Iris are enchanting flowers and are just starting to flower now in parts of the Southwest. I appreciate iris because the plants are tough as nails, and grow well in the alkaline soils of the Southwest. They will need more water than a cactus to keep going, but they need less than many other non-native plants frequently planted – like roses. 

What’s in a Name

Since this is Gardening with Soule – you know that I’m talking about plants on this site, but iris can also be:

     part of the eye
     an ambiguous color term
     the Greek goddess of the rainbow
     a female name in English

Iris is one of those plants where the common name and the scientific name are the same, Iris and iris. There are some other such cases, as I mused a while ago. More about Scientific Names – but since people usually run away from that topic, I called it the much gentler “Language of Plants.”  

All this fluff aside – I really appreciate the fact that iris are named for the Greek Goddess of the Rainbow – since iris flowers come in every color of the rainbow!   

Iris Overview

There are over 300 species of Iris, and about a bazillion named hybrids. There are all manners of ways to divide them – flower type, root structure, origin, with names like bearded, unbearded, dwarf, Dutch, Siberian, Louisiana, reticulate, flag, and so many more names and categories to confuse the newcomer or casual gardener.

This same sort of proliferation of names and micro-division of “types” is found in all groups of plants that are widely cultivated. There are cult-like societies of dedicated fanatics, I mean dedicated people, that focus on one specific plant alone. There are societies for all manner of plants including amaryllis, bonsai, bulbs, cactus, camelia, chrysanthemum, dalia, gardenia, herb, lichen, mint, oak, orchid, succulents, tulip, water lily, zinnia, and so many many more that I have not even named. Suffice to say that by and large they are all great people, but they can be very picky about the terminology.

So when I say “iris” in this post, I am referring to the common, widespread, cultivated iris originally from Europe and grown from rhizomes. In general the standard “bearded” iris originally from Europe. European bearded iris include genes of iris from Asia Minor (Persia) and even the Negev Desert. This means they can tolerate our alkaline soils and dry air.

How to Grow Iris

For the iris that do well in our region, the part of the iris you plant is a type of underground stem called a rhizome.   Ginger “root” from the supermarket is technically a rhizome, as is Thai ginger, also called galangal.    Rhizomes and bulbs are plant parts modified to store energy underground.   

Iris rhizomes look like chubby little hands with a few fingers.    Despite how root-like they look, the “fingers” do not go down into the earth, they must be planted horizontally.    The tips of the “fingers” are where the iris will grow new leaves and flowers.

Earth = Soil

Plant bearded iris in well-drained garden soil.    They do well in our alkaline desert soil, but flower better with a soil pH of 6.8 (slightly acidic).    For an ideal iris bed, add about 50 percent compost to desert soil, and add some sand too if your soil has a lot of clay or caliche.

Air = Temperature

Not too hot and not too cold. In general, bearded iris survive from 20F to 110F.

All iris do best if planted in a non-windy site. Some air movement is okay, but excessive wind drys them and they will not thrive.

Of all the cultivated iris, the Siberian, Dutch, and Japanese iris are more cold tolerant – down to -10F, and even -30F if well mulched. If you live in the Upper Elevations (mountains) of the Southwest, you should lean towards these types.

Fire = Light

Websites and books say to plant iris in “full sun.”    Not our desert sun!  Not even our desert mountain sun! Less humidity in the air means that more ultraviolet light gets in, and the plants can get sunburned in summer.  The iris in this video is in sun for the video but has afternoon shade in summer.

The iris in my yard do best with afternoon shade in the summer.    This means an east-facing yard if you have one.    They also grow well in deep shade under a mesquite tree in the north-facing yard, but bloom is scanty.   

If you plant iris in full summer sun, make sure they are watered two to three times per week in summer heat. Even with extra water, iris might not survive full sun in Las Vegas or Phoenix.

Water

Newly planted iris will need moisture to help get their root systems established.  Once established, deep waterings every few days is better than daily soaking.    Overwatering is a common error – and it can easily rot your iris.

The group of iris that grow in wetlands can be grown in a pots in a Water Garden with the bottom inch of the pot under water.  It’s how I grow many of my moisture loving herbs (like mint).

Planting and Care

Plant

In the Desert Elevations, plant the rhizome (or bulb) so it is covered with at least one inch of soil.   This will help them survive and not sunburn in our hot summers. Some websites and printed books tell you to “barely cover rhizomes with soil.” That may work in England, or maybe back East, but here the rhizomes will sunburn and die. 

Meanwhile, if you live in the Upper Elevations, like Reno, Flagstaff, or Taos, you do need to plant your iris deeply as well. This is so that they will not freeze. Three inches deep is fine, but not more. Ideally, mulch over them with leaves or pine needles for the winter months.

Spacing

Iris do best when spaced one to two feet apart.    Close planting gives a more dramatic flowering effect, but the iris will need to be thinned or divided more often to keep the patch growing in a healthy fashion.

Prune/Divide

Iris are perennial plants with no wood, so there is no “pruning,” but really there is.  Instead of pruning above-ground stems (branches) with clippers, we prune the below-ground cluster of stems (rhizomes) by digging and clipping. Here is a clump ready for dividing.

In general you will need to divide your iris every few years as they become crowded. Dividing Plants article.  When it comes to tucking iris in new places around the yare – you need to know that javelina root them right up and eat them, so they are not a wildlife resistant plant.  Not too sure about elk or deer.

When to divide? Late August is good, into September and even into October in the Lower Elevations.  Not in spring.

Fertilizer

Plants feed themselves by doing photosynthesis and making sugar water. Yes, they live on sugar. Fertilizer provides the “vitamins,” (actually minerals) that help plants feed themselves more better. There is a recent book calling plants “Light Eaters,” which is a very apt name.

While fertilizer is not necessary with iris, a bloom fertilizer in early spring will boost their flower production.    Avoid a high nitrogen fertilizer in spring. It leads to more leafy growth and less flowers.    After flowering is the time to use a high nitrogen or general purpose fertilizer.

Enjoy!

Iris do well in our climate.  With nominal effort on your part, iris should reward you with rainbow bright flowers every spring for years to come.

Thanks for reading!

Jacqueline

More Iris Care in my book

The Month By Month Guide offers tips for your landscape (yes even lawns and roses) in every month of the year.  I have a few copies left and am offering them to you – my loyal readers. When you buy from me you get a signed copy!

From the review:

“A great reference book is key to successful gardening in the region where you live. Arizona, Nevada & New Mexico Month-by-Month Gardening takes the guesswork out of gardening for anyone residing in the Southwest. With this book, you’ll know what to do each month to enjoy a thriving garden all year, from January to December. Chronologically organized, this guide is full of critical gardening when-to and how-to advice, along with illustrated step-by-step instructions.

The book’s author is Jacqueline Soule, a Tucson-based gardening expert. She knows this arid region inside and out, and she’s written several articles and books packed with her gardening advice. Arizona, Nevada & New Mexico Month-by-Month Gardening showcases Soule’s expertise in one easy-to-read guide.”

Profits from the sale of this book go to the Horticulture Therapy non-profit Tierra del Sol Institute.  

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