In South Florida we are fortunate enough to have the opportunity to grow food all year long. In this climate zone it very rarely ever gets cold enough to kill our vegetables however what most people do not realize is that being too hot and humid can be just as much of an impediment as frost for veggie production.
In many climate zones north of South Florida gardeners use special methods such as greenhouses, cold frames, and hoop houses to create a warm hospitable environment for plants in the colder months of the fall and winter. In South Florida if we want to grow vegetables even through the steamy dog days of summer we have to find ways to cool our plants down, which in some respects can actually be more difficult than keeping them warm.
You see, if plants are going to fruit they need to be pollinated. When the weather becomes too hot and humid the pollen becomes very sticky and doesn’t transfer as it normally would. Another factor that affects the viability of vegetable growth in summer is rapid rate of growth induced by the long daylight hours and copious sunlight. This is what makes plants and trees in this zone grow so rapidly but it also intensifies a gardening phenomenon that we call “bolting”.
When we say that something has “bolted” we are most likely referring to lettuce. When lettuce is growing under ideal circumstances it grows tender, sweet, delicious leaves that we can harvest and use in our salads. When the plants are subject to excessive hours of high heat and sun exposure they invariably want to flower and go to seed. When a lettuce plant enters this stage it is no longer fit for consumption and its leaves fill up with a very bitter white compound and that is what we call “bolting”.
A very effective method of preventing or delaying this process is to create what is called a “micro-climate”. A micro climate is when you use a particular technique to create different climatic conditions in the same general area. Often these techniques involve the use of neighboring plants, unconventionally shaped beds, and/or extraordinary soil additives. Of course you can use conventional commercial methods such as a shade house which simply utilizes a large structure that supports dark mesh cloth to block the full spectrum of sunlight but allow rain and air to filter through. Shade houses can be effective but due to the materials required in their construction, they are not very sustainable and it is very difficult to make them look as beautiful as a plain natural garden space.
Natural methods of micro-climating are just as effective, much more inexpensive, more sustainable and bring a beautiful and more natural appearance. One of the easiest ways to create a microclimate in any garden space is to use larger shrub or tree type plants to create a canopy that you can plant your vegetation under. This will provide a cooler space with cooler soil that will slow down the bolting process of your lettuces. This type of natural canopy allows filtered light to penetrate and feed the plants while keeping excess light and heat away. Of course any plant will demand a particular balance of light so as you observe the process you can prune your canopy accordingly. If the plants do not seem to be getting enough sun, simply prune away the canopy a bit from time to time.
One of Brent’s “go-to” methods of lettuce micro climate is to plant at the base of his specimen bamboo plants. It’s just one more way out of countless others to utilize bamboo in the garden. When you surround the bamboo with beds of lettuce you are limiting the amount of daylight hours each plant is exposed to. As the sun moves across the sky the bamboo plant acts as a sundial of sorts and provides relief to part of the lettuce bed while the other plants are getting their turn photosynthesize. This method is better for plants that are slower to bolt or require more sunlight than a natural canopy could afford it.
Another way to utilize the landscape to create a microclimate is to plant your bolt ready plants on the north side of a hill or berm. Even when the sun seems to hang straight up in our sky it is always slightly drawing South to greater or lesser degrees depending on the season. If you plant on the north side of a hill or berm, your plants are going to get far less direct sun exposure during the entire daylight cycle while still receiving enough to carry out their functions.
Of course here in South Florida hills are very hard to come by but when you are undertaking any landscape or excavation project in your yard consider the permacultural value of a hill and use some extra soil to build yourself something. Also, many trees, including palms and bamboo, appreciate being planted in a nice berm. You can even utilize that subtle slope to give a bit more relief to some of your more vulnerable plants.
Speaking of hills or mounds let’s talk Hugelkultur! Hugel is German for mound and the Germans have been using this brilliant method for hundreds of years. In a Hugel bed you dig a trench in which you place entire tree logs. You stack this timber up to 6 or 7 feet in height and cover the larger trees and logs with sticks and mulch. You then cover the wood with about 8 or so inches of topsoil that you can plant in. As the wood at the core of the bed breaks down it releases plant food into the bed. The rate of decomposition supplies ample food for even heavy feeders and the density of the wood provides up to 80 or more years of fertilization! Furthermore the decomposing biomass within the bed becomes a massive sponge capable of holding enough water to account for over 5 months of drought. People using Hugel culture beds have reported occurrences in which beds have gone for over 6 months without being watered and over 30 years without being fertilized while still producing abundant and delicious foods.
Hugel beds create a dual micro climate that is as versatile as it is effective. The north side of an East to West lying bed provides an outstanding cool zone due to the extreme slope of the 5-7 foot mound. In addition to the cooling properties of the bed, the perpetual breakdown of such a large mass at its core is constantly generating heat at its depths. The heat generated has preserved plants well into the colder some months of the fall and winter in northern climates and permacultural icon Sepp Holzer has even used this core warming process to grow citrus trees as far north as Austria!
There are plants whose need for abundant sunlight can make it very difficult to utilize some of the aforementioned strategies. Tomatoes require an abundance of direct light but at the same time are subject to the sticky pollen syndrome we discussed above. This is where we go back to the Native Wisdom that Brent is always so keen on. When plants live in a particular climate they learn to cope. The South Florida native, Everglades’s tomato, is immune to the oppressive hot sun of Miami summers. This super sweet and delicious cherry tomato does great in the heat of the summer and will last the whole season with enough food.
Brent Knoll utilizes these easy and innovative natural methods to give his clients delicious organic food all year. It has been said that it is easier to heat a greenhouse to grow food in the northern winter than it is to cool the plants off in the tropical southern sun but when you learn all the secrets of nature you get certain gardening privileges that remain elusive to the horticultural convention.