The Plant Lady: It’s time to work on soil. Here’s how to get the best for your plants

When prepping your garden beds it can be a bit confusing and overwhelming deciphering which soil amendments to use. Gone are the days of just compost and chicken manure as choices. With companies competing for gardener’s business, they are getting tricky with marketing and mixtures. Here I will help break it down for you.

Compost and Humus

Compost and humus are organic material (leaves, wood debris) that has broken down. The terms can be used interchangeably. Compost can be used at varying degrees of decomposition. Technically, humus is the most broken-down state of compost. Rarely (if ever) will companies add additional nutrients to the bag. Quality compost and humus contain nutrients and microorganisms that will make a healthy garden. Over time, the addition of compost/humus can help restructure the soil particles leading to better drainage and aeration. In addition, both can be used as a mulch around plants.

Top soil

Top soil is often “fill dirt.” Gradients in quality will occur based off of the source rockyard, but for the most part this is soil that you use to fill in an area — and is not desirable to plant directly in. Often it is heavy clay soil with low nutrients and poor draining properties.

50/50

Often found in bulk, each rockyard can have its own recipe for a 50/50 blend, but generally it is a mixture of top soil and compost. These blends can be used to raise soil volume in large garden areas. I would avoid using them for any other purpose unless it is of extremely high quality.

Planting Mix, Soil Conditioner, Garden Soil, Garden Booster

This is where the labeling and choices can get quite confusing. In a sense, if you see a bag labeled with any of these names, they are to be used in the same matter. All these mixtures are meant to be used in existing garden soil to add nutrients and help with soil structure. Each company will have its own blend. However, because of the added nutrients they are often too “strong” to be planted directly into. Some companies may label them for more specific planting — such as “planting mix for vegetables” or “planting mix for roses.” The nutrients vary little and for the most part they can be used interchangeably.

Oftentimes, bat guano, kelp meal, earthworm castings and/or mushroom compost will be added as sources of nutrients. The base is generally fir bark and aged compost. Ingredients can vary, but in general it is meant to give a punch of nutrients to your existing soil. These mixtures can be used instead of compost/humus.

Potting soil

Potting soil is designed to plant directly into, whether in a pot or in a raised bed. In general, these are made up of redwood compost, peat moss, sand and perlite/pumice in varying ratios. Often a nutrient component is added — such as earthworm castings, bat guano or chicken manure. These are added in smaller amounts than in a planting mix, making it safe for plants to go directly into. Some may be more specific based on plants needs. For instance, African violets do better for some people in a peat mixture. Succulents prefer great drainage, so mixtures will contain more pumice/sand.

Potting soil quality varies greatly. Avoid purchasing potting soil that is primarily redwood compost or peat, as these alone can cause poor water retention and drainage. Additionally, if only comprised of compost or peat it will break down quickly – resulting in reduced soil volume. It is possible to buy an inexpensive potting soil and enhance it by adding ingredients such as sand, perlite, pumice etc.

One question I receive a lot is “why is fungus growing on the surface of my potting soil and is it safe to use?” Yes, visible fungus on potting soil is benign — it is actually breaking down the organic matter. Sometimes it can be a sign of overwatering, but in general it is common on high organic mixtures.

Chicken manure/steer manure

These manures are used to add nitrogen back into your garden. There are other ways to incorporate nitrogen — such as alfalfa meal/pellets and cover crops — but this is a quick and relatively inexpensive way. Chicken manure is slightly stronger in nitrogen than steer, so use it sparingly. Both should be mixed well into the soil.

The key to picking the correct amendment is reading the label to see what ingredients are listed and matching those to your garden needs.