Save the Date! 13th Annual Denver Master Gardener Plant Sale May 19-20th

8th Annual CMG Plant Sale, Harvard Gulch Park, Denver CO 5-18-13 (6)Saturday May 19th 8am – 3pm & Sunday May 20, 2018 10am – 3pm

CSU Denver Extension, 888 E Iliff Ave, Denver CO 80210

Rain or shine. Now accepting credit cards!

For more information: (720) 913-5270 or 

Heirloom and modern hybrids
Annual and perennial flowers
Sweet and hot (New Mexico) chiles
Gardening questions answered


Indoor Plants & Clean Air


Over thirty years ago, NASA began researching methods of air purification in space crafts to pave the way for long-term human space flight. The study, found here, concluded that many common houseplants are highly effective at removing toxins such as benzene, formaldehyde, ammonia, xylene and trichloroethylene. The findings have been replicated many times over. Their relevance today is unmistakable, especially given the number of man-made products which off-gas chemicals in our homes and workplaces, current energy-efficient construction practices, our focus on healthy living and concern for the environment.

The following are answers to commonly asked questions about the relationship between clean air and indoor plants.

How exactly do plants clean the air?

Plants are effective at absorbing gases through pores on the surface of their leaves. It’s this skill that facilitates photosynthesis, the process by which plants take in carbon dioxide and release oxygen. In effect, all plants can purify the air to some extent, but some do a better job than others.

Studies show that plants can absorb many gases, including a long list of volatile organic compounds (VOCs). Benzene (found in some plastics, cloth and pesticides) and formaldehyde (found in some cosmetics, dish detergent, fabric softener and carpet cleaner) are common indoor VOCs that plants help eliminate.

Plant roots and the microorganisms that live in healthy soil also absorb VOCs and other pollutants.

Which plants were used in the NASA study?

Most were common, easy to care for plants which you may have in your home or office right now. Top “air filters” included: Peace lily (Spathiphyllum wallisii), golden pothos (Scindapsus aures), mother in law’s tongue (Sansevieria trifasciata ‘Laurentii’), bamboo palm (Chamaedorea sefritzii), dracaena (Dracaena marginata), spider plant (Chlorophytum comosum), English ivy (Hedera helix), Chinese evergreen (Aglaonema commutatum). Gerbera daisies (Gerbera jamesonii) and potted mums (Chrysantheium morifolium) are also effective air purifiers, but tend to be short-lived flowering houseplants.

Can plants reduce the harmful effects of cigarette smoke in the air?

Cigarettes contain formaldehyde, one of the toxins that plants can remove from the air. However, the plant/cigarette smoke connection was not the focus of the NASA study. A 2010 study by the American Society of Horticulture Science found that ferns were among the most effective plants in formaldehyde removal.  Check out the study for specifics on which ferns offer the best results.

Do I need to live in an indoor jungle to reap benefits?

Hardly! Studies found that approximately one 6″ to 8″ pot per 100 square feet, or 15-18 plants per 1800 square foot house makes a measurable difference.  The more vigorous the plant, the more pollutants it will draw from the air.


Photo credits: Bing free images

Written by: Linda McDonnell, a Denver County Master Gardener






How to Read a Seed Packet

seed packetsIf you can read and follow instructions, you can grow a garden.

Most seed packets have all the information a gardener needs to plant and grow whatever seeds are hidden inside. Whether you want to plant flowers, herbs, fruits or vegetables, let the seed packet be your guide.

Instead of falling for the picture on the front of each packet, study the back, especially the number of days to harvest for fruits and vegetables. Our area has a limited number of days for growing each season, and the fewer the days to harvest (especially for tomatoes), the more success you’ll have.

Here’s the most important information seed companies want you to have — and to use:

Plant name–Both the common name, like Bloomsdale Longstanding spinach, and the scientific name, Spinacia oleracea.

Type of plant—Types can include heirloom, hybrid, organic and other identifiers.

Plant description—The description includes basic information on whether the plant is an annual, biennial or perennial and some of its key features. The plant’s history, height and width may also be included.

Packed for date—Seeds are packed for and sold by the current year; however, seeds packed for previous years are usually good to plant for several years.

Planting time—Planting time depends on weather conditions for a specific area. Some packets include hardiness zone maps with a month or a range of months for planting.

Seed packets will also give information on whether to start seeds indoors or to plant seeds outside.

