It amazes me how many of the plants we have here at Kona Kai can do so well despite the severe lack of water during what is aptly called the "dry" season, the last part of which I like to call the "4th Quarter" for the plants, when they really have to give it their all to not only survive but look good as well. We do irrigate the grounds to help them make it through, but not heavily. As I discussed in my previous post, it is to our advantage to choose plants that have evolved to deal with annual drought periods. For example, some plants, such as our pineapple plants (Ananas sp. - photo on left), along with many succulents, have an alternative way to photosynthesize (a plant's way of making food), which allows them to divide photosynthesis into two parts, one taking place at night and the other during the day; this is called CAM photosynthesis. CAM plants can open their stomata (pores for gas exchange) at night to fix carbon dioxide and close them during the day, thereby significantly reducing water loss over the more common method of photosynthesis (C3 photosynthesis), which requires stomata to be open during the day. Plants that use the C3 method can lose over 95% of the water they bring in through their roots to transpiration out of stomata, thereby giving CAM plants a big advantage in dry environments. Elephant bush (Portulacaria afra - photo on right), of which we have two plants, can even switch between these types of photosynthesis depending on the conditions; now that's pretty smart!
Many bromeliads are also able to do without water for some time because of their water storage techniques. Water is stored at the bases of their overlapping leaves and, in some species, in specialized "tanks" designed to hold water for use during dry periods (photo below on left). Bromeliads also have microscopic structures covering their leaves called trichomes, which are cells designed to reflect sunlight, absorb moisture and limit moisture loss. Trichome density varies from species to species and the presence of many trichomes results in the grayish color frequently seen on air plants (Tillandsia - photo below on right).
One of the ways in which succulents combat drought is by storing water within their leaves. Below is a photo of a succulent, desert cabbage (Kalanchoe thyrsiflora), in our Gardens. Many plants, including succulents, have root systems that are shallow rather than deep to rapidly absorb water after short periods of rainfall typical in drier climates/seasons.
Despite all these modifications, plants adapted to dry conditions can be pushed to their limits, but the plants here at Kona Kai are still doing very well considering the lack of rain. Even though the grounds at Kona Kai are as great a place as any plant could wish to be, they still have to play hard, especially in this dry 4th quarter, if they want to stay on the team. If you find yourself at the Resort near the end of the dry season, don't be surprised to be startled out of your hammock by what seems to be Bobby Knight on a motivational tirade (without the profanity of course): "Sweat it out! Come on, this is the last stretch! Finish line's in sight! It's the fourth quarter, baby! You're Eric Dickerson, not LeBron James...Mr. 4th Quarter, not 75 Cents! You gotta keep goin' - rain's coming soon! This is what you've been training for your whole life! Now show these guests what kind of photosynthetically efficient, water-conserving, drought-tolerant monster you are!" Pay no mind, it's just me - an impassioned botanical coach inspiring his team of plants to sweet summertime victory.