How to Fertilize Orchids

No subject is more hotly debated among orchid growers than how, when, and if to fertilize these spectacular, unique plants. Despite what some naysayers maintain, orchids need fertilizer in order to thrive, just like almost every other flowering plant. It's true that orchids need less than most other plants—and too much fertilizer can quickly burn an orchid’s sensitive roots—but there is no doubt that well-fed orchids are healthier, hold their leaves longer, and bear more flowers. Thus, it's crucial to know the best way to feed your orchid collection.

When to Fertilize Orchids

This is an old rule of thumb among orchid growers: "Water weekly, weakly." This means that most orchids need a weekly feeding, but with a fertilizer mixture that is more diluted than is normally used for most flowering plants.

You can judge the strength of commercial fertilizer by the concentration of the major nutrients. In general, you'll probably be safe using a standard 20-20-20 fertilizer at 1/4 strength, and a 10-10-10 fertilizer at 1/2 strength. If you are using specialty orchid fertilizers, make sure to follow the label directions precisely.

Unlike most flowering plants, which are most in need of fertilizer during the active flowering period, fertilizing orchids is most critical during the period of vegetative growth that takes place before flower buds appear. Once the plant begins to flower, fertilizer can be withheld until the plant completes its next dormant cycle and is beginning to emerge into its active growth cycle once more.

While vegetative growth is underway, experienced growers sometimes use a "three weeks on, one week off" routine, fertilizing weakly for three weeks, then taking a week off to flush any built-up salts out of the potting mix by simple watering.

Before Getting Started

There are many, many species of orchids comprising several different genera, so it's a mistake to think that all orchids will respond to the same feeding routine. Generally speaking, most orchids alternate active growth periods culminating in flower production, followed by a dormant period. These cycles usually correspond to the wet season-dry season cycle found in their native habitats. These are the orchids that will need to be fed during their active growth seasons, then slightly starved during their dormant periods. But there are a few orchids, such as Maxillaria tenuifolia, which seem to actively grow constantly, and with these, you should feed lightly year-round.

Do a bit of research on the types of orchids you are growing and feed them in a manner that's appropriate to the species—your collection may well have different types with much different feeding needs.

It's increasingly easy to find specialized bloom-boosters that offer slightly different nutrient balances or micronutrients designed to enhance orchid flowering. These are tempting, but unless you're a professional grower, there's little benefit to these products. First, many home orchid collections carry species in multiple genera that flower at different times of the year. Second, different genera have different flowering requirements and different needs for feeding—not all will respond well to so-called "bloom-booster" fertilizer products.

When you get down to basics, a high-quality, well-balanced fertilizer is just as effective at producing blooms as a booster, and it will benefit all your plants, not just the bloomers.