Rooftop Gardening: A Learning Process

by Mari Pintkowski  (Feb. 2015)

Life for my husband, Lou, and me as onsite B&B owners/operators in Tulum, is all about learning and sharing through little projects that we engage in. Planting and nurturing our organic vegetable garden is one such example. For the last five or six years we have dabbled in the art of vegetable gardening and have discovered that there is so much to learn. We can spend many hours researching on the Internet about how to raise the tastiest tomatoes, or how to recognize what is ailing your plants, or we can learn firsthand by trial and error. This method, however, is slower and leaves many unanswered questions.

In my last article on gardening in Sac-Be, How Does Your Garden Grow, I ended the story with, "Don’t hesitate to reach out beyond the Internet and look for answers firsthand." I believe that when you have reinvented your life and are living in a foreign country or even a new region, meeting your neighbors and sharing is key, but it takes time and effort and, in return, you may find the missing element in the trial and error method: first-hand information.

Our gardening history took a sharp turn after reading an article in Yucatan Living by Robert Kimsey. We decided to see what we could learn from his methods of rooftop vegetable gardening in downtown Mérida. After the second visit with Robert and Tonia, we re-evaluated our own rooftop gardens in the Maya jungle near Tulum and decided to make some drastic changes.

Our 2 1/2 foot high x 2 1/2 foot wide concrete block gardens built above our carport and storage shed were going to need to be renovated if we were to come close to the results that Robert was getting from his gardens. We had originally built these gardens on the rooftop to keep our dogs and other jungle creatures from destroying the plants or eating the crops. We soon learned that we had made a few mistakes that could be resolved. Each year we filled the gardens with a mixture of our compost and locally harvested soil that attracted nematodes and other local insects. We realized the first year that the simple self-watering system with tiny sprinkler heads did not function after a few months because they became clogged with lime and other minerals. The seeds we planted directly into the soil were purchased in our home state of Colorado. Our garden grew like this for two years, but our crops were hit or miss and the growing season was shortened especially when there was a hot/dry spring or a very rainy fall. We delighted in each tiny tomato and lettuce leaf that sprouted, but after seeing Robert’s garden we knew we could do better.

From our conversations with Robert and Tonia, we learned many tricks, and were inspired by their wisdom, not to mention their harvest. We took lots of photos and copious notes.  On one visit to Mérida, Robert took us to a supply house in the market district to purchase vermiculite and organic fertilizer. They did not have the soil we needed, but were told that we could buy large bags of sterilized soil and peat moss at Home Depot. He even shared seeds and loaned us one of his newly invented portable garden boxes with a self-watering system, which we would later replicate for our existing rooftop gardens.

We headed back to Macario Gomez to make more adjustments in our current garden and plant the gifted box. We were still planting seeds directly into the soil, whereas he used seed flats to give his seedlings a better start.  We planted and nurtured each young sprout. To our surprise, there were few weeds and the self-watering system was less labor intensive than our current hand-watering system. In this old-style garden, even when we watered the plants in the morning, the soil was bone dry by the late afternoon and we would have to re-water.  We quickly saw the advantage of Robert’s system, as the plants in this small space far surpassed the others in size and quality of fruit even though they had been planted a month earlier. When I walked out to tend my garden, Lou would often call to me and recite the familiar nursery rhyme, “Mari, Mari, quite contrary, how does your garden grow?” I would smile because we both knew our research was paying off, but this 75 cm wide x 2.5 meter long x 40 cm deep portable box was not enough to serve our B&B guests and ourselves. I envisioned a harvest that I could share!

When the high season winds down each year at La Selva Mariposa, Lou and I make plans for new projects and improvements. The garden was at the top of our list. I went back to Pinterest and other sources to read about growing organic crops in small spaces. Our TO DO list had begun:
• Order organic seeds from Region 10 (Florida, not Colorado)
• Plant in late fall
• Review notes from visit to Robert Kimsey’s
• Locate seed flats
• Make sure a hose with sprinkler head is accessible on the rooftop
• Buy in bulk: sterilized soil, peat moss, vermiculite and some local cow manure
• Attend an organic gardening class at Green Beat in Tulum
• Check to see if our compost is ready. We had covered one side of the pit with plastic tarp and let it “cook” while we used the other side to refresh our gardens
• Get extra tarps to lay out the soil and mix the ingredients
• Purchase enough: Dura-Rock, block, sealer, epoxy paint, acrylic roofing material, rebar, plumbing parts and PVC to reconstruct half of our rooftop garden
• Refill the other half of the rooftop gardens with the new soil mixture
• Explain to our gardener, José, what his role in the renovation and replanting of the organic gardens will be

