Horticultural Vermiculite: For iris gardens from clay to sandy soil

It's almost time to dig and divide your irises... so now is the perfect time to take a look at soil amendments for better plant health. One of my favorite amendments is horticultural vermiculite. My southern bearded iris garden would not be possible without it, but even my moisture-loving Louisiana irises are happiest when this beneficial amendment is included in the soil blend. No matter what your climate or soil type, the addition of horticultural vermiculite can have a positive effect in your garden. 

'Flying Down to Rio' (Moores 2005) planted in vermiculite-amended soil

Vermiculite is a naturally-occurring geological material, more specifically a group of aluminum-iron magnesium silicates that closely resemble mica. When processed for horticultural use, vermiculite is introduced to intense heat, causing it to expand into multiple layers of very thin plates. The end result is accordion-shaped granules of sterile, disease-free planting medium. Vermiculite has been used by nurserymen and gardeners for decades, in potting soils and outdoor mixes, in turfgrass and outdoor plantings, for 100% vermiculite growing applications, and for hydroponic growing. Horticultural vermiculite improves soil aeration, assists in temperature regulation, and retains moisture and nutrients necessary to feed rhizome roots for superior growth.

Close view of coarse-grade horticultural vermiculite

Consider the following reasons for using horticultural vermiculite in your iris garden:

• Soils amended with horticultural vermiculite are better able to retain air, nutrients, and moisture, and release them to the plant as needed. Therefore, a planting medium mixed with vermiculite promotes faster root growth for quick anchorage of newly planted rhizomes.

• Because vermiculite has cation exchange properties, it holds ammonium, potassium, calcium and magnesium and makes these trace minerals available to the roots as needed.

• Horticultural vermiculite is a perfect growing culture for irises. The pH of vermiculite is neutral to slightly alkaline (7.0-8.0). It will not deteriorate quickly like most planting materials, and it will not turn moldy or promote rot.

SOIL AMENDING OR CONDITIONING
Coarse grade vermiculite is preferred for outdoor horticultural uses, though medium grade may also be used. With heavy soil, the addition of vermiculite creates much-needed air channels to greatly improve soil aeration. When soil is sandy, the addition of vermiculite helps the soil retain much-needed moisture. Soils may be amended up to a rate of two parts soil to one part vermiculite.

With a large garden area, you may choose to condition only the planting rows. If this procedure is continued for three to four digging cycles, the entire garden area will eventually be conditioned. Because horticultural vermiculite is inorganic, it will continue to function for many years.

Medium grade vermiculite is preferred for potting applications. When used in potting new rhizomes, vermiculite improves soil aeration and diminishes the risk of tender roots breaking as the irises are transferred to the garden. If starting with commercial potting soil, check the label before adding vermiculite, as it may already be present. If making your own potting mix, vermiculite may be added up to a ratio of one part compost material or soil to one part vermiculite.

Planting mix of two parts soil and one part horticultural vermiculite

SUMMER MULCH
If you live in an area that has little to no summer wind, you can use vermiculite to mulch around the rhizomes in the hottest summer months. Vermiculite acts as a constant reservoir of moisture without promoting rhizome rot, protecting your irises from dehydration and scorching during dry spells. This can be especially helpful immediately after digging time, when replanted rhizomes are settling in. After the intense heat passes and winds return, you can remove the vermiculite mulch and save it for use in potting or amending the following year. Or, you can mix it into the soil in other areas of your garden. Used as a mulch, vermiculite may be applied up to 3 inches thick.

FLORAL ARRANGEMENTS
After your irises begin blooming, you will want to bring some of those lovely blooms inside to enjoy. Fill a vase with vermiculite, saturate with tap water, and allow the vase to sit for a few minutes. Repeat this process until the vermiculite is no longer absorbing and water is visible on top. Then, pour off the excess water. Arrange your flowers as you would normally. Your flowers will remain fresh for many days without refilling, and the stems won't develop that unattractive slime that normally occurs when a stem sits in water. When placing flowers in vermiculite, be sure to cut the stems at a slight angle to facilitate wicking.

