Thursday, February 19, 2015

Part Two: Remineralizing soils and the PCI response in my Garden

Kathleen Sayce

Yes, as a result of my soil experiments there were more flowers than ever in my garden in 2013. But it's the number of Pacific Coast Iris (PCI) pods that was astounding. In prior years I'd seen around 50-70 seed pods in total. I know this because I use organza mesh bags on ripening pods to keep them from tossing seeds all over the garden, and I could count the bags as they went out. I'd purchased 400 bags and used 70 in 2012, on every pod I could find. And this had seemed typical at the time, based on prior years' seed sets.

Tools of the seed collecting trade:  mesh bags, paper bags, and somewhere in the bottom of the basket, a writing implement and clippers. 

By 2013 I used every mesh bag, some of them several times, shifting from early ripening pods to later ripening pods. A friend found a few more bags at a yard sale and gave them to me; I used them as well. I cut pods off many plants, needing at most 15 pods of each variety for the SPCNI seed exchange, and threw away at least 100 pods. So in one twelve-month period, my irises went from producing around 70 pods, to producing around 500 pods. The only thing that changed was the soil's mineral nutrition.

Some of the extra pods.  Look closely at the top of the image to see seeds spilling out in the lawn. Just a few of the many pods I tossed in 2014, from the plants that set seeds.

There was also a major weather difference that reduced the seed set for many PCI. Many of my well established plants are hybrids that flower in May and early June. A typical year has PCI in flower from April until late June or early July. We had a late wet spring in 2013. I did not get any seeds from the early flowering PCI. The later flowering species and species crosses that bloomed in mid June were more successful, as they flowered in drier weather, and bumblebees could actually get to their flowers. So this astounding pod production was despite very poor early-season weather for seed setting.

One hybrid I very much wanted seed from, 'Finger Pointing', did not set any seed at all!

PCI 'Finger Pointing' managed to hit the wrong weather to set seed in 2014. 

In 2014, I resampled the soil, had another mix of minerals formulated based on the new soil test, put these out in winter––this time we did it all in one application, and then I again waited for spring. I also added compost to most beds, and continued to plant new plants with a mix of compost and biochar. My hope is that these high-test carbon compounds will help with mineral retention in coming years. Ongoing soil tests will tell me how successful this is.

Again the weather did not cooperate. In spring 2014, my area had an early, very warm hot spell that lasted several weeks, with temperatures in the low 90s to low 100s––for the South Coast of Washington, it was hot. In response, irises that normally flower over three to four months all flowered in less than six weeks. The bumblebees were badly overworked! Early flowering (April to early May) PCI responded with heavy seed sets and a short intense flowering period. This unseasonal heat was followed by cool rainy weather in late May into June, so late flowering PCI did not set as much seed, the reverse of the prior year, though the tenax x innominata plants again set many extra pods. I once again used all my mesh bags, and again cut off more than 100 extra flower spikes with more than 200 pods to reduce final seed volumes on those plants that did set seed.

PCI 'Mission Santa Cruz' is an old, tried and still true iris for gardens. Even this one failed to set any seed in 2014. 

Observant readers will note that I have not written about Nitrogen or N-P-K formulas. I did not add N or N-P-K in 2013 or 2014. A properly mineralized soil does not need much N. When healthy, the soil contains microorganisms that fix N and make it available to plants. There's another very important reason to not add N: Nitrogen fertilizers stimulate microbes to metabolize carbon compounds in the soil. My soil is acidic sand; I do not want to lose any carbon if I can find a way avoid it. Also, post World War II, the use of N fertilizers has wreaked havoc with historic soil carbon levels around the world. So I save money by not using standard N-P-K mixes, and instead spend it on custom blends.

If you read about historic versus current levels of minerals in vegetables, it's staggering to learn that mineral levels in food plants have dropped by 3-10X from those of a century ago. This bears directly on food health for all of us, as well as flowering and seed setting capacity for those plants we eat, not to mention those we grow for pleasure. It seems clear that improving minerals in soils leads to improved seed sets (see Jeff Lowenfel's Teaming with Minerals).

Other gardeners have commented on my use of inoculated wood chips. Most native plants in the West, especially in forest and woodland conditions, grow with soil fungi. In my garden,it is a measure of success to have mushrooms growing among ornamental plants. When I dig up iris plants, I see abundant feeder roots interacting with aged wood chips and soil fungi. In Fall 2013, chanterelle fungi were fruiting on a garden path next to several iris plants; this path is layered with several years worth of wood chips. Success!

In Winter 2015 I'm about to sample my soil again, and take the results to my local soil consultant. I can't wait to see how my PCI respond this spring. No guesses on the weather, though. In the past two years, I've seen both early and late flowering plants shut out by weather from successful seed sets. What I do know is that those PCI that manage to set seed are likely to set a lot of it!

1 comment:

  1. Knew this in theory, but how wonderful to have detailed data and feedback from a real world iris garden. Eagerly looking forward to future results.


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