Lettuce and salad greens — covered cropping

Low-tech commercial covered cropping structures require at least 10,000 sq m of flat land. This is to support the tunnel houses, plus space for infrastructure such as driveways and outbuildings.

High-tech modern greenhouses need an area as small as 2,000 sq m plus room for infrastructure.

Design and build

Covered cropping can be very technical. Get advice from qualified, experienced consultants when planning and building your system. Ask for advice about:

• row width
• plant spacing
• substrate
• irrigation
• heating systems
• computer controls systems
• hygiene.

Selling your crop

Many of the larger growers in New Zealand deal direct to supermarkets. Most small growers sell direct to a wholesaler, who then on-sell to retailers.

Covered cropping provides a steady amount of work year-round. This makes it easier to secure and keep workers and reduces the need for seasonal labour. Although seasonal staff are still needed for picking in the summer peak, when the workload increases by around 30%.

Most growers would need 3.5 to 4 employees per ha, including a manager. This may be lower in a very efficient operation. Or higher in a very modern operation with higher production.

Learning how to grow different varieties takes time and experience.

Manager

Greenhouse managers need:

• an understanding of plant physiology
• a high level of technical ability
• horticultural experience
• people management skills, including the ability to manage changing seasonal labour demands.

Understanding whenua management

Team leader

Depending on the size of the operation you may need 1 or more team leaders to direct and instruct the crop workers. Team leaders spend much of their time on inspection and monitoring tasks. This includes detecting diseases and pests.

Crop workers

Typical day-to-day tasks when working in a covered crop include:

• planting
• harvesting, including picking, cleaning and packaging
• mixing fertiliser
• pest and disease monitoring, identification and management, and
• spray handling and application.

Depending on your operation, you may need forklift and truck drivers or maintenance workers.

Consultants

Choose consultants with the specific skills and experience you need to help you. Make sure your consultants have either:

• relevant experience as head growers or operation owners, or
• specialist qualifications and knowledge – like a plant nutritionist for example.

With all businesses, there are compliance regulations. These are things like:

• health, safety and wellbeing
• employment law
• tax obligations.

Levies

Horticulture New Zealand and industry body Vegetables NZ support growers across the country.

• Horticulture New Zealand collects a compulsory levy of $0.15 per $100 of sales
• Vegetables NZ collects a compulsory levy of $0.30 per $100 of sales.

These levies can change, check their websites for the latest information.

Horticulture New Zealand membership levy

Vegetables NZ commodity levy

Food safety

All growers must meet the requirements of National Programme 1 under the Food Act 2014. This ensures produce supplied to the market is safe to eat. The requirements include rules about:

• how growers handle their crops
• managing spray residue, and
• withholding periods.

National Programme 1

Food Act 2014

New Zealand Good Agricultural Practice (NZGAP)

NZGAP is a system that helps growers to keep up with compliance requirements. Becoming NZGAP certified:

• gives you confidence that you're meeting compliance requirements
• makes it easy to find out when regulations have changed, and
• makes your product more attractive to buyers.

NZGAP system

Process heat

Covered cropping requires heating and is usually generated by burning fuel. The Ministry for Business, Innovation and Employment (MBIE) defines this type of heating as 'process heat'.

In New Zealand, process heat is used in the commercial and industrial sectors. MBIE produce fact sheets about process heat and its use.

Process heat in New Zealand

Licensing or royalty costs

Licencing agreements protect some commercial varieties. This means that you must pay royalties or a licence cost for each plant that you grow. These costs are usually included in the price when you buy the plant. Check with the nursery selling you your plants.

Local council regulations

Each council has their own rules. You may need:

• permits for your tunnel house or greenhouse structure.
• consent for or access to water
• to comply with regional environmental obligations

Getting access to irrigation water can be hard in some areas and you may need to get help from a hydrologist to put your application together. Make sure you can get a water consent before you commit to developing your whenua.

Talk to your local council before you start any work.

Meeting council compliance obligations

Local council contact details

National policy statement for freshwater management (NPSFM)

The National Policy Statement for Freshwater 2020 gives local authorities direction on how they should manage freshwater under the Resource Management Act 1991. As such, some local authorities require growers and farmers to create a Farm Environment Plan (FEP). Make sure you're familiar with the FEP expectations in your region. Check with your local council about the requirements for your whenua or planned development.

Even if your region doesn't yet require an FEP, it's good practice to put one in place for your whenua as part of your business plan. The Foundation for Arable Research (FAR) provides templates you can use to create an FEP.

Developing a business plan

Farm Environment Plan templates

The yield potential from protected cropping is much higher than is possible to achieve from normal outdoor production. Covered crops can be grown anywhere as long as you provide the right amount of heat and light.

