Issue 40: Lisianthus: A Specialty Cut Flower

Issue 40
July/August – 1998
Story Title: Lisianthus: A Specialty Cut Flower
Author: Roger Fox

A commercial flower farm in NSW has adopted Lisianthus as one of its permanent crop lines, achieving a year-round production cycle.

Lisianthus (Eustoma grandiflorum) are a North American wildflower, native to the prairies of Nebraska, Colorado and Texas. They are also known as Prairie Gentian or Texas Bluebell, the latter name a reference to the blue flowers of the wild species. Cultivars in production today offer a wide range of colours, including purple, rose, pink, white, and various bicolours.

Lisianthus grow best where the minimum temperature is above 15°C, and the daytime maximum temperature is less than 25°C, though plants will tolerate much higher temperatures. While open-field production is possible, Lisianthus are usually grown in open-sided greenhouses to provide protection from rainstorms that can devastate a crop in flower. It is claimed that production in full sun can result in 60% shorter stems than the same varieties grown in greenhouses or in outdoor shadehouses.

Good drainage is essential for Lisianthus, and hence they are commonly planted in raised beds. Since the plants are native to the American prairie, outdoor crops in areas of heavy summer rains are very prone to root rots.

Lisianthus grow best at a pH between 6.3 and 7.0. They favour high calcium levels as well as adequate phosphorus. The flowers have a good postharvest life – generally 10 – 15 days.

Lisianthus are a relative newcomer to the Australian commercial flower scene – and something of a ‘wild card’. On the plus side, they are a striking bloom with great consumer appeal, command excellent prices and are often in short supply. Conversely though, they are considered ‘tricky’ to grow and stories of crop problems are commonplace among growers who have trialled them.

Lake Munmorah Flower Farm, near Doyalson on the Central Coast of NSW, has adopted Lisianthus as one of their signature crop lines. Under the direction of production manager Neil Shackleford, the farm is now successfully growing them year round, a result of pinpointing the exact cultivation requirements and idiosyncracies of this crop. The enterprise also has plans in place to become a reliable supplier of high quality Lisianthus seedling stock to commercial growers around the country.

Neil has been involved with the enterprise for only a year, having gained his experience at major Victorian commercial producer Van Wyks. Together with the farm’s owner Joe Oliveri, he is now overseeing major changes to the operations and infrastructure of the farm – a process he describes as ‘going from the old to the new.’

It is a large scale operation, comprising around 7 acres of flowers under cover and another 7 acres of outdoor production.

Growing Systems
The Lisianthus crops are grown in tunnel houses, in what looks like a light sandy soil. But according to Neil, the medium is essentially inert – it is the nutrient feed that sustains the plants.

“They’re growing in ‘dust’ with some rice hulls added,” he explains. “There’s no organic matter of any sort in it. It’s essentially sand that’s been overworked for 30 years to the point where it’s just dust – its more or less an inert medium.”

Because the sand is so fine, it contains very little air space, and consequently oxygenating the nutrient has been one of the important tricks for successful growing.

“Unless we oxygenate our water, we simply don’t get results,” Neil says. “They also cope with heat much better if the water is oxygenated.

“The Dutch have examined this aspect – and growing in sand this fine is almost the same as growing in a rockwool slab. There is very little air space in this sand. It’s so fine and dusty that it holds a lot of water.”

However, according to Neil, this medium does offer certain advantages over pure sand, when combined with a T-Tape irrigation system.

“It offers some lateral capillary action, which is essential when using T-Tape and which you don’t get in pure sand.”

To ensure excellent drainage, the beds have been constructed with submerged layers of sand and gravel, as well as drainage pipe at the very bottom of the bed profile, to carry away excess water (see diagram).

“Its only on the top I’ve retained that bit of soil, to give it some lateral capillary action.

“Before that, this area was unusable – it was heavy black clay that flooded. So we had a couple of options: we could have gone into boxes, which probably most other people would have done, but the fact is we were not sure of the economics of Lisianthus over winter. So we left our options open – this can be ploughed up and planted with chrysanthemums if required.”

