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

Top 10 ways to kill a houseplant

It’s easy to kill a houseplant.

No matter how green his or her thumb, every gardener has a sad tale about the orchid that expired, the pothos that went to pot, or the weeping fig that dropped every blessed leaf.

You can gnash your teeth, rend your garments and fume. Or you can get busy and figure out what went wrong.

Houseplants fail for a handful of reasons.  Here are my top ten:

Overwatering

The number one killer of houseplants is overwatering. Roots need both water and air to thrive.  Waterlogged soil chokes roots.

Most plants like to dry out between each watering.  Stick your finger in the soil. If it feels dry, water until the water runs out the bottom of the pot.  Let the water drain and dump the excess.

Water needs vary. Cacti like it dry. African violets like moist soil.  Find out what your plant needs and give it just that.

Improper drainage

Poor drainage also causes roots to rot.  So, make sure every pot has a drainage hole.

Low humidity

Our winter homes are dry, dry, dry.  When the heat comes on, humidity takes a nosedive.

Set plants that need higher humidity – like orchids – on a tray of pebbles with a bit of water.  Mist humidity-loving plants such as ferns once a week.  Or get chummy and shower with them.

Low light

Too much or too little light is tough on houseplants.  Read the tags and do some research in books or online to find out what your plants prefer.

Sun-worshipping orchids need strong light while dracaenas are happy in lower light.  Place each plant where it will get what it needs.

Drafts

Oh, how houseplants hate a burst of cold air or a blast of heat.  So keep them away from doors, fireplaces, radiators, vents, or chilly windows.

Overfertilizing

Indoor plants don’t photosynthesize at the same rate as outdoor plants, so they need less fertilizer.  In winter, fertilize at half the suggested strength or not at all.

Ignore pests

Bugs hitchhike on houseplants that summered outdoors.  Be vigilant and deal with pest problems swiftly.

Look for spider mites’ webs, sticky leaves from aphids or leaf bumps that are scale.  Contact your local Extension office for an ID or fix or contact the Ask Extension experts.

Shock

If your houseplant is happy, don’t move it.  Most plants resent a change of scenery.  Drama queens like ficus weep copious leaves with even the slightest change.

Pot-bound

Roots too small for a pot circle madly, strangling houseplants.  If you notice roots circling or peeking out of the bottom of the pot, it’s time to repot.

Choose a pot an inch or two bigger than your existing pot and repot with fresh soil in the spring.

The wrong soil

A light soilless potting mix is good for most houseplants.  Garden soil is a no-no, too heavy to drain well.

Some plants need specific blends.  Cacti like a sandy mix while orchids need a special chunky orchid potting mix.  Do your research.

Stop killing houseplants.  Avoid the dreaded top 10.  Your plants will love you for it and reward you with years of health and beauty.

 

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.

 

How Horticulturists Turn Quarantine Into ‘Gardentine’

While it seems that everything in our world is different today than it was two months ago, one thing hasn’t changed — nature! Maryland’s stay-at-home order has given everyone the opportunity to explore their natural surroundings and given them the itch to garden to relieve tension and do something productive.

So what do University of Maryland Extension horticulturists do to stay grounded during ‘gardentine?’ Just like you, we take pictures of our flowers, gardening projects, and all things nature and send them to each other, natch!

Stephanie got us started by wishing us a happy Earth Day!

horticultural distancing is not a thing

Stephanie and I went on a socially distant walk, participating in the City Nature Challenge iNaturalist project for the Baltimore area. Here are a few of the 53 species we identified for the project. Not too shabby!

Scroll over or click on the images to see the plant names.

One of my neighbors really upped the game by providing informational signs along the sidewalk for everyone’s enjoyment! Thanks, Kathy!

Christa started her “Sketches from the Yard” journal on the 10th day of quarantine. She says drawing, painting, and writing about her observations around the yard and garden is a creative thing she can do at home and is something that helps her relax during these strange times.

“When I look at the details of a plant and try to document it, it gets my mind off the coronavirus news for a while and helps me focus on what is still normal and beautiful around me. I have appreciated my garden harvests of fresh greens, herbs, and even a few carrots that survived our mild winter. And the new tulips I planted last fall were delightful to see in bloom! At the end of this project, I will have a record of my garden and how meaningful it was to me as a place of serenity during this quarantine time.”

She is quite the garden journalist! You can follow her on Instagram @mrscarignan.

