For:
By: Daniel E. Mullins
Extension Horticulture Agent
Choosing the Right Potting Medium
Not all packaged potting media is the same. There are some excellent potting mixtures on the market, as well as some that are so unacceptable that plants suffer regardless of the care given after potting. Put as much thought into choosing a good potting mix as you would in choosing the right plant, container and fertilizer. It’s that important.
A good potting mix is one that has the right texture. It has a good balance of large and small pore spaces. The large spaces are for allowing air to reach the roots. The small spaces are for retaining moisture.
A
high quality product is therefore made by mixing just the right amounts of both
coarse and fine materials. One of the
first artificial or soilless potting mixtures is known as the “peat-lite
mix”. If memory serves, it was developed
by
Since the introduction of the peat-lite mix, numerous similar products have been developed. Several potting mixtures are now available that are based upon combinations of these and other coarse and fine materials. Some that are on the market contain peat moss, pine bark, perlite and vermiculite in various combinations.
These mixtures contain no soil, so amendments are added. The high quality mixtures have had the pH adjusted to an acceptable range by incorporating lime. Many also come with enough nutrients to start new plants, while some even contain minor elements.
Good potting mixtures are not cheap, so choose carefully. You can eliminate some by checking the weight. If the material is fine like soil and is extremely heavy, it is probably a poor choice for growing containerized plants.
Note that soil was not mentioned in the making of a good potting mixture. The use of soil in a plant container defeats the purpose of using an artificial medium. In general, soil does not perform in a pot the same way that it does outside of a pot. Moisture is extremely difficult to control if soil is used. It is also very heavy.
Another of the major reasons for using an artificial mix is because it is relatively clean and free of disease organisms, weed seeds and nematodes. If soil or “yard dirt” is placed in a pot, these organisms are frequently introduced, and they can reproduce quickly under container growing conditions.
Question of the Week: Can I make my own medium for growing grapes in containers?
Answer: With reservations, this gardener was sent a recipe for a home made potting mixture. I hope that I was successful in persuading him to purchase a good packaged product. Considering the effort that it would take to locate, purchase and mix the half dozen ingredients required, it would have been less expensive to simply buy a prepared product.
Some
nurseries no longer bother to mix their own potting media, preferring to order
it in bags or custom mixed in bulk. If
the professionals are finding it cost effective to purchase a premixed growing
medium, then it is obvious that most gardeners would be better off doing the
same.