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Chapter 3: Constructing a Window Box Cocal

Coca, even more so than the grape, is a highly specialized shrub and needs highly specialized climatic conditions and soil in which to grow. Like vineyards, the best of which grow well only in northern California and e few scattered coastal regions in Europe and South America, cocals are generally grown in the mountains of South America. The montana of Brazil, Columbia and Peru where most types of Erythroxylon coca grow, is one of the few places that naturally provide this climate. Although some species have been known to grow at sea level, most (and the best) prefer the coolness and humidity of the higher altitudes. Cocals flourish best at 4,000 to 6,000 feet above sea level. These lofty heights provide the several conditions that are conducive to their growth.


The temperatures of the montana are very equable. The variations between night and day, winter and summer, are a matter of only a few degrees. The temperature is nearly always in the middle to high 60's, although temperatures of over 68F generally tend to cause the coca leaves to become somewhat brittle, and the plant will lose its strength. Even though higher temperatures may cause more prolific growth, the leaves will not have the delicate aroma and flavor of choice coca. Too cool a climate will cause the plant to grow much smaller leaves and the alkaloid yield will be inferior. Even the slightest frost will probably destroy the most hardy coca bush.


Humidity is water suspended in the air as a vapor. The familiar phrase “relative humidity” refers to the percentage of the moisture in the air at a given time and location, as measured against the total amount of moisture the air could hold without it condensing and becoming droplets.

Another peculiar feature of the montana is the high degree of humidity present. It is either hazy or drizzling during some portion of the day, nearly every day of the year. A huge bank of fog is nearly always blocking the sun out. It follows then that the coca bush will want, and need, a constant supply of humid air. The warmer the climate the more humidity they need. If it is not forthcoming, the leaves will brown, yellow or drop off. Flower buds will shrivel and fail to open, and the bush becomes vulnerable to pest or disease attacks.

Coca normally draws its water up from its roots to aid in the many processes of growth. Some of the water is transpired; that is, given off as a vapor from the plant’s stoma, or pores. Because heat without humidity will dry them out, the warmer it gets the more the bushes will transpire in an effort to raise the humidity in the atmosphere. But a coca bush’s supply of water is limited, and once it is exhausted the plant will be left parched, lacking the moisture for other necessary operations. You will do well then to keep the relative humidity of your cocal between 60-80% - or even higher. This will allow the plants to use moisture drawn up through the roots for the growing process.


The soil of the montana where cocals grow is rich in mineral matter, yet free from any trace of limestone. Like the tomato, coca is truly an acid-loving plant. A small trace of alkalinity will cause the plant to grow poorly with scant foliage. Generally, a rich, red clay soil with good drainage is required. It is possible that metallic soil might have some influence on the production of alkaloid, but much more will be said about soil and alkalinity in a following chapter.

It has probably become obvious that you will not grow your cocal out in your backyard, unless you are favored with an exceptional climate. But this should certainly not discourage you from cultivating what might become your favorite shrub. There are simple and inexpensive methods of climate control, and the greater accuracy you care to achieve, the greater the regards your plants will bestow upon you.

Because of the high degree of atmospheric control you will need for your coca, a green house becomes a necessity. But if your pocket book is short and you have visions o an expensive glass and metal piece of architecture rising up from the ground, don’t despair. For the short pocketbook, a window greenhouse can be added to your house or apartment for next to nothing, and should be sufficient to house two well-pruned bushes. Below we will include in this chapter the basic design for a low cost greenhouse. If you feel a great deal more expansive, there are several ready-to-assemble kits that are available. For those of you who are both expansive and have a flair for building there are numerous plans available for every kind of greenhouse, from a simple lean-to to large geodesic domes, but they are unnecessary for the beginning cultivator and beyond the scope of this book. In any case, a simple windowbox cocal and a lot of love will be adequate for your plants. It is, in fact, best to start with a small unit and a couple of plants and expand after you are successful with those.

Before we delve into greenhouse construction, it is important to note than any greenhouse, whether you buy or build it, must be modified slightly before it will be a good home for your coca bushes.

Direct sun, allowed to strike your plants more than infrequently, will lower the alkaloid yield. Too much sun will wither and dry out the leaves of the plant. Prolonged sunlight could even kill a hardy plant. In any case, the south exposure favored and desired by most greenhouse growers can easily be avoided unless you live in the mildest of climates. Shade trees, another nemesis of most greenhouse growers, are a helpful item to coca growers. Deciduous trees are especially good to have around your greenhouse. They will shade the plants from the hot summer sun and will shed their leaves to allow you to cull what you want of the weak winter rays. A southern exposure with little shade will also drive the temperature of your greenhouse up to a very unfavorable range, making it difficult to control. Even if you used an air conditioner your utility bill would be enormous, and you would still have to be concerned about your cocal being too warm and bright. It is better that the location you select has too little sunlight than too much, particularly in the windowbox model. It is easier and cheaper to supply artificial light than have to artificially cool the air.

