How to make comfrey fertiliser

Comfrey fertiliser's great. Comfrey has really long roots, so it unlocks nutrients from deep in the soil. Turn it into fertiliser to let your other plants benefit from those nutrients too. The liquid can be used as a general plant food, but is particularly good for tomatoes. Here's how.

1. Find some comfrey. It looks like this:

Comfrey

2. Fill a plastic milk bottle with comfrey leaves (use a stick to poke them down to the bottom so you can fit as many in as possible).

3. Fill up with water and seal the lid.
4. Leave for 3 to 5 weeks.
5. Dilute 1 part fertiliser to 20 parts water for use.

Making fertiliser from weeds

So far in the coronavirus lockdown, it's been hard to get gardening supplies. In particular, I haven't been able to get hold of the composted stable manure I usually fertilise the garden with. I do have the compost I make myself, but in the past I've given my plants that together with composted manure. To make up for this as best I can, I ordered a 5 litres of liquid fertiliser, but I'm also making my own fertiliser from garden weeds.

Back when I went on a vegetable growing course in 2014, they taught us how to make fertiliser out of comfrey. The reason you use comfrey is that it has deep tap roots (those very long roots that go deep into the soil like dandelion roots). This means that it can access minerals from deep in the soil that other plants with shorter roots can't get to. It brings these minerals up into its leaves, so when you turn these into fertiliser you're filling your fertiliser with all these minerals. I don't have comfrey growing in my garden, but what I do have is its relative green alkanet.

Green alkanet

As all my past attempts to dig it up have shown, green alkanet too has very long tap roots. I would also have considered dandelions for my fertiliser, even though their tap roots aren't usually as long as green alkanet's seem to be. Making the fertiliser couldn't be simpler. I took an old, clean plastic milk carton with a lid and stuffed as many green alkanet leaves into it as would fit. I used a stick to make sure they got all the way down to the bottom.

I made no attempt to remove the flowers or the stalks, as I couldn't see a reason why they might be a problem. It's surprising how many leaves you can fit in when you start pushing them down. You want to fit in as many as you can.

When it was jam-packed in, I trickled water into the top, so the milk carton was completely filled with water. I used rainwater from my water butt, but if you don't have rainwater, tap water is fine. The reason I trickled rather than poured the water in was that there were so many leaves jammed tight into the carton. I tried pouring at normal speed, but the water just ran over the sides.
I'm now putting it aside and leaving it for 3-5 weeks to stew. When it's ready, it will stink to high heaven (don't worry, that part's normal) and I will dilute it one part to 20 with water. So, to summarise, here are the steps:

1. Find some weeds with a long tap root, such as comfrey, borage or green alkanet (or even dandelions).

2. Fill a plastic milk bottle with its leaves (use a stick to poke them down to the bottom so you can fit as many in as possible).

3. Fill up with water and seal the lid.

4. Leave for 3 to 5 weeks.

5. Dilute 1 part fertiliser to 20 parts water for use.

Fertiliser - you only get back what you put in

We all know that plants need nutrients to grow. If you're like me pre-gardening course, you just stick them in the soil and assume that that has everything they need in it. After all, that's all they get in the wild. But actually it turns out that there's more to it than that. We don't grow plants – either on farms or in gardens – like they grow in the wild (not even organic farms). In the wild, no one goes round clearing up all the dead plant life that ends up on the soil - or for that matter the animal excrement or dead animals. Sure, some things eat some of these things, but actually they themselves tend to produce excretions that end up back in the soil.

Modern human life avoids this. We clear up dead plants and, if the garden's lucky, put them in a compost heap and return them to the garden. If it's not so lucky we send them off to the council's green waste collection or just put them in the bin, and after we've up eaten plants we don't return the waste products we create from them to the soil, we transport them away via the sewer system.

Now, don't get me wrong, I'm not suggesting turning you garden into your toilet. For health and disease reasons, that would be a truly bad idea. You don't want the excrement of anything that's not a herbivore on your garden (so horse manure = good, human "manure" or dog or fox mess = health risk). But this does mean that we're taking a lot of nutrients away from the soil in our gardens and farmland that never leave wild areas (because we take away the plants that have grown there). This leaves the soil depleted and less able to support plants. We need to add it back in the form of compost or fertiliser.

