Loading... Please wait...

Top Dressing – Mulch & Mulching

Posted by

Walking your dog in a nearby forest or park in winter is quite a unique experience, with the array of autumnal colours and the trees bare and naked. Stepping on old leaves along your path, you are unknowingly helping nature with the composting of its own unique top dressing or mulch.

Natures own top dressing/mulch

What exactly is a top dressing? An elegant suave Waldorf dressing or maybe some other kind of salad liquid garnishing comes to mind. Although we may be growing the salad with our beds of tomatoes and lettuce, top dressing has nothing to do with sprucing up salads. It’s more to do with sprucing up your garden or pot plants. Whether gardening indoors or outdoors, but it’s more to do with maintenance and giving yours plant a great natural enhancement.

This article explores a number of top soil dressings, some conventional and some nutrient rich and why they should be used. Now top dressing or mulch has been around in agriculture since man's early farming days. But to most gardeners a top dressing in gardening terms usually means a covering of fertiliser spread on soil without it being ploughed under. This is indeed true but not all top dressings need nutrients in it, as some top dressings may be just for light blockage for plant roots or for simple water retention. Some of the top dressings and mulches could also include organic fertilising components and excellent nutritional additives. The more organic the mulch/ dressing, the more it will benefit your soil. Please see previous article Re: Feeding your soil not your plants.

A top dressing is also used to control thatch, to protect from extreme temperatures and amend the soil medium around the roots. Whereas Thatch may not be of a concern for indoor gardeners it certainly is for outdoor gardeners. So if enhancement of the soil is the goal, it is best to aerate prior to spreading a top dressing. In fact some gardeners go as far as to cover their planting area. Whether it is a pot or garden with a plastic covering or plastic domes for pots the idea is to keep temperatures warm in winter and cooler and moister in summer.

Classic pot top dressing/mulch

Top dressings or mulches with mixtures of sand and various organic amendments, such as peat, have been used extensively in premiership football stadium pitches. The golf industry has used top dressings for their greens and fairways for some time and more recently it has been commonly used for other turf areas including cricket fields, gardens and lawns.

Ultimately the goal of a top dressing, especially when growing indoors is protection. Additionally it will still aid our soil and our plant/s with extra minerals, micro nutrients and beneficial bacteria, it also helps as a shield. But bear in mind that every dressing has its own purpose, so choose one according to your actual needs. Needless to say a vibrant plant will probably just need added protection opposed to extra nutrition etc. Here is a list of some top dressing/mulches to consider:

Worm Humus is a great top dressing if your time is limited. Worm humus is the excrement of worms and this nourishes your soil very well.Humus is high in nutritional values too but it does dispense into your soil fairly rapidly. This means you may have to reapply every few weeks or when needed due to the quick usage. Worm humus is also known as worm castings. Worm humus as a dressing is recommended for both indoor and outdoor gardening.

Resembles compost but humus is black gold in the garden

Wood Chips/Bark is another top dressing but it is a more subtle dressing and aimed more at aeration and water retention rather than just nutrition. This type of dressing is more of a sunlight and heat protector for your soil and roots and also keeps everything moist. A great dressing if you’re medium is drying out far too quickly due to excessive heat. Also the added moisture retained in the bark adds to your humidity too. You must ensure that your wood chips and bark are not treated with any harmful chemicals that will destroy your plants, so please read the label carefully. Wood chips opposed to wood bark and sawdust is preferably the best choice as wood chips retain more moisture effortlessly. Something important consider in regards to wood chip mulches has to do with the subject of allelopathy. Allelopathy is when the growth of one plant is affected by chemicals produced by another plant growing nearby. These are the types of wood to avoid if using outdoor:

1. Eucalyptus

2. Several types of pine, juniper, and cedar trees

3. Walnuts/shells

4. Tree of Heaven (also known as ‘ghetto palm’ or ‘stink tree’)

5. Sage brush

Wood chips/bark is recommended for both indoor and outdoor gardening.

Sand/White sand is a great top dressing if you have any gnat issues as the sand acts as a barrier and does not allow the larvae to get any oxygen. This causes them to suffocate and die. White sand in particular, acts as a reflector and helps your plants undergrowth to produce better. The down side of sand; is unless you’re using cloth pots it will also limit the amount of oxygen your roots receive, so if you do apply this top dressing please bear this in mind.We strongly reccomend this type of dressing if your indoor garden is infested with gnats.  Please see previous article Re: Gnats.

Sand/White sand is recommended for indoor use for gardens with gnat problems.

