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Heirloom, Hybrid, Open Pollinated, Organic and GM Plants and Seeds

There has been a lot in the media over the last few years in particular about GM foods and to some extent, seeds. As a result, gardeners often go searching for alternatives but the information on the internet in particular can be confusing so I've described the four types of seeds here. Hopefully this information will give you the tools to make an informed decision next time you're buying seeds.


In order to understand the different kinds of seeds you first need to know how flowers are pollinated.
The anther (part of the stamen which is the male part of the flower) produces pollen. The pollen is transferred to the stigma (a female part of the flower) and then the ovary (another female part) becomes the fruit which contains seeds.
Perfect flowers have both male and female parts. Imperfect flowers only have either the male or female parts. Plants with imperfect flowers may have male and female flowers on the same plant or there may be male and female plants that only produce flowers of the same sex.

Self Pollination

Some plants have flowers that can be pollinated by other flowers from the same plant. In this case, flowers may be perfect or imperfect. Other plants have flowers that can even pollinate themselves, often before the flower opens (beans are a good example of this). Only perfect flowers can do this because both make and female parts are required. Both of these situations are called self pollination.

Cross Pollination

When the flower from one plant pollinates the flower of another plant, this is called cross pollination. Both perfect and imperfect flowers can be cross pollinated. Plants of the same variety and species can cross pollinate. Importantly, plants of the same species but different variety can also cross pollinate. In some cases, plants of different species can cross pollinate but this is less common. Even less common (but not impossible) is cross pollination between plants that are more distantly related (different genus and very rarely, different family).


When two plants of the same species but different varieties are cross pollinated, a hybrid plant is the result. The same can be said of two different species that cross pollinate.

Such offspring (daughter plants) display some of the characteristics of both parent plants and often plant breeders use this phenomenon to produce plants that show the best characteristics of each parent. This generation of plants is called F1 (the plants are referred to as F1 hybrids) and you might see this written on seed packets. When a daughter plant shows vastly different characteristics to those displayed by the parent plant (from witch the seeds were harvested), the seeds/daughter plant are said not to be 'true to type'.

Seeds saved from F1 generation plants will not always produce more, identical plants. Instead, these seeds will produce plants with a wide range of characteristics from the parent plants and the original 'grand parent' plants (the original plants in our scenario). If the F1 hybrid was pollinated by another variety (rather than by itself or another F1 hybrid of the same parents) these grandchildren plants can show characteristics of that plant as well. If two F1 hybrids (from the same parents) are cross pollinated, the resulting seeds and offspring are often called F2 hybrids and again this might be written on seed packets.

If hybrids from each generation are crossed in this way, eventually, after eight or so generations, the seeds will all produce plants with similar characteristics. If all this is a little confusing, take a look at the following two diagrams.

The examples in these pictures are of Mendelian genetics. These are simple examples where only two characteristics are taken into consideration. As you can probably imagine, it’s a lot more complicated when you take into account all of the different characteristics a plant may have. To complicate matters still further, alleles may be codominant (two or more alleles are equally dominant and both are visible – for example a petal that is red with white streaks or a plant that has both red and white flowers) or incompletely dominant (two or more alleles are equally dominant and are blended – for example a snapdragon with pink flowers, which results from the presence of a red and white allele). Hopefully you can now understand why hybrid plants do not necessarily produce seeds that will breed true to type.

Genetic Inheritance Picture 1

So what does this mean for us as gardeners? Firstly you can get some very good hybrid plants that are disease resistant and which produce great tasting produce or beautiful flowers. If you want to save some of the seed from such plants though, those seeds might not produce plants that are identical to the plant you purchased. The resulting plants may be very different indeed. For example, I have a friend who bought a particular variety of pumpkin seed. She grew a great batch of pumpkins and saved some of the seed so she could grow some more the next season. The following year however, she ended up with a completely different variety of pumpkin - one that she had never grown in her garden. She thought that the previous year's batch must have cross pollinated with pumpkins in a nearby garden. She hadn't seen anyone else with pumpkins though so it's more likely that the original seeds were F1 hybrids and the resulting F2 generation plants reverted to the original parent varieties.

Note that hybrids of different species can be drastically different to their parents (more so than hybrids of the same species but different varieties). Such inter-species hybrids may not produce fertile seeds however - that is, the resultant seeds may not germinate.

Hybrids may be produced naturally via wind or insect (or other pollinator) pollination. Humans can also produce hybrids artificially by manually transferring pollen between flowers.

Genetic Inheritance Picture 2

Open Pollinated

Open pollinated seeds are a result of natural pollination only. They may or may not be hybrid seeds depending on whether more than one variety of a particular species is grown in the same area. Usually though, seeds marked as open pollinated are produced in areas where only one variety of a particular species is being grown.

