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SOIL/POTTING MIX

By Wayne Handlos

Many geraniums/Pelargoniums can be grown outdoors in the garden. The scented types

of Pelargonium do particularly well in the Mediterranean climate areas of California. These

plants are tough and can be very long-lived. A little supplemental water in summer will

keep them happy. However, the newer cultivars of any of the commercially available plants

are not usually so tough and require some pampering. In the ground most will require a

steady supply of water. In many parts of the United States, rainfall will keep the soil reason

-able moist but in dry areas supplemental water is needed. If dense and clay-rich, the soil

might benefit from the addition of organic matter. Home-made compost can be worked into

the native soil. The organic matter holds water and nutrients and slowly releases these to

the plants.

In these days of small plots of land around the home and/or apartment and condo-living,

plants are more conveniently grown in pots. Here is my recipe for a potting mix. (All

nurseries and garden centers sell potting mixes usually in a variety of types with a variety

of prices. Most of these mixes have a minimal amount of nutrients in them so fertilizers of

some type must be added to keep your plants growing.) Mix the following ingredients

thoroughly in a wheel barrow.

Potting mix A 1 cu.ft.

Potting mix B 1 cu.ft.

Coir 2 x 6 " pots full

Perlite 2 x 6 " pots full

Azomite cup

Milorganite 1 cup

Osmocote (pelleted slow release fertilizer) cup

Cotton seed meal 1 cup

Vermicompost 1 cup

Commercial organic fertilizer with mycorrhizal components 1 cup

The first four ingredients of this combination provides a porous well-drained potting mix with reason

-able water holding capacity. I use two different commercial potting mixes (usually the least expensive

ones I can find) because none of them is fully suitable so this evens out the differences between them.

SuperSoil is commonly found. Less common is a Red Star mix. In the west, decomposed "forest

products" form the base of the mix but in the eastern and Midwest of the United States, peat moss

probably forms the base material. The coir is coconut hull "stuff" and the Black Gold Just Coir brand

is of the right texture and resembles peat moss. Baled coir I have found does not "fluff up" to the extent

claimed and seems very fibrous to me. Perlite and vermiculite are frequently recommended as interchange

-able but they are very different products. Perlite provides the drainage properties required and holds

water as well. I have not found any use for vermiculite and as an expanded mica product it quickly

compacts to its original form is then useless as a soil lightener and water reservoir.

Nutrients are provided by the remaining components. Azomite is volcanic ash that was deposited in an

ancient seabed in Utah and it now mined as a soil additive to provide trace elements to soil or potting

mixes. Milorganite and Osmocote are slow release fertilizers which will not burn the roots of your plants.

Milorganite is Milwaukee sewage sludge and is used extensively on golf courses. Osmocote and similar

fertilizers are effective for a few months. The cottonseed meal is a slowly decomposing substance which

provides nutrients over the long term (a year or more).

The vermicompost and organic fertilizer plus mycorrhizal components provide many living organisms for

 the dynamic interactions between the plant and the "soil". In human terms, think "probiotics". Soil is a living,

dynamic ecosystem and, when all parts are functioning well, will provide your plants with nutrients and water.

The probiotics may enhance the absorption of nutrients and water from the soil, release organic compounds

to protect your plants from various disease organisms and provides a degree of resistance to plant pests,

in particular whiteflies. The "probiotics" include various bacteria, ectomycorrhizae (which work outside the

roots) and endomycorrhizae (which penetrate the roots of the plants).

                         

                               ^  Endomycorrhizae ^           ^ Ectomycorrhizae ^

While I am not a fanatical organic gardener most of the ingredients above are natural products (Osmocote

excepted) and, I believe, are healthier for our environment and planet than artificially produced substances.

This mix recycles well in the vegetable or flower garden and remains loose and friable even after years in

a pot or planter.

 




 

 

2017, Central Coast Geranium Society (CCGS )