Some Culture Notes

If you ask 10 orchid growers about fertilizer, or about media, you will get 12 different answers. Some new growers find all this very confusing. It shouldn't be, though - the phenomenon simply demonstrates that there isn't just one "right answer". Orchids have some basic needs (some of which are different than for other plants), but if one keeps the fundamental objectives in mind, there are usually a variety of ways that those objectives can be met. Since orchids are so diverse, there are exceptions to almost every rule. Learning about those "outliers" is one of the delights of orchid growing. With these thoughts, here are some "Orchids 101" tips.

Water and Air

Most of the common cultivated orchids are epiphytes - they grow on trees or rocks, with roots exposed to the air. However, in their native environments, the humidity is very high. We put them in pots, both to provide sufficient moisture and to make it more convenient for us to accommodate them in our living spaces. When watering an orchid, water it thoroughly, so that water runs through the pot. This process pulls air through the root zone, and also flushes out the salts that would otherwise build up from fertilizer and hard water. Then, let it dry out a bit. The interval between waterings will vary widely depending on temperature and humidity. But even for orchids that need to stay damp (such as Phragmipediums) they should not be so wet that the air is crowded out of the pot. You can't water an orchid too much (so flush it well, don't just "spritz" AND NO ICE CUBES!!), you can water it too often (so let it dry out a bit before watering again, epiphytes such as Cattleyas benefit from going almost dry, others prefer "damp"). Do not let the pot sit in water (orchids hate wet feet). Mounted orchids do need daily watering, since they dry out very quickly - and epiphytic orchids grow very well that way. An automatic sprinkler system is very beneficial for those, so that you can take a vacation without harming your orchids.

Air movement is critical. Outside, the natural afternoon breeze may give them all that they need. But in the house or greenhouse, a fan is important for the orchids to get the needed air movement. This facilitates the wet-dry cycle that orchids crave, and also helps to control insects and fungal diseases.

Fertilizer

This is probably the least important factor in successful orchid-growing. Orchids certainly need some fertilizer, particularly since they typically grow in media that provide essentially no nutrients. Think of fertilizer as "vitamins", rather than "food". Orchids, like all green plants, produce their own food through photosynthesis. Fertilizer provides the additional building blocks for cell growth. Compared to other plants, orchids are light feeders, since they grow slowly. While one can possibly enhance growth or blooming by manipulating the ratio of major nutrients at different times (nitrogen for vegetative growth, potassium for flowering), a good starting point is a balanced fertilizer (all three numbers the same, such as 20-20-20). Use half the recommended strength. "Once weekly, weakly". If you fertilize weekly, every fourth week skip the fertilizer and flush pots well.

Media

The objective is to provide humidly and air. There are many ways of doing that. Probably the most common orchid medium is fir bark. Select the size based on the size of the plant and the roots, the amount of moisture that you want. Therefore, Cattleyas that need to go nearly dry, and which need lots of air to the roots, should be in rather large bark. Cymbidiums (which need to be fairly moist) or small plants with small roots, can go into smaller bark. Coconut husk chips also work well, and all of these benefit from an inorganic amendment such as large (#3 o4 #4) sponge rock (Perlite), pumice, or diatomite, etc. to keep the mix well aerated. Sphaghnum moss is often used by commercial growers, and it works well for some small plants in baskets to provide moisture and air, but it can have some difficulties. It holds lots of water, so that plants don't need to be watered as often; it is very easy to over-water plants in this medium. On the other hand, if it dries out completely, it requires considerable soaking to re-wet, and it tends to hold salts. Whichever medium you use, you will need to learn its properties to maintain the fundamental "air and water" requirement. Organic media, such as bark, break down over time, which can suffocate the roots and lead to rot. Plan to re-pot most orchids at least every two-three years, more often for those that stay more damp.

Many epiphytic orchids grow better mounted or in a basket. If you can sustain the frequent watering that these require, you will be delighted to see the vigorous growth that will occur when you set these plants "free" as they grow in nature.

Pests and Diseases

The better the air movement, the fewer insect problems you will encounter. Vigilance is vital, so that if you do find any, you can deal with it before it becomes severe.

Mealy bugs - These particularly attack Phalaenopsis, damaging leaves and especially flowers. For a small collection, rubbing alcohol on a cotton swab (for one or two) or in a spray bottle, will help control these, and is safe to use in the house.

Scale and aphids - these sucking insects can destroy a plant. Ants are also the enemy - they don't harm the orchids directly, but they "farm" aphids. The least toxic remedy is soapy water. Insecticidal soap is great, but you can accomplish much the same thing with a few drops of dishwashing detergent in a spray bottle with water. Insects breathe through pores in their bodies, so the soapy water drowns them. Neem oil or very light horticultural oil in soapy water have similar action (but be very careful to avoid these in the heat of mid-day)

These "contact" remedies have no residual effect, so they need to be re-applied repeatedly until the infestation is controlled. If these are not sufficient, pyrethrin pesticide sprays, or imadocloprid (Bayer's Advanced©) have fairly low toxicity to people and pets. Follow the directions on the label. These also work for thrips and other sucking pests that you may encounter.

Snails and slugs - metaldehyde works very well. It is toxic to pets, so use with caution. Iron phosphate - based products such as Sluggo© are not toxic to people and pets, and so may be preferable.

Fungal disease (rot) - cut out the rotted tissue with a single-use single-edged razor blade, and dust the cut with sulfur or cinnamon. Physan© may help to control fungal problems.

Virus - PREVENTION IS THE ONLY WAY. These cannot be cured, and if an orchid has a virus, the only "cure" is to discard it - which is heartbreaking. Any time that you must cut any tissue on an orchid, either use a single-use razor blade, or use a sterile clipper. A 20-minute soak in 10% bleach will sterilize the clipper blade, or heating with a propane torch (1200 deg. F) for a few seconds (my preference) is fast and effective. Put newspaper on your potting bench so that each plant gets a clean surface. Wear disposable gloves when potting, so that material from one plant is not transferred to another.

Potting, etc.

It's all about roots. The time for repotting (or mounting) is when the roots are in active growth. With healthy roots, any issues with leaves or flowers are usually a matter of minor adjustments. (If an orchid is not doing well, take it out of the pot and see if the roots are rotted or sparse. With fresh medium, you can often rescue a distressed plant if you don't wait too long. If it is not the ideal time to pot, do it anyway to give the plant a fighting chance.) Don't overpot an orchid. The new pot should accommodate no more than about two year's growth. A too-large pot has lots of wet, airless space that can be devastating to roots. Timing can be critical. Some orchids are growing new roots constantly (example, Phalaenopsis) and so they can be potted at any time. Others, especially in the Cattleya group, have very distinct seasons of active root growth, and resent being disturbed at any other time. The ideal time to pot them is just before the new roots emerge. (If you catch them just after they have started to show themselves, you'll be OK). The need for watching for that new root growth is particularly critical with mounting. New roots will be quick to establish on a mount, and they are the only ones that will do that. Older roots provide nutrition to the plant, but the new ones are most efficient. Blooming, and even appearance of new growth, may or may not indicate the timing of root growth. You'll need to observe your plants carefully to seize that perfect moment. If it has flowers (or buds) and new roots are starting to appear, don't wait. The flowers will probably be fine, but even if not, it's the long-range health of the plant that guarantees the flowers of the future