How to Fix Common Compost Problems

, written by Benedict Vanheems gb flag

Compost worms

Compost is the foundation to a thriving garden. The trouble is, few of us have the perfect conditions to make ideal compost every time. We’ll look at some common compost problems, and easy ways to solve them.

The Perfect Compost

Perfect compost has a fine, crumbly texture and pleasant, earthy smell like a forest floor. The original ingredients used to make the compost will no longer be visible, having been transformed into dark-looking organic matter with an even consistency. Mature compost is gardeners’ gold. Use it to mulch around plants, make potting soils or to dig into soil to improve its nutrient content and moisture-holding capacity.

For instructions on how to make good compost by adding the right balance of ingredients, read our article How to Compost – Easy Steps to Success.

Compost Problems

Few gardeners get composting right every time. Common problems include smelly compost bins, slimy ingredients that have become excessively wet, or compost that has simply stopped rotting down before it's ready.

Wet, slimy compost

Problem 1: Too Wet

The most common problem is excess moisture, which causes foul odors, flies, and the production of substances harmful to your plants. Adding too much fresh material, instead of a balanced mix of fresh and dry materials, is the usual culprit.

Fresh materials such as vegetable peelings and grass clippings have a high water content, which makes them heavy. If too much is added to your compost heap at once it can become compacted, excluding air or filling air spaces with water. These oxygen-starved ‘anaerobic’ conditions enable harmful microbes to thrive – the same microbes responsible for creating the unpleasant smells that arise from such putrid conditions. Fresh materials are mostly 'greens' which have a high nitrogen content, so mixing in more carbon-rich 'browns' will help solve the problem.

If your compost heap is too wet, dig it out completely, then turn the ingredients to incorporate more air before restacking. Add dry materials into the mix to get a balance of greens and browns, improve drainage and prevent the compost from clogging up again.

Ingredients such as shredded prunings, sawdust, straw and cardboard torn into smaller pieces will create channels within the compost that allow air to percolate and excess moisture to drain away. Scrunched up newspaper makes a good short-term option if you haven’t got enough of these dry ingredients to hand.

Rotting grass

Problem 2: Grass Clippings

Grass clippings are often generated in large batches. Don’t be tempted to add thick layers to the compost bin just to get rid of them or they could create a soggy mat. Instead, sprinkle grass clippings in thin layers and balance them with dryer ingredients. If you have too many clippings lay them as a mulch around fruit trees and bushes where they will slow down weed growth and lock in soil moisture.

Be aware that enclosed plastic compost bins let less air in than open heaps. They require extra care to ensure a balance of dry to fresh materials. Never stamp or force materials down in order to fit more in, or you run the risk of over-compacting your compost ingredients and artificially stimulating anaerobic conditions.

Problem 3: Too Acid

Compost is naturally slightly acidic but sometimes an abundance of some 'wetter' ingredients can upset the balance. This can cause the compost heap to become a bit smelly and slow to decompose.

Acidic ingredients such as citrus fruit can also contribute to an excessively acidic compost bin. Counteract the acidity by sprinkling handfuls of ground lime or wood ash into the mix, plus plenty of 'browns' if the bin is wet and other fresh, green material to kick-start the composting process again.

Problem 4: Too Dry

If your compost bin is too dry it will stop decomposing as the bacteria and fungi responsible for the composting process won’t be able to work effectively. Re-wet the heap by watering it - ideally with rainwater, but if you don’t have any stored rainwater ordinary water will do. Apply it evenly using a watering can fitted with a rose, mixing the materials at the same time if you can.

Bins with too many dry materials can be given a boost by adding lots of fresh material to balance out the ingredients. Dig out the compost bin, add your fresh materials then refill the bin. Or, if you have two bins side by side, mix the extra materials and water as you turn the materials from one bin into the other.

The exception to the rule is leafmold, which is a form of compost made entirely from fallen leaves. Leafmold naturally takes up to three years to fully mature before it’s ready to use, by which time the leaves should no longer be visible.

Good rich compost for the garden

Using Compost

Mature compost can be sieved into sturdy plastic bags or garbage cans for storage. Any lumps or part-rotted materials left behind in the sieve may be thrown back into an active compost bin to continue decomposing, helping to transfer beneficial microbes into the next batch.

