Welcome to the first day of our Better Gardener Challenge on biodiversity. If you’re wondering why on earth you’ve pitched up here at all, here’s a brief explanation.

Why be a green gardener?

At first glance, gardening sounds like a pretty green hobby anyway. You are growing plants. You are producing your own fruit and veg, rather than buying shop-bought produce imported halfway across the globe.

But gardeners can still do a huge amount of damage - not just to their local environment, but to habitats around the world - with the wrong practices. Many fertilisers rely on petroleum for their creation (geeky bit: petroleum is used as a “feedstock” for converting atmospheric nitrogen to ammonia). That process is energy-intensive. Petrochemicals are also becoming scarce. They come from volatile countries. They are also demonstrably bad for the environment.

This might be controversial, but all the evidence on organic food says that it is great for the environment, but has negligible benefits for your health. But just because scientists say eating non-organically-grown produce probably won’t damage your body, it doesn’t mean your choices aren’t making a huge impact on the environment around you. Pesticides wipe out fauna indiscriminately. Synthetic fertilisers have damaging origins and damage the local environment by disrupting the nitrogen cycle. Because they are synthetic, they damage your soil in the long-run. They do not replenish all the nutrients needed for growth. Whether or not you believe that organic fruit and vegetables are good for you, they are proven to be good for ecosystems.

And what about all that water that gardeners use to keep their plants lush, leafy and cropping heavily? Significant parts of the UK are now under water stress, according to the Environment Agency. We release carbon as we dig up more and more peat bogs to fill our pots and planters, and contribute to global carbon emissions with our lawnmowers. Gardening can be immensely damaging to the environment, but there is another way, which this course will teach you.

So that’s the theory. Now it’s time to get cracking and make you a green and biodiverse gardener. For the next two days, we’ll be looking at how to cut out chemicals from gardening.

Cut out chemicals part 1: forget fertilisers

It’s pretty clear that synthetic fertilisers are actually pretty unfriendly potions. But how do you keep your plants blooming and cropping and your lawn as green as can be? There are plenty of organic alternatives.

Organic fertilisers are made from plant or mineral matter. They release their nutrients slowly into the soil rather than in one big blast, and supply reasonable levels of food rather than over-feeding plants.

Types of organic fertilisers

Seaweed This acts as a soil conditioner, adding potash and nitrogen as well as trace elements. Dig into the soil in the autumn.

Bonemeal This is sprinkled in the planting hole for shrubs and trees - especially fruiting plants - and provides phosphorous.

Comfrey concentrate You can buy this, but it’s just as easy to make (here’s a guide).

Hoof and horn This releases nitrogen over a period of a few weeks. Add to the soil surface in spring.

Blood, fish and bone This supplies nitrogen and phosphorus. Apply to the base of a plant.

Chicken manure This is produced in pellets and contains nitrogen and phosphorus. Apply as a top dressing to the soil.

Worm casts Often sold as ‘Black Gold’. High in nitrogen. Apply to the soil surface or mix into compost.

Click here for a series of recipes from our last Better Gardener Challenge for compost tea, spent hop fertiliser and nettle tea.

Pledge to stop using synthetic fertilisers in your garden. Have a hunt online for organic replacements.

Well-fed soil

If you cultivate your soil properly, you’ll find it easier to wean yourself of synthetic fertiliser. A soil which has regular additions of bulky manure and garden compost will feed your plants throughout the growing season. You can read more about improving your soil in the Better Gardener Soil Series.