Foliar Feeding - Does it Work?

In the past couple of weeks, I have toured several different farms and gardens where the caretaker sung the praises of foliar feeding. “The plants absorb the nutrients so much faster and growth just explodes!” said one farmer enthusiastically. Every time I hear a comment or recommendation regarding foliar feeding, my inner bullshit alarm goes off. I just don’t believe it actually works. But is my hunch true, or am I just stuck in old thinking?

Years ago, I was enamored with the idea of making compost tea and then spraying it as a foliar feed on my veg and fruits. I was sure it would improve the health of my plants, deter pests, and increase yields. Making compost tea is a lot of work; it requires a bubbler in order to oxygenate the mixture as it’s steeping, keeping the organic matter in a mesh bag so it doesn’t clog the bubbler, then decanting the mixture into a sprayer, etc etc etc. And then the spraying itself, messy and time-consuming. All of this has associated costs, too - you need to buy a big sprayer, a bubbler and tubing, several containers to hold everything, and mesh bags or cheesecloth. This is all after the regular work of making compost, which is noble and important but not exactly a hands-off project. After all this fuss, I really didn’t notice much of a difference in my plants when I performed foliar feeding.

Not long after, I took a Plant Nutrition class as part of my ‘nursery management’ coursework at Merritt. Several students were convinced that foliar feeding worked better for plant nutrition than any other method. My instructor was dubious. She explained that leaves are not designed to take in nutrients. There are nearly microscopic holes on the bottoms of leaves, called ‘stomata,’ which evolved to provide gas exchange - these holes allow for oxygen and carbon dioxide to move between the plant and air as part of the process of photosynthesis. They can expel water, but actually repel water that’s trying to come in, using a waxy coating for that purpose.

More recent research has revealed the existence of micro-pores on the surface of leaves, and they are lined with negative charges which attract positively charged cations (things like calcium, magnesium, and potassium). This research has shown that nutrients can enter these pores as ions in water, but sprayed leaves dry very quickly and limit much absorption, and only about 15% of the nutrients applied this way are absorbed.

And as my professor then told us, even if leaves do take in nutrients in this way, the plant is really not designed to move nutrients other than sugars from the leaves to the roots, or to any other part of the plant. The whole system is designed to draw nutrients from the soil solution (a pool of available water at the rhizosphere that contains nutrients) up through the roots and into the xylem, which is a kind of fluid river that moves water-soluble nutrients from the roots to the rest of the plant. There’s a downward river, too - the phloem - but it’s carrying sugars made in the photosynthetic process down from the leaves to the root zone. That’s what it’s designed to do, not carry nutrients from the stomata down to the roots. So even if nutrients are entering the leaves, they are stuck in the leaves. They are immobile due to that stronger positive charge.

Let’s take calcium for instance. A gardener recently told my class that she sprayed her tomatoes using a foliar feed of liquid calcium to prevent blossom end rot. But calcium will not move from the leaves to the fruit. It can only move from the roots to the fruit. Tomatoes also do not absorb calcium through the skin. So this is arguably not helping the plant avoid blossom end rot. (And if you’re a long-time reader of this blog, you already know that blossom end rot is not really a calcium issue.)

Remember my plant nutrition class? My professor posited that what was really happening in foliar feeding was that the nutrients were dripping off the plant and down into the soil, thereby entering the soil solution. But she was not married to that theory and was game to experiment. So, in lab, we planted a bunch of leafy vegetables in 4” pots. Then we covered the whole surface of the soil with plastic wrap. Then we turned the plant on its side and sprayed the leaves with a foliar feed (I can’t remember what the actual fertilizer was, unfortunately). This way the feed dripped off the leaves onto the ground, instead of down into the pot. And the plastic wrap was there as insurance to make sure that nothing entered the soil. We let the plants drip dry before righting them, removing the wrap, and watering them with plain water before replacing the wrap. We cared for these plants over the course of the whole semester.

Care to guess the result? The plants in 4” pots with only foliar feed did very poorly indeed. They were yellowed, diseased, and wilted. We concluded that foliar feeding didn’t work, or at least it didn’t work well enough to supply enough nutrients to the plant.