To make a general-purpose potting soil suitable for growing most vegetables, mix two parts compost to one part sieved garden soil and, for added drainage, one part vermiculite. For a potting soil suitable for containers and window boxes combine two parts soil to one part compost and one part sharp sand. Garden compost is likely to contain weed seeds, so to avoid a flush of weed seedlings, cap your home-made mix with a layer of sterile potting soil.

Compost is an excellent soil amendment. Apply it directly to beds and borders. Fork it in or leave it on the soil surface as a mulch. This valuable organic matter will work gradually to improve your soil’s nutrient content and overall structure, resulting in healthier plants and better crops for you.

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Show Comments


"I have a question. When I turn a new area for a future garden, most times I start by cutting the existing growth materials (grass, weeds, twigs and sticks) down and laying it out on the surface area of the new garden. With a sharp hoe, I start the daily chopping. At first it is just the cut down vegetation getting chopped up, but by the third and fourth day I notice I am breaking into the top layer of the soil and starting to mix dirt and chopped vegetation together. After the first week of working with the hoe daily I back off to two or three times during the second week, and then just once a week through the winter months (taking advantage of the nightly freeze heaves of the worked soil). My question is; Am I being lazy by not taking up this material and putting it into the compost bin (which I do have an active bin) or am I actually helping the new garden space get prepared faster? I just started a new 20X30 foot area today with this method and just got curious after watching and reading your video and writing on composting."
Steven on Sunday 14 August 2016
"Hi Steven. I'd say your method would work just fine. Ultimately all the plant matter will be incorporated into the soil, helping to improve it in the same way as applying compost to the soil would. The frosts of winter will certainly help to break it all down. Your method is a very valid one."
Ben Vanheems on Monday 15 August 2016
"Hi there, I have two rotating compost bins, (which I love-easy to turn and not rats) plus I have a worm farm. I noticed recently that my worm farms has thousands of little white worms along with my thousands of compost worms. What are they and should I get rid of them? Judy"
Judy Lawrence on Monday 12 September 2016
"Hi Judy, I just found them in my bin yesterday as well! At first I was concerned that they were maggots but I do not put any animal products in my bin. After a little research I realized that they were black soldier fly larvae and they are VERY beneficial. They break down your compost better than red worms so leave them!!"
Lori on Tuesday 13 September 2016
"I have a White root growing in my compost bin, it is very rubbery and sticks to tea bags and leaves, everything in the compost bin is great compost. What is this root. I am careful what I put in the compost bin, no perennial weeds."
Marion on Saturday 28 October 2017
"Most helpful video and information to solve all of my composting issues. Thanks. "
Natalie O on Sunday 29 October 2017
"Thanks Natatlie. :-) Marion - It's hard to say what the rubbery root might be. It could be a couch grass or bind weed root. Even the slightest fragment that's made it into the compost bin can quickly establish. I would advise digging out the root and remaining hyper-vigilant for it's reoccurrence. You might consider covering over the compost bin to make sure every last scrap of light is excluded. This way any roots that re-grow will quickly run out of energy as they won't be able to produce any viable leaves to power the plant. "
Ben Vanheems on Monday 30 October 2017
"hi I used the compost I made last year in one of my raised beds where I grow vegetables and I noticed a lot of slug damage compared to the bed without home made compost. I realise slugs are part of the "demolition" process in making compost but I could do without the demolition of my veggies. Any solutions? I tried nematodes but didnt make any difference "
annette wass on Friday 1 December 2017
"I have browm, maggot-like worms in my compost. I do not put any animal-based material. There are hundreds of them. Today they were covering corn cobs. How can I get rid of them? I have composted for 20 years and have never seen this."
Louise Marcella on Tuesday 4 September 2018
"The maggots may be helping the composting process, not hindering it. A quick internet search reveals other gardeners have experienced similar maggot infestations - e.g. one gardener whose heap become overrun with black soldier fly maggots. It sounds like your heap could have similar inhabitants. Perhaps wait and see whether the maggots hatch and become a nuisance? If they don't 'swarm' or become an issue, then there's little point removing them as they'll only be helping to break down those compost ingredients even quicker."
Ben Vanheems on Monday 10 September 2018
