For the past year or so we have been watering the garden container plants with banana skin fertiliser.
Each week the banana skins go into a big jar or jars of tap water (we use 2 x 1 litre jars, to fit all the skins in - as we get through 14 bananas a week in our house!) By the time the jars are full, the banana fertiliser is ready to use. The banana-infused water only is poured into a watering can (the skins are held back, ripped up and composted). The watering can is topped up to about halfway full with tap water (I add the same volume of new tap water as that which will fit in the jars twice each, so for us that is 4 litres of water extra in total, on top of the banana-ish liquid from the two jars). Then we water the garden container plants with the diluted banana skin fertiliser.
Obviously it doesn't have the same impressive effect as the polluting-to-produce liquid fertilisers you can buy in a plastic bottle, but having the banana-ish water build up each week has made me more likely to remember to water the container plants in the garden (on 'Feeding Friday') and they are looking much happier for it.
The plastic-free fertiliser pellets we use to feed the rest of the garden plants (and the container plants sometimes too) come from our pet guinea pigs - as you can put their poo straight onto the garden, without risk of damaging the plants! Below are the super-cute Lego models my eldest made of our two guineas - complete with brown single Lego studs for poo, although not fully visible on the photo sadly...
For those not lucky enough to have guinea pigs, a new plastic-free fertiliser pellet product made from vegetation-waste, on farms in Cambridgeshire looks perfect. Natura Grow's 'All Purpose Feed' is in pellet form - you just scatter the pellets around your plants and dig them slightly into the soil. The product is made from the waste material leftover from bio energy units, so it's sustainable and it is also vegan. The cardboard box used to come with plastic tape on it, but the packaging has now been made 100% plastic free - hurrah! If we didn't have guinea pigs then we'd be using this product regularly throughout the growing season. It's available direct from the manufacturer's website above.
The nutrient-rich compost from the tumbling composter (which we then decant into a static wormery) is spread - once well rotted, thanks worms! - onto the fruit and vegetable beds in Spring. If you'd like to know more about how we compost in our garden then here is a whole blog post on the subject of composting!