Gardeners, by their very nature, are intrinsically conservationists. What we do in tending and caring for our plants is surely conservation in its strictest sense. I don’t know any individual gardener who doesn’t show a deep empathy for the natural world and the wonders it brings humanity. Put a gardener out in the countryside and the thing they invariably notice first is the plants. Most gardeners do not suffer from plant blindness.

Robbie Blackhall-Miles is a Plant Heritage Plant Guardian for Aristolochia curcurbitifolia, a vulnerable species from China and Taiwan. Photograph: Robbie Blackhall-Miles

We live in a time when the world’s plant life is more at risk than it ever has been. There are an estimated 400,000 species of plant on this planet and at least a quarter of them are threatened with extinction. Climate change is one of the largest challenges the world faces: it saw us hit a 1C increase in global temperature this year. The world’s governments agree that the planting of vast numbers of trees could be a first line of defence against it. Is it us gardeners who will be growing these trees in order for them to be planted?

Conservation however does not always have to happen on a large scale for it to be effective. The planting of a trillion trees seems like the kind of big conservation that is beyond the individual, yet for me, as a gardener, planting trees is a normal part of my life. Planting a single tree in your garden is a big step toward better air quality, reduced noise pollution, increased shade, reducing carbon dioxide in the atmosphere and overall a much nicer, more biodiverse, environment.

In 2002 the United Nations Convention on Biological Diversity (CBD) set 16 targets to halt the loss of plant diversity worldwide by 2020. These targets are called the Global Strategy for Plant Conservation (GSPC); gardens and gardeners are important to many of them.

One of the targets set by the GSPC is that we should have more than 75% of threatened species in plant collections and that 20% of these should be available for restoration programmes in the wild. In the UK we have surpassed this target, with 77% of our threatened native species in plant collections and 40% available for restoration, but worldwide there are less than than 30% of threatened species in cultivation. The majority of these are in seed banks and botanic gardens, yet you don’t have to be either to be able to count toward this target – you just have to make sure that the conservationists know about the threatened plants you are growing. One way is through joining Plant Heritage’s National Plant Collections scheme or their Plant Guardians scheme.

The GSPC concentrates on wild species, but plant conservation is about all plant diversity. A simple act can result in a species or cultivar, a set of genes, being saved; particularly in a time when plant life is being so severely affected by new and emerging pests and diseases.

Anne Tweddle, a member of Plant Heritage, asked if she could take cuttings from many of the unusual box varieties held in the then National Collection of Buxus. The collection had to be withdrawn due to box blight (Cylindrocladium buxicola and Pseudonectria buxi) but Anne had registered her box cuttings as part of the Plant Guardian Scheme and is now able to provide disease-free material of Buxus species and cultivars which would have otherwise died out in cultivation. This is real plant conservation being done by an individual in their own back garden. Anne had not kept the information about the plants to herself; she let a conservation organisation, Plant Heritage, know they were there.

Another of those GSPC targets is that we need to conserve at least 70% of crop diversity and the associated local knowledge that goes with it. With climate change and those new pests and diseases to worry about, who knows when we may need the genes held in the older “heritage” varieties of food crops or their wild relatives in order to sustain humanity. So when you buy that “heritage” marrow or old variety of carrot, you are not just growing a novelty; you are sustaining a resource for the future of humanity. Make some effort to maintain that rare “heritage” variety your grandma grew in cultivation, propagate it and spread it far and wide.

Growing an expanding collection of plant species in my North Wales back garden has led me to register these on the Plant Search Database run by Botanic Garden Conservation International. This database is another source of information for the GSPC, and it allows scientists and conservationists to see what plants are being grown in botanic gardens and other plant collections around the world. I am on the verge of taking it one step even further and setting up a research nursery, so that I can help conserve even more of the world’s threatened plants. However, plant conservation must not be the mission of the few. If humanity is to survive and have any resilience toward climate change, plants will be our first line of defence.

All of us gardeners are conservationists. By growing just one species, cultivar or variety of plant, you could save it from extinction. By telling others about it, you make sure it is available for reintroduction or breeding. By sharing it around you make sure that, should anything happen to yours, it, and the valuable genes it holds, will never be lost.