A 1.2L bottle of PowerFeed Pro Series tomato and vegetable concentrate is $18.29 at Bunnings right now, down from $21.95. A 2.5kg bag of Yates blood and bone is $15.20, which works out at $6.08 a kilo. I have bought both over the years. I have also not bought either for about three seasons, because the four cheapest feeds in my garden cost nothing and they were already sitting in the yard.
People ask me which homemade fertiliser is the cheapest and most effective. Those are two different questions and the honest answer is that no single brew does both jobs. Here is what each one actually costs, what it actually feeds, and the order I would build them in.
The short answer
A bucket of comfrey or weeds steeped in water. It costs nothing, it takes about three weeks, and it produces the one thing a fruiting crop runs out of first, which is potassium. If you only ever make one thing off this page, make that.
The catch is that it leans potassium heavy, so it will not carry your leafy greens. Nitrogen has to come from somewhere else, and that is where the ranking below matters.
What each one actually costs
| Feed | What you pay | Time to ready | Strong in |
|---|---|---|---|
| Comfrey or weed tea | Nothing. One plant, one bucket | 3 to 4 weeks | Potassium |
| Worm castings tea | About $2 a brew | 24 to 48 hours once the farm runs | Balanced, plus soil biology |
| Banana peel and eggshell | Nothing. Kitchen scraps | 2 weeks | Potassium and calcium |
| Composted horse manure | Nothing but a trailer trip | 3 to 6 months | Bulk nitrogen and organic matter |
| Yates blood and bone, 2.5kg | $15.20, or $6.08 a kilo | Immediate | Nitrogen and phosphorus |
| PowerFeed Pro Series, 1.2L | $18.29 | Immediate | Balanced liquid |
Cheapest is not the same as most effective
Cost per bucket is the easy half. The half that decides whether your patch grows is what is in the bucket, and the four free feeds do not overlap as much as people assume.
Comfrey and weed tea is your potassium. Comfrey is a deep rooted perennial that pulls nutrients up from below where your veggies can reach. I get three or four cuts a season off one plant and it keeps the whole patch in liquid feed. Weekly on tomatoes, capsicum, chilli and pumpkin once they start setting fruit. Fortnightly is plenty for anything leafy.
Worm castings tea is your all rounder. It is the only one on the list that feeds the soil biology rather than just the plant, and it is the fastest to turn around once the farm is established. A brew is ready overnight. I use it on seedlings and anything I have just transplanted, because it is gentle enough not to burn.
Banana peel and eggshell patches two specific gaps. Potassium for fruit fill, calcium for cell strength. That calcium is the one that matters if you have ever lost a row of tomatoes to blossom end rot. It is not a general feed and I would not treat it as one.
Composted horse manure is your nitrogen and your bulk. This is the only free option that fixes soil structure as well as feeding it, and it is the closest thing to a complete replacement for bagged product. It is also the slowest and the one with the real risk attached, since a contaminated load will take out your solanums. Run the bean pot test on any new source before you trust it near food.
The order I would build it in
- Start the comfrey. Put a plant in now. It is the highest return per square metre of anything in this list and it does nothing until it is established, so the sooner it goes in the sooner it pays.
- Get a bucket going. Weeds you already pulled, water, lid on loosely, three weeks. You do not need the comfrey to be mature to start this.
- Build the worm farm. This is the one that changes how the soil behaves rather than just what the plants get fed.
- Chase a manure source. Only worth it if you have somewhere to stack it and the patience to compost it properly.
Kitchen scraps sit outside that order because they cost nothing and need no setup. Keep a jar brewing at all times and you will always have a batch ready when the tomatoes start fruiting.
What this looks like in your zone
Steeping time is temperature driven, so the same bucket behaves differently depending where you are. In the tropics and subtropics, check a weed bucket from the two week mark. Mine is often done in under three weeks through a Dayboro summer. Warm temperate growers should budget the full three to four weeks. Cool and cold zones, Hobart, Canberra and the Southern Tablelands, want four to six.
Horse manure runs the other way. A pile needs to get hot to kill weed seeds and pathogens, and a cold zone pile through winter will not get there. Build it in the warm months and let it sit. If you are unsure what is worth planting into it once it is ready, the what to plant now calendar is filtered by zone, and the growing guides tell you which crops are the hungry ones.
One thing that catches people out. If you have just laid a fresh woodchip or sawdust layer, feeding harder will not fix the yellowing, because the mulch itself is locking nitrogen up as it breaks down. That is a mulch problem rather than a fertiliser problem and no amount of comfrey tea solves it.
The payoff
One comfrey plant and a bucket replace an $18.29 bottle of concentrate. A worm farm and a jar of scraps cover the calcium and potassium a fruiting crop burns through. A trailer load of manure, composted properly, replaces the $8 to $15 a bag compost that is the real annual cost of running a patch. Add it up across a season and the fertiliser bill for my garden is a bit of bucket space and some patience.
None of it is complicated. All of it is slow, which is the actual price you pay. You are trading $18.29 and a trip to the shops for three weeks of waiting and a shed that smells off.
The only genuinely hard part is remembering which bucket is which before you water. I have dosed a tray of seedlings with full strength brew by mistake once, and it was not a good week for that tray.
GardenBuddy