But that’s not a rigorous study, so I consulted some other recent research. According to a 2016 study by the University of Wisconsin-Madison’s Agriculture Department, “for many nutrients, there is little or no published information showing a valid relationship between crop yield increase and tissue nutrient concentration that provides good reason for making widespread recommendations to apply a foliar- or soil-applied fertilizer that includes that nutrient,” and, “for many of these essential nutrients, we lack proven research that defines the exact minimum nutrient concentration below which yield is harmed and verifies that a beneficial yield response to foliar feeding occurs.” And according to a 2020 article from Ohio State University’s College of Food, Agriculture, and Environmental Services program, “results (in foliar feeding) were inconsistent and didn’t reveal a cohesive pattern of increased yield or… plant health for the sites in this study.”

I suppose it’s possible that spraying the leaves with a nice compost tea might help protect the leaves from some fungal infections, or pest predation. But as a method of actually feeding the plant, I think it’s an inferior choice. The best thing to do for any plant is to provide it with plenty of organic matter, which allows the soil biology to process all the nutrients in the organic matter and make them available in soil solution for the plant roots.

Reference: “Why I Typically Do Not Recommend Foliar Fertilization,” by Caleb P. Goossen, Ph.D, MOFGA Crop Specialist, June 2023.

Guest Speaking Event

I’ll be speaking about Resilience in our Urban Gardens on Tuesday, April 11, at 8 pm (PDT) via zoom. It’s a free event through the Albany Healthy Garden Talks series, if you’d like to participate. If you heard me speak for the Landscape Horticulture Design Forum back in August, this is a very similar talk with very few changes.

Here’s the link to sign up. This series (and particular talk) is sponsored by the City of Albany. I am grateful for the opportunity to speak with a wider audience about my favorite subject, resilience! Many thanks to Patricia St. John for the invitation.

IPCC Mitigation Report

My news feeds are full of commentary on the IPCC’s release of their mitigation report. Of course, since I have long been a student (formally and informally) of environmental issues, this is the kind of news I look for - maybe you haven’t been reading as much about it as I have. Plus, I do find these reports confusing for the average layperson. So imagine my delight when I came across a great eight-minute video, summing up the report.

This video was recommended by Katharine Hayhoe, climate scientist, University professor, and recently-named Chief Scientist for The Nature Conservancy. I have read several of her books, and she has a unique take on environmental issues, being both a Christian and a scientist, and someone who believes in active faith and hope. She is a good resource for scientific facts, but also for a positive outlook in the face of very frightening information. So, I knew this video would be helpful and I feel confident recommending it. I hope you enjoy it too, and are able to learn something from it - I sure did.

All the Trails

We’ve always been a family of hikers and walkers, but since the pandemic began, our daily excursions have become quite sacred to us, whether in our neighborhood (blessed by many regional open spaces with great hilly walks) or in the greater Bay Area. We have been using an app called Gaia in the last year, which records our walks, and also shows us the many trails we have yet to travel (the free version is great). This has allowed us to find trails that we didn’t even know existed, and especially on weekends, we tend to go further afield to find new favorites.

One thing that has become so clear to us is that the Bay Area is littered with extensive trail systems, some maintained by local park systems, and some by state parks or even national parks. These are all non-profit groups, often dependent on volunteers to establish or maintain trails. We are so thankful for all of these organizations, and all the people, who make this kind of recreation possible.

We have long been supporters of East Bay Regional Parks. Many of these parks are free to enter, but supporting them by purchasing an annual pass is great. Individual memberships run $60 for a year (the price of three movies, or 10 fancy coffees). A family membership is $105. The wonderful thing about EBRP is that they have an extensive system which includes urban trails and parks, as well as more suburban parks. This promotes equity in the outdoors and makes these open spaces accessible to everyone, which is something that is really necessary.

EBRP also oversees two of the longer, linked trail systems we often find ourselves using. The California Riding and Hiking Trail is mainly a Contra Costa County trail system that links Mt. Diablo with Martinez, and will encompass 16 miles of trail. The Martinez-Concord section is already completed and will link to Mt. Diablo State Park in the future. The East Bay Skyline National Trail is part of the 1968 National Trail Systems Act. It begins at the Alvarado staging area in Richmond, and ends at the Proctor Gate station in Anthony Chabot regional park. We’ve hiked most of both of these trails and have found them quite interesting.

