Houseplants – The Garden Thyme Podcast

two houseplants on a windowsill

Happy New Year! It is hard to believe that we are already in a new year. We are kicking off our third season by sitting down with Extension Educator Ginny Rosenkranz. Like many of you, during the pandemic our acquisition of houseplants increased exponentially. Ginny guides us on caring for all of our botanical beauties.

We also have our: 

  • Native Plant of the Month, Musclewood, Ironwood (Carpinus caroliniana) at ~24:55
  • Bug of the Month, Ice crawlers or ice bug family Grylloblattidea at ~29:05
  • Garden Tips of the Month at ~31:50

To listen to the podcast visit https://www.buzzsprout.com/687509.

podcast sound wave image

We hope you enjoy this month’s episode and tune in next month for more garden tips.

  1. If you have any garden related questions please email us at UMEGardenPodcast@gmail.com
    or look us up on Facebook at https://www.facebook.com/GardenThymePodcast.
  2. For more information about University of Maryland Extension and these topics, please check out the UME Home and Garden Information Center website at https://extension.umd.edu/hgic.

The Garden Thyme Podcast is a monthly podcast brought to you by the University of Maryland Extension. Hosts are Mikaela Boley- Senior Agent Associate (Talbot County) for Horticulture, Rachel Rhodes- Agent Associate for Horticulture (Queen Anne’s County), and Emily Zobel- Senior Agent Associate for Agriculture (Dorchester County). Theme Song:  By Jason Inc.

Why light levels are important for indoor plant growth

plants growing under artificial light indoors
Photo: Miri Talabac

This is the second article in our four-part series about indoor plant lighting. You can also read the firstthird, and fourth articles.

Typically, insufficient lighting is the limiting factor for indoor plant growth and flowering, plus the reason for spindly seedlings. Most light fixtures in our homes and offices – especially those still using incandescent bulbs or those with energy-saving bulbs that mimic incandescents – don’t give off enough energy for plants to survive or thrive on long-term. In addition, windows block a surprising amount of sunlight intensity compared with the same spot just outside the glass. Insect screening outside a window reduces intensity even more.

Artificial lighting can either supplement natural light or be the sole light source for plants. Plants tolerate levels of light outside of their preferred range, but sensitivities vary from species to species. Over time, the consequences of inappropriate light levels may impact a plant’s health and alter its appearance, even if it isn’t immediately noticeable.

The importance of light to plants

For plants, light is food. We think of fertilizer as plant “food,” but in reality, it is more akin to a multivitamin than it is a meal – it supports how they use their food (carbohydrates from photosynthesis) and helps build tissues, pigments, hormones, defensive chemicals, and so forth – but it’s not providing the calories they need to survive and grow. They certainly can “fast,” so to speak, such as spending a few days in a box in transit or remaining semi-dormant in winter, but prolonged light deprivation from insufficient lighting will have negative impacts on plant health akin to slow starvation.

Plants may lack eyes, but they can still “see” light by detecting its colors, intensity, and duration. Coupled with temperature or precipitation, it can tell them what season it is for the purposes of growth and reproduction (flowering). Weather can fluctuate from year to year, but the patterns of daylength and general light intensity remain the same and are the most reliable environmental cues for the plant.

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Norfolk pine is a charming Christmas tree

branches of Norfolk Island pine trees
Norfolk Island Pine

Uh oh. You need a last-minute gift or a tiny tree to brighten a corner of your holiday home. Here comes a Norfolk pine to the rescue. Whew. That was close.

Looking like miniature Christmas trees, Norfolk pines pop up at garden centers and other stores over the holidays. Bedecked with bows and balls, they’re festive and cute as can be.

With a graceful, pyramidal shape and tiers of gently arched branches, they are loaded with appeal. They look delicate but are actually tough, long-lasting little trees.  

Technically a Norfolk Island pine, this pint-sized evergreen is native to – you guessed it – a place called Norfolk Island, just east of Australia. Captain James Cook discovered this tree on his second expedition to the South Pacific in 1774.

Norfolk pines are subtropical, hardy in zones 9 to 11. So they can’t handle our winters but are happy to summer outside and hang out with us indoors when the mercury drops. 