The main nutrients plants need are nitrogen (good for leaves and shoots), phosphorous (good for roots) and potassium (good for flowers and fruits) N, P and K on the periodic table of elements). So non-organic farms make sure they add these to the soil. They do it by deriving these from petrochemicals. The problem with this is that although these are the main nutrients plants need, they're not the only ones that they need, and when you use NPK fertilisers made of petrochemicals, these are the only chemicals the soil gets and therefore the plants and ultimately, if you're eating the plant, you get. This gets worse year after year, as the levels of other elements the soil originally contained get further depleted. Also, plants need a wide range of nutrients to help them stay healthy. Here's a page with a really useful picture on it that shows you how to diagnose missing nutrients based on what's wrong with you plant - some things that look like disease actually turn out to be a lack of nutrients.

Organic fertilisers come from things that were originally living organisms and contain more than pure nitrogen, phosphorous or potassium (although not all of them are high in all of those). Here are some organic fertiliser options:

Bone meal

The nitrogen-phosphorus-potassium ratio of bone meal is generally 4-12-0, though some steamed bone meals have a ratio of 1-13-0. Bone meal is also an excellent source of calcium, but does not provide enough nitrogen to be beneficial to plants. Research suggests plants can only get phosphorus from bone meal if the soil pH is below 7.0 (acidic soil).*

Seaweed

Helps to bind soil crumbs together, and it contains all soil nutrients (0.3% N, 0.1% P, 1.0% K, plus a full range of trace elements)*.

Organic chicken manure

According to the RHS website, pelleted poultry manure is a good source of ntirogen and generally contains 4% nitrogen (as ammoniacal nitrogen), 2% phosphorous (as phosphorus pentxide) and 1% potassium (as potassium oxide).Most poultry manure is in the range of pH 6.5-8.0, being neutral to moderately alkaline, so unsuitable for lime-hating plants. According to this website, it also contains a range of trace elements, with amounts varying depending on the diet of the poultry and how they're kept.

Manure

I assume this is horse manure. According to this website, horse manure is only about half as rich as chicken manure, but richer in nitrogen than cow manure. Horse manure is considered "hot", which means it should be composted before it's put on the soil so it doesn't burn the plants it comes into contact with. Also, horse manure often contains a lot of weed seeds, which means it's a good idea to compost it using a hot composting method or to buy it already hot composted.

Green manure - mustard

Green manure - buckwheat

Green manure - red clover

Green manure - alfalfa

Green manures are plants you grow between other crops (often over winter) and then dig into the soil before planting your next crop. They suppress weeds while they're growing and make nutrients in the soil more available to other plants. Many are leguminous and fix nitrogen in the soil. Some also acidify soil. Which nutrients or effects you get depends on which green manure you pick.

Comfrey

Because comfrey has deep roots, it sucks nutrients from deep out of the soil. Comfrey fertiliser makes these available to plants with roots that don't go so deep. My next post will tell you how to make your own comfrey fertiliser.

* Information from Wikipedia on 12 October 2014.

What are brown and green compost and how do you balance them?

At my last gardening course lesson, I finally found out what they mean by "brown" and "green" compost. You're supposed to keep a balance of in your compost heap, and I'd been doing it all wrong because I'd been taking the brown and green instruction too literally.

In fact, in this context, the word "brown" is used to refer to matter that's rich in carbon and "green" is used to refer to things that are rich in nitrogen. A lot of the things that are rich in nitrogen (like grass clippings) are genuinely green and a lot of things that are rich in carbon (like wood) are genuinely brown. The problem is that not everything in the brown (carbon) category is actually brown and not everything in the green (nitrogen) category is genuinely green (for instance, tea leaves, coffee grounds and potato peelings all fall under the "green" category).