Debbie is growing microgreens in a salad box on her balcony.

microgreens in a salad box
Half of the box is arugula and half is lettuce that has just started to germinate. Proving that you don’t need a lot of space to grow some of your own food! Photo: D. Ricigliano

salad box
This is what a salad box can look like when it’s ready for the first harvest. Yes, you can get multiple harvests from salad greens. Photo: HGIC

Miri has quite the impressive indoor garden! The ridiculous volume of houseplants keeps her sane! (Her words, not mine!) Maybe Miri will write a blog post featuring her various mini orchids and Tillandsias and include the routine she uses to keep them all so happy! (Hint hint!) She also entertains herself by secretly diagnosing plant problems on walks through the neighborhood. No photo evidence of that here!

Marian is helping her daughter plant a salad box from a distance by sharing the Home & Garden Information Center’s salad box instructions. See how you can build and plant a salad box or a salad table too!

salad table
I can see that Marian is also using a floating row cover to protect those seedlings from frost and/or marauding squirrels and chipmunks! Photo: M. Hengemihle

Jon has a huge and very productive garden every year! He always gets his garlic planted in the fall.

garlic
This spring the garlic tips have turned yellow either from the cold or the beginning of his perennial problems with white rot and bulb mites. Oh no! Photo: J. Traunfeld

Jon also grows his own seedlings every year and generously supplies the office with baby plants! Thanks, Jon!

growing transplants on a light stand
Here is Jon’s light stand setup. He’s growing downy mildew resistant ‘Prospera’ basil, many varieties of pepper, tomato, eggplant, zinnia, and tithonia. Photo: J. Traunfeld

Wanda enjoys tending her orchids indoors.

orchids indoors
She soaks them in a container of water for about 10 minutes every 2 weeks in the winter and once a week when it gets warm. Photo: W. MacLachlan

Wanda has lovely gardens outdoors too.

raised beds
Here she and her husband are revamping their raised garden beds in an attempt to exclude deer, raccoons, groundhogs, rabbits and (fingers crossed) chipmunks! When finished, these 3 raised beds will be in a closed cage. Stay tuned for a progress report! Note from Wanda: The dark piles in the 2 beds are castings from her indoor vermicomposting project. Wow! Photo: W. MacLachlan

Jean has a passion for pink and her houseplants prove it!

plants on a windowsill
Luckily, she has a south-facing window so she gets a lot of light. For the succulents, she mixes potting soil with some perlite and avoids overwatering. High sun exposure and good drainage is key to her healthy and happy houseplants! Photo: J. Burchfield

Ria – I sheltered in place for part of the last 6 weeks at the home where I grew up in Virginia. I went on several walks taking photos of things in bloom, but I needed to get my hands in the dirt! I had assured Jon in February that I was absolutely not going to create another garden to manage there. He had a good laugh when he saw the photos of my new garden! So much for my resolve, I needed to garden!

For the last 40 years, only daffodils and a perennial hibiscus have grown in the small triangle of space bordered by the split rail fencing, if you don’t count that sneaky Bermuda grass. If you look closely, you might be able to see the pomegranate that I got in Colonial Williamsburg about 5 years ago. It has never even bloomed, let alone produced fruit!

bare ground new garden
To create the new 24’ x 12’ kitchen garden, I killed the grass (mostly Bermuda grass and various other weeds), spread thick layers of newspaper over the area and covered it with soil that had been excavated to install French drains. Photo: R. Malloy

add organic matter to a garden
Then I spread ten bags (2 cu. ft. each) of media labeled for raised beds in 3 rows each about 2.5’ wide, leaving room for a path between each row. I mulched between the rows and around the perimeter of the garden with wood chips from 3 tree stumps that we ground up last summer. I made sure not to incorporate the wood chips into the soil with the plants. Photo: R. Malloy

planting a new garden
I planted a variety of herbs, sweet cherry and grape tomatoes, salad greens, and flowers to attract pollinators. Photo: R. Malloy

new garden
My husband extended the split rail border. I surrounded the garden with green plastic covered wire mesh fencing to deter the rabbits and groundhogs. I am under no illusions that it will really prevent them from getting in! At some point I will need to add a solar powered electric fence like the one I have in Maryland. Photo: R. Malloy

Please join us by taking time each day to connect in some way with nature and stay grounded during ‘gardentine’ and beyond!

By Ria Malloy, Program Coordinator, Home & Garden Information Center, University of Maryland Extension