Monday, June 25, 2018

Finding the Goldilocks Zone for Pacifica Iris

June 19, 2018
Kathleen Sayce

Pacifica Iris are like Goldilocks when it comes to growing conditions:   Not too wet, not too dry, not too cold, and not too hot. Soils should be mildly acidic and well drained, with ample carbon and mulch. Avoid at all cost the combination of humid hot weather and warm alkaline water—plants will be toes up in days if they experience these conditions. Despite this, we have brave gardeners in summer-hot climates who continue to experiment with this fussy iris. 

Iris tenax in the garden; grown from seed in a protected styrofoam container

Water preferences:  Cool temperatures in summer, and slightly acidic at all times.  Not warm, never alkaline.  Established plants tolerate drought, but this statement hides the reality that in their native climates, Pacifica Iris have deep roots and cool root runs despite long dry summers. When in doubt, water more than less. 

Bare styrofoam--it does work, but it's fragile; this planter houses PCI seedlings for Garry Knipe's cross climate/cross continent experiment. 

Light:  Varies with temperature—the hotter the climate, the deeper the shade for this fussy group.  SPCNI members in Idaho, Arizona and Texas have grown Pacifica Iris for at least a few years by mulching, planting under roof overhangs, watering in summer, and arranging deeper and deeper shade as summer heat builds up. They also expect to grow new plants from seed whenever an extremely hot summer wipes out all their Pacifica Iris. 

Soils:  Moderately acidic, well drained, never soggy or saturated. Good carbon levels help promote soil fungi, which are probably key partners in keeping these irises happy. Carbon can be biochar, compost, or decomposing wood chips. 
Painted styrofoam:  The color is less obnoxious than white, but it is slowly wearing away, and the planter is only slightly less fragile.

Mulch:  Shredded bark or wood chips, or gravel. I use granite gravel, AKA chicken grit, to top all pots and planters, which helps keep seeds off the surface, soil from flying around in heavy rain, and slows down birds and rodents determined to eat iris seeds. 

Pots:  Like many gardeners, I began with dark colored plastic pots for growing plants from seeds. Lightweight, stackable, easy to store and reuse, it took me too many years to discover their drawbacks. Lightweight—they heat up quickly, soils dry out quickly, and roots heat too. 

Styrofoam containers followed, and the results were wonderful. Roots are cooler, plants are happier. But these materials are fragile, easily damaged by pecking, chewing, or as I learned when we had danger trees removed, by having large tree-like objects dropped on them. 

Styrofoam with epoxy cement coating, patched in two corners (upper right, lower left):  this planter survived a tree falling on it, and after patching, went to housing Iris hartwegii australis, which is happier under house eaves than in the garden. 

Treatments were tried to protect the soft surface, including:   
1. Paint, using various colors to make rock-like objects, as Ian Young and others in the Scottish Rock Garden Club have done). 

2. Epoxy concrete patch, mixed in small batches and troweled on thickly, mimicking rocks. This works well enough that the planter that did have a falling tree dropped on it was resurrected with additional patching material, and now houses a happy Iris hartwegii australis. 

3. Not yet tried—painting on cement, or troweling on hypertufa mix.

Hypertufa planter with PCI seedlings--the best solution so far.

4. Then came hypertufa planters, which are made with various combinations of perlite, cement, water, and peat / coir/ compost, or minus any organic material, and using a variety of containers as forms. Joseph Tychonievich, editor, The Rock Garden Quarterly, wrote an article about the wide variation in recipes for hypertufa in the Winter 2017/2018 issue. 

It’s my new favorite material for planters. Irises/lilies/crocus/tigridias/brodiaeas love it. Cool roots; never soggy, not even in 11 inches of rain in 8 hours; not too cold in winter, nor warm in summer. Tougher than styrofoam, and porous, so roots are well aerated. It’s also easy to make those important wire mesh covers to keep voles and jays off the seeds and tiny seedlings. 

Now, all I need is the time to make 50+ new planters!

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