This time of year gardeners plant seeds that will grow into flowers and vegetables once the weather warms up.

The recent very cold weather has delayed that process, but nature usually catches up. Climate change threatens to undermine this process. It creates major problems for food-growers. Crops that may once have thrived in a particular region might fail if it becomes much hotter or colder, wetter or drier.

To combat this uncertainty we need a broad plant gene pool. The more varieties of seed available to growers the more likely it is that some of them will adapt to a more hostile environment.

Yet now when we are most in need of greater plant diversity, the range available is shrinking. Worse still, the plant gene pool is being deliberately diminished. For example, the European Union levies a hefty registration fee on any seeds that go on sale within it. The cost of registration means that only commercially viable seeds are registered. Unregistered seeds are illegal to buy and sell.

The result is that three global corporations – Syngenta, Monsanto and Bayer – own the copyright to most registered seeds. These corporations can only copyright hybrid (F1) varieties and genetically modified seeds. They cannot copyright traditional (heritage) varieties.

F1 varieties are useless when their seeds are saved and planted, unlike heritage varieties, which remain true to the characteristics they inherit. Thanks to seed legislation, the seed varieties that we most need if we are to survive the challenge of climate change are the ones that are disappearing.

Globally there are a number of seed banks that protect the wider gene pool. In the UK we have the wonderful Heritage Seed Library run by Garden Organic. Many gardeners save and sow much of their own seed. But as things stand, with more and more varieties disappearing for good, we are fighting a losing battle.

So, if you grow vegetables or fruit this year please join the cause. Avoid using F1 hybrids and only sow heritage varieties. You will be playing a small but important role in protecting our future.