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FAQ about sunflowers

Frequently Asked Questions

Click here to download a pdf version:
SF3 Sunflower FAQ pdf  (358kb) 

When do you drill?

Wait until the average daily soil temperature exceeds 7°C (at 10 cm). Typically, sowing dates in
southern England are between 16 April and 5 May. Sunflower will not germinate in a cold soil, and only very slowly when the soil temperature is around 5°C. Slow germination increases the risk to the crop from pests and diseases.

Is pest control a problem?

Measures to prevent slug and pigeon damage should be taken in all crops.

Is weed control a problem? 

The late drilling date of sunflower allows the use of a stale seedbed and the seedbed can be sprayed off with a non-selective herbicide. Currently in the UK herbicide choice within the crop is limited to pendimethalin, a pre-emergence herbicide which can give good control. Sunflowers grown in wide rows allow an ideal opportunity for the use of tractor mounted steerage hoe. The crop can compete very effectively with weeds from about the fourth week after emergence and generally weeds are not a major problem.

How tall are they? 

The shorter varieties can be less than 1.5m tall and the taller ones up to 2m tall. Wetter seasons lead to taller crops.

When do you harvest? 

Harvest can take place between September and into October. Dates achieved at Boxworth,
Cambridgeshire have ranged from 18 September to 16 October in the 1990s. Harvest usually occurs when the seed has dried down naturally to 15-20% moisture.It is generally best to wait until the average daily soil temperature exceeds 7°C (at 10 cm).  Typically, sowing dates are between 16 April and 5 May.  Sunflower will not germinate in a cold soil, and only very slowly (up to 35 days) when the soil temperature is around 5°C extending the germination period increases the risk from soil pests and diseases.

How do I know it's ready to harvest?
The seed is at 30% moisture when the back of the head is yellow and the bracts have begun to turn brown.  By 20%, the bracts are 75% brown, the back of the head is becoming mottled and 75% of the lower leaves are senescent. During ripening the crop loses all its leaves and eventually the whole plant becomes dark brown in colour.  In this state the crop stands well and dries quickly after rain or during windy weather.

 

Are there any storage problems?

The seed should never be stored wet (>15%) as it can heat up and go mouldy.


How do I dry them?

Use of a drying floor is the safest method and the seed should be at a maximum depth of 1m. The best method of drying is to use cold air until the moisture content falls to 15%. The seed can then be cleaned and heat (using the same temperature as for oilseed rape) used to reduce the moisture to 9% for long term storage. The seed should be left for seven days to allow the seed moisture to equalise before drying again if necessary. Sunflower seed has a lint-like coating that can easily be rubbed off to form a light oil bearing dust. If this is taken into the unprotected intake of a continuous drier there is a high risk of fire. Drying methods, which include any form of agitation or movement of the seed, should therefore be used carefully. A method that has proved successful is to reduce the bulk of the moisture on a floor dryer and then complete the operation in a continuous dryer.

Is marketing a problem?

No, UK suppliers are happy to source seed from the UK. A range of sunflower buy-back contracts is available and can be either pool price or open price where the merchant markets the produce at a time agreed after harvest. It is also possible for the grower to produce a crop without a contact, though it is essential to have good contact with the market if best prices are to be realised.

Written by Sarah Cook, ADAS UK Ltd (sarah.cook@adas.co.uk ).

This document was funded through the Defra Innovation Network, led by the University of Warwick (www.warwick.ac.uk/go/climatechange/innovation-network), G B seeds Ltd and HGCA. January 2009.

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