Orchids (Phalaenopsis) are readily available this time of year in nurseries and even grocery stores. They are popular hostess gifts. I find them quite beautiful and I am always tempted to add another one to my collection. However, I usually repot them as soon as I get them home, because they are often planted in sphagnum moss. I have found that phalaenopsis grow better in other planting mediums.
Many small plants that you buy—not just orchids—are planted in sphagnum moss. The trouble I have with that is that even though I water the plants, the moss can dry out, and it needs to be soaked to reabsorb water. This is a tedious process, so I change the soil as soon as I can. For plants that are not orchids I use soil mix with organic amendments such as compost.
Years ago I attended Rod McLellan's orchid open house in South San Francisco. He was an orchid dealer, and this is where I learned about the planting mix to use for orchids. I use the same one for cymbidium as well as phalaenopsis. The mix is equal parts bark and crushed red lava rock. The pieces should be chunky, about a half inch or so. Eventually the bark breaks down and can clog the open root areas, causing the plant to retain too much water. The bark should be replaced in that circumstance.
When I was in Hawaii, I visited a cymbidium orchid farm and the growers used red lava rock only, with no bark. That is because Hawaii gets more rain than we do so the bark isn't needed for moisture retention.
If an orchid is in bloom, I usually wait to repot it, but recently I repotted a flowering phalaenopsis and it did well. First, I clean all the peat moss off the roots. If there are long roots on the plant—hanging over the edge of the pot—I remove some of them. I prune the brown roots, not the white ones. I usually put my phalaenopsis in slightly bigger pots than they arrived in. Orchid pots have slits on the side, sometimes in patterns. This is to let air in and moisture out. Root rot will occur if plants remain soggy.
Once I pick out a pot I put some orchid planting mix into the bottom and insert the plant to make sure it fits. I also put pieces of Styrofoam in the bottom of the cymbidium pots. This blocks the drainage holes and makes the potted plants lighter and easier to move around. Sometimes the roots will grow right into the Styrofoam. Styrofoam peanuts work too, but not the water-soluble ones.
I use a wooden dowel or chopstick to move the soil around to fill up any air holes. You want to fill these spots so that insects or disease do not find a home. Cymbidiums can attract spider mites and aphids. You can treat them with a horticultural oil.
Once my pots are filled, I top the planting mix with worm compost. You can learn how to make worm compost—or “gardener's gold,” as some people call it—by attending the UC Master Gardeners compost workshops in 2025. I use worm compost on almost all my plants and it works well. During the winter I top my cymbidiums with 0-10-10 fertilizer to encourage blooms. This is a plant food that contains no nitrogen but is rich in phosphorous and potassium.
I reuse the sphagnum moss by drying it in my hot house, sifting it, and mixing it into my used soil. I can use it for other plants.
I have grown orchids for many years and my repotted orchids have bloomed for me many times. The cymbidiums stay outside until they develop “spikes.” Spikes is another work for flower stakes. I then move them to the hot house—now you see why I don't want the flowerpots to be too heavy. When I see the spikes forming, I put cotton balls around them to discourage slugs and snails. I read that the slimy scourges don't like to crawl on cotton. Note: over half of my cymbidiums have spikes on them as of New Year's Day. I repotted all of them this past fall.
The orchids stay in my hot house in the winter, and I move them to a shaded area outdoors in the summer. My hot house is passive solar and stays warm from the water tanks there. They heat up during the day and emit heat during the night. I also leave a couple of shop lights on during the coldest winter nights.
Cymbidiums and orchids are long lasting plants if you know how to take care of them. I know people who have kept theirs going for twenty years.
Rose Pruning Workshop: Join UC Master Gardeners of Napa County for a workshop on “Winter Rose Care” on Saturday, January 11, from 10 am to noon, via Zoom. Learning pruning techniques for all types of roses along with everything you need to know to make your roses a success in 2025.Attendees will be invited to a hands-on pruning workshop at Fuller Park Rose Garden on January 18 to practice what they learned. Register here.
Home Orchard Workshop: Join UC Master Gardeners of Napa County for a workshop on “Winter in the Home Orchard” on Saturday, January 11, from 1 pm to 3 pm. Learn about winter fruit tree pruning and how to plant a bare-root tree. The workshop will be held outdoors at a private residence. You will receive the location after registering. Be prepared for muddy soil and hand-on practice. Register here.
QWEL Training: Napa County landscape and irrigation pros are encouraged to become Qualified Water Efficient Landscapers (QWEL). Earn this EPA WaterSense award-winning professional certification and save water and money for clients. The City of Napa is sponsoring free in-person QWEL training in English on four Wednesdays starting January 15. Space is limited. Register at qwel.net/pub/class/491.
Help Desk: The Master Gardener Help Desk is available to answer your garden questions om Mondays and Fridays from 10 am until 1 pm at the University of California Cooperative Extension Office, 1710 Soscol Avenue, Suite 4, Napa. Or send your questions to mastergardeners@countyofnapa.org. Include your name, address, phone number, and a brief description of the problem.
