Sea Holly (Eryngium spp)How well established is this crop?
This is a very new crop to the Otago region. The plants should grow but information on markets, commercial returns, current growers, and any form of regional research may be difficult to find.Background
Sea Holly or eryngium plants are commonly mistaken for thistles. They have spikey foliage with flowers in a range of blue colours from 2cm through to 10cm long.
The plants are thought to originate in America and Europe but production as a cut flower is now spread around the world. Holland still leads statistics and only a few growers are known to produce this crop in New Zealand.
No exact levels of winter chilling are known for this crop. It appears however that all areas of Otago can get this crop to flower.Winter Chilling and Frosts
No exact levels of winter chilling are known for this crop. It appears however that all areas of Otago can get this crop to flower. These plants are dormant during the main frost period in winter. Plants growing in Southland have shown some frost tolerance in the late spring.Rainfall and Irrigation
Rain will not affect an eryngium crop at any stage of its growth. The one exception to this is near flowering where the weight of water in the head may cause the stem to tip over. A single layer of FloraNet is recommended to prevent this problem.
If rainfall is not enough regular irrigation will ensure good growth and stem length on the flowers. Dripper systems are probably the best as these will keep the roots damp without wetting foliage.
Like most high value flower crops, shelter from the wind is essential. This can take the form of natural tree shelter or artificial shelter using wind cloth. A good rule of thumb when designing shelter is to multiply the final height of the shelter by 5. Use that measurement as the distance you position your shelters apart. For example, when using 2m high windbreak cloth, you will need shelters every 10m. Some consultants are recommending a multiplier of 10 for crops, but with a aluable plant such as this, a more conservative approach is advised.
If using natural tree shelter, make sure the shelters running east-west are deciduous. This will allow sunlight into the blocks in the winter. Position all shelters at right angles to the prevailing winds. Talk to your local nurserymen when deciding on the right tree type for your property. They may also be able to help with design.
The key physical requirement of the soil for growing Eryngium is that it is free draining around the root zone. They are prone to rots such as Phythphora if the roots are in constant contact with water.Fertility
Eryngium require a moderate soil fertility to grow well. Specific information is hard to give but a simple soil test followed by an expert analysis of the results will allow the owner to easily fix any potential nutrient imbalances.Weed Control
Hand weeding appears to be the only way of effectively managing weeds in an eryngium block. Many overseas growers lift the crop after 3-4 seasons as they get overrun with perennial weeds. In New Zealand, white clover is likely to be a major problem.Varieties
There are no preferred varieties of eryngium in the marketplace at the moment because they are such a new crop. Eryngium alpinum ‘Superbum’ is relatively common large plant. Eryngium planum is a small flowering variety suitable for exporting due to its size and ability to pack down.Pests and Diseases
Selecting free draining soil is the key to successful growth as eryngium suffers from Phytophthora root rot. Insect pests include spittle bug, aphids and in some years thrips.Layout
Eryngium are planted in beds approximately 1m wide to allow access from either side for picking. 3 plants, 30cm apart is the usual manner of planting down a row. This equates to 9m2 (this can vary from 6-12 plants m2 depending on variety. The rows can be as long as is practical and the distance between them is only to allow for foot traffic or tractor access depending on machinery.General Management
Growing eryngium is very straightforward, as long as the beds are weed free at the start of the season. Irrigation and then an insecticide before harvest is all that is required.
After harvest the bushes continue to grow until the end of March when they start to die back. They require less water over this period. They are then cut back and the excessive foliage removed from the block so pests and diseases cannot overwinter on it.
Harvesting Eryngium is relatively straightforward as the stems are simply cut with a knife or secateurs. The difficulty is deciding when the stem is ready for cutting. In general, the flowers on the stem should be turning an appropriate blue colour. This process can take up to 10 days from the time it is first noticed. After harvest they can be placed in a bucket of water but if the blue colour is fully developed they can be stored and shipped to market without water.Equipment
Most eryngium blocks will be small and can be managed with a back-pack spray unit and general gardening equipment.Returns
Current export returns are unknown but on the local market stems are making 70c -$1.00 each.Contacts
If you are thinking of growing eryngium contact your local Flower Growers Groups for the names of other growers.