Urban farming is on the rise here and green-thumbed Singaporeans are developing new solutions to cultivate plants in better and more efficient ways.

These include ways to "talk" to plants through technology, making vertical farms the size of wine fridges or creating special enzyme solutions to boost plant health.

The Straits Times checks in with three groups from the new generation of innovative gardeners.

From waste to enzyme solutions

Every six months, several volunteer gardeners from Bukit Batok go to wholesale vegetable and fruit markets to ask stall owners for rotting produce.

They then take the bags of wilted goods back to their community garden at Block 106 Bukit Batok Central.

The produce is used to make enzyme solutions, which help plants better absorb nutrients. Unlike chemical fertilisers, the enzymes are made from natural and organic materials.

The garden uses five types of enzyme solutions made of ingredients such as banana shoots, over-ripe papayas and bananas, egg shells, milk and lemongrass.

The different mixtures aid plants in different ways. The lemongrass enzyme mixture helps strengthen roots, kill weeds and deter pests; the banana shoot enzymes help plants get more nitrogen; and the over-ripe fruit enzymes aid plants in getting more potassium.

The process to make these enzyme mixtures can take up to between one week and 21 days to produce.

Although techniques vary, most require the raw materials to be mixed with sugars and fermented for eight to 10 days before the liquid is filtered and used in the gardens.

Because the process is so laborious, they make huge batches twice a year, when the volunteer gardeners and members of the community - including children from schools in the neighbourhood - all come together to help.

The garden is led by three gardeners who live in the neighbourhood: Ms May Lee, 62, who works in her family business; Ms Cheryl Wee, 55, a housewife; and Mr Tan Swee Ching, 48, who does sales in the raw materials industry.

In 2015, all three attended a course in Maejo University in Chiang Mai, Thailand, about organic farming, which included information on how to make enzyme-based solutions.

For the past two years, they have been making these special solutions and using them on the plants.

Do they work?

The garden certainly looks great. Called Cosy Garden, it is a delightful space for the neighbourhood. The garden comprises three separate plots of land with sculptures, landscaping, flowers, herbs and a butterfly enclosure.

Mr Tan says: "Because no chemicals are mixed or used, the soil and plants stay healthier and more fertile for longer."

Since 2014, the garden has won numerous awards from the National Parks Board and many gardening enthusiasts have visited it to learn more about how the garden is run.

Always ready to share their knowledge, Mr Tan, Ms Lee and Ms Wee hold ad-hoc sessions for groups interested in learning to make enzyme solutions.

They also meet people from other community gardens around Singapore to share their expertise.

So far, they have talked to the likes of those at Yuhua Community Centre, Kim Tian East Residents' Committee and the Institute of Mental Health.

In December, the trio, along with seven members of their community garden, will go to Cambodia to share their skills with villagers and farmers there.

Ms Lee hopes to teach them how to grow plants "in a better and more cost-effective way".

She says: "It is better for everyone - not just us, but for the plants and the environment."

Keeping an eye on plants with sensors

If plants could talk, what would they say? This is the question Mr Veera Sekaran, 55, is hoping to answer with his company's newest innovation - a network of sensors that can help humans "communicate" with plants.

The sensors, which are placed into the soil and surrounding ecosystem, react with compounds in the environment to measure variables such as light levels, tilt of the plants and the amount of water in the soil.

This information is transmitted wirelessly to a mobile or tablet device, so users can monitor the state of their plants 24/7.

Mr Veera has already begun using the sensor system in all his recent projects, including at the Apple Store in Orchard and in his company's own urban farms.

He adds that the sensors are small and light enough to be used anywhere, including along green walls and on roadside trees.

The technology is not new, he says. There are sensors on the market that can monitor whether plants are getting enough light or water.

But his systems take it one step further, by monitoring other variables, such as the amount of fertiliser in the soil as well as the tilt of the plants. The information is also presented in one user-friendly, integrated platform.

This allows for "predictive maintenance", which prevents mishaps such as falling trees because the user is alerted the moment a treebegins to tilt dangerously.

