What Are Treated Seeds? (Reading time: 5 minutes)


Figures from Agriculture, Fisheries and Conservation Department (AFCD) in 2021 and 2022 shows that, agricultural land use in Hong Kong is approximately 733 ha, and organic agricultural land is about 101 ha. If we calculate it by the 1160 km flat land area of Hong Kong, agriculture land only accounts for 0.6% while organic farms only 0.08% of the area. But we should not forget that there are many farms which operates with an organic or natural farming principles, even though they do not obtain an organic certification.

Seeds – should forever be Non-GMO in organic farming.
The seeds that we sell on Clover Seed Online Retail are all non-GMO. While we cannot provide all organic seeds right now, we always mark the “treated” seeds for our gardeners/farmers to distinguish them. So – What Are Treated Seeds? Before we talk about the seed itself, let’s look at some rules for seed in organic farming.

菜心種子 Choi Sum

沒有拌藥菜心 Non-treated choi sum

A contrast between coated and non-coated Choisum seeds

Seeds For Organic Farming

The Hong Kong Organic Resource Centre Certification LTD. (HKORC-Cert) publishes an Organic Production, Aquaculture and Processing Standard accredited by the IFOAM. This processing standard requires that ‘All seeds or vegetative propagation materials used shall be certified organic’. When organic materials are not available, the next option is to use conventional materials that have not been treated. An extra note is that perennial seedlings can only be sold as organic if they have been cultivated in a certified organic farm for more than 12 months.

Factors such as government’s support and market demand influence the market share of organic seeds, for the fact that the cost of producing organic seeds is three times compared to the production of conventional seeds. Thus, even though organic seeds can be produced practically, we also have to ensure that farmers are capable of paying for the seeds. Technically, production of seeds requires more plants at the same time, and the mother plant must be healthy and sufficient for producing the next generation of the variety. In terms of certifying process, seed companies are responsible for supplying seeds that are healthy and pure – healthy seeds means that they do not carry any virus or bacteria, while purity means that the genetic structure of the seeds is not invaded by weeds – which are something quite difficult to be determined in organic production of seeds.

Clever as you may ask: if virus, bacteria and weeds are all omitted during the production of conventional seeds, then the next generation of the variety probably cannot cope with an organic environment? A solution is to conduct pathogen testing after seeds are produced, and to test grow them in an environment that is closest to an organic farm. At Clover Seed’s laboratory and field in Hong Kong, these are exactly what is being done at the moment, as well as Hong Kong local seeds saving without any pesticide.

What Are Treated Seeds?

The history of seed treating started as early as 300 B.C., with early treatment done by saline water, metallic compounds, and even poisonous arsenic trioxide, mainly for the purpose of storage. Since 1930s, seed coating techniques emerged. Seed Coating is constituted of three main components:

  1. Material for coating, such as clay, perlite, quartz etc.
  2. Adhesive component, such as starch or polymer
  3. Components added according to purpose such as pest control, anti-bacteria, fertilization, or supplement of micronutrient. Some seed coating also contains oxide to allow oxygen intake during the germination process

Apart from Seed Coat or Film Coating that are intended for the above chemical purposes, there is also Seed Pelleting which allows small, light and irregular seeds such as carrot seeds to be sowed more evenly by increasing their size, which makes seeding more easily, especially with the case of machine seeding.

Seed Coating has always been focusing on preventing the invasion of pests and bacteria (e.g. Fabaceae such as pea and beans is susceptible to weevils), increase the survival rate of seedlings, and reduce the amount of insecticide spray by treating seeds before they are sowed. With increasing concerns of sustainable development, as well as technological development, more and more biological coating technologies are proliferating. For example, there are seed coat made with chitin. Recently, there is research done by MIT suggesting a silk covering that is useful for protecting seeds from saline soil, which will come useful under climate change, especially for desert and coastal areas that are experiencing severe soil salinization. However, the most common seed treating component remains as Thiram, a sulphur fungicide with soil half-life of 15 days, thus decomposing when harvest is ready. However, if you are pursuing organic farming, avoid using seeds treated with Thiram.

金山白豆 豆角種子


Fabaceae seeds are susceptible to weevil, some varieties should be treated. Image of treated Jin-Shan White Yard Long Bean seed and untreated Dark Green Yard Long Bean seed

Finding Organic Seeds and Untreated Seeds

Back to Hong Kong, we do not have an extensive agricultural area, but the unique agricultural history of Hong Kong preserved a lot of unpolluted land that are suitable for organic or natural farming. To widen the selection suitable for Hong Kong local farmers or gardeners, we also provide organic seeds or seeds with organic treatment that have undergone grow trial in our Wong Chuk Hang farm. Look for Organic Tomato - Sunrise Bumble Bee, Organic Tomato – Black Cherry, Carrot – Rainbow, and Carrot – Deep Purple. What’s more, some oriental vegetables varieties which once only available as treated seeds, are available in untreated version too. Look for Chinese Kale – Swatow Think Stem and 45-days Choi Sum.

Then of course —— there is always the option of trying to save your own seeds. Check out our Seed Saving Principles blog post to learn more!

Reference (in Chinese only):

黃玉梅(2007- 種子披衣處理技術之應用與發展

鍾伊婷,郭華仁(2006- 有機農業:有機種子與品種之選擇

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