I’m not perfect but I try to take a plastic-free challenge in my garden and on my allotment.
One alternative to plastic plant pots is to use biodegradable ones. I particularly like Vipots (they look and feel like regular pots but are plastic-free) – if cared for they last several years. When they do finally crack, they can go straight on to the compost.
Another option is to re-use kitchen plastic like yoghurt pots, takeaway containers – perfect for seedlings. Afterwards you can recycle them in the council system.
Diverting plastic from landfill is well worthwhile. Plastic plant pots are hard to recycle, but local horticultural groups or garden centres might take them. Companies like TerraCycle and Filcris are also good for repurposing old plastic and other materials into products that are useful for the garden.
If you have enough space for a greenhouse you can grow year-round salads and greens. Try eBay, Freecycle and Gumtree for pre-loved plastic-free ones. Metal greenhouses are easier to put up than wooden ones in my experience, but the latter are easier to fix.