Zygopetalum (zye-go-pet-a-lum) Culture

The Zygopetalum originates from the mid to high elevations of Central and South America. It is a relatively small genus made up of roughly 20 or so species, with the most popular being Zygopetalum mackayi.

Commonly called Zygo, these plants produce unusually colored flowers consisting of green, brown, white and purple. Along with their oddly colored flowers these plants are also noted for their incredible fragrance which resembles that of a strong Hyacinth aroma. Their blooming longevity will range from 1 to 3 months if kept out of direct sun during their flowering stage. When the flowers have expired simply remove the stem from the point where it had emerged from the plant.

To ensure good growth and profuse flowering, the Zygopetalum requires bright light year-round. While growing indoors, a bright east or west exposure that receives some direct sun is recommended, or a south exposure where the plant is receiving only a few hours of direct sunlight daily.

Zygopetalum does best when grown outdoors here in Wisconsin during the months of June through October. Hang them from a tree or the overhang of your house, or place in a screened porch where they can receive some dappled sunlight. Zygopetalum can benefit from higher intensities of light as the day length decreases towards fall and into winter, and vice-versa for the spring and summer. Try to provide as much light as possible for your plant throughout the year without causing sun burn on the leaves. Once your Zygopetalum is in the flowering stage it is best to shade it from any direct sun to prolong the life of the blooms.

An important cultural element for Zygopetalum is that they do best when exposed to a 10 to 15 degree differential between day and night temperatures. It is for that reason we recommend to grow Zygopetalum outdoors from June until early October. While growing outdoors these plants do not mind periodic temperature dips into the 40’s at night, as long as the temperature rises at least 10 degrees or more during the day. It would be time to bring your Zygopetalum indoors once the temperature differential between day and night becomes narrow; for example when the October day time temperature is consistently 45 degrees and the nights are 40 degrees. Do not ever allow your Zygopetalum to freeze.

Once you have brought your Zygopetalum indoors for the growing season of October through May, it is best to place them in a brightly lit area that experiences nighttime temperatures between 50 and 55 degrees. In the home this can be best achieved by using a basement area or a spare room that you are able to reduce the nighttime heat source. For the day time, it is still important that the plant experiences a rise in temperature of at least 10 degrees or more. On cloudy winter days an artificial heat source may be needed to achieve the proper daytime temperature differential, while the sunny days should generate enough warmth for an adequate temperature differential.

Proper indoor watering requires allowing the bark mix to approach dryness just beneath the surface between watering cycles. Factors such as how root bound your pot is, how much light the plant is receiving, and what size pot it is in, will all play a role on how fast it dries out. Typically while growing indoors a good thorough watering every 5 days should be sufficient. In cases of root bound plants grown in warm, high light areas, watering twice a week is needed. When watering, water the bark thoroughly until water runs freely from the bottom of the pot. Always remove your pot from any decorative container to allow for proper drainage. Never allow your pot to stand in any water as this will cause root rot. Never use softened water on any of your orchids.

For outdoor growing it is best to maintain slightly more moisture than for indoors. During the highest temperature periods (mid summer) we recommend to keep the Zygopetalum moist but not soggy. A watering twice a week is needed during that period. As the temperature begins to drop towards the end of the outdoor season, begin letting the bark become dry just beneath the surface, much like the indoor watering schedule. While outdoors the natural rain on the plant is beneficial

Zygopetalum are active growing plants producing multiple new growths per year and therefore fertilizer is essential for good growth and profuse flowering. We recommend applying a 20-20-20 or similar balanced type fertilizer once every 2 to 3 weeks throughout the entire year. A safe dilution ratio is one level teaspoon of fertilizer mixed in one gallon of water. Do not over-fertilize as this will cause permanent root damage.

Like most orchids, the Zygopetalum enjoys a moderately humid climate of 50% or greater. While growing outdoors this is not an issue since we generally have adequate humidity in our Wisconsin summer climate. While growing indoors it is recommended to increase humidity around the plant simply by placing your plants on a humidity tray, misting them adequately in the morning, or grouping your plants all together in one area.

We recommend repotting Zygopetalum once a year, preferably after flowering. If you are not experienced or comfortable doing this yourself we offer the repotting service at our greenhouse for a small fee. Your recently purchased Zygopetalum may be ready for a repotting job as soon as it has finished flowering. Inquire with us as to when your individual plant was last repotted. Good indicators for a repot candidate are: when the rhizome and roots of the plant have protruded over the edge of the pot, when the potting medium starts to break down and drain poorly, or when the plant is completely root bound in the pot. It is best to repot after flowering has completed or in the springtime as the plant becomes actively growing again.

Zygopetalum may be divided if the plant has enough pseudobulbs to safely do so. A division should consist of a minimum of three pseudobulbs to allow enough strength for future growth. Larger divisions of 4-6 pseudobulbs are preferred, which in turn will make for a specimen plant the next blooming season. If your plant is not dividable at this time simply repot it into a slightly larger pot.

To make a proper division, start by locating the pseudobulb that had most recently produced flowers. From there, follow the rhizome which connects each pseudobulb and count back from there three to four pseudobulbs. At that point, cut the rhizome and root mass using a pruning sheer or large stiff knife to make your division. Repeat this process with the remaining portion of the plant. After doing that, you may have a clump of leftover pseudobulbs called back-bulbs. These will not have a recently flowered pseudobulb attached and are not viable or worthy of potting and should be discarded.

A note about orchid viruses: most commonly the transmission of orchid viruses is caused by using the same cutting tool on multiple plants. The most effective method to reduce virus transmission from plant to plant is to briefly flame sterilize all your cutting tools between use on each plant. A simple Butane torch or a gas stove are handy items for this purpose. This practice should be implemented when repotting as well as when cutting off expired flowering stems.

Once your division is made, select a new pot in the appropriate size to allow for another two years of growing. Unfortunately, there is not a set rule for choosing the proper pot size, but generally you will need to increase the pot size by one to one and one half inches. Do not use too large of a pot because these plants like to be somewhat crowded, even after repotting. Zygopetalum prefers to be potted into plastic pots for the benefit of moisture retention. Place the cut side of the division against the inside perimeter of the pot and fill the pot with our moistened fir bark orchid potting mix. Try to keep the rhizome about 1/2” below the potting mix and pack it firmly with a blunt tool to ensure the plant is secure in the pot. Wait a few days and then water thoroughly.

For more assistance with your Zygopetalum or any other Orchid, please call us at 608-831-4700, send an email, or visit our store.

Happy growing, from Orchids Garden Centre & Nursery!