"This is efficient - we don't have to send our staff to check on the plants unnecessarily. For the corporation or owner of the plants, they, too, are aware of how their plants or green walls are doing at all times."

A basic system, such as for a green wall at home, costs about $550 to $650 a square metre. Prices range in the hundreds of thousands for more sophisticated systems.

His company Greenology , set up in 2008, offers urban greening and farming solutions. Its clients include Shaw Centre, Changi General Hospital and Changi Airport.

Mr Veera, who is a botanist by training, has worked as an assistant curator of horticulture at the Singapore Zoo and Night Safari and curator of horticulture at Changi Airport.

In 2008, during the Asian financial crisis, he decided to start his own company, which became one of the pioneers of green walls in Singapore. It now has an annual turnover of between $3 million and $4 million.

And do not talk to him about not being a "green thumb".

Through technology, he hopes to dispel the myth that being a good gardener is an innate talent. "People have said to me they can't talk to plants and, as a result, they can't seem to keep plants alive. But the dynamics of living systems are the same - we just need to tap them and communicate within the habitat."

He is now working with a local company on improving his remote sensor technology. A year ago, he also began refining the sensitivity of the sensors that monitor plant tilt and invested about $100,000 into research. He hopes to start selling the improved version next year.

He is also interested in incorporating advanced digital technology into horticulture, such as the proprietary system he has developed for users to access the sensor data remotely.

He says: "For a long while, digital technology has been developing much faster than innovations in horticulture. I hope to integrate the two.

"I want to use technology to create the most healthy and effective green ecosystems for our communities."

Harvest greens at home

About the size of a wine fridge, the G-Cube Cultivator is a special machine that allows users to grow crops in the comfort of their home.

The temperature, humidity and light inside are programmed to suit different plants, which means non-local varieties of lettuce, spinach and round baby carrots can be grown. These species require lower temperatures of between 18 and 22 deg C.

To grow the greens, soak and sow the seeds on the lowest level of the cultivator. It is a hydroponic-style system, so there is no soil, only water. Ten days later, move the seedlings up one level.

On the lowest level, new seeds can be sown again. And 10 days later, they are moved up again. By day 30, the crops are ready for harvest. And the next harvest is in 10 days.

The product, which retails at $3,999, was launched by social enterprise Project G-Cube in April this year. It is the first climate-controlled vertical farming equipment that can be used at home in Singapore.

Its makers say the cost can be recouped in under two years, with a yield of an estimated 50kg or 1,088 heads of leafy greens a year.

Based on its studies, the team estimates that it costs about $50 a month to run the machine. The time required to manage it is one minute a day and an hour every weekend.

Project G-Cube was started earlier this year by Mr Lester Chan and Mr Kelvin Koh, both 32, two long-time friends and ex-schoolmates at Chinese High and Hwa Chong Junior College.

Mr Chan is the executive director for Asia Pacific for a global Japanese multinational company and Mr Koh is a full-time lawyer. They have a silent third partner.

Their social enterprise aims to promote sustainable agriculture in Singapore and encourage urban farming in homes.

Besides selling the Cultivator, they also want to work with food charities.

The technology for climate-controlled cultivation is not new. It is used in vertical farms, but on a larger scale, and is often operated out of shipping containers or purpose-built warehouses.

Mr Chan came across a small cultivator prototype in China while on a business trip, and decided to bring the product to Singapore through a white-label arrangement, meaning that while that Chinese company makes the product, his company will brand, market and sell it.

His aim was to "decentralise urban farming" and "bring down the cost for the consumer".

Project G-Cube has donated three cultivators to Hwa Chong Institution, which in turn is giving all the crops to Food from the Heart soup kitchen. The company also pledges to donate a cultivator for every 10 that it sells.

Mr Chan says they are "not selling any sort of proprietary technology" or "looking to compete with local farmers". "We hope this is a way for more people to introduce healthier, chemical-free greens into their lives. It's a big lifestyle change, but one that people can easily achieve without sacrificing much time or money."

•For information on the Project G-Cube Cultivator and how to buy it, go to www.projectgcube.com