They are fairly carefree houseplants. Put them in a bright spot with some direct light. Water them when the top inch of soil feels dry. 

Norfolk pines love humidity, so mist them or group them with other plants. Fertilize them every week to two from spring to fall.

Transition them to outdoor living in the summer by putting them in the shade for a few days, then introducing them to bright light. Just remember to keep them watered and bring them in before the first frost hits.

Norfolk pines’ roots resent disturbance, so repot them only every few years. Once they get three feet tall, replace only the top few inches of soil instead of repotting the whole plant. 

They are slow growers. Norfolk pines generally top out at three to six feet indoors, but they take their sweet time getting there. In their native climes, they can top out at 200 feet.

Oh, and did I mention that a Norfolk pine is not a true pine? Technically Araucaria heterophylla, is part of a genus of 19 species of pine-like conifers. 

But let’s not split botanical hairs. 

The Norfolk pine is an appealing tree. For those with small spaces, it’s an ideal Christmas tree. For the rest of us, it is just a tiny charmer, a sweet little elf of a tree.    

Big or small, I hope your holiday tree is the center of a warm and blessed holiday season spent with family and friends.

By Annette Cormany, Principal Agent Associate and Master Gardener Coordinator, Washington County, University of Maryland Extension. This article was previously published by Herald-Mail Media. Read more by Annette.

An introduction to gardening under lights

This is the first article in a four-part series about the ins and outs of gardening under lights, both for newcomers curious about a different way to grow plants and for more experienced growers who want to build on their understanding of lighting options. Read on for the second, third, and fourth parts of the series.

plants growing under an LED light indoors
A variety of plants growing under an LED light indoors. Photo: Miri Talabac

Why use lights for plants?

It’s sensible to think, “why provide artificial light for indoor plants? Isn’t natural window light enough?” After all, natural light is certainly what the plants get when growing outside. If you’re fortunate and have sun-soaked windows in your home, you may have little need for artificial lighting. Anyone who has insufficient window light or who otherwise can’t utilize their windows for growing plants, though, would benefit from giving their plants brighter conditions.

We’ll address this in more detail in upcoming posts, but light levels play a significant role in keeping plants healthy, vigorous, and looking their best. Plant lights give you more control over this aspect of plant care.

Who benefits from using plant lights?

Anyone who doesn’t have ideal natural-light conditions for their plants would benefit from using plant lights (also called “grow lights”). You don’t have to be a tropical plant aficionado to make use of them, and anyone with an available power outlet can try it. Setups can be as simple or as complex as you’d like. Seed-starting enthusiasts can produce more robust seedlings, and anyone trying to overwinter a lemon tree, some herbs, an aloe, or patio tropicals could have more vigorous plants if their winter slog could be brightened with some extra light.

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Christmas cacti make lovely gifts and décor

Christmas cactus are popping up everywhere. They’re lovely living gifts that enliven holiday décor and add beauty year-round. If you like floral irony, this is your plant. Even though they are fleshy succulents, they originated not in arid regions but in the rainforests of Brazil where they drape themselves over tree branches as epiphytes.  

Arching stems on cactus
Arching stems give Christmas cactus – and this Thanksgiving cactus – handsome structure when not in bloom. Photo credit: Washington County Master Gardener Lauri Ricker

As with many tropical plants, Christmas cactus delivers a double dose of drama. The first is the strong architectural form of arching stems made up of a series of scalloped pads. But it’s their cascading flowers in pink, salmon, red, or white that are the real showstoppers. Stacked layers of swept-back petals with prominent stamens, they are very oh-la-la. They also have a long bloom time, flowering from two weeks to two months.

Heavy blooms are a hallmark of Christmas cactus and its cousin, this Thanksgiving cactus.    
Photo credit: Washington County Master Gardener Wilma Holdway.

Also long is their lifespan. They can live for decades, often becoming family heirlooms. I once received cuttings from a plant started by a – ahem – mature friends’ grandfather. This caused a commotion at airport security.  What IS that thing on the x-ray? And yes, the kindly man let me keep my cuttings once I showed them to him and shared their story.