Flowers being arranged in a vase filled with water-saturated horticultural vermiculite

HOLDING OR SHIPPING RHIZOMES
Vermiculite can also be used at digging time. After you have provided a bleach bath for your newly dug rhizomes, allow them to air dry in the sun. Be careful not to let them bake; the idea is to let the exterior dry without dehydrating the interior. After the rhizomes are fully dry, place them in a storage container and pour vermiculite around them. The vermiculite will prevent moisture fluctuation during the storage period and will provide protection against temperature changes. Though iris rhizomes should never be stored long-term like a bulb, use of vermiculite allows your rhizomes to stay fresh many days longer before replanting. An exact length of time cannot be predicted here, as the timing is dependent on the hydration level of the rhizome (internally) prior to placement in the vermiculite. Vermiculite can also be used when shipping rhizomes to friends.

Rhizomes being placed into a shipping box filled with horticultural vermiculite

A FEW WORDS ABOUT SAFETY
In the past, you may have heard about a link between vermiculite and trace amounts of asbestos. For almost seventy years, vermiculite was used safely and effectively for many purposes, including construction and industrial applications. Then, in 1990, asbestos particles were discovered in vermiculite originating from a mine in Libby, Montana. This mine was primarily used to produce vermiculite for industrial, not horticultural, applications, under the tradename Zonolite. The discovery brought worldwide production of vermiculite to a screeching halt as scientists and regulators worked to determine if any other mines were contaminated. Since that time, strict inspection and safety procedures have been put in place. Though a warning label may still appear on the bag due to past Libby-related incidents, vermiculite is not listed on the OSHA List of Hazardous and Toxic Substances. Gardeners can feel confident that the horticultural vermiculite found in stores today is non-toxic and safe for use in their garden. Just remember, it is wise to use caution when working with dusty garden amendments of any type, including use of a dust mask and watering the garden area prior to application. 

What amendments have been useful in your garden? Post your comments below!

Learn more about horticultural vermiculite with these resources:

Material Safety Data Sheet for Vermiculite, SunGro Horticulture, issued March 1, 2008. This publication details the chemical and physical properties of vermiculite, verifies that vermiculite is not considered a hazardous or  toxic substance by OSHA, and provides useful supplemental information.

Statement by The Vermiculite Association on the USA Government Studies of Vermiculite and the Potential Asbestos Exposure, May 2005.

EPA Sampling and Analysis of Consumer Garden Products That Contain Vermiculite, August 2000. This report details the results of the first large-scale study of consumer garden products that contained vermiculite. Since the publication of this report, significant advances have been made in the processing and inspection of horticultural vermiculite sold to consumers.

Iris Bloom Season in NW Louisiana - Part III

by Ron Killingsworth

As promised, here is Part III sharing photographs of irises from the Caddo Lake area in NW Louisiana.  I have included a bit of history of the region and hybridizers, and I hope you enjoy the photographs.


The hybridizer Pat O'Connor lives just outside New Orleans and loves to name his irises for local features such as bridges, cities, canals, swamps, and streets in New Orleans.   Poverty Point is a World Heritage Site with ancient mounds built by native Americans.  This beautiful iris with great coloring and signals is a fitting tribute to the site.

'Poverty Point' (Pat O'Connor, 1999)

The Rigolets is a 12.9 kilometer (8 mi) long strait in south Louisiana. "Rigolets" comes from the word rigole, French for "trench" or "gutter." The name is locally pronounced "RIG-uh-leez."

'Rigolets'  (O'Connor, 2004)

Two of my favorite Louisiana irises side by side:  'Cest Si Bon' is about as "cajun" as you can get and this Louisiana iris is really a beauty.  'Rusty O' was named by Charles Arny for Rusty Ostheimer (now McSparrin).  Rusty and her husband Bud grow many Louisiana irises down below Lafayette, LA.

'C'est Si Bon' (Taylor, 1983) on left and 'Rusty O' (Arny, 1991) on right

Harry Wolford lives in Palm Bay, FL, and used to watch the lift off of the space shuttle from his back yard.  That's Seminole country and Harry has named quite a few Louisiana irises Seminole this or that.  I love the veining in this iris.

'Seminole Autumn' (Wolford, 2004)

And here is 'Seminole Moon', with a bit of orange in the yellow.

'Seminole Moon' (Wolford, 2009)

And finally, 'Seminole Sunrise', a fine red.

'Seminole Sunrise' (Wolford, 2004)

This iris is a tetraploid Louisiana iris that is quite different from the other few tetraploids on the market.  Tetraploid irises have more diversity in their genetic make-up and thus are highly prized by hybridizers.

