How to pellet seeds

By Simone Pedrini and Khiraj Bhalsing

Native seeds come in all shape and sizes. That's what makes them special, but at times, this overwhelming diversity and complexity make life difficult for restorationists. 

This is the case for very small seeds, those that are oddly shaped and those wind-dispersed seeds that are difficult to put through sowing machines. Then there are native seeds where you want just the right amount of germination promoter near the seed at the time of sowing.  

Seed pelleting (and encrusting) can solve most of these issues.  The process consists of covering seeds with external materials such as talc and clay powders that are retained onto the seeds by binding agents (a type of glue). This process allows seeds to be uniformly increased in size and weight, making them more homogeneous and easier to mix and sow. Moreover, this coating can be loaded with active ingredients that improve protection from insect and fungal attack or promote germination and seedling growth.

 Example of pelleted tomato seed and encrusted Microlaena stipoides (Australian grass)

Example of pelleted tomato seed and encrusted Microlaena stipoides (Australian grass)

But the problem has been until now that the technology has been locked in the crops and horticulture industries where the process is widely used to improve seed handling and protection.  With the “recipes” owned and kept secret by private seed companies it has been difficult for the fledgeling native seed industry to use this technology. For native seed scientists, native seed companies, and users it has been almost impossible for them to perform and test seed pelleting.

But after 3 years of careful testing, ‘ reverse engineering' of coating materials, and refining techniques on test-crop and native seed species, researchers at the Centre for Mine Site Restoration based in Curtin University, Western Australia, have finalised and published the first Protocol Development Tool for seed pelleting and encrusting.

The publication provides the first public domain and practical step-by-step guide on how to do seed pelleting, along with the list of materials and equipment needed.  A standardised Pro-forma is provided to guide and record every step of the process, along with an excel spreadsheet to keep track of your trialling methods so that customised approaches can be developed.

 Laboratory setting, equipement and tools required for the developement of seed pelleting and encrusting protocol

Laboratory setting, equipement and tools required for the developement of seed pelleting and encrusting protocol

These instructions and materials will help scientists develop seed coating technologies capable of overcoming logistical and biological barriers to the more effective use and deployment of native seed across the world while enabling the native seed industry to improve seed-based restoration.

The paper is published in the Official Journal of the International Seed Testing Association, Seed Science and Technology. The paper is open access and free to download at http://www.ingentaconnect.com/content/ista/sst/pre-prints/content-21_sst46-2-393-405