Growing Lisianthus in a pure sand system is not an option Neil favours. “I would suggest that in pure sand, you would still need a bit of cocopeat, or some other peat, in the top couple of inches to move the water laterally, because there are a lot of times when you can’t irrigate overhead, because of diseases.

“The plants are too hard to establish in straight sand, but if you’ve got a little bit of organic matter in that surface, it makes the difference.”

Neil has also trialled growing a crop of Lisianthus in cocopeat in boxes. He found they were about 3 weeks faster than those in soil. “It’s a bit of a contradiction actually, because Lisianthus don’t like it wet around the roots, but if you’ve got enough oxygen around there, from the nutrient, they dont seem to mind.” “I also think they’d grow very well in a reasonably coarse, free-draining bark,” he observes.

Irrigation & Feeding
The nutrient conductivity used for growing Lisianthus varies according to the season. In warm weather, the conductivity is run at 1 – 1.2mS/cm, while in winter it is raised to 1.5 – 1.6mS/cm. While the other flower crops on the farm share a common nutrient formulation, better results are obtained from Lisianthus by using a specific mix.

“It is better if you give them their own feed, which is fairly high in calcium, and preferably no ammonia, which tends to give softer growth – they tend to stretch and get a little bit too thin, which doesn’t help the vase life.”

The plants are drip irrigated through T-Tape at least twice a day, with a well-oxygenated nutrient solution, at a pH of around 6.8 – 7.0. In hot weather, a supplementary watering from overhead sprays is also applied, to ensure the whole volume of the medium is evenly wet – including the areas the drip irrigation may not get to. The overhead watering is timed to ensure that the leaves are not wet as night falls.

The water source for the farm is a vast dam, which covers several acres. The water passes through primary mesh filters, but its quality is variable and must be analysed regularly, with the nutrient adjusted accordingly. It also tends to have quite a high pH, thus requiring the addition of acidifying agents to suit certain crops.

A lack of information on growing Lisianthus has meant that Neil’s approach has often been based on trial and error. But he is in no doubt that the biggest cause of problems and failures with this crop is root diseases, to which they are especially prone, and that a rigorous program of soil drenching has been one of the main secrets of his success.

“A good understanding of soil drenches is paramount for good results,” Neil explains. “This starts from day one. The biggest threat when they’re first planted is pythium, which needs an appropriate drench.”

Other soil drenches are used when necessary, including one based on phosphoric acid, which works by making the plant think it’s under attack, so that its immune system responds. In between crops, the beds are sterilised with methyl bromide – a chemical for which an alternative will have to be found, as its use becomes restricted.

Neil believes he has root diseases beaten, providing he follows his regimen of drenching. And the results certainly support his claims. “We couldn’t grow lisis 12 months ago, and now we’re getting a re-crop from the plants. We’re not even losing 1%,” he says.

Year-round Production
The Lisianthus seedlings are grown on the farm in plug trays and transplanted into the beds by hand. The first flowers are picked when the plants are about 12 weeks old, with a second crop ready about 7 – 8 weeks later.

Winter crops have been successfully grown at Lake Munmorah Flowers with heating of the houses, but their viability in winter comes back to the profit margin.

“Winter crops are certainly possible,” Neil explains, “but there’s a fair debate about the economics of it, because production per square metre just isn’t there. It’s not a light intensity problem, so much as light duration – the day simply isn’t long enough.

“So you can grow excellent crops in winter – they tend to grow much bigger, much taller, much thicker because the carbohydrate accumulation of the plants is far superior – but you’re waiting much longer for your flowers.”

The question therefore, Neil says, is whether there are crops that will give you a better return per square metre in winter. The prices for Lisianthus however, are excellent in winter, and last season Lake Munmorah Flowers was one of the few growers who had any stock available. Supplementary lighting is also an option that Neil is considering.

“The price of winter crops almost makes it worth it, I think. They need about 4500 lux minimum.”

For winter cropping, the houses can be sealed and heated through a network of hot water pipes (the water is heated to 60°-70°C). The heat source is a coal-fired boiler, a reasonably economical option according to Neil, with reliable coal suppliers nearby.

