How-To soil preparation

Topdressing Trees and Shrubs with Compost

Hillary is communications director for Super-Sod. She earned her BS in Horticulture from UGA and has spent the last 30 years marketing plants and gardening products. She used to be a tree snob, but after walking barefoot on a Zoysia lawn, is now a Zoysiagrass snob. When not picnicking on her own Zeon Zoysia lawn, growing vegetables, identifying roadside weeds, or planting hydrangeas and Japanese maples, she spends her time pursuing the domestic arts of knitting, cooking, canning, making things like beeswax candles, and throwing dinner parties. Her great love is helping customers learn how to take care of their lawns, garden better, and enjoy the journey.

April 13, 2018 3 minute read

Topdressing trees and shrubs with compost is an enriching activity for you and your plants. I like topdressing for the productive exercise while my trees and shrubs are enriched with natural nutrition and soil improvement.

It’s particularly beneficial to topdress all newly planted trees and shrubs in your landscape with Soil³ compost, continuing this practice for several years as they establish. This regular nourishment helps to accelerate their growth and improves the soil structure, gradually building a rich, dark layer of organic matter while supplying and attracting beneficial microorganisms.

For certain shrubs that particularly thrive in enriched soils—such as roses, blueberries, figs, clematis, and hydrangeas—annual applications of compost are advisable to maintain their lush, vigorous growth.

To clarify, we are not talking about planting trees and shrub in this article, only topdressing them. Planting is a different process that does involve topdressing towards the end. In short, when plating a tree/shrub: backfill with your native soil, don't plant them deeply, topdress with compost, then water, water, water. You can read the long-winded version here: The Truth About How to Plant a Tree

Why Should you Topdress Trees & Shrubs with Compost?

It's recommended to topdress trees and shrubs to introduce essential nutrients and enhance soil quality. The nutrient-rich composition of our compost not only feeds your tree from above but also facilitates the downward movement of these benefits as it integrates with the soil.

This integration is aided by beneficial organisms and microorganisms present in compost, which work to improve soil structure, aeration, and overall fertility. Examples of these organisms are earthworms, fungi, mycorrhizae, and protozoa.

These organisms, along water and the roots themselves, help incorporate the compost deeper into the soil, enriching it further and creating an optimal environment for root growth.

When to Topdress Trees & Shrubs with Compost

My favorite time to spread compost around my woody plants is during winter, when they are dormant and I can get around the base of the shrub a little better without the leaves on them. However, it can be done any time of year.

I get BigYellowBags of compost especially for the purpose of topdressing my trees and shrubs, but topdressing is also a good use for that last little bit in the BigYellowBag that you want to use up so you can order more.

What to Use for Topdressing Trees & Shrubs

When selecting the appropriate Soil³ product for topdressing, we recommend the straight compost version rather than Veggie Mix, which contains 25% bark because it is formulated for improving drainage when building in-ground beds, raised beds, or for filling containers.

The straight compost provides a more concentrated nutrient profile for topdressing trees and shrubs, ensuring they receive the full benefits without the slight dilution effects of some bark.

How to Topdress Trees & Shrubs with Compost

Order Compost: Order Soil³ humus compost for pickup or delivery.
Spread Compost: Spread 2-3 inches of compost underneath your trees and shrubs. However, be careful to avoid the roots at the base of the plant (buttress roots). This is one of the places that a tree exchanges gas (such as carbon dioxide and oxygen) and you do not want to smother it! Extend the compost around the width of the tree or shrub to reach the diameter of the canopy of the plant.
Mulch over Compost: Compost is not mulch, it is nutrition. Top off with a layer of mulch to conserve moisture and suppress weeds. Spread mulch to a depth 2-4 inches, but keep it 2" away from the trunks of trees and shrubs. Mulch is a cover for insects that protects them while they attack your tree, so if you leave the 2" mulch gap, insects are less likely to damage your tree. Another reason to keep mulch from touching a tree is to prevent the root flare (talked about above) from being smothered - for this reason we advise you to not put a mulch volcano around your tree!

While these blueberries are a couple years old, compost added on the surface will still help them in the compacted clay soil. In the back you can see where mulch was applied on top of the compost.

topdressing-trees-and-shrubs-Soil3-compost2

Amount of Compost for Topdressing

1-gallon tree or shrub: Use 1/2 a Mini Cube or 3 shovelfuls of Soil³ compost

3-gallon tree or shrub: Use 1 Mini Cube or 6 shovelfuls of Soil³ compost

Larger or matured trees and shrubs: Start with 1 or more Mini Cubes or 6 or more shovelfuls of Soil³ compost. I fill up a wheelbarrow and dump half on one shrub and half on another. You'll get the hang of it and learn to gauge a suitable amount.

topdressing-trees-and-shrubs-Soil3-compost3

Now that you're armed with all this knowledge, it's time to order your BigYellowBags of organic humus compost for topdressing your trees and shrubs. Find your nearest Soil³ dealer by clicking below.

Have we missed an important step or could have explained something better? General questions? Let us know. If you have a question, that means other do too. They may be too shy to ask. Be the bold one.

Pictures by Nina Johnson and Hillary Thompson.

Topdressing Trees and Shrubs Compost