'Texas Toast' (Mertzweiller, 2005)

This is definitely an "oldie but goodie", just one of many that Caroline Dormon registered. If you are ever in central Louisiana, don't miss her old home which is now Briarwood Nature Preserve located near Saline.

'Violet Ray' (Dormon, 1949)

'Wheelhorse' is a well know Louisiana iris and can be found in the genealogy of many fine Louisiana irises.

'Wheelhorse' (Dormon, 1952)

And here is 'Wood Violet', aptly named.

'Wood Violet' (Dormon, 1943)

This picture of a clump of award-winning irises was taken by my Koi pond; the whooping crane statues in the background watch over the irises.

'Red Velvet Elvis' (Vaughn 1991)

And here is a massive planting of mixed Louisiana irises -- the view from my front porch.

Finally, I thought I'd share one of the tall bearded irises my wife Sue has successfully grown in our hot and wet climate:  'Violet Shimmer'.  

'Violet Shimmer" (Moores, 1995)

Well that about wraps it up, and I hope you enjoyed the show.  If you want to learn more about Louisiana irises please visit the website of the Society for Louisiana Irises, and to learn more about many other species of irises, visit the website of the American Iris Society.

The Iris Grower's Struggle, Part II

by Carlos Ayento

As mentioned previously, the Chicago iris gardener is presented with many problems: humid summers, cold winters without snow cover, and the pests such as grey squirrels, rabbits and iris borers.  While pest can be controlled to an extent, weather cannot; and only the toughest irises survive and thrive in the Windy City. 

In my last blog, I provided a sampling of some West Coast iris originations that have grown well in the City of Chicago.  Today, I present a listing of modern irises by introduced by various iris hybridizers that have proven themselves to be superb growers.  If you have some difficulties growing iris, give these a try!

From Anthony and Dorothy Willott, we have Hallucination (2006).  It is a remarkable standard dwarf bearded origination for its red-violet bands, veining and dotting.  The carrot-red beards make a nice touch.  It has proven extremely resilient and vigorous.  It was attacked by squirrels in June and has made a remarkable comeback.

Bijou (George Sutton, 2002) was an iris that I received as a gift from an order placed in 2007 or so.  I’m am so glad that I received it.  It has been nothing short of amazing and is quick to form clumps in the garden.  I’m also a sucker for blue-pink irises, especially ones with blue beards!

Direct from Canada, one of my personal favorites of Chuck Chapman’s introductions is his Summoned Spirit (2002).  It’s an intriguing medley of pale gold and blues, almost as if each petal was individually brush stroked.  The bonus of it being bred in Canada is that it is completely cold-hardy and snuffs at Chicago’s most brutal winters.

 Named after a computer graphic movement, Walter Moores’ ASCII Art (2007) is fine plicata.  But, the fact of the matter is that it isn’t just your average plicata.  The light purple coloring is heavy strictly on the hafts and style arms of the petals.  The strokes of purple are seemingly bleached away the further it encompasses the standards and falls.  It has bloom consistently since planting it in 2014 and has outstanding growth qualities.

A favorite iris amongst myself the Region 9 iris gardeners is Emma’s Laughter (2008) by our very own G. Steve Poole.  While Mr. Poole has registered and introduced irises since the early 1980s, it is only recently that his originations are taking notice.  I appreciate Emma’s Laughter for its exquisite ruffling, pale powder blue coloring and crisp texture.

Ernie Hoch is a new iris hybridizer based in Washington state.  He only has a handful of registered introductions, but that consistently impressed me is his 2014 introduction Chevron Three.  I purchased the iris as a new introduction in 2014 and it does not disappoint.  As a matter of fact, it has bloomed every year so far, since planting it in 2014.  Growth is just outstanding.  It produced rhizomes like no other.  I’ve literally had to divide it every year because there were just so many new rhizomes.  Highly recommended!

 From overseas, the wonderful French-import Pause Douceur (2014) from fourth generation hybridizer Richard Cayeux, is proving its worth here across the Atlantic and in Chicago.  A delectable confectionary, Pause Douceur has classic form, strong substance and superb growth habits.  Having purchased this iris directly from the Cayeux Iris firm in 2014, I have sadly yet to see this wondrous iris for sale by any U.S. iris growers.  I’m sure it will prove to be a popular iris variety in the years to come.