Christmas cactus has beautiful cascading blooms. Photo credit: Washington County Master Gardener Leora Smith

Care is fairly basic. They like bright indirect light, not full sun. Keep the soil slightly moist. Mist regularly or put the pot on a dish of moist gravel to boost humidity.

Christmas cacti need cooler temps and less water to nudge them to bloom again. They need a chill to give you a thrill.

Master Gardener friends report that the natural drop in temperature and day length in fall is enough to encourage buds indoors. Others let their cactus summer outside in light shade, keeping them out until fall temperatures drop to 50 to 55 degrees. Regardless of how you stimulate flowering, resume regular care when buds form. After your cactus finishes blooming, give it a cooler rest period and less water for two months.  

And yes, Christmas cactus has many cousins including Thanksgiving cactus and Easter cactus, all named for the times they bloom. Mine never consulted calendars and bloomed as they liked. 

How can you tell which cactus you have? Easter and Thanksgiving cactus have pointed edges on their leaves while Christmas cactus leaves have more rounded scalloped edges. 

Thankfully, Christmas cacti are a snap to propagate, so they are easy to share.  Just break off a stem at a joint, slip into well-drained soil and keep the soil moist. It will root in a few weeks. 

I love a good story, and these plants have several. My favorite is a Brazilian legend that tells of a poor boy in the jungle who prays repeatedly for a sign of Christmas. One day he awakes surrounded by colorful flowers on the tips of cactus. And so the cactus became a symbol of answered prayers. 

So Christmas cacti are a symbol of hope. With their long lives, colorful blooms, ease of care, and sharing, they make wonderful gifts for friends, family, and your very own green thumb. 

Annette Cormany, horticulture educator, University of Maryland Extension – Washington County

Orchid Care: Consistency Is Key

Phalaenopsis
Creating an environment that mimics an orchid’s native habitat will ensure plentiful blooms. To thrive, each orchid needs the right spot. Check your orchid’s individual profile. Photo: Rachel Rhodes

My love affair with orchids began in college. It was the winter of 2007 while in Belize for a winter semester class “Tropical Agriculture, Conservation, and Ecosystems.” Sitting along the tranquil headwaters of the Bladen River, our guide detailed the dynamic relationship of the ecosystem that surrounded us.

In the heart of the rainforest, the delicate balance of our environment beats like a drum. As our guide described the four layers of the rainforest from the emergent layer, to the canopy layer, to the understory, and the forest floor, birds chirped and vivid blue morpho butterflies fluttered around. Our guide pointed above us to the most beautiful mesmerizing orchid I had ever seen; the black orchid.

The black orchid gently dangled off the leaning tree beside us, its greenish-yellow petals and sepals had the most beautiful purple blotches near the base. While the “lip” was shaped like the valve of a clamshell, it was deep purple to black and radiated with purple veins. I had never encountered such a fascinating flower.

After the class ended, I dove headfirst into all things orchids to absorb as much information as I could. The orchid family boasts some of the most extraordinary and diverse flowers in the plant kingdom, with around 30,000 species and 120,000 hybrids.

Generally, orchids are divided into two groups; epiphytic and terrestrial. Epiphytic orchids are usually the orchid we most frequently see (Phalaenopis and Cattleya). Epiphytic orchids use their tough roots to anchor themselves to trees. They receive nutrients from rainwater and leaf debris and they absorb moisture from the air. Terrestrial orchids grow with their roots in the ground. They are most commonly found in grasslands or boggy areas. Understanding the type of orchid you have, their growing conditions, light requirements and flowering season is integral in ensuring your success.

orchid
Glazed pottery and ceramic orchid pots come in varying hues, shapes, and sizes. Decorative pots are fun but make sure to keep an orchid in its original plastic container and place it inside the decorative pot. If you take it out of its plastic container, too much air will get to the roots and the orchid will dry out faster. Photo: Rachel Rhodes

After much trial and error, I have learned a few things. With orchids, consistency is key. A majority of our orchids such as Phalaenopsis only bloom once a year in late winter through early spring (January to March). Getting them to rebloom is the ultimate prize as a gardener. The best way to encourage flowering is make sure that you have the proper lightening, ample water, and the right amount of food.

