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!

Part One: Remineralizing Soils––A Winter reading assignment for Pacific Coast Iris Growers

Kathleen Sayce, January 31, 2015

Originally published in Pacific Iris, Spring 2013, and updated Winter 2015

In 2010 I began to learn about providing better nutrition to soils so that plants will grow in optimal conditions. Healthy plants not only overcome herbivory, disease, drought and other adverse conditions to flourish, they grow larger, flower more and set more seeds. These plants have higher levels of secondary plant compounds, sugars, and other metabolites. Optimal nutrition for healthy soils to produce healthy plants is not a matter of applying N-P-K fertilizers; instead the focus is on balancing minerals and adding carbon compounds.

Systematically testing soils is the first step; the second step is adding those minerals that are low or absent from your soil. Adding additional organic matter, or carbon, in the form of compost, fungi-inoculated wood chips and biochar is another good step for some soils, particularly temperate forest soils. Plus patience, and resampling soils every year as you change the mineral composition. I was excited to see how my plants would respond, even though I grow few food plants (some herbs, a few parsley plants––all plants that deer usually avoid).

In my garden, historically I used compost and biochar every time I planted a new iris. Every two or three years, a new layer of compost was added over each garden area. I've also used wood chips, preferably red alder chips, aged for a year so that fungi have inoculated them before they go into the garden beds. I've done this for more than 20 years, and until 2010, I thought I was doing pretty well. That year I began reading about minerals, soil carbon, and soil health.

First, I read the latest book from Steve Solomon on vegetable gardening, The Intelligent Gardener. Steve lives and gardens in Tasmania; in a former life he lived in Oregon, where he started Territorial Seeds, a vegetable seed company for the Pacific Northwest. He and his family lived on what he could grow in the garden for several years. He composted, irrigated, added manures, and generally followed traditional organic farming guidelines. It took him decades to learn about how to make high quality composts, and even longer to learn about soil minerals and soil health. Now in his 70s, Steve's latest book is a tour de force for gardeners, distilling a lifetime of gardening knowledge for all of us. Whether you garden for pleasure, or food, or both, read this book.

Second, I read Michael Astera's book on soil nutrition and cation-base exchanges, The Ideal Soil: A handbook for the new agriculture. IMO, a gardener with high school chemistry will understand both Solomon's and Astera's books. 

For a third read on this subject, there is Jeff Lowenfel's Teaming with Minerals, a companion to Teaming with Microbes. Read both of them too.

Jeff Lowenfel's books on soil health are
great reading for gardeners. 

Living in a high rainfall area, it makes sense to me that water soluble nutrients are low in my soil; the opportunities for them to mobilize are too good. Yet compost and well-inoculated wood chips are not be putting back everything that my soil needs in the way of minerals. In fact, water soluble nutrients probably wave at plant roots as they wash past during the wet season. Hi! Good-bye! And they are gone.

In 2012 I took a bold step forward, and sampled my soil. The samples were sent to a soil testing lab. A bold step for me, that is; thousands of farmers and gardeners do this every year. The report came back, full of numbers, a few were high, most were low. The conclusion was that my soil had three minerals in sufficient or excessive amounts (Iron, Zinc and Magnesium). All other elements were nonexistent or at very low levels.

The facts:  too much Mg, Fe and Zn, not enough Ca, and some minerals were incredibly low.

I measured the area of all my garden beds, and took the soil sample results plus the area measurement to a local soil consultant to have a custom blend of minerals formulated for my garden. The soil consultant avoided Calcium compounds that might change the pH of my naturally acidic soil or add more Magnesium. 

My soil consultant did the calculations by hand, but there are websites where you can plug in your numbers and have the needed amounts of minerals calculated for you. For example, http://growabundant.com has an online calculator. 

We settled on a formulation that would build up minerals over several years, not trying to bring this garden to an optimal mineral level in one year, but rather to bring it up more gently over three to five years. It was a cautious first step, in hindsight. I went home with three bags, to apply in midwinter, late winter and early spring.

To learn what happened, see Part Two later this week.