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How to Grow Pacific Coast Irises in Your Garden. Hint: Ignoring Them Works Best!

How to Grow Pacific Coast Irises in Your Garden. Hint: Ignoring

Them Works Best!

By Bob Sussman: translated into understandable and grammatically correct English by Sarah G. Sussman Ph.D.

(All I know is what I read on the internet and sometimes it’s true)

Pacific coast irises grow in nature mostly along the West Coast from Sant Barbara County into Washington state.  We own a native plant nursery in Southern California and have been growing California native plants including pacific coast irises for several years. You’d think this would be an easy addition to what we grow at the nursery. They sort of are, you just need to find the right level of “letting them be.”  Our first attempt to grow pacific coast irises was a bit of a failure. We planted a series of these irises in early spring and all was well until summer.

In summer, most California native plants begin to shut down with some level of dormancy. We reduced our watering frequency to 1x week. All the irises died. We tossed the dead plants into the mulch pile under some trees and never watered them. Why would we? This was our graveyard of mistakes. However, we got a big surprise at the end of winter during our rainy season. Damn, up they came and they flowered beautifully, it all seemed so easy.

Immediately, I went to the source of all information, the web. I read all that I could find and hit “images” too to see pictures. There are 11 or 12 species of pacific coast irises. The species generally grow along the Pacific Coast but some in the mountains, all pretty much in grassy, sunny meadows. The irises are relatively short around 1’ to 2’. The flowers are a reasonable size at 2” to 3” across in a range of colors.

Some shots from the field:

 

As a side note, these will all easily cross pollinate. They will naturally cross in the field and in your garden too. A cool thing, as the years go by, you’ll get new and different looking irises popping up.

And in your garden?

If pacific coast irises in nature grow from coastal Santa Barbara County up to Washington state, how will they grow in my garden in Los Angeles or San Diego or Pasadena?  It’s important to understand that in our region in Southern California is different than Northern California and the Pacific Northwest.

Where to plant?  To grow these in our region, the closer to the coast the more sun they can tolerate and grow well. This was an observation made by one of my friends at  the Society of Pacific Coast Native Iris Society, Kathleen Sayce. Translation, if you live in Pacific Palisades, Ventura, Laguna, or Santa Barbara facing the ocean they will do fine in mostly sun. If you live in Camarillo, Brentwood, Beverly Hills, or most of San Diego plant in part to full shade. In places like the San Fernando Valley, Simi Valley, or Pasadena they need to go in full shade.

Okay, now when should you plant? Pacific coast irises should be planted from about mid-September until maybe late March. Beyond that period of the year you can still plant them but you’re on your own and here’s why. In southern California you can plant all year but you can’t plant everything all year. Pacific coast irises have a strong dormancy and while they maintain their green leaves the roots stop growing and even die back to the rhizome from about the end of May until roughly September. In September new white roots begin to grow. Take a look below.

The picture above from dividing some of our irises shows the new white roots growing form the rhizome and when the roots begin to grow it’s time to plant!

Now, how to plant and care? This is pretty straight forward. Generally, you’re planting in a shady spot. Dig a hole with a depth such that when you take your irises out of their pot they will sit even with the surrounding soil or a little above. To measure and get the right depth just put the pot in the hole and see. Next, fill the hole up with water and water the soil you took out of the hole. Finally, flip the nursery pot with the iris upside down supporting the plant with one hand and pushing the pot off with the other. What you want to do here is separate the plastic pot from the plant. The root ball should look like a round jello mold. Place your new iris in the hole without breaking the roots and cover in with soil. Then water, water, water…..

Next, once your iris is planted keep up the watering with heavy watering 1x/ week until about May. In May drop, the watering frequency down to about every other week. The issue here is again, that the irises are not growing during this period and when you water too frequently they can rot.

A couple of notes that will make your irises grow better and other California natives too. First, mulch, mulch, mulch….but leave a space around you plants/irises so they can dry around the rhizomes. Too much mulch over the top of the plants will rot them. Second, a small amount of time release fertilizer in say December/January seems to do a lot of good to produce more growth and bigger irises. The fertilizer should be well balanced like 14/14/14, which is what we use at the nursery. A couple of tsps. around the base of the iris should do it.

Problems

 Irises if set on “ignore” are usually good for years until there can be things to watch for. Rotting is the biggest problem. If they are planted too deep, watered to frequently (especially on a hot day) the leaves at the base will turn black and the rhizome is done for. The other problem can be from the wild things. If your area is rural and you have gophers you might want to put chicken wire in the planting hole. Rodents do not really like irises much but if there’s nothing else to eat, they’ll eat what there is. Lining the hole with chicken wire before planting will give you good protection for many years. It’s inexpensive and a little more work but in the domain of the Gopher Kingdom it’s just what you have to do. 

When do they Flower and what do the flowers look like?

 Pacific coast irises are more or less spring flowering plants. Our first irises begin in February and end in very early June. What do the flowers look like? I think you can divide them into two groups. The first group are more species like. These tend to be simpler flowers – not so many colors or patterns within one flower. They also tend to be more of a traditional triangular shape. They look particularly good in a mass planting. Below are some examples of the more species like irises that we grow at the nursery.

The second group of pacific coast irises we grow are the more complex and hybridized ones that are more often looked at as individuals. We hybridize most of our own at this point. Our hybridized ones seem to be more heat resistant than many of their parents. Their colors and designs stand out as individuals. The flowers are also bigger typically ranging from 4-1/2” to 5” across.  A few of these are below for you to take a look at. These are really just a “few”……

One cool consideration about growing these more complex hybrids are the offspring you can grow in your garden. We cross pollinate specific individuals but you can collect or leave seeds in the garden that result from “open pollination”.  This means that the pollinators, mostly bees, pollinate the flowers. We get some of our very, very interesting creations that are bee pollinated and you will too. The more interesting individuals interesting offspring you will have in your garden too.

 

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GoldenHoneycomb

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Iris 'Golden Honeycomb'

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Iris 'Golden Honeycomb'

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Gold

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Part Shade / Shade

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Drought Tolerant / Occasional
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