe Hoak, both in the ground and in containers were unaffected.

This type of damage also occurs occasionally to Agave attenuata in landscapes around Santa Barbara and is usually associated with cool overcast moist conditions that we have in early summer months.

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