How To Add Compost To Existing Plants

Digging up planted growths and setting them aside in pots temporarily for adding compost to the entire garden is a pretty common practice. This is absolutely frustrating and unnecessary! Spare yourself the extra labor and read along to find out more on how to add compost to your already existing plants.

Adding compost

As you might already know, adding compost to a new garden bed involves spreading a 2 to 3-inch layer of it across the area followed by mixing some more with a few inches of the top soil. But, clearly this won't be possible in case of an already established bed. Below we have shared some techniques and suggestions that you can follow when adding compost to existing plants.

adding compost to existing plants

1) As a top layer

For garden beds with perennials, shrubs or bulbs, digging at the roots can be a problem. For that, you can spread the compost in a uniform layer of 2 to 4 inches around the plant, leaving about a gap of 12 inches between the stems / trunks and the compost. Leaving a foot gap is vital to avoid any unwanted attack by the active microorganisms on the compost. Then rake the soil where you just added the compost - it enables aeration and causes the nutrients to leach in quicker. Finish up by watering the bed.

For potted plants, simply take a handful of compost (more if required) add spread it on top of the soil. Using any suitable tool, gently mix the compost with a few upper inches of the soil.

For grass beds, it's even simpler. Spread around a 2 to 3-inch layer of compost and rake it, followed by watering. Continue raking every day until all of the compost is no longer visible. The more frequently you rake, the quicker the compost will move underground.

2) At the roots

Dig up the soil around the plant very carefully; avoid causing any damage to the roots. Once the roots are visible, spread the compost evenly around them. Mix some more compost with the soil you removed previously and put the soil-compost mixture back to into the pot. This can be done in case of both potted plants and garden beds.

3) As Compost tea

Make a tea bag out of an old pillowcase or any other thin cloth and fill it up with compost. Brew it in a bucket of water for 2 to 3 days, shake it a couple of times in between. The water will darken over time as the nutrients leach out into it. You can use this tea by pouring in appropriate amounts of it or spray it around using a spray bottle. This method too is applicable for any type of setting.

how much compost do i need?

A general rule of thumb suggests 0.25 to 0.5 inch of compost is enough as a top soil layer and 1 to 2 inches as a soil amendment. For vegetable or flower gardens, or to use as fall cover crop, 1 to 3 inches will suffice.

To get a volumetric estimate, a 100 square feet of garden bed needs around 0.7 cubic yards (0.45 m³) of compost. This results in a 2-inch thick layer. Use the following formula to find out exactly how much you need: garden area (square feet) X compost layer height (inches) x 0.0031 = cubic yards of compost.

when should i add compost to existing plants?

The soil itself decides on the time to add compost. Generally, applying once before planting season is enough, but it varies based on geographical locations.

In regions with a colder climate and one growing season, compost can be added only once a year, preferably in spring. For regions with a warmer climate and where plants can grow year-round, the frequency is double - during spring and fall.

That being said, it is best to apply compost in late August or early September for the winter seasons. As for the warm seasons, when planting usually starts from late February and runs through March, add compost before the planting season begins in your area. 

Alternatively, during intense seasons when your garden lies bare, cover up the fallow soil with compost to maintain moisture, abate erosion and weed growth.


Keep these three things in mind before adding compost:

  • Make sure the compost is fully decomposed before using.
  • Uproot and remove all weeds, which will otherwise compete for the nutrients and growth.
  • For a limited amount of compost, apply it in planting holes or around the roots of plants instead of spreading it around the whole garden.

Enhancing the health of your soil without agitating any plant can be tricky for sure, but not impossible. With some extra patience and care, you can certainly add compost to existing plants and overcome any issue your garden might be facing.

If you are using raised garden beds, here are some tips to improve drainage in them. 

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