Soil Amendments- How Can They Help Your Garden

If plants are the divas of your garden, soil is the stage crew making sure the show goes on. Despite being the literal foundation of every planting, soil is often overlooked. In Ann Arbor and surrounding, the soil beneath our feet has poor structure (too dense) with a high ph (basic). There are benefits to this clay-rich soil - it retains nutrients and moisture in the ground much better than other types of soil. However, there are also challenges to trying to cultivate a garden in clay soil. One major problem is that clay has poor drainage and struggles to transfer that nutrients it retains into the plants that grow in it - And that’s where soil amendments come in.

Soil amendment ready to be mixed into the garden soil

Your first question might be “Just what is a soil amendment?” A soil amendment is any material mixed and added to existing soil to further optimize the growing medium for plant growth. Typical amendments include organic matter (usually compost), bark/mulch, peat, and sand. Other helpful amendments could include leaf mold, grit (small, angular rock), and sulfur, lime, or fertilizer. Mixing amendments such as these in with the ground soil changes the structure of the soil, and improves plant growth if done correctly.

Amendments can be done incorrectly - the most common mistake is adding find sand to clay. It can make soil even harder (think of concrete - it contains a binder (cement) and aggregates. Clay acts as a binder. Sand is an aggregate. The best way to improve soil structure in clay is to use grit or a very coarse sand together with organic matter. The organic matter is worked into the soil over time by microorganisms, loosening the soil.

One of our team leaders, Jacob White, preparing a garden for soil amending

Atzinger Gardens has a standard soil amendment that blends together composted bine bark, peat, and compost (mostly leaf compost). It also includes slow release fertilizer and mycorrhizae. The mix is customized for certain plants and situations by adding decomposed granite as an acidifying grit and soil acidifier. More or less peat is used based on the need for drainage.

Firstly, the pine bark fines included in the amendment to help with drainage, all while improving moisture retention through the inclusion of peat. Drainage is a remarkably important thing to consider in gardening. Having soil with good drainage means that you are always aware of how much water your plants are getting and puts you in full control- Plus, roots that are constantly soaking can rot and kill the plant. The organic material also helps counteract one of the largest problems with clay soil, and helps it release the nutrients it stores to the plants that grow in it. But the benefits don’t simply end with nullifying some of the issues with clay soil! In the southeast Michigan area, the soil has a high PH. This soil amendment can help tone it down and make it a much more welcoming environment for plant growth by raising the acidity of the ground, which creates better growing conditions for a broad variety of plants. This soil amendment even includes mycorrhizae, which is the underground real ‘body’ of a mushroom (as opposed to the fruiting body that we see above ground.) The presence of this mycorrhizae essentially functions as an extension of the roots of the plants growing in soil, allowing for greater intake of water and nutrients. 

Normally, we apply soil amendment with a shovel, but in small gardens like this we can do so with a soil knife. Here, Jacob White carefully works around a wide variety of freshly-installed small plants.

So now that you know what this soil amendment does, the next question might be, “What kind of plants does this actually help?” This kind of treatment can benefit many types of plants, especially plants that require good drainage, such as rhododendron catawabinse and other big-leaf rhododendrons, azaleas, pieris, and stuartia. In fact, these plants take so well to this soil amendment that we will plant directly into it, without mixing it with the soil already in the ground! We amend soil with this mix before planting new gardens to start off new growth right, and also use it in planting perennials. Even in established beds, it can be used as a mulch. It may not function as well as a weed preventative, but over time it will mix with and amend the soil already present for long-lasting positive effect. 

Nature, and by extension, gardening, is one of the most complex and intricate things to study and learn about. Every component of gardening has its effect on the outcome, from the fertilizer to the sunlight to the very soil the plants grow in. Learning to control the conditions of the soil to help your plants grow strong and healthy can make a major impact on the health of your garden. Atzinger Gardens always takes soil and its qualities into account when working with clients. Our soil amendment is made of Gardener’s Delight potting soil, with added fertilizers based on the plants and situation, as well as peat, compost, pine bark fines, and slow-release fertilizers and mycorrhizae. If you are interested in our soil amendment services, feel free to reach out to us!