  • Start seeds inside according to the packet’s recommendation, usually 6-8 weeks before the average last frost date.  CSU Extension offers a guide to frost dates to help with garden planning. Avoid planting seeds too early.
  • Plant seeds outdoors after the soil has dried and warmed to the optimum soil temperature. A CSU Extension handout and a kitchen or digital thermometer will help determine when to plant specific vegetables. Planting too soon or too late could be a reason some seeds fail to sprout.

Light needs—The amount of sunlight plants need from full sun to partial shade. Most fruits and vegetables need at least 6 hours of sun every day.

Row spacing—The amount of space between rows allows enough space for plants to grow without being crowded.

Planting space—Spacing is also critical between individual plants. Spacing may include how closely to plant seeds and how to thin the plants once they start growing.

Seed depth—Use a ruler or other guide and follow seed depth recommendations. If seeds are planted too deep, they may have a hard time reaching the top of the soil.

Days to sprout or germinate—Keep track of germination dates so you’ll know the timing of when plants start to grow. If seeds fail to sprout, replant seeds and they should catch up quickly.

Days to harvest (or mature)—For vegetables, the harvest dates will vary depending on the variety or cultivar. Harvest fruits and vegetables when they’re at their peak and avoid leaving vegetables on plants too long.

Special information—Depending on the seeds and seed company, there may be growing notes, staking information, fertilizer recommendations, suggestions for cutting or harvesting, recipes and other tips for success.

By following the seed packet instructions, gardeners can guess less and get more enjoyment from their gardening experience.

By Jodi Torpey
A Denver Master Gardener

Denver Gardeners Needed for Research Study

community gardenWould you like your gardening efforts to contribute to important scientific research? If you live in Denver and are relatively new to gardening, CAPS needs you.

CAPS stands for the Community Activation for Prevention Study. The University of Colorado at Boulder and Denver Urban Gardens are working together on a randomized controlled study to discover how community gardening affects health. Other partners include Michigan State University, the University of South Carolina and Colorado State University.

The three-year study is funded by a grant from the American Cancer Society. Gardeners are now being recruited for the second wave of the study. When CAPS ends, more than 300 gardeners will contribute to the study and help researchers understand if and how gardening can prevent serious health issues, like cancer.

Study participants will be randomly selected for one of two groups: those who grow a garden in a DUG community garden and those who are on a DUG wait list (the control group). Researchers measure both groups and compare the results based on their diets, physical activity levels and other health indicators.

CAPS is looking for Denver-area folks who are over 18 and have an interest in gardening. The participants need to be new gardeners or gardeners who haven’t been actively gardening for the last two years. Study participants will be matched to a nearby DUG community garden and their garden plot fees are covered.

Experienced Denver-metro gardeners are encouraged to spread the word about CAPS to beginning or lapsed gardeners. Find out more about the study, the investigative team, and the study’s partners at the CAPS website or get in touch with Angel Villalobos, program coordinator, at 303-724-1235 or

By Jodi Torpey
A Denver Master Gardener

Five Nature Activities to Do With Children in Winter

Want to share your love for nature and plants with children this winter? Here are five activities to spark curiosity, teach and amuse.


Adopt an insect-eating plant. The Venus Flytrap (Dionaea muscipula) is fascinating to watch as it traps spiders and insects for its meals. This animation explains the process.


Start a worm farm. It’s a fun way to learn about the composting process and add to the garden later in the year. All that’s needed is a plastic lined or wood box with a lid, vegetable scraps, shredded newspaper and a few red wriggler worms. Kept moist and cool, the worms will get to work making valuable compost.  Find full instructions here.

FairyGardenPeekInside-e1403316493327-2Plant a terrarium or fairy garden. Assemble a collection of small plants in an open-topped container or create an imaginative, kid-friendly scene with structures and characters – perhaps a park for superheroes or dinosaurs! Children love to play in the dirt, so this makes for great hands-on learning of planting basics. Stick to easy to grow, petite plants and add a bottom layer of pebbles if using containers without drainage holes. pineconebirdfeeder-1

Feed the birds. Gather some pine cones and tie a string to the top of each, slather with peanut butter, then roll in bird seed. Hang in a nearby tree and watch the feast begin.


Sprout an avocado pit. Stick the perimeter of an avocado seed with toothpicks and suspend it, rounded side down in a glass of water. Watch for roots followed by a green shoot. Avocado is a fast growing plant and will soon need to be transplanted into soil.

What nature activities do you do with children?