First, getting the light right is one of the most important factors. Phalaenopsis and Paphiopedilum like morning light from an east-facing window. This provides an orchid with a few hours of direct sunlight without hurting the plant. The sun can be very damaging to the leaves of an orchid, so the right placement is key. If you do not have an east-facing window, you can make other spots work by following these principals. North facing windows simply do not provide enough light to sustain the healthy growth of an orchid. If this is your only option, you will need a grow light to give your orchid the boost of light it needs. If your orchid is in a west-facing window put up a sheer curtain to protect it from the heat of the summer sun. Furthermore, if using a south facing window a sheer curtain is advisable year round. Unlike Phalaenopsis and Paphiopedilum, Cattleya like bright light from a south or west facing window.

applying water to orchid roots
Water your orchid once a week. Make sure that you take it out of its decorative pot, leaving it in its plastic container. Run water over the roots for a few minutes avoiding the leaves. Allow the plant to air out for a while before putting it back into its decorative container. Photo: Rachel Rhodes

Just as getting the right lighting is crucial so is watering. When watering your orchids, always water in the morning. This guarantees that the moisture has time to evaporate. If you water at night, it allows water to settle in the nooks of the bark, which promotes fungal growth. Avoid watering or misting the leaves. Misting tricks the guard cells on the leaves to think that the humidity is higher than it actually is. This can cause your orchid to dry out faster. Additionally it can lead to crown rot if water settles in the nooks of the leaves. Orchids love humidity. To increase humidity you can use a humidifier set at 40-50% or use a humidity tray.

mealybugs on orchid buds
Mealybugs are a common orchid pest, especially on moth orchids (Phalaenopsis).They are little white fluffy insects that are closely related to scale insects. They love new growth and flowers. Unlike scales, mealybugs wander in search of feeding places. They damage the overall vigor of the plant, weakening it and causing the loss of leaves, buds, and flowers. Photo: Rachel Rhodes

All plants require nutrients to grow and thrive. Epiphytic orchids like Phalaenopsis live in trees where they receive nutrients from rainwater and leaf debris. Pot-grown orchids depend on feedings to produce healthy leaves and beautiful blooms. With proper feedings, a well-fertilized orchid will keep their leaves longer and will produce more flowers. When feeding, it’s best to use orchid-specific fertilizers. Orchids also thrive from “weakly weekly” feedings when blooming by diluting fertilizer to ¼ strength rather than a full dose once a month.

By Rachel J. Rhodes, Master Gardener Coordinator, Queen Anne’s County, Maryland, University of Maryland Extension. Follow the Queen Anne’s County Master Gardeners on Facebook. Visit the UME Master Gardener webpage to find Master Gardener events and services in your county/city. 

Q&A: Why Is My Clivia Plant Starting to Yellow?

clivia plant
Q: Many years ago, I purchased a Kaffir Lily (Clivia miniata) at the Philadelphia Flower Show and it has special meaning to me. Recently, the bottom leaves are turning yellow. What is causing this and what should I do? Also, sometimes it does not bloom well. Is it true that they need a rest period?

Answer: It is normal for the older leaves to turn yellow and eventually shrivel as the plant ages. Prune off the affected leaves. The rest of the leaves should be green, strappy, and healthy. Yellowing of younger leaves can indicate overwatering: a more-serious symptom. The potting mixture should dry out slightly between waterings when it is actively growing and completely dry out during the rest period.

Clivias do need a dormant period to help with blooming. Starting in late fall or early winter, withhold water and fertilizer and move the plant to a cooler area where temperatures are in the 40–50° F range. Keep it there for about 6–8 weeks, then move it back to a sunny location and begin to water again. You will soon see some
new growth and a flower stalk. At this point, begin to fertilize it every two weeks with a water-soluble houseplant fertilizer at half-strength. They bloom best when pot bound. Repot your Clivia every three to five years in the spring, after the flowers fade, when necessary.

Visit the Home & Garden Information Center website for more information about houseplant care.

By Debra Ricigliano, Lead Horticulturalist, University of Maryland Extension Home and Garden Information Center. This article was published originally in the December 2019 issue of Washington Gardener magazine. Read more posts by Debra.

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