You Can Grow Iris in the Southwest

Iris flowers are enchanting and the plants are tough as nails. They grow well in our alkaline Southwestern soils, needing little extra water to keep going. Named for the Greek Goddess of the Rainbow, iris flowers bear almost every color of the rainbow.

It is March 4th so this is a “You Can Grow That” post.  You can search for others, like You Can Grow a Colorful Garden in the Heat (last July).

Iris Overview

The part of the iris you plant is a type of underground stem called a rhizome. (Supermarket ginger “root” is technically a rhizome.) There are also some species of iris that grow from bulbs. Both types do well here.

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Ginger – but iris rhizomes look very similar.

Rhizomes and bulbs are plant stems modified to store energy underground. The rhizomes look like stubby little hands with fat fingers. Despite how they look, the “fingers” do not go down into the earth, they must be planted horizontally. The tips of the “fingers” are where the new leaves will arch up out of.

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How to Plant Iris

For best survival in our hot summers, plant the rhizome so it is covered with one inch of soil. Not much more than this though, they do not grow well when planted too deep. Planted less deeply than this may work in England, but here the rhizomes will sunburn and die.

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 more often to keep the patch healthy.

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Light

Books say to plant iris in “full sun.” Not our Southwest sun! 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 tree in the north-facing yard, but bloom is scanty. If you plant them in full summer sun, make sure they are watered two to three times per week in summer heat.

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Iris in my garden love the early morning light. The do get afternoon shade in summer.
Soil

Plant 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.

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Water

Newly planted iris will need moisture to help get their root systems established. Once established, deep watering every few days is better than daily splash. Over-watering is a common error that can rot your iris.

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Fertilizer

While fertilizer is not necessary with iris, a bloom fertilizer in early spring will boost their flower production. Avoid a high nitrogen fertilizer for this first fertilization of the year – it leads to more leaves and less flowers. After flowering is the time to use the general or even high nitrogen fertilizer.

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

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soule-southwest-growIf you live in Southeastern Arizona, please come to one of my free lectures that I mention on my Facebook page. After each event I will be signing copies of my books, including Month by Month Gardening for Arizona, Nevada, and New Mexico (Cool Springs Press).
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2 thoughts on “You Can Grow Iris in the Southwest

  1. Hi Linda –
    Thanks for being so precise! It helps me answer. This sounds like a very good fit.
    I use cactus/palm potting mix (Kellogg brand) now for almost all my container plants. It drains well so plants don’t get waterlogged and had ample organic matter so plants are nourished.
    Your iris should respond well with fertilizer after blooming and again at Labor Day. You might want to divide them every 2 years, and start with fresh potting mix for best blooming.
    Happy Gardening! J

  2. Is iris okay in a 24-inch glazed container using potting mix, or is sand and extra desert dirt mixed in? I would love this in my north facing yard that has six hours east and midday sun. The afternoon has filtered shade from an old mesquite. During the summer, it gets 8 hours sun.

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