Images:  Bing Images (Royalty Free)

Written by: Linda McDonnell, a Denver County Master Gardener



Your Yard is Thirsty


When I moved to Colorado three decades ago I expected to be knee-deep in snow and cold to the bone for months on end. Little did I know, Denver winters have long dry stretches, moderate daytime temperatures and bright sunshine that melts snow before it needs to be shoveled. So much easier than the New Jersey winters of my youth. The downside is that plants often suffer from lack of moisture. This year I’m being especially diligent about winter watering to help  newly planted trees, shrubs and perennials make it through their first winter and thrive in the future. Whether nurturing young plants or insuring the longevity of established ones, here are Colorado State University’s recommendations for cold season landscape care.

  • From November to March, give plants a good drink when four weeks elapse without snow cover or adequate moisture. March is the metro area’s snowiest month (11″); January (7″) and February (6″) average the least.
  • Water when temperatures are above 40° and early enough in the day for the moisture to soak into the ground before temperatures dip below freezing.
  • Reflective heat from buildings, the lower angle of the sun and areas prone to intense wind cause root systems to dry out more quickly, watch plants in these areas closely and water accordingly.
  • Newly planted trees establish slowly – one year for every inch of trunk diameter, (measure 6″ above the soil ). A good rule of thumb is to apply 10 gallons of water per inch of trunk diameter each time you water. Water around the tree, out to the drip line and beyond. The goal is to send moisture to the tree’s entire root system at a depth of 12″. I’ve found running a sprinkler for 30 minutes does the job nicely.
  • Newly planted shrubs require more moisture than established ones (over one year old). A first year, 3′ tall shrub requires 5 gallons per watering.
  • Mulch is a plant’s friend – it helps maintain moisture and mitigate the damaging thaw/frost cycle.
  • Newly seeded lawns and perennials (especially fall planted ones) will benefit from supplemental watering if precipitation is low, too.

According to, we’ve received just .02″ moisture in the last two weeks and are about 2.5″ below average precipitation year-to-date. Given our dry days and spring-like temperatures, it’s  about time to unwind the hoses.
For more information:
Planttalk Colorado: Fall & Winter Watering
Colorado State University: Fall & Winter Watering Fact Sheet 7.211

Photo credit:, a source for royalty free images
Written by: Linda McDonnell, a Denver County Master Gardener

How to Enjoy a Living Christmas Tree

When considering the price of trees these days, it makes sense to buy one that offers the biggest return on investment. That’s why I’m a big fan of living Christmas trees.

A living tree is one that makes the season bright, but also adds beauty to the landscape long after the holiday is over.

Before investing in a living Christmas tree, there are a few things to keep in mind about its care:

1. Buy a tree that fits both inside and outside the house. A smaller tree will be more manageable for moving into the house for the celebration and then outside for planting. In addition, smaller sized trees will take less time to get established in the yard after planting.

2. Select the planting site and prepare a planting hole for the tree before the ground freezes. Dig a saucer-shaped hole that’s at least three times the size of the root ball. The hole should be shallow (no deeper than the root ball) and wide. Planting too deep slows root growth and can harm the tree. Be sure to reserve the soil to fill in the hole at planting time.

3. Locate a cool spot to store the tree after getting it home. Keep it in its original container in the garage or on a sheltered porch or patio until it’s time to move it indoors.

4. Unlike a cut tree, a living Christmas tree can be indoors for just a short amount of time. Plan ahead to move the tree indoors for 5-7 days around the holiday. Then move it back to the garage.

5. Place the tree in the coolest room in the house. Avoid placing it close to the fireplace and keep it away from furnace vents that cause hot-cold temperature swings.

6. Water wisely to keep the soil moist. One easy method for watering is to put the tree’s container in a larger container, like a metal tub. Elevate the tree off the bottom of the container with a layer of gravel to keep roots away from sitting water.

7. After the holiday is over, allow time for the tree to get re-acclimated to the outdoors before planting. Place it back in the garage or cool, sheltered spot for a few days. Then take it outside and plant.

CSU Extension gives all the best practices for tree planting in the Garden Notes called The Science of Planting Trees. Be sure to remove any burlap or wire baskets before backfilling the hole and watering in the tree.

Keep your new tree watered through the winter, at least once a month or more frequently if the weather is dry and warm with a lack of snow cover.

A living Christmas tree may need a little extra TLC, but it’s one of the best ways to keep the holiday spirit alive throughout the year.

By Jodi Torpey
Denver Master Gardener since 2005

Shedding Light on Houseplants


Daylight saving time is on hiatus, the gardening season has drawn to a close and  the long shadows of winter will soon be here.  It seems like a good time to turn our attention to the light needs of indoor plants.