Crop requirements

You can plant lettuce and leafy greens at all times of the year. The amount of light and heating influences their volume of production. 

It's important to ensure any structures are level for even air temperature as slope will see temperature variation.

Time to harvest

Influenced by the growing environment, low-tech structures are normally open sided limiting cropping potential. Weather dependent, harvesting is 4 to 16 weeks post planting.

When harvesting through the winter, light and temperature are two of the most regulating factors. Using supplementary lighting, helps maintain positive production outcome levels.

Different operations have their own replanting schedules based on market requirements.

Lettuce will grow in low-tech structures – with no sides allowing for ventilation and air flow. Though air flow is important, so is light and temperature. The key for consistent winter growth is heat. A plant can grow 4 to 5 times faster in the warmer months than in winter.

Growers prefer netted greenhouses, as pests are an issue in the warmer months. Shade or diffused screens help prevent excess summer temperatures.

Greenhouse buildings need protection from strong winds to prevent damage.

Planning for climate change

Lettuce is grown in a ‘fully recirculated hydroponic system’, recycling all the water and fertiliser around the channels. Water quality helps reduce the likelihood of waterborne disease.

Keeping your irrigation water cool in summer is important. Warmer water means less oxygen increasing the risk of root diseases. Carry out regular water analysis to monitor this.

Understanding water usage per ha for your crop requirements is critical. Drippers deliver water into the growing substrate for each plant.

Considerations for water are:

• the variety of your crop
• the substrate the plant is growing in
• the amount of light the plant gets
• your annual requirement
• capacity for water storage 
• your irrigation equipment.

Hydroponic greenhouses use a computer control system, linked to light meters to manage water delivery. A hydroponic greenhouse operation will use less water than an outdoor crop.

New Zealanders consume on average 5 kg of lettuce each per annum. Approx. 99% of the 8,400 tonne annual crop (2016) is consumed domestically, with only 1% exported.

There are around 60 recorded growers covering approx. 50 ha of covered cropping.

Covered crops have an advantage because of higher production volumes, lower risk of crop failure in a well-run operation. They also offer better working conditions for workers, making it easier to find and keep staff.

The New Zealand Hydroponic industry is mostly made up of a large number of small to medium sized commercial growers as well as a segment of large corporate growers. is well established in New Zealand with positive growth and improvement opportunities for the future.

Growers are adopting new technologies to improve efficiency and production.

For example, rolling benchtops are becoming more common. Seedlings get planted and loaded at one end. At the other end they're picked and delivered to the packhouse.

In a fully automated system other than monitoring and testing there is no need for employees to do any work inside the greenhouse.

Operational costs for a covered growing system are higher than for outdoor cultivation. You need to allow for:

• consumables including fertiliser and other hydroponic inputs
• equipment maintenance and overheads, like electricity and fuel, and
• the cost of buying, cultivating and harvesting the crop.

You can expect annual operating costs for a medium-range greenhouse of around $860,000 per ha. This is dependant on a range of factors and scheduled maintenance.

Get qualified, experienced advice on:

• the set up and administration of your operation, and
• preparing your annual budget.

Search for funding opportunities

Grower returns are dependent on the crop and the system used.

Grower returns

The benchmark farmgate income is around $110 per sq m or $240,000 per ha, after operating costs. Your operating costs will depend on:

• market conditions
• your business model, including employees and administration systems, and
• the efficiency of your operation.

Growers can increase their return by:

• improving technical systems
• having efficient business processes
• careful selection of high-return varieties.

These figures are a snapshot of a new 1 ha medium – low-tech production unit.

Seek advice early, before you invest in any design or development.

Talk to your local Te Puni Kōkiri office to see how they can support you through the decision-making process. They will be able to provide advice and find out if your project qualifies for funding.

Talk to Vegetables NZ to see what support and resources they can offer if you're thinking about growing lettuce and salad greens.

If possible, seek out advice from:

• wholesalers
• people who grow covered crops in your area, and
• knowledgeable suppliers.

Talk to qualified consultants in your area with experience in covered cropping, lettuce growing, and sales. They'll be able to provide detailed, impartial advice on what will (and won't) work on your whenua.

Find your local Te Puni Kōkiri office

Vegetables NZ

This fact sheet provides general information to help start and inform conversations. It's not comprehensive or detailed enough to support detailed decision-making.

Information in this fact sheet was provided by Grower2Grower and Te Puni Kōkiri kaimahi. Additional data has been sourced from StatsNZ or provided by the contributors.

You can provide feedback on the content on this or any fact sheet by emailing the Whenua Māori Service at whenuainfo@tpk.govt.nz.