Straw/Hay is a cheap and inexpensive way of simply covering the soil mass at the base of your plants stems. Hay insulates your soil and keeps temperatures from jumping up or down depending on the time of year. The downside when used outdoor is the fact that wildlife especially rodents will use hay as a means of shelter and they will eventually eat away at your harvest. Indoor gardens can you use straw/hay without the worry of little critters. Unfortunatelythe straw/hay may carry in unwanted fungal spores or even weed seeds or insects. Due to this straw/hay is probably the least preferred top dressing/mulch. Straw/Hay is recommended for outdoor gardening although can be used with indoor gardening but is difficult to manage as you may be bringing in unwanted pathogens.

Used for garden pathways too

Spent Mushroom Mulch/Compost is a favourite top dressing amongst avid gardeners and the benefits are huge. The mulch you use MUST be SPENT, meaning used. Spent mushroom mulch is laden with mycorrhizae and many other natural nutrient benefits such as N,P,K, Sulphur, and also Ca, Mg, Na, Fe, Mn, Cu and Zn. Spent mushroom mulch/compost is an organic nutrient source and soil improver, especially on soils with low organic matter. Once you see the results with this top dressing it will be difficult to to find better. Mushroom compost often contains chalk and is alkaline in nature. Use it in the vegetable and ornamental garden because of its alkaline nature. Avoid using mushroom compost around ericaceous (acid-loving) plants. Spent mushroom mulch/compost is excellent in both indoor and outdoor gardening.

Spent mushroom mulch is amazing indoor or outdoor

Compost is probably the most commonly used top dressing. Perhaps the primary and most often recognised benefit from using compost as a top dressing is the provision of nutrients. Composts will contain a range of both macronutrients (e.g., Nitrogen, Phosphorus, and Potassium, etc) and micronutrients (e.g., Manganese, Boron, Zinc, and Copper, etc) largely in an organic form.As the nutrients in the composts are in organic form, they are released slowly over longer period. The drawback with compost as a mulch is that it will need replenishing especially if you need thatching, or you could simply use hotter compost that will kill off any potential weeds. Top dressing with compost is generally the preferred dressing for mostly outdoor gardeners.

Compost is a common garden dressing/mulch

Newspaper Mache is an inexpensive way of giving your garden a top dressing and mulch. It is an excellent landscape contour coverer as when slightly moistened the paper becomes skin like on the surface that you’re covering. It can look quite ugly having newspapers all over your garden, but you could coincide another dressing to cover the newspaper with wood chips or even some compost mulch. Stick to using only black and white newspapers opposed to coloured newspaper as the ink dyes may be hazardous to your garden. The black carbon ink is biodegradable whereas the coloured inks have many unwanted additives such as sulphur. Newspaper Mache is excellent for both indoor and outdoor gardens.

A very cost effective mulch

Pumice rock – Pebbles – Clay pebbles - Gravel - Rocks - Perlite can be used as a top dressing too. Pumice is a very lightweight, porous rock that comes from volcanic eruptions. It is often used as mulch in flower beds. It has the ability to trap and retain moisture, because it’s so porous, which none of the other rock mulches are able to do. Clay pebbles can relatively do the same job as pumice rock unlike general pebbles or rocks as they cannot retain water but do provide shade and some defence against the elements. Gravel and pebble mulch can also absorb some heat from the sun during the day, and give it off at night, creating a mini micro-climate which is ideal.

Ideal for thatching and insulating

Ten Top Benefits of a Top Dressing/Mulch:

So to recap a top dressing is primarily practiced as a means to improving turf quality. Specific benefits that have been found to include the following:

1. Providing more nutrients

2. Increasing organic matter and organic life

3. Improving soil structure: soil life web

4. Reducing irrigation, saving on water bills

5. Reducing nutrient losses to surface and ground water

6. Improving surface irregularities

7. Adding beneficial microbes and bacteria

8. Reducing cold damage and in some cases heat damage

9. Reducing weeds and stopping them from stealing any nutrients

10. Reducing thatch material allowing your soil to breath


  • 1.Spent Mushroom Mulch
  • 2.Wood Chips
  • 3.White Sand
  • 4.Pumice/Perlite/Clay Pebbles
  • 5.Compost
  • 6.Worm Humus

These Top dressings are not in any specific order but are our favourites that have been tried and tested for indoor gardening.

So remember a top dressing is the process of adding a thin layer of material over the surface of your soil in your garden or pot. A variety of materials can be used in a topdressing program including sand, soil, and compost, as well as mixtures of sand and composts together. Adding materials in very thin layers over the surface of turf makes it possible to add organic amendments and gradually change the soil without disturbing the actively growing plants not forgetting your active soil too.

If you have any further questions please pop into the shop or give us a call on 0203 609 4067