Much of what she and five other workers grow here will feed an entire neighbourhood and what's left is sold to foreign diplomats and business people.
By the BBC's Greg Morsbach from Cuba
Cuba - one of the world's last socialist regimes - has surprised many economists by surviving a US trade embargo lasting more than 40 years.
The small Caribbean island nation has continued to defy expectations that it's about to collapse under the strain of a run-down state economy.
One reason is the radical changes to Cuba's agriculture. A recent report by the American agency for sustainable farming, Food First, said annual production of fruit and vegetables is growing at 250% a year.
And the produce is grown without any help from chemical fertilizers, pesticides or herbicides.
Urban farms
Clara Hernandes is proud to display the fruits of her labour on a small community farm on the outskirts of Cuba's capital. She produces anything and everything from eggplants, mint, cucumbers and onions to radishes.
Much of what she and five other workers grow here will feed an entire neighbourhood and what's left is sold to foreign diplomats and business people.
Senora Hernandes is in charge of one of hundreds of small urban farms dotted around, Havana.
Like thousands of other such "huertos" or gardens across Cuba, hers produces nothing but organic vegetables.
"Last year alone we produced 27 kilograms of vegetables per square metre. When we first started this farm three years ago it stood at 18 kilograms. And we expect this year's harvest to yield no less than 30 kilograms. That's an increase of around 30% year on year."
State-of-the-art watering systems, greenhouses and nurseries for plants are these days all part of urban farms. But they weren't always so well equipped.
Food shortages
In 1993 and 1994 the country experienced a severe food shortage with the population on the brink of starvation.
What was to be done? The Cuban government's answer was transform derelict city plots into well-funded vegetable gardens under the supervision of organic farming associations.
Doctor Fernando Funes, who heads the association of agricultural and forestry technicians (ACTAF), says back in the 1990's when prices were high many people were despairing.
"But me and others began to work applying all our resolve and scientific background. And we were successful. Cuba is now ahead of the other Latin American countries in organic production."
The Cuban government has made organic farming a priority, since handing over 80% of state-owned land to private shareholder enterprises.
Farmers such as Carla Hernandez are now in the top 10% of earners, ahead of many medical doctors and academics.
The government passed a law this year making organic farming compulsory and Nilda Perez, one of ACTAF's top food scientists, says all food production should be based on organic elements both domestically and industrially.
Some of the bigger farms producing crops such as organic oranges and sugar cane have even started to export small amounts of their produce.
But despite all the advances made in boosting vegetable production, the price of most other food on the shelves of Cuba's supermarkets remains high.
Rationing of some basic products is still in place, so that fresh milk is only available for children under the age of seven.
The country still has a long way to go before becoming a major food exporter in the region. But Cuba has certainly overcome the worst of its food supply problems- thanks to organic farming.