Breeding Reblooming Irises: An Eye to the Future-2

by Betty Wilkerson

Zone 6, KY

An Eye to the Future-2.

People love to talk about their favorite finds in the seedling patch.  Dr. Lloyd Zurbrigg talked about ‘Renown’ because it was a seedling that rebloomed well for him.  Then he introduced it in 1992.  There were many reports of it reblooming throughout the country.  After a false start (growing an iris as ‘Renown’ that was incorrect) I finally got the real ‘Renown’ the summer after I moved to Allen County in 2003.  The first bloom was ugly and I questioned the authenticity.  In 2005 I grew ‘Renown’ it an upper bed and it blossomed very well!  I’ve used tons of pollen from this bed, since my final success.  ‘Renown’ reblooms in garden zones north of mine, yet only one stalk has developed here in the off season.  

'Renown'  (Zurbrigg 1992)

I decided to do some serious breeding with ‘Renown.’  It was a bit of a research project for me and there are several seedlings that I like. At this point, my favorite ‘Renown’ seedling, 2155-01, is from (Treasured x Renown.)  This seedling was a sole survivor from about 50 seed.  It has given some lovely seedlings.  I was going to name it ‘Wormhole,’ but I was told the name would offend Dr. Zurbrigg!  Hope springs eternal in my reblooming heart, so it’s been introduced this year as ‘About Tomorrow.’  It’s my belief this is a very good iris.  It’s not missed a spring since maiden bloom, it has always given a good stalk to fan ration, and it’s very pretty, for a white!    

'About Tomorrow' (Wilkerson 2013)

'About Tomorrow' (Wilkerson 2013) 

After a winter of gnashing of teeth, and wringing of hands, I decided to spend my 2013 spring working toward strong chances of rebloom.  Only a handful of irises rebloom well here, so I decided they would be a good match with ‘About Tomorrow.’  I was also looking for tangerine beards so I searched the blooming irises for something that rebloomed for me and had the right beards.  Seed are now waiting to be planted from ‘About Tomorrow’ by ‘Cameo Blush’ and ‘Summer Radiance.’

'Cameo Blush' (Weiler 1998) 

Photo by Loic Tasquer

'Summer Radiance' (Wilkerson 1996)

One day I had a couple of blooms in my hand and didn’t know what to do with them, so, now, I have seed waiting from ‘About Tomorrow’ X ‘Star Gate.’ Although  'About Tomorrow' is white, I expect this cross will breed to the blue/purple side since the two share ‘Violet Miracle’ genes.  

'Star Gate' (Wilkerson 2005)

'Violet Miracle' (Zurbrigg  79)

At the end of August, I’m enjoying bloom on 1907-10Re.  It is a sibling of ‘Cool Character.’  1907-10Re bloomed all summer in 2011 without missing a day. It looks like I need to line this one out and consider introducing it.  It's still purple but it has many good qualities. Maybe the next generation will have other colors!  

1907-10Re (Wilkerson seedling) 

There are more seeds resting in the envelope rack.  They will all be planted in pots this fall.  Once again, I’ve enjoyed sharing the workings of my mind and the reasoning that went into making the latest crosses.  Will any of them produce good rebloomers of introduction quality?  I really think the potential is here.    

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.