People sometimes use other terms instead of brown and green, but I don't actually find those any more helpful. The greens are sometimes instead referred to as "soft" or "hot" and the browns are sometimes referred to as "hard" or "cold", but actually, that wouldn't help me work it out either. What I find most helpful in distinguishing the two lists is that the nitrogen-rich greens are quick to rot and the carbon-rich browns are slow to rot. I've got enough experience of compost heaps to have a sense of what's going to rot quickly and what's going to stick around for ages that I can quickly work out which is which. But having a list is really helpful, so here it is:

Greens (= nitrogen-rich ingredients = soft ingredients = hot ingredients) (quick to rot)

Grass clippings

Raw vegetable peelings

Tea bags, tea leave, coffee grounds

Young green weed growth (avoid weeds with seeds)

Soft green prunings

Animal manure from herbivores (e.g. cows, horses, rabbits, guinea pigs) - don't use manure from non-herbivores at all

Comfrey leaves

Nettles

Urine (diluted with water 20:1)

Browns (= carbon-rich ingredients = hard ingredients = cold ingredients) (slow to rot)

Cardboard (e.g. cereal packets, egg boxes, toilet roll tubes etc.)

Paper (including junk mail and shredded paper)

Bedding from herbivore pets (e.g. rabbits, guinea pigs) - hay, straw, shredded paper, wood shavings

Tough hedge clippings

Woody prunings

Old bedding plants

Bracken

Sawdust

Wood shavings

Fallen leaves (but a better use of them is to make leaf mould)

Now you need to what to do with these ingredients. This depends on whether you want a cool heap or a hot heap or to go a hybrid route. I'll either be going the cool route or the hybrid route, as the cool route's the easiest and my back thanks me for doing everything the easiest way possible. Here are the three options:

Upcycled compost bin at the Carshalton Community Allotment made from discarded fridge doors to help keep the heat in (the perspex lid on the top is usually kept shut)

Hot heap
1. Gather enough material to fill your compost container at one go. Some of this may have been stored in a cool heap and have started to rot slightly. Make sure you have a mixture of greens and browns.
2. Chop up any tough items using shears, secateurs, a sharp spade (laying items out on the grass to avoid jarring) or a shredder.
3. Mix the ingredients together as much as possible before adding to the container. In particular, mix items that tend to settle and exclude air, such as grass clippings and shredded paper, with more open items that tend to dry out. Fill the container, watering as you go.
4. Within a few days the heap is likely to get hot to the touch. When it begins to cool down or a week or two later, turn the heap. Remove everything from the container or lift the container off and mix it all up so that the outside of the heap is on the inside and vice versa. Add water if it is dry or dry material (browns) if it is soggy. Replace the bin.
5. The heap may well heat up again. The new supply of air you've mixed in allows aerobic microbes to continue their work. Step 4 can be repeated several times, but the heating will be less and less each time. When it no longer heats up, leave it undisturbed to continue composting.
NB If you have a bad back you can compost in smaller containers. The smallest container our teacher knew of anyone composting in was the one in the picture below and he said she got results in just six weeks by tossing the compost regularly.

Cool heap
1. Collect enough compost materials to make a layer at least 30 cm high in the compost bin. Add green materials then mix in some straw, woody prunings and/or scrunched up cardboard to help create air spaces in the heap. It might help if you start the heap with a few woody plant stems or small twigs at the bottom, as this will help improve circulation and drainage.
2. Continue to fill the container when you have compostable material. Make sure you put both greens and browns in.
3. When the container is full (which it may never be, as the contents will sink as they compost) or when you decide you've added enough just leave it to finish composting (which could take up to a year) or go to step 4.
4. Remove the top layers of the heap. If the lower layers have composted use these on the garden. Mix everything else together thoroughly. Add water if it's dry or dry material (browns) if it's soggy. Replace in the bin and leave to mature.

Hybrid heap
1. Fill your heap as you create waste (like for the cool method).
2. Turn it when you have time (this will help it heat up).
You can turn it as much or as little as you want, but the more you turn it the quicker the compost will be ready.

How to balance brown and green materials whichever method you're using:
1. Add both greens and browns.
2. If the heap gets soggy and smelly add more browns.
3. If the heap gets dry, add more greens.

When is your compost ready?
When it turns dark brown and smells earthy. This can take as little as six weeks if you're using the hot heap method and put a lot of effort in, but is pretty likely to take over a year.