"Do Not Fertilize in Winter" applies to orchids, too

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Does the 'do not fertilize house plants' suggestion also apply to Cattleya orchids? I have always fertilized them "weakly weekly" as the orchid societies suggest. I summer mine outdoors and have lots of flowers forming right now. They do not get extra light, but are in south facing windows.
- C.D. -

 

You are missing four words from that good rule. It goes "Weakly weekly while in active growth." Orchids require a rest period of drier, cooler time and most take it in winter. Then they're "on hold", even if a flower stalk has made its appearance. Fertilizer then does no good so it's a wasted resource and can accumulate to burn and weaken roots. It may also cause long, weak growth in leaves or leaf tip dieback.

However, no one tells Ma Nature these rules. Where orchids grow wild, attached to tree limbs and rocks, they get their nutrients from organic sources such as bird droppings. Perhaps guano decays into soluble form more slowly during the orchids' resting period, since that rest tends to coincide with a dry, cool season. That might keep the nutrient flow in check, but we doubt the birds wait!

 

Orchid grower's formula

Ron Ciesinski of Taylor Orchids in Monroe, Michigan grows thousands of orchids and is just about to quit fertilizing most of them until March. "They don't grow in winter, even under lights. When they start growing again, usually in March, I use a high nitrogen fertilizer. Then once the new leaves are formed I switch to one with lower nitrogen, such as 6-30-30 and keep that up into fall."

 

Orchids are pretty, and fertilizer can help bloom size and color. However, the plants can't use fertilizer in winter when they are dormant, no matter how leafy, and not even if they have initiated flower stalks.