Check all of your possible locations and calculate how much sunlight each will receive during the different seasons. Four or five hours a day is more than sufficient for your cocal. And remember: with sunlight comes heat, which you are to avoid. If all of the places you have to select from are too bright and hot, you still don’t have an insurmountable problem. You will in any case want to construct sun filters from cheesecloth. There is also a filtering/reflecting paint available from most greenhouse suppliers that will help you reduce unwanted sunlight and heat.

If you build a freestanding greenhouse you will without question need a humidifier. For this item again we refer you to books on greenhouse construction. There are many different models available and may cost from thirty dollars to thousands of dollars. In the small window greenhouse we are going to describe, we have found that a regular (daily at least) misting with a very fine spray from one of the commercially available plant misting bottles is adequate, and at a cost of less than $2, much more practical. Besides raising the humidity, misting gives the bushes the regular moisture on their foliage that they enjoy. You can also keep the humidity up by keeping a shallow box filled with moist gravel. This will be described in more detail when we get to the actual construction later in this chapter.

The frame is best constructed from redwood 2X2. Only two kinds of wood should be used in the framework of a greenhouse: redwood and cypress (although cedar has been found to be adequate). Both of these types of wood are resistant enough to moisture to withstand the high humidity of a greenhouse without rotting. Cypress is used less often because it is more difficult to buy. Redwood is light, durable, shrinks very little and is resistant to insects, moisture and decay. It is also easy to work with. In any case, buy only heartwood. The term refers to that part of the tree the wood has been cut from. Heartwood will be of much better quality because it is the older growth of the tree.

The frame can be nailed together with 6d (six-penny) finishing nails. A half-pound of these will be more than adequate. For stability it is strongly suggested that “L” brackets be used on at least the frame sides and top. These can be purchased at any hardware store, and are best secured with the appropriate quantity of #8-1.5 screws. The sides of the windowbox can be screwed right to the window frame with #8-3” screws. A pair of small hinges will be needed for the top cover. This is important because it allows for ventilation. For the bottom of the box it is best that all seams be filled with silicone tub and tile caulk, then painted with one of the new water-resistant plastic enamel paints that are on the market. They are available at most paint and hardware stores (CAUTION: Do not put the plants into your cocal until the paint and sealer have dried completely, preferably with a day or two of airing out. The fumes are very detrimental to your plants and could possibly kill them).

The covering you put over the frame is without a doubt the most important material as regards selection. Glass is best. It is most durable and best as a transmitter of light. It will outlast any other covering you use 10 to 1. Other factors to consider are the cost and ease of construction. Glass is considerably more expensive than plexiglass or polyethylene plastic and complicates the construction because it must be insert into the frame and glazed. If you decide to use glass, doublestrength window glass is best and can be purchased cut to size.

Plexiglass will last nearly as long as glass and some manufacturers claim it is a better transmitter of light. It is somewhat less expensive than glass, depending on the strength and thickness you purchase, and will not shatter. It can also be cut with a good sharp handsaw.

Polyethylene plastic is by far the cheapest covering for your cocal. It is extremely easy to work with and can be cut with a pair of scissors. The major drawback is its lack of durability. It must be replaced once a year or more often and will not stand up to a harsh climate, such as hot sun or snow. If you use polyethylene for your cocal, remember that direct sun will deteriorate it quickly – and it should be watched (especially along the folds) for cracks or wear. Sears and Roebuck have a polyethylene substitute that is stronger and more durable. It is called “butyrate” and for only a slightly higher price than polyethylene will last two to three years.

The following step-by-step construction is set out with an eye to cost, durability, ease and of construction and the application of the finished greenhouse to use as a cocal. Material substitutions can be made if better materials are available, but the list provides adequate materials and methods at a low cost. The entire greenhouse can be built for less than $40.

STEP 1: Find the best window as regards light, heat and size. A south window with no shade should be avoided unless the climate is very mild. If your cocal is to be two bushes strong, the window should be at least four feet in height and over three feet in width. Even with these dimensions, some adjustments will have to be made, so try to find a window at least this size. If you have no windows this large, you are not lost. You will just have to cut down on the access space to reach and care for your cocal. You will also not be able to see it as well and watch it grow. (This last consideration was found to be very important incidentally. A sympatico seems to develop between cultivator and cultivated until it is hard to distinguish one from the other). Note: if the window is too small, the exterior of the apartment building or house must be made of a material to which you can attach the cocal frame, i.e. wood. Brick or concrete, although not impossible, is difficult.

STEP 2: Once you have located an appropriate window, the frame should be carefully measured. It would be best to consider carefully how a frame at least 78” high and 48” wide can be attached outside of it. Measure the window again! Now a plan, including measurements, should be sketched out carefully. In this step, as in all of them, care should be exercised. Many difficulties can be avoided by careful planning. After your plan and measurements have been sketched out, a materials list should be made out.

