Issue 46: Winter Light

Issue 46
May/June – 1999
Story Title: Winter Light
Author: Roger Fox

High intensity greenhouse lighting has revolutionised winter production at this Sydney-based flower enterprise.

Like heating systems, greenhouse lighting offers undisputed benefits to the growth of crops in winter. Recreating summer’s warmth and sunlight via artificial means, can trick most crops into continuing production right through their usual dormant season. For growers though, it comes down to a question of economics, and whether this off-season production can justify the cost of the technology.

At Linton Fresh Flowers in Sydney, high intensity greenhouse lighting has proved a worthwhile investment for winter production of the high value flower crop Lisianthus. Last winter, one of the enterprise’s 3-span sheds (comprising 12,000sqm of growing area) was fitted with 1100 watt metal halide lamps, as a complement to the existing heating system. The improvements in crop quality which followed, and the consequent improved prices through winter, have convinced the Lintons of the benefits of artificial lighting and inspired them to look at expanding its use throughout the enterprise.

According to David Linton, Lisianthus have steadily grown in popularity over the years and now consumers are demanding them year round.

“The market is growing more and more towards Lisianthus and diminishing for Carnations, so we’re really following the trends,” he explains.

David’s father, Tony Linton, was one of the first flower growers to produce Lisianthus crops in the Sydney region, initially starting out with small plantings. As the market grew, production was increased, but the climatic sensitivity of the plant was a major limiting factor.

“You can stretch a Lisianthus crop through to the end of May,” David explains, “but after that they go to sleep. They don’t like cool nights – the temperatures have to be well above 13°C.

“They also like a minimum of 13 hours light. In fact Lisianthus are a crop where, the more light they get, the better they grow. The optimum amount of light is 16 hours a day.”

Accordingly, David began to consider greenhouse lighting systems, with a view to extending the Lisianthus season through the winter months. After much research, he identified a high output lamp from Sunmaster, the Warm Deluxe 1100 watt, which offered him a balanced range of light in both the red and blue spectrums. This meant he could run just one type of bulb right through the house, an important consideration. He also liked the high wattage they offered.

“I needed a light that was going to shine 5.5 metres each way – these bays are 11 metres wide. And I needed to make sure the plants on the end weren’t going to suffer. These were the only lights that I found that would do it – they were the latest thing from Holland.

“I first bought 4 lights and trialled them, hoping they would work – then I went and bought the other 8! Twelve lamps does it perfectly – in the middle of the night it looks like daylight in here.”

Conveniently, David was able to buy the lamps locally, from hydroponic company Simple Grow in Wetherill Park, who are the NSW agent for Sunmaster lighting products.

Lighting Schedules
There are different schools of thought on lighting periods for flower crops. After some initial experimentation, David adopted an approach of breaking the night for the Lisianthus, rather than extending daylength.

“We don’t actually light for 16 continuous hours, because we found that breaking the night gives better results. Some growers do extend the daylight instead, but our conditions and crop timing suit the broken night schedule.”

The flowers are lit for 4 hours a night, exactly midway between dusk and dawn. This includes a slow wake-up period for the plants, as the lamps warm up to full strength.

“I always believe that when you light, the first half-hour doesn’t count – thats the theory I work by. A lot of Dutch growers work by the same theory, especially when you’re using sodium vapour or metal halides, because they take so long to come on. In any case, when you break the night, you’ve first got to wake the plants up.”

The lighting system comes into operation each year as soon as the days start to get shorter in autumn – usually around late April. And after a year of operation, the results have been excellent, David says. The plants have shown improved length, bigger stems and better flower quality.

“We’re very very happy with the lights,” he comments.

The other essential input for winter cropping is, of course, greenhouse heating. At Linton Flowers a two-pronged approach to heating is used, including both air and soil heating systems, in conjunction with overhead thermal screens.

The heating systems are fueled by natural gas, which David finds very clean and economical to use. The Gas Company actually negotiates a special rate for high users such as greenhouse growers. The air is heated through a network of perforated inflatable pipes, while the beds are warmed by hot water tubes layed along the surface – both systems are controlled through separate thermostats. To produce Lisianthus successfully in winter, greenhouse temperatures must never fall below 13°C at night.

But heating on its own had not been able to deliver David the flower quality he was after.

“Last July and August, after we had installed the lighting, I was able to pick Lisianthus stems of perfect height. Before that, when we only had heating, I always found the plants would flower short. The light element has given me the extra stem length.”

The climate control system at Linton Flowers has made it possible to get three good harvests from a Lisianthus crop. The first harvest starts in May and continues through winter; another harvest takes place in November/December; and a third crop of flowers comes on in late summer around Valentine’s Day. On the flip side, however, Lisianthus are a fairly slow plant to get started.

“From the day you seed them, till the day you first pick off them, it’s around 51/2 – 6 months – half a year,” David comments.

The Way Ahead
Having revolutionised the climate control systems at Linton Flowers, David’s next plan involves redesigning the entire irrigation system for the farm, through computer-linked solenoids in each house. The current system he describes as “semi-hydroponic”.

“We still grow in the soil, but we supplement with nutrients in the irrigation water.”

In many ways, the lighting installation has provided Linton Fresh Flowers with the ‘missing ingredient’ in their market plan to supply year-round flowers, to regular clients.

“We want to be able to grow three main lines – carnations, chrysanthemums and lisianthus – grow them all year round and guarantee our customers supply,” he says. “Customers like to deal with consistent quality.”

And further improvements will inevitably follow, as the next generation of greenhouse control and mechanisation becomes available.

“I’ve always believed you’ve got to keep up with technology,” David says. “If you don’t, you’ll be left behind. And the flower business is one that’s changing dramatically.”