In the world of irises with ruffles galore, sometimes an iris with a more tailored appearance is a welcome reprise.  As a historic iris enthusiast and collector, some of my favorite irises are from the 1950s through 1970s.  These irises were ruffled just enough to be pleasing.  So, when I saw the Schreiner’s introduction Better Together (2014), I was very pleased so a highly contrasted iris in a tailored (to modern iris standards) bloom.  To me, the most eye-catching quality is the subtle brushing of buff-cream on the pale violet-blue standards.  It is very appealing, especially when offset by the much darker, wine-purple falls.  So far, it has been proving itself in Chicago and it has been one of my personal favorites the recent Schreiner introductions.

  

New, Exciting Mohr-type Irises

By Bryce Williamson

In my one and only year at Chico State, one of the highlights was the ability to go to Leo T. Clark’s garden at Corning and to see his aril and arilbreds in bloom, irises that sadly had a limited growing range for growth. As a result, I have been keenly interesting in the new generation of Mohr-type arilbreds being introduced, often from a combination of medians and half arilbred irises. Current hybridizers have pushed the colors and patterns into new, exciting directions and the flowers, although only a quarter aril, show more of the aril characteristics that make this exotic group of irises so much fun to view especially since growing the half aril hybrids and pure arils can be a challenge in many climates.

Eye to Eye (Keppel) is an example of more aril-like flowers, including the signal,

and the winner of the 2017 American Iris Society Mohr Medal.

Image by Keith Keppel.

The hope of these new Mohr types is that they will expand the areas where they can be grown with little trouble and bring these exotic, flamboyant flowers to a much larger audience both in The American Iris Society and the general gardening public. For a background on these interesting hybrids, Tom Water wrote a informative World of Irises blog,  Arilbred Iris: A Little History.

Older Mohr type hybrids tended to be crosses of tall bearded irises with, at first, William Mohr, but the new hybrids are using medians and tall bearded irises with variety of arilbred hybrids. I do hope you, as I have done, will add some of these varieties to your garden, expanding your bloom season and bringing fresh colors and patterns into your palette of spring flowers.

Calypso Dancer (Tasco)--image by Rick Tasco

Confederate (Rick Tasco)--image by Rick Tasco

At the present time, the leaders in producing this new generation of Mohr type arilbreds includes Keith Keppel, Paul Black, Thomas Johnson, and Rick Tasco.

 Octave (T. Johnson)--image by Paul Black

 Sri Lanka (T. Johnson)--Image by Paul Black

Suspect (T. Johnson)--image by Paul Black

These are garden irises of limited fertility.  Paul Black in email wrote, "For most here is no fertility, especially the 1/2 breds X SDB....There is a very limited fertility with a few--meaning a seed of two."

His seedling V351A, pictured below, is "the result of Brash and Bold X reblooming TB seedling and there was only 1 seed in the cross, though V351A does show some limited fertility."

Brash and Bold (Black)--image by Paul Black

Black V351A--image by Paul Black

He was extremely lucky with the cross that produced four introductions, ‘Heart of Hearts’, ‘Galaxina’, ‘Perry Dyer’, ‘Red Ahead’ and ‘Soaring Falcon’ are all siblings.  As he wrote, "What a cross!  I’ve gotten a few seed from a couple of them and Adam Cordes has gotten 7 seeds from ‘Heart of Hearts.’"

Soaring Falcon

Red Ahead

 Heart of Hearts

Perry Dyer--images by Paul Black

In responding to my question about the range where these hybrids will grow and bloom, he wrote, "Yes, the aril-medians (1/2 bred X SDB) will grow further south than SDBs.  ‘Desert Snow’ has grown well and bloomed in Manitoba, Canada, and also for Walter Moores in Mississippi.  That probably accounts for its popularity."

Desert Snow--images by Paul Black

At this point, there are only a few sources for plants. Two reputable sources are Mid America and Superstition. Click on the nursery name and it will take you to a link where you can find out more information from the garden owners.