Other local trail systems include the scenic San Francisco Bay Trail, which is a planned 500 mile walking and cycling path around the entire bay, going through all nine counties, 47 cities, and seven major bridges. 350 miles are already in place. This project is also restoring wetlands around the Bay. They have a really cool navigational map that shows existing trails (whether paved or dirt) and planned trails. We’ve walked much of this trail system, too, including two bridges, and always enjoy these walks on days when it’s prohibitively hot in our neighborhood and we need the cooling influence of the Bay. The Bay trails are often flat, as well, offering an easier but longer walk, and there is always good wildlife viewing with shorebirds.

The Bay Area Ridge Trail, however, offers a completely different kind of hiking experience, taking walkers over the peaks that ring the Bay. This trail was the vision of William Penn Mott, Jr, who was Director of our National Park Service as well as EBRP and California State Parks. He wanted a 550 mile trail encircling the ridges of the Bay Area. 393 miles of trail have been established and they are all great, challenging miles! They have some neat trail maps and tools which include ‘curated’ trail adventures such as wheelchair accessible loops, or training ridge to bridge trails for those who want a challenge.

There is an interesting state trail system that we are just recently learning more about. This is the Mokelumne Coast-to-Crest Trail, which is planned to go all the way from the Bay to Yosemite. Currently three sections are complete: the East Bay/Contra Costa County section, the Camanche-Pardee Reservoir section, and the Upper Mokelumne River Canyon section. We have been on the Contra Costa section many times, as it winds through and over Mt. Diablo, Black Diamond, and Contra Loma parks. We are hoping to eventually get to the sections east of here and explore those, as well.

There are two interesting interstate trails here, one being (of course!) the Pacific Crest Trail, which runs from the Mexican border to the Canadian border, through California, Oregon, and Washington. We have been on a very short section of this trail when hiking in Yosemite, but other than that, this trail has been beyond our reach, as it runs through the interior mountain ranges and is primarily in wilderness. It has long been a dream of mine to hike this trail, and maybe we’ll have more time in the future to section hike portions of it, at least.

Another interstate trail which I have just recently discovered is the Juan Bautista de Anza trail, which is part of the National Park System and is a National Historic Trail. It runs through Arizona and California, following Juan Bautista de Anza’s route in 1775 as he established (colonized?) a settlement in San Francisco bay. I don’t know how much we should be celebrating the takeover of land from California Native Americans, but while we don’t need to honor questionable historic activity, we should certainly learn about it and face the truth of it, and what better way to do that then to walk those same paths?

The final trail that I want to bring to your attention is the American Discovery Trail, which runs from the West Coast to the East Coast, 6800+ miles of continuous multi-use track. It does run on some roads, but the organization is working to make the trail completely off-road in the future. It is not a wilderness trail, like the Pacific Crest Trail. It passes through cities, towns, farmland, and wild areas. It is meant to be a voyage of discovery of our country as a whole. On the website, you can find the trails in your state (if it passes through your state); the California portion starts in Pt. Reyes National Seashore, and goes right over Mt. Diablo, over to Lake Tahoe, so we’ve found ourselves on this trail many times.

We are lucky to live in the San Francisco Bay Area, a place that celebrates outdoor living year-round. That doesn’t mean the conditions are always idyllic (see my previous post), but it does mean that we are provided with a lot of opportunity to get out into nature, and explore. We have come to realize that this is extremely important to us, and it will dictate how we move forward into retirement (which isn’t happening anytime soon, but that doesn’t mean we don’t think about it). We don’t necessarily see ourselves living in California forever, but we do want to live in a place that offers a lot of outdoor recreation, no matter the season. That might mean that we need to get good at snowshoeing! But that’s years in the future, anyway. Right now, we are just happy to have plenty of adventures located right outside our front door.

PS: If you like to hike and get outdoors, and you’re looking for a new adventure, let me know - Tom and I have plenty of suggestions for great walks all over the Bay Area!

Indigenous Land Acknowledgement

I’m taking a really interesting summer class called Social Issues in Agriculture. In it, we are exploring and learning about agroecology, biocultural memory, and political ecology. I have a lot of knowledge and experience in growing things, but I’ve never really considered the history of the land and the indigenous peoples who lived here first. It’s one thing to plant a ‘three-sisters garden;’ it’s another thing entirely to look at the garden from the perspective of the present while honoring the people who gathered, grew, and ate here long ago. I’ve looked at the geology and land processes, the geography and natural hazards of my property, without acknowledging the people who were here first, and the ones that moved in by colonization.

