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Prepping terracotta pots for the rooftop garden

The holidays and family visits are over, garden goals for the new year have been set, and after nearly four months of constant precipitation the plants are feeling the shock of a sudden shift to the dry season. In the tropics, our work never ends.

On our rooftop, we have a mix of containers with unglazed terracotta pots making up the majority. Plastic is never my first choice, but even if it was it is very expensive in Sri Lanka. Terracotta became the most attractive option (financially and aesthetically) when I was collecting large planters for fruit trees. They are locally made, hold up well to the sun while the plastic becomes brittle after only one season, and they look good without paint or fuss.

However, they are far more porous than the other planter options. This is great during the monsoon season when roots desperately need the oxygen (our crops did fine while many farms flooded and vegetable prices continue to rise), but now the scorching sun and steady breeze are drying the pots faster than I can reasonably keep up with watering. Mulch and compost are great fixes for the soil, but in our extreme location I am finding that extra measures must be taken.


Obviously buying an outright glazed ceramic pot would be easiest, but these are another costly option. Additionally, the shapes of such pots are most often decorative and not practical for anything that might need up-potting in the future. The shape of the pot usually narrows at the top like a vase would, making it difficult to remove a root ball without harming the plant or breaking the pot.

So I have been exploring different sealant options:

Silicone is a common base for spray-on sealers and wooden deck sealants. But I hate working with the fumes and aerosols, so it cannot be all that safe to use around my sources of food. I could empty the pots before sealing, but a) I would rather seal the outside to keep roots away from any potential leaching of chemicals, and b) my pots are full of perennials, such as my fruit trees.

Acrylic is looking like a great back-up option. Several forums have discussed the efficacy of common artist’s acrylic, which applies easily and dries clear. This can also be diluted to be more cost effective and aim for a degree of porosity, though I am still researching how to maintain some airflow. The soil drains well, so this might not be a real concern.

Bentonite, however, looks like the best choice. This is a natural clay application where its fine particles fill in the pores of terracotta to significantly reduce evaporation. Supposedly. This might be slightly harder to find in Sri Lanka, at least in an applicable form. If I can track it down, you will be sure to hear the results of a comparison with acrylic.


As I mentioned last November, we mostly mulch during the rainy season. Now that drier weather has come we will be moving the surplus finished compost from the garden to the rooftop containers. This will be detailed for you in the coming weeks.


As always in a permaculture application, we will be adding more diversity with every season. On Thursday you will get a look at which varieties grew well and new guilds of plantings that emerged.


Margie is the founder of IG and is passionate about the therapeutic benefits of working with nature in the garden. She enjoys mangosteen, the rainy season, hammocks, and wild visitors in the garden.

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