Most indoor plants hail from the tropics, making their ideal growing conditions far different from what we offer in our typical homes. Thin new leaves, loss of lots of older foliage and limbs stretching towards a window can all be signs that your plant is craving more light. Without adequate light plants are unable to store energy for growth.

Indoor light is more subtle than the light in our gardens, which can make it trickier to assess. For more precision, a photographer’s light meter or a simple light meter app on your phone will measure the light in foot-candles or LUX units. Horticulturists use foot-candles, so if you have a device which gives a LUX reading, search the web for an easy LUX to foot-candle calculator.

In general, growers characterize plants as needing high, medium or low light.  Here are some guidelines to help assess the type of light in your environment with greater accuracy.

High Intensity Light

  • 1,000+ foot-candles
  • 4-6 hours of sun per day
  • Crisp shadows and dark contrast at the brightest time of day
  • Within 2’ of east facing windows
  • Within 2’ of south-facing windows (October-March)

Medium Intensity Light

  • 500+-1,000 foot-candles
  • Within 2’ of north facing windows (April-September)
  • 2-6’ from an east or west-facing window
  • 1’ to the side of an east or west-facing window
  • Approximately 10-14 hours per day of fluorescent office light

Low Intensity Light

  • 50-500 foot-candles
  • Faint shadows at the brightest time of day
  • Within 2’ of north facing windows (October-March)
  • 6-10’ from south-facing windows (April – September)
  • Few plants survive in fewer than 50 candles

Knowing the light intensity will help determine the best placement of  plants and select  plants which will thrive. Variables such as humidity, drafts and temperature also factor into a plant’s health, so be sure to take this into consideration, too.  As always, knowledge and keen observation skills are key to successful plant care.

Additional information on plants and light:

Plantalk 1352: Interior Plants and Light

Plantalk 1314: Houseplants: Artificial Light

Starting Seeds Indoors

Christmas Cactus Care (effects of light on bloom)


Written by Linda McDonnell, a Denver County Master Gardener





What’s In The Cauldron? The Meanings Of Plant Names


“Fillet of a fenny snake,
In the cauldron boil and bake;
Eye of newt and toe of frog,
Wool of bat and tongue of dog,
Adder’s fork and blind-worm’s sting,
Lizard’s leg and howlet’s wing,
For a charm of powerful trouble,
Like a hell-broth boil and bubble.”

Doesn’t that just send a shiver down your spine? The immortal words of Macbeth’s witches tend to hang in the air, and you can almost hear the cauldron bubbling.
But what is that stuff in the cauldron?

Guess what? Most of it is plants!

Anyone who has worked in the garden has noticed that many plant names have odd, fanciful or gruesome names. If you really consider them, names like ‘dandelion’, ‘foxglove’ and ‘mistletoe’ are pretty odd, aren’t they?
The reason is multi-faceted. A large contributing factor is a socio-historical phenomenon known as ‘linguistic drift’, which is the term for the fact that words are changed over time. Originally, according to Oswald Cockayne’s ‘Leechdoms, Wortcunning, and Starcraft of Early England: The History of Science Before the Norman Conquest’, Dandelion was originally ‘Dent De Leon’, or ‘Lion’s Teeth’, referring to the dentition of the leaves.  Andrew Yang notes another good example in his work ‘Plant Names in Old and Middle English: Problems and Trends in Taxonomy’ : “The tan of mistletan, notes Sauer, “originally meant ‘twig,’ but it was later associated with tan [as OE] toe,” to form mistletoe.”

Another main contributing reason is pragmatic: it’s hard to forget a plant called ‘dead man’s fingers’ or ‘bear’s breeches’ as a rule, which made remembering and passing on plant knowledge much easier.

The Tryskelion Press gives us a short guide to the 16th century English plant name meanings in their August 2015 issue.

Old Name for Part Actual Part of the Herb Used
Eye Inner part of a blossom
Paw, Foot, Leg, Wing, or Toe Leaf
Guts Roots and stalk
Privates Seed
Hair Dried, stringy herbs
Tail Stem
Head Flower
Tongue Petal
Heart A bud or seed

Here’s a few examples of the common names in the 16th century and the same plants today.