STEP 3: Once the materials have been gathered you can begin construction. Begin with the frame as pictured. It is best, and easiest, to begin with the sides. The height of the sides should be a minimum of 78” (inside height), but can be more if you are blessed with a taller window. Remember that coca will grow to a height of twelve feet if it is not pruned. Well-pruned bushes will be about six feet high, so you must provide adequate space for them to grow properly. When the height is determined, cut four pieces of your redwood 2X2’s to the proper length. At least make doubly sure that they are all the same lengths. The side cross members can be cut now. Eighteen inches is quite an adequate depth, and it is suggested to not make the box deeper or it will become unwieldly and difficult to support. Again, four side members should be cut, making sure they are the same lengths. Now you have the sides cut out and ready for assembly. Nail them together one at a time with 4d finishing nails. It is strongly suggested that you apply a liberal coat of white glue to all surfaces before joining them. This will give you considerable added strength. When finished you’ll have two rectangular frames for the sides. Do not screw on the “L” brackets until the sides have been joined together by the cross members. Allow the frame sides to dry and cut the four cross members. They will be a minimum of 48, more if you are blessed with a nice, wide, bay window. When these have been cut, and when the side frames have been allowed to dry, they can be nailed and glued to the sides. You will now have, hopefully, a good square rectangular frame. Use your framing square and make sure each of the corners is square in three directions. As each corner is squared the L” brackets can be applied. Lay them on the corners and drill the holes with a 1/8’’ drill. Screw the brackets down tightly with #8 woodscrews.

STEP 4: Now that the basic frame is complete, cut the bottom from marine plywood. (Other grades of plywoods will quickly deteriorate and cause an expensive and difficult repair job in a very short period of time). After it has been cut and tried for size, a liberal bead of silicone tub and tile sealant should be applied to the surface that will be connected to the frame then. The bottom can then be nailed to the frame with 6d finishing nails. Now apply another generous bead of sealant to all inside bottom seams. The entire frame should be set aside to dry for at least 24 hours. In the meantime you can construct the top.

The top will also be constructed of redwood 2X2. It is strongly suggested that the corners of the top be mitred for greater rigidity and durability. The top will, of course, be cut to measure the same size as the top of the frame. Once the four side pieces have been cut, they can be glued and nailed together. Now the hinges can be laid on the back cross member and the holes marked for drilling. Drill out all of the holes and screw and screw the hinges down tightly. Now take a piece of metal strap iron about 8” long. It is necessary that it has holes in it as the illustration. Most hardware stores or builder’s supply houses carry it with the holes already stamped out. It is no more costly than solid strap iron and is a lot less difficult than attempting to drill several holes in an iron strap. This can be screwed to the center inside of the front cross member. It will be used to prop the top open when ventilation is necessary. When the top is attached to the frame, a screw can be put part way into the top frame cross member corresponding with the piece of strap iron. In this manner the top can be raised or lowered by simply putting the appropriate hole in the strap iron over the screw. Before mounting the top to the frame, it is best if they are both covered with the Butyrate or polyethylene.

STEP 5: The covering material should be cut to size for the sides, front and top. If possible try to cut full size pieces. The work will be much simplified if there are no seams in the covering material. The covering material will also last longer if there are no seams. If you find it absolutely necessary to have seams (i.e. you are not able to get the covering material in sufficient widths) use double, overlapping seams (look at the seams in the legs of your Levis). A thin coat of plastic cement will help hold it, or you can use a warm iron to seal it, provided you use tinfoil between the iron and the polyethylene, making sure the iron is not too hot. In any event, avoid seams if you can. Most of these covering materials are sold in sufficient widths. Polyethylene is sold in widths over twenty feet. IMPORTANT: when cutting the covering material leave an inch or two extra on all sides. It is much easier to trim with a pair of scissors than to try and stretch a short piece.

After the material is cut to size, the wood lath can be cut. There should be a piece on every edge of the sides, front, and top. You can use the inside measurements of the frame itself for cutting the lath. Now apply the covering to each side one at a time. It is best to apply it on one edge, first making sure that it is kept taut as the piece of lath is nailed over it. When the first edge is complete, do the edge opposite it. The other two edges can be done in any order, but be sure the covering material is kept taut at all times. If the material is kept taut it will last longer, transmit light better, and give you a better-looking cocal. The front, top and both sides should be done in the same manner.

STEP 6: You are now ready to attach the top. Set the top on the frame making sure it fits flush on all sides. Once it is sitting flush, mark the holes for the hinges and drill them out with a 1/8” drill bit. The hinges can now be screwed down tightly.

STEP 7: You should now have a finished cocal ready to be attached around the window frame you have selected. Have a friend, or two, help you by holding the cocal in place. Blunt the ends of two 16d nails with a hammer so they do not split the wood, and drive them through either side of the frame, the top third preferably, into the building leaving about ” protruding. Now drill 3 holes through the frame and into the building with your drill. Screw six #8-3” screws into these holes, making certain they are secure. Now, carefully, pull the 16d nails out.

STEP 8: This step is not a necessity, but our experience has shown it to be very helpful in providing the necessary humidity. Obtain a sufficient quantity of pea rock from your nurseryman. (You should be good friends by now). Pour about 1-1/2” into the bottom of your cocal in an even layer. This layer of gravel will hold a considerable amount of water, which as it evaporates, will raise the humidity of your cocal.

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