During winter, leaf diseases of Lisianthus also tend to be more prevalent, notably Downy mildew, Grey Mould and Botrytis, all of which require regular preventative spraying. However, heating the houses reduces them significantly.

“The best control for all of these diseases is what we call ‘heating to waste’. That means keeping our top vents open a crack all night (only an inch or two) and keeping the pipes as hot as you can.”

According to Neil, Downy mildew is one of the worst diseases. “It attacks very quickly,” he says. “Generally if you’ve got consistent temps over 27°C and fairly low humidity, you’ll be reasonably safe from it. But once your night temperatures start falling and day temperatures drop also, its a problem. We don’t take risks, we have a preventative spray routine. “With botrytis you may have to spray twice a week, depending on severity.”

In summer, the only climatic modification which is currently available to Neil, is whitewashing the greenhouse rooves. He applies a light coat around October (mid spring) and then reapplies successive coats during the summer months to build up a suitable level of protection. This, he says, is essential.

“Shading screens are the optimum, but if you haven’t got any, then you must do this.”

The climate of the NSW Central Coast is really hotter in summer than is ideal for Lisianthus, though conversely the winters have the advantage of being frost-free. The preferred temperature range that the Dutch have established is around 25°C, though like most crops, they will grow outside such statistical ranges.

Ultimately however, Neil plans to introduce major improvements to both climate control systems and the greenhouse structures. He believes that greenhouse walls generally need to be higher – at least 4.5m to the gutter – to give larger interior air volumes and more stable environments. Currently, three such high-wall structures are under construction at the farm.

One of the new houses is to be used for large-scale production of Lisianthus seedlings, for supply to the commercial industry. It has been built to meet quarantine standards, with thrip netting to counter Western Flower Thrip problems, and sophisticated controls which will enable the temperature to be kept within 0.5°C of the set-point.

“That will let us guarantee the best seedlings, without any rosetting problems, for our customers,” Neil says.

Plants can ‘rosette’ if temperatures get too high during propagation and young growth stages. The condition is characterised by a cluster of leaves, with very short internodes on the stem.

Computer Control and Automation
A major recent development at Lake Munmorah Flower Farm is the updating of the computer control and nutrient delivery system. A Priva Integro computer system from Holland has recently been purchased which, according to Neil, is the most advanced such system in the country. Controlling the irrigation, fans, vents, heating, temperature, etc, the computer will ultimately manage all the houses and a range of crops. The options which it offers are vast – irrigation, for example, can be controlled according to the radiation intensity or humidity in the houses. The system also offers the capacity to meet the future growth and expansion of the enterprise.

“It will run 200 valves, with capacity for more; it can run 8 different programs at once just on irrigation, and control as many different compartments as we want.”

The crops are fed through a Nutriflex nutrient injection unit, featuring a Venturi feed system which oxygenates the water as it enters – an essential ingredient of Neil’s cultivation success with the Lisianthus. The injector unit was carefully chosen to meet the capacity needs of a large scale operation.

“We can turn one tap on or ten taps on and this will handle a massive exchange and still keep the EC constant,” Neil enthuses.

Harvesting and Marketing
Lisianthus are best picked in the morning, and are placed straight into a cool room, in a solution of very clean water, with a preservative added.

“We try not to take any shortcuts at this stage,” Neil says, ‘because we want to ensure the vase life.”

The flowers are mostly sold through the Sydney markets, but Neil also gets a lot of inquiries from interstate. At this stage, he says, they have not been able to meet demand.

After a crop of flowers has been harvested, Neil goes through and re-cuts the plants to ensure that they will re-crop evenly the next time. The Lisianthus plants are usually cropped twice and, though they will start to produce a third crop, plant vigour dictates against a third harvesting.

“On a third crop you know you’re not going to get the same amount of vigour as you did off the first crop.”

Even so, Lisianthus do offer growers a 5-6 month crop, making them a worthwhile proposition for pots, boxes and other hydroponic systems.

It has been said of Lisianthus that they are susceptible to all known plant diseases – plus a few others. But in learning how to meet the specific needs of this unusual crop, and pre-empt problems, Lake Mumorah Flower Farm has made this crop one of their trademarks.