When we returned in Oct. 2014 from our annual vacation to visit family and friends in the United States, we were ready to begin. Lou directed José and his helper, and together they took out the old dirt and redistributed it around the property. Next they leveled the top of the old garden.  We than spaced rebar to give the Dura-Rock something to rest on, as it was the platform we would start our new garden from. We then Fiberglas-seamed all the joints. Fifteen cm block was cut in half and cemented on top of the Dura-Rock to make the outer walls. The block also created a ledge that the acrylic roofing material would sit on. Next, one row of 10 cm block was added. Cement was mixed and used to seal the block interior sides and bottom. We had to apply first a rough coat of cement, followed by a smooth covering. This layer was finished with a coat of swimming pool epoxy paint. We had to be very careful that there would be no leaks, since we were creating a reservoir. The drains and automatic float were installed. We cut the acrylic roofing material and drilled holes in the lower rounded portion every four inches so that water could seep through before laying it in place on the ledge. We put two inches of peat moss on top of the acrylic. On the tarps that had been laid out on the floor, we mixed bags of potting soil, compost, vermiculite and a dash of cow manure. We added four inches of this mixture on top of the peat moss. We completed the project by adding PVC pieces to support the growing plants or to add a shade cover during the hotter summer months.

The purpose of the peat moss is to keep the soil mixture moist so that air can circulate around the plant roots as they wick down to reach the water. We knew the system was working even before we put our seeds and seedlings into the soil because fifty or so tomato plants sprouted from seeds that were in the compost. We had to give many of these volunteer tomato plants away as there was no way there would be enough room for even half of them to grow.

You might not think finding seed flats would be a difficult task, but Lou and I looked on the Internet for places that might sell them from Cancun to Tulum. When none were listed, we checked with small nurseries, back street shops selling plastic containers, and asked everyone whom we could think of who might have a contact with gardening. No leads were found and I could not wait any longer to plant, so I used egg cartons, plastic soda bottles cut in half, toilet paper tubes, and a few peat pots that we found at Home Depot. The delicate seeds of tomatoes, lettuce, arugula, mesclun, beets, spinach, parsley, basil, cilantro, peppers and cucumbers were planted into the make-shift seed flats.

One day Lou came home from a shopping trip in Playa and excitedly handed me five seed flats that he got for free from Home Depot's trash pile. He did have to ask permission from several floor attendants who called their supervisors who asked Lou questions. In the end, Lou was allowed to walk proudly out the door with the flats.

The new seed flats were just in time for the second planting. The first sprouts were transplanted on November 7 in the garden and by January we were harvesting the sweetest lettuce, arugula and herbs you could imagine. It is now February 11 and in another few weeks, the tomatoes and other vegetables that are heavy on the plants will be ready to garnish the breakfast plates and be incorporated into many tasty dishes. The smiles of surprise are our reward for a long-awaited harvest when we bring a bowl of seven or eight different greens to accompany a tasty quiche or other egg dish.

To my delight, we have a comparison study in process with half of the gardens being watered by the plants wicking down to the reservoir and the other half, without a reservoir, being hand watered. Few weeds grow and the soil in the new gardens never dries out: and when you pick up a handful of soil, it sifts through your hands. The other advantage of our new gardens is that it is a perfect height for tending without having to bend over.

One day last month, we got an email from a neighbor inviting us to join them at the first meeting of Macario Gomez's Garden Club. Finally there would be an avenue to share what we are learning about our gardens. At the first meeting, Laurie shared an aquaponic garden idea she is starting in Akumal for a restaurant. We were learning how a tank of live tilapia fish is connected to the reservoir that carries the fish waste to the plants that are wicking down to the water. We are both thinking and wondering if the other half of our rooftop gardens can be turned into an aquaponic garden! We can see that endless ideas will begin to flow as we reach out and share gardening secrets with our neighbors.

Thanks Robert for the inspiration!

Mari and Lou Pintkowski are owners/operators of an elegant jungle B&B, La Selva Mariposa, in Macario Gomez (Tulum). To read more about their life in the Maya jungle see the archives of Sac-Be, or Mari’s books can be purchased on

La Selva Mariposa Rooftop Garden

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