Old Herbal Name Herb/Plant Name
Adder’s Fork Adder’s tongue
Adders Tongue Dogstooth Violet
Ass’s Foot or Bull’s Foot Coltsfoot
Bat Flower Tacca
Bat’s Wings Holly
Bat’s Wool Moss
Bear’s Foot Lady’s Mantle
Beggar’s Buttons Burdock
Beggar’s Tick Dianthus
Bird’s Eye Germander Speedwell
Bird’s Foot Fenugreek
Black Maidenhair Black Spleenwort
Black Sampson Echinacea
Black Snake Root Black Cohosh
Blind Eyes Poppy
Click Goosegrass
Clot Great Mullein
Corpse Candles Mullein
Corpse Plant Indian Pipe
Courtesy Summer Wind
Crocodile Dung Black Earth
Crow Corn Ague Root
Crow Foot Wild Geranium
Crowdy Kit Figwort
Crown for a King Wormwood
Cuckoo’s Bread Common Plantain
Dead Man’s Ashes Mandrake root
Death Angel Agaric
Death Flower Yarrow
Devil’s Apple Datura
Devils Dung Asafoetida
Devil’s Eye Henbane, Periwinkle
Devil’s Flower Bachelor’s Buttons
Devil’s Guts Dodder
Devil’s Milk Celandine
Devil’s Nettle Yarrow
Devil’s Oatmeal Parsley

So what was in that cauldron? Black mustard, Crowfoot, Holly, Horehound, Wormwood, and a lot of other rather powerful plants. I wouldn’t drink a cupful myself, but if you want to see visions and fly this brew would definitely do it.
Happy Halloween!


The Shakespere Standard,

Cockayne, Oswald.  Leechdoms, Wortcunning, and Starcraft of Early England: The History of Science Before the Norman Conquest, vols. 1-3.  Bristol, England: Thoemmes Press.  1864-66.

Gledhill, D.  The Names of Plants, 2nd ed.  Cambridge: 1989.

Andrew K. Yang, Plant Names in Old and Middle English: Problems and Trends in Taxonomy 

The Old English Herbarium (OEH) and Medicina de Quadrupedibus.  Hubert Jan de Vriend, ed.  Toronto: Oxford.  1984.

Tryskelion Press, Old World Names For Herbs And Plants,


A Poison Plant Primer for Halloween

While on a garden tour a few years ago, I crossed over to the dark side. Instead of admiring the frilly flowering ornamental plants, I spent my time inside the Poison Plant garden. 

The gate, decorated with a large iron spider in a large iron web, creaked eerily on opening and then slammed shut behind me.

The spider signified the potential dangers that grew inside that garden, like Oleander (a glycoside). This innocent-looking plant can cause respiratory difficulties and heart problems. Although this Mediterranean shrub can be a fragrant addition to the landscape, every part of the plant is poisonous when eaten. The smoke is also toxic if plant parts are burned.

Other glycosides in the garden included foxglove and lily-of-the valley.

Why would a perfectly nice botanic garden include harmful plants among the others? For the same reason so many other plants are on display: to educate gardeners and the general public.

We can’t escape poisonous plants because they can grow anywhere. Jimson weed and nightshade; soapwort and poison ivy; stinging nettle and even St. Johnswort were a few of the other plants growing in the garden.

“A recent increase in herbal usage has given rise to misuse and mistaken identities,” explained a sign near the poison garden’s entrance. “It is important to consider means of preventing a toxic encounter as well as enjoying the contributions of poisonous plants around us.”

Because Halloween is a time for delightful frights, I recommend taking a read through Amy Stewart’s entertaining book called “Wicked Plants: The Weed that Killed Lincoln’s Mother & Other Botanical Atrocities” (Algonquin Books of Chapel Hill, 2009).

She includes poisonous plants familiar to most gardeners, like Castor Bean, Henbane, Hemlock and Deadly Nightshade. But she also includes some surprises like Habanero Chile, Sago Palm, Tobacco, Junipers and Bermuda grass.

“We assume if it grows out of the ground, a plant is natural and natural is good for you,” says Amy. But cyanide is also a natural substance that comes from some plants, and it definitely isn’t good for you.

Speaking of deadly plants, what do you think is the world’s most wicked plant? Scroll past the following poison plant resources section to learn the answer.


A nice addition to Amy’s book is a list of poison gardens throughout the world and a well-research bibliography with many poisonous plant resources and identification guides. Here are a few links to help get you started:

CSU’s Guide to Poisonous Plants database lists trees, shrubs and perennials that can be harmful to animals.

Cornell University’s College of Agriculture and Life Sciences has a searchable database of plants that are poisonous to livestock and other animals. The color images help with plant identification.

The University of Illinois Extension has a comprehensive list of links to poisonous plant information. 

The World’s Most Wicked Plant?

By Jodi Torpey
Denver Master Gardener since 2005