I grow tomatoes every summer. I have always used organic methods which involve a high potassium feed made from Comfrey leaves. Well in fact I’ve found that Blue Alkanet (Pentaglottis sempervirens sometimes called Green Alkanet or Bugloss), which grows prolifically in our garden and has some nice blue flowers, works just as well – it’s a relative (Comfrey’s, not mine).

“Overblijvende ossentong Pentaglottis sempervirens closeup” by Rasbak – Own work. Licensed under CC BY-SA 3.0 via Wikimedia Commons – https://commons.wikimedia.org/wiki/File:Overblijvende_ossentong_Pentaglottis_sempervirens_closeup.jpg#mediaviewer/File:Overblijvende_ossentong_Pentaglottis_sempervirens_closeup.jpg

One method is to steep the leaves in water, and use the resulting liquid. But, it is extraordinarily smelly, a real pig dung smell! Get it on your hands, or clothes and it will last for a while. By the way, this method works for any weeds – nettles make a high nitrogen feed.

So the alternative is to make a concentrate, and it’s very easy.

Here is my machine:

Liquid comfrey machine. (c) Mark H Burton

An old 5 litre bottle, with the bottom cut off, and inverted. I use a simple wooden frame but you could prop it up on bricks. A glass jar goes under the original bottle opening – mine’s an instant coffee jar.

There is a bit of wire mesh, or similar over the opening to keep the fibrous material back and to allow the liquid to dribble out.

Cram the bottle with leaves. I use a piece of thin wood cut roughly to size and fitted with a recycled plastic facing and wire handle to sit over them and a half brick as pressure on top of that.

The machine packed with comfrey leaves (or alkanet here). (c) Mark H Burton

All pressed down with a half-brick. (c) Mark H Burton

Put a little water over the leaves, (just a few millilitres) on the leaves, add a bit occasionally: you’ll get to know how much – just enough to facilitate the rotting process. And that’s it for the summer. Top up with leaves as they sink down, turn black and yield their liquor. Take out the jar and use it diluted – say 60 mls to a 2 gallon watering can.  On tomatoes, use it once the first truss has set.

This little plant makes enough for a small greenhouse full of tomatoes – about 16 plants, plus a few in the garden. Those in the greenhouse I grow using ring-culture and those in the garden are in pots and border soil.

Tomato ring culture. (c) Mark H Burton

There is no smell but you will get a few flies that drown in the dark brown liquid, which resembles a good jar of Porter. Yes, “60 mls of plain is your only man! when it comes to tomato growing, as Flann O’Brien would say.

In the winter, grow salads in last year’s ring culture pots before changing the medium for next year;s tomatoes. (c) Mark H Burton