Harbinger of heat
When saguaros bloom, the stubby buds on the top of the cacti poke out overnight. One day stands a stately saguaro, and the next day a goofy cap points nodules in every direction, each soon to be an extravagant white blossom. The saguaro is a night-bloomer; under the cover of darkness the calyxes peel back and waxy petals pop open with a puff of pollen and melon-like fragrance. Bats are drawn to the sweet flowers, finding nectar conveniently located in the sturdy blooms thrust high into the spring night. But scientists believe that daytime visitors, the white winged doves and native bees, are more important pollinators for the saguaro. The plant produces another batch of nectar at sunrise and the petals stay open until mid afternoon to accommodate diurnal visitors. Then the blooms close until nightfall. The pollinated flowers produce fruits in early June and July. This is a time of natural scarcity of food in the desert and the moist and abundant fruit is consumed by a variety of birds, mammals and insects. The Tohono O’odham Indians started their year in early summer with the saguaro harvest moon, so important was the fruit to their diet and cultural ceremonies. The long life of a saguaro is legendary, reaching to two hundred years or more. In an interesting irony the desert icon’s fully hydrated stems are more than ninety percent water and weigh eighty pounds per foot. The tap root of a saguaro only probes two feet into the earth, but an extensive network of surface roots stretch out as far as the plant is tall. These tiny roots are capable not only of supporting the cactus that may grow forty feet tall, they also gobble up any available water before it reaches the deeper root systems of competing plants. Saguaro seedlings require several consecutive years of relatively wet mild weather to become established. Such a weather pattern produces a crop of similarly aged and sized saguaros that is known as a cohort.