Astilbe (Saxifage 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

Astilbe are a perennial plant, grown commercially for the sale of their cut flowers for both the domestic and export markets. In the southern regions of New Zealand they flower from the middle of January to the beginning of February. This short growing season does cause some problems in the export market because customers would like to buy them for a longer period. Some research work in Southland is trying to extend the flowering season by growing this crop in a number of different locations.

Winter Chilling and Frosts

Astilbe require a period of winter chilling before they will send up flowering shoots. No work has been done on the exact amount of chilling but it appears all areas of Otago are suitable.

The levels of frosts in coastal Otago do not seem to have any affect on Astilbe as they are wintering beneath the soil at this time. It is unknown how the harder Central Otago frosts will affect this crop.

Rainfall and Irrigation

Rain will not affect an astilbe crop at any stage of its growth. Even near flowering they are not affected.

Supplementary irrigation is beneficial as the flowering stems start to develop. Without it the tips become malformed and unsaleable.

It is unknown how these plants will grow in the heat of Central Otago. Overhead watering systems may be better than drippers in this situation because the water can also cool the leaves and prevent sunburn.

Wind

Like most high value flower crops, shelter from the wind is essential. This can take the form of with 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 valuable crop such as this, a more conservative approach is advised.

Soil

The key physical requirement of the soil for astilbe growing is a relatively free draining root zone combined with good levels of organic matter. Many Otago soils have this. If your soil does not, drainage is easily improved with the use of field-tiles and/or plastic drainage products. Contact a drainage specialist for more information.

Fertility

Astilbe prefer a pH between 5.5 and 6.5. Most Otago soils fall within this range. 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

Weed control is relatively straightforward in an astilbe crop. Starting the process in the spring is absolutely essential. The beds must be free of weeds as the astilbe shoot away in mid September. They grow quickly and will smother any weeds that try to grow. When the plants die back in the autumn, a clean-up before winter is all that is required.

Varieties

Flowers can be considered a fashion item and as a result preferred varieties change over time. Those that are considered ‘hot’ at the moment include Cattlya which is a tall late pink and William Reeves which is a early red. Be very careful when choosing plants for your property. Consult with local growers and do your homework.

Pests and Diseases

Astilbe suffer very few pests and diseases. Fungal problems do not seem to affect this crop. Make sure that they are growing on a free-draining soil to prevent any root/crown rot diseases. Spittle bug does affect the flowers near harvest and thrips are a major problem. Field insecticides and then fumigation after harvest should ensure the crop is clean for export.

Layout

Astilbe are planted in beds approximately 1m wide to allow access from either side for picking. Plnts are usually planted 30cm apart in a row. This equates to 9 per m2. The rows can be as long as is practical with sufficient distance between them to allow for foot or tractor access depending on machinery used.

General Management

Growing astilbe is very straightforward. As long as the beds are weed free at the start of the season, they essentially look after themselves. 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 excess foliage removed from the block so pests and diseases cannot overwinter.

Harvest

Harvesting astilbe 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 90% open before harvest. Astilbe do not open any more once they are cut.

After harvest the stems should be placed immediately in a postharvest solution and transported back to the packhouse. They should stay in this solution in the chiller until they are packed for export.

Equipment

Most astilbe blocks can be managed with a back-pack spray unit and general gardening equipment.

Returns

Because most of the astilbe crop is exported, returns vary widely depending on the season, exchange rate, world events etc. Production costs per stem to grow pick pack and ship vary from $0.18-0.23. Returns vary from $0.40 - $0.90 (2003-04 season prices).

Plant material is usually around $1.00 per plant. This will not produce any flowers in the first year, but you should start cropping in year 2. In years 3 and 4 you should be able to harvest and sell over 100 stems per m2. After year 4 the plants will need to be dug up and divided.

Contacts

If you are thinking of growing astilbe, contact your local Flower Growers Groups for the names of other growers.

Also check out gross margin and detailed seasonal information for Astilbe at www.cropsforsouthland.co.nz