Container Gardening Complete

Job:06-700309 Title: CPS - Container Gardening Complete

700309 - ContainerGardens_001-272_FINAL.indd 48 5/24/17 10:58 AM
Job:06-700309 Title: CPS - Container Gardening Complete
Job:06-700309 Title: CPS - Container Gardening Complete

700309 - ContainerGardens_001-272_FINAL.indd 49 5/24/17 10:58 AM

48 chapter 1

minerals, animal byproducts, plant materials,

or manures—not synthetic chemical fertilizer.

Natural fertilizers provide a long-term, stable

and eco-friendly source of nutrients for your

containerized plants. Check the ingredient list for

items such as alfalfa meal, blood meal, bone meal,

cottonseed meal, crab meal, feather meal, fish

meal, greensand, kelp meal, dehydrated manures,

and rock phosphate, among others. Synthetic

fertilizers present in potting soils may or may

not be included on the bag’s ingredient list, but

they’ll often be announced on the front of the bag

by phrases such as “feeds plants for 6 months” or

“includes slow-release fertilizer.”

Composted pine bark. Composted pine bark

lightens up potting mixes by increasing the size

of the pores between the particles, allowing air

and water to travel freely in the mix. It’s slow

to break down but may rob nitrogen from the

soil as it does, so the addition of a small amount

of nitrogen fertilizer is necessary when using

composted pine bark as an ingredient. Composted

pine bark is most commonly found in potting

mixes designed for potted perennials and shrubs.

Compost. Containing billions of beneficial

microbes, and with superior water-holding

capacity and nutrient content, compost is an

The primary ingredient in most commercial potting

soils is sphagnum peat moss, a well-draining and

well-aerated material that’s harvested from bogs.

Perlite is a mined, volcanic glass that’s heated until it

expands. Its lightweight nature improves the drainage

of potting mixes.

Vermiculite. Vermiculite is a mined mineral

that is conditioned by heating until it expands

into light particles. It’s used to increase the

porosity of potting soil mixes, but it can also be

found in everything from acoustic tiles and brake

linings to insulation and plaster. In potting soil,

vermiculite also adds calcium and magnesium,

and increases the mix’s water-holding capacity.

Although asbestos contamination was once

a concern with vermiculite, mines are now

regulated and regularly tested.

Sand. Coarse sand improves drainage and adds

weight to potting mixes. Mixes formulated for

cacti and other succulents tend to have a higher

percentage of coarse sand in their composition to

ensure ample drainage.

Limestone. Pulverized calcitic or dolomitic

limestone is often added to peat-based potting

mixes to neutralize their pH. These minerals

are mined from natural deposits and are readily

available and inexpensive.

Fertilizers. Additional nutrient sources are

often added to peat-based potting soils, as

they don’t naturally contain enough nutrients

to support optimum plant growth. Ideally, the

potting mix you select should contain a natural

fertilizer derived from a combination of mined

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Getting Started 49

excellent addition to potting mixes, though it isn’t

found in very many commercial brands. Because

it plays such a huge role in promoting healthy

plant growth, I suggest mixing it with potting

soil to create the ideal mixture for container

gardening (more on this in the next section).

When selecting a particular brand of potting

soil for your container garden, don’t be afraid to

ask the garden center if you can open a bag and

check it out. Good-quality potting soil should be

light and fluffy, with a well-blended mixture of

ingredients. It should not shrink significantly or

pull away from the sides of the container when

it’s dried out.

Avoid the following things when choosing a

potting soil for your container garden:

• Do not purchase bags of potting soil if they’re
  very heavy. The mix is likely to be too dense
  for good container performance. Plus, it
  may contain a high percentage of sand or be
  saturated with water.


• Do not use mixes that contain topsoil or
  garden soil. Often poorly draining and not
  sterile, these mixes may contain weed seeds
  or plant pathogens.
  
  
  • Do not use mixes that smell bad. Potting soil
    with excessive amounts of nitrogen may smell
    like urine. Foul-smelling mixes could also be a
    sign of the presence of harmful pathogens or
    it may indicate that the mix is fermenting in
    the bag.
  
  
  • Don’t purchase bags of potting soil that
    contain sprouting seeds, moss, or mold.
    Commercial potting soil should be free of
    such items.
  
  
  
  

After using a particular brand of potting soil,

it’s important to evaluate its performance. At the

end of the growing season, make note of which

brands worked best for you and plan to use them

again next year. It may take a few seasons to find

your favorites, but once you have the chance

to test and evaluate a few different brands, the

differences between them will be clear.

It’s also worth noting that potting soil is not

the same as “garden soil,” “topsoil,” “peat mix,”

“manure soil,” “mushroom manure,” or several

other bagged products you may find at your

garden center. These items are best used as soil

amendments, not as a growing medium to fill

your containers.

Vermiculite increases the water holding capacity

of potting soil. It’s a mined mineral that expands

when heated.

Some potting mixes come with fertilizer already

added. Choose brands with natural fertilizers, rather

than synthetic chemicals, for a more stable and eco-

friendly source of plant nutrients.

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