"hi, I am just a starter to gardening and wanted to try composting at home. Used a plastic open tub and went on adding fresh veg peels, dried flowers, etc along with layer of mud. Had kept it open and drainage holes weren't big enough and by having surprise rains the compost pile has become too wet and cloggy and is smelling bad. So confused what to do now !! Should i dry them in sun for few days and then put them back in plastic tub with bigger holes ? should i then close it with a lid or should i leave it open in a sheltered area ? Pl help me guide in detail to get rid of this problem ! Many thanks, Anu"
Anu on Saturday 6 October 2018
"hi, I am just a starter to gardening and wanted to try composting at home. Used a plastic open tub and went on adding fresh veg peels, dried flowers, etc along with layer of mud. Had kept it open and drainage holes weren't big enough and by having surprise rains the compost pile has become too wet and cloggy and is smelling bad. So confused what to do now !! Should i dry them in sun for few days and then put them back in plastic tub with bigger holes ? should i then close it with a lid or should i leave it open in a sheltered area ? Pl help me guide in detail to get rid of this problem ! Many thanks, Anu"
Anu on Saturday 6 October 2018
"Hi Anu. You're generally better off composting in a compost bin/container without a bottom to it. This way the worms can get in and the water can get out. In fact, a container isn't even necessary - you can have good success simply piling your compost ingredients up in a heap, though a container with sides does help to keep things neater and offer some protection from extreme cold. I would dig out your sodden ingredients and leave them to drain (no need to dry out entirely) and then re-stack. If you are able to find a tub without a base to it that would be ideal - or cut it out from the tub you have. Compost heaps are always best laid directly onto the ground."
Ben Vanheems on Monday 8 October 2018
"Hi Ben Vanheems, many thanks for your guidance !! Shall follow accordingly :-)"
Anu on Monday 8 October 2018
"No problem. Just come back with any other questions should you encounter further problems."
Ben Vanheems on Monday 8 October 2018
"Thanks for this article and the suggestion about sieving finished compost into a container. My question: What about the non-beneficial worms and insects in the compost? For example I have lots of June bug grubs and earwigs, among other things. I don't want them going into the planting area with the compost. The big grubs are reasonably easy to pick out but not the smaller ones. I have tried laying out the finished compost on a tarp on the ground and letting it dry out before storing or using but it's not an ideal method. Can you suggest something better? Many thanks!"
Robyn on Saturday 17 November 2018
"i have store bought compost tha i mixed in with the soil., now my plants leaves are turning white , Do you have a cure to stop leaves dieing off, "
braith on Thursday 3 January 2019
"The white could be any number of things, but is probably some sort of mould. It can quickly take hold. It's best to always start with fresh, clean compost. It is likely that the mould may have been in the soil. Or if the plants are very young and the compost/soil is kept very damp, then this can sometimes promote the perfect conditions for moulds."
Ben Vanheems on Friday 4 January 2019
"hi i have a question about seeds from weeds and other plants please. If i put weeds with seed heads in my compost tumbler, will the seeds die or will they pop up where ever i put my compost? Thanks for all the info, great ideas and wonderful help and support : )"
melanie on Monday 7 January 2019
"To kill seeds of any plants you need a very hot composting process. In a compost tumbler my concern is it wouldn't get hot enough. It's therefore best to make sure you exclude weed seedheads from your compost, to avoid any complication from seedlings popping up in the finished product."
Ben Vanheems on Monday 7 January 2019
"Hi Ben Vanheems! A composting problem: our compost heap has just attracted a colony of black ants. The bin is made of plastic, and the ants have built a column-like structure up the inside of the bin, extending around the rim. The texture of the 'nest' is like wet coffee grounds. Are the ants beneficial or do I need to take action against them? Generally, the compost is too slimy, so I'll try adding saw-dust as you have recommended."
Robin Charleston on Monday 6 May 2019
"Ants aren't bad for the composting process because they will be helping to aerate it and introduce fertility into the heap. However, if there are lots and lots of them - i.e. the heap is completely overrun with ants - then this isn't ideal. To deter the ants, completely dig out your compost heap, turn it and re-fill the bin. Also make sure that any fresh kitchen scraps you add from now on are turned into the top layer of compost, so that ants aren't attracted. Turning the top of the pile every few weeks will also help to deter ants."
Ben Vanheems on Tuesday 7 May 2019

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