Open pollinated plants are more genetically diverse than hand pollinated ones because, when wind, insects, birds and other pollinators transfer pollen, any plant in the area can be pollinated by any other plant (it takes a lot of work to hand pollinate plants so usually only a small number of plants are used in this situation). The resulting diversity allows plants to adapt (slowly) to local growing conditions such as sunlight, water availability and temperature variation.


Heirloom seeds are produced after many generations of open pollination. Often growers will purposely grow only one variety to avoid cross pollination. Each year, the best plants are selected for seed saving so after many generations, a superior plant is created.

The good characteristics desired by growers may differ though. Growers in areas with short summers may choose to save seeds from only early ripening fruit so that they can produce varieties that will produce more fruit during the short growing season. Growers in hot areas might save seed from flowers that tolerate the heat better (don't wilt or burn as quickly for instance) so that they can create heat tolerant flowers. In areas that get late frosts, growers might select the seed from fruit trees that flower late so they can create a variety that isn't affect by late frosts. Growers might save the seed from higher yielding vegetables, fruits and flowers so that they can create more prolific producers.

Regardless of the desired characterises though, all heirloom seeds are 'stable' because they have been saved over many generations - that is, if you grow plants from heirloom seeds and then save the resulting seeds, the offspring will be very similar to the parents (true to type). They are also usually very disease resistant because seed savers only save seeds from healthy plants each season. Note though that heirloom seeds are bred to grow well in the climate and conditions of the area they have been saved from. If you try to grow them in a different climate or altitude, they may not perform as well.

Heirloom seeds are becoming more widely available but you could always start saving your own seeds to create varieties of plants that grow really well in your unique climate. You could even start a local seed swap initiative so that lots of gardeners can pool a wide variety of seeds suited to the local climate without having to worry about grow every variety themselves and without worrying about preventing cross pollination between related varieties (gardeners living at opposite ends of town can easily grow two different varieties of cucumber for instance, whereas if the same gardener grew both varieties they would have to manually pollinate and then bag individual flowers to prevent the two varieties cross pollinating).


GM stands for genetically modified. GM plants have had their genetic material directly altered by scientists. Often the aim of genetic modification is to improve yields or produce crops that are tolerant of herbicides used to control weeds on commercial farms. In many cases, scientists who produce GM food crops do so with the aim of producing high yielding plants for areas that struggle to grow sufficient food to feed the population. With GM foods, growers may have a tool (though not the only available tool) that has the potential to end starvation.

GM crops cause problems though in areas where farmers and gardeners wish to grow organic crops as GM pollen can pollinate the flowers of organic crops meaning that fruit and seeds produced on the organic farm is not organic. Also, GM crops are subject to patents and saving the seed from GM crops for replanting, whether you grow the crop or a nearby crop has contaminated your usual crop, is considered a breach of the patent. As only genetic testing can identify GM crops, farmers may not even realise their non-GM crop has been pollinated by a nearby GM one and this has caused a number of legal disputes.

There are also safety concerns surrounding GM crops. There is a reasonable amount of research, the impartiality of which is sometime dubious, that examines the safety of GM foods for human consumption. There is evidence indicating it is safe as well as evidence indicating it is unsafe (some reports indicate that some GM foods can cause cancer for instance). Regardless of which evidence you chose to believe, humans have not been ingesting GM foods for long enough for research to be able to establish long term safety. We cannot know what 50 years of eating GM foods will do to a person. Nor can we know what effects long term consumption of GM foods may have on our children and grandchildren. GM foods might be harmless or even good for us over the long term or they might be bad for us - we simply do not know.

The other issue with GM crops is connected with pesticide use. As I said above, some GM crops have been designed to be tolerant of pesticides and herbicides such as glyphosphate (round up). This means that farmers can use greater levels of chemicals to prevent pest damage and competition with weeds, resulting in higher food, fodder and flower yields. The problem is, heavy use of these chemicals can pollute waterways, kill beneficial insects (such as bees) and spur the evolution of pesticide resistant insects and herbicide resistant weeds.


Organic seeds and plants have not been treated with any synthetic chemicals. They are also entirely natural - that is they do not contain any genetic material that has been artificially modified by humans. If something is certified organic, it has only been treated with chemicals that are also certified organic. That means any pesticides, herbicides, fertilisers and mulch used on or near the plant have been certified organic.
Be aware that organic doesn't necessarily mean safe however. Red back spider venom is organic but no one would call it safe. Likewise, things like copper based pesticides that are certified organic can still kill earthworms and homemade chilli and garlic sprays can kill beneficial insects.

On the other hand, non-organic plants, especially ornamentals, might have been treated with high levels of chemicals that can kill beneficial insects as well. The difference is, organically produced plants and seeds come into your garden as safe inputs - it's what you do to them that makes a safe or dangerous garden for humans and insects alike. Plants that have been spraying with dangerous chemicals before you get them however, enter your garden as dangerous inputs and no amount of safe chemical use (or lack of chemical use) can reverse that damage.

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