"Talking Irises" TALL BEARDED IRISES: IN FULL BLOOM--A Wonderful Combination of Color and Form

By Susanne Holland Spicker

         Spring 2016  "In Full Bloom"

(Tall bearded irises l to r) 'EVER AFTER' (Keppel '86),  'MONTMARTRE' (Keppel '08), 'RANCHO ROSE' (Gibson '75), 'NEW LEAF' (Ghio '97), 'EPICENTER' (Ghio '94), 'ARTIST'S TIME' (Schreiner '74), (Back, l to r) 'BOLD EXPRESSION' (Ernst '03), 'ARTISTIC WEB' (Tasco '10), 'CITY LIGHTS' (Dunn '91) 

From mid-May through mid-June, a wonderful combination of color and form unfolds in my zone 6 flower beds. Tall bearded irises are in full bloom, and with companion plants that coincide with their bloom, the gardens are a sea of color for more than a month. It is my favorite time of the year!

(Tall bearded irises, from top l) 'EVER AFTER' (Keppel '86), (Group photo, l to r) 'CHINESE TREASURE' (Blyth '83), 'POND LILY' (Jones '95), 'DATE BAIT' (Meek '85), 'CUPID'S ARROW' (Ghio '90), 'RINGO' (Shoop '79), 'JENNIFER REBECCA' (Zurbrigg '85), 'RASPBERRY WINE' (Schreiner '01), (top r) 'QUEEN'S RANSOM' (Van Liere '12), 

(2nd row) 'NIGERIAN RASPBERRY' (Kasperek '95), 'WEARING RUBIES' (Blyth '00), '00)(Bottom r) 'ROLE MODEL' (Denny '88), 'QUEEN IN CALICO' (Gibson '80)

(Tall bearded irises top l to r) 'DEEP CURRENTS' (Johnson '09), 'OXFORD COUNTESS' (Blyth '07), (background) 'MING LORD' (Blyth '06), 'LENTEN PRAYER' (Schreiner '98), (Bottom l to r) 'PLUM PRETTY WHISKERS' (Spoon '03), 'ARTIST'S TIME' (Schreiner '74), 'EMBRACE ME' (Van Liere '08)

Tall bearded irises are spring's "universal companion plant" because of the plethora of colors and color combinations these "queens-of-the-garden" have. I have found there are several of these tall beauties to go with any perennial I have, or can even think of. The combinations are endless! I always keep my eye out for perennials that not only go well with the irises, but ones that bloom at the same time, with similar light, water, and fertilization requirements.

(Tall bearded irises top l to r) 'BUBBLING WAVES' (Ghio '06), 'GLOBAL CROSSING' (Van Liere '12), 'BY DAWN'S EARLY LIGHT' (Van Liere '12), 'PROUD TRADITION' (Schreiner '90), 'BUBBLING OVER' (Ghio '92), 'EMBRACE ME' (Van Liere '08), 'CLASSIC LOOK' (Schreiner '92), 'CROWNED HEADS' (Keppel '97), 'CITY LIGHTS' (Dunn '91)

(Tall bearded irises l to r) 'HAPPENSTANCE' (Keppel '00), 'SWEET

SERENADE' (Schreiner '11), 'ASCII ART' (Moores '97), 'HEATHERIDGE' (Gatty '85), 'BUBBLING OVER' (Ghio '92), 'WINNING EDGE' (Ghio '97)

(Tall bearded irises top l to r) 'DESIGNER LABEL' (Ghio '03), 'LACED COTTON (Schreiner '80), 'ELISA RENEE (Gaulter '83), 'SLY FOX' (Wood '97)

(Tall bearded irises l to r) 'BOLD EXPRESSION' (Ernst '03), 'MAGHAREE' (Blyth '86),'PURPLE SERENADE' (Schreiner '05)

Someone once said there was "nothing more heaven-like than a field full of irises." I echo that sentiment.  As spring approaches, the anticipation of the beauty that unfolds is indescribable! I look forward to the gardens when "in full bloom."

(Tall bearded irises front to back) 'GARDEN BRIDE' (Chapman '98), 'FABULOUS ONE' (Nicodemus '06), 'FANCY STUFF' (Brown '01), 'BOLD EXPRESSION' (Ernst '03), 'PURPLE SERENADE' (Schreiner '05), 'CHAMPAGNE ELEGANCE' (Niswonger '87), 'MIDNIGHT REVELRY' (Schreiner '05), 'LATIN LOVER' (Shoop '69)

Do you have a favorite iris bed?  Are there combinations of companion plants, or irises that go well together that you have planted that have wonderful combinations of color and form?

'DAUGHTER OF STARS' (Spoon '01)

I would love to hear from you--I'm always interested in what others are doing in their iris gardens!