We have had several interesting lectures in my class, and one of them was proceeded by a verbal Land Acknowledgment and moment of silence to honor those that came before. I had never seen or heard of a Land Acknowledgment before, and I found it moving and important. In this time of increased awareness of the issues Black Americans face, I am also finding that there is a need for awareness of those that Indigenous People face.

What is a Land Acknowledgment? According to Northwestern University, it is “a formal statement that recognizes and respects Indigenous Peoples as traditional stewards of this land and the enduring relationship that exists between Indigenous Peoples and their traditional territories.” Why do we recognize them? It is “an expression of gratitude and appreciation to those whose territory you reside on, and a way of honoring the indigenous people who have been living and working on the land from time immemorial. It is important to understand the long standing history that has brought you to reside on the land, and to seek to understand your place within that history.”

So, I’d like to try my best to acknowledge the people who historically lived on the land on which I live and work. It is apparently better to do this badly then not at all, so here is my attempt. I live in what is now south Walnut Creek, California, a land originally populated by the Bay Miwok tribe. The Bay Miwok tribe was split into several other tribes, whose names were recorded in 1769 when the Spanish first came to California in force (there is some confusion about whether or not the Spanish actually gave the tribes these names): The Chupcan, Julpun, Ompin, Saclan, Tatcan and Volvon tribes. The Saclan tribe lived where I live now. According to our local San Ramon Valley Museum, “the Bay Miwok tribes each had one to five semi-permanent villages and numerous temporary camping sites within a fixed territory of about 6 to 10 miles in diameter. Each tribe knew its land and boundaries intimately and owned the land communally. They probably lived within different watersheds, consumed seasonal foods such as acorns, seeds and salmon and took advantage of their proximity to waterways. The Bay Miwok tribes each ranged in numbers from 200-500 at the time of European contact.”

The Saclan were apparently leaders in several rebellions of the region, and resisted the Spanish troops who came after them in several expeditions between 1795 and 1805. The refused to go peacefully to the Missions, but were eventually “subdued” by the Spanish military. The Spanish Colonial period extended to 1821, and the Missions were in charge of various areas; the San Jose Mission was likely the one that incorporated the Saclan people into its territory. The land was used for grazing animals (which destroyed our native ecosystems). In 1821 Mexico gained control of Alta California, and this period was dominated by rancheros and traders. Four Mexican land grants divided present-day Walnut Creek, and our area belonged to Jana Sanchez de Pacheco. His grandson is apparently the first person to build a roofed house here, in 1850, according to our local history. He named the territory Rancho Arroyo de Las Nueces y Bolbones (“Walnut Creek” and “Bolbones,” another name for the local indigenous people). He owned 20,000 acres, employed Mexicans and Natives, and bought sheep and cattle from San Jose Mission which continued to graze on these lands.

Of course, the Gold Rush began in 1849, and the miners continued to decimate the land and the tribal peoples. California became a state in 1850, and according to our county history, passed laws allowing the natives to be enslaved by any white man. Women and children were taken and sold. In 1863, this law was repealed.

In 1855, the first hotel was built in our city, and in 1856, Hiram Penniman laid out the town site and called it “The Corners.” That community was largely a farming one, planting vast pear and walnut orchards. In 1862, the first Post Office was built here, and the town was renamed Walnut Creek. In 1949, our immediate neighborhood was built, along with all of the schools our children attended.

We moved here in 2004.

I found it fascinating to research all of this, most of which I knew in bits and pieces before, but having a more complete picture is really good. I want to honor those that came before. I think it’s important that we all do. I encourage you to take some time and do the same. You might already know most of it, but you may learn something new, and it’s very good for us to acknowledge the harm our ancestors did to both the land and the people that came before. I am sad that there is a whole range of local knowledge that has been lost due to colonization, slavery, and genocide. There are very few Bay Miwok people left, and the Bay Miwok tribe has never been recognized by the federal government of the United States. Some California tribes signed treaties with the United States government in 1850, which gave up quite a lot of their ancestral land; it appears the Bay Miwok was not one of these tribes (for a fabulous history of the tribes in our area, click HERE to see a school curriculum put together by East Bay Regional Parks).

There is a cultural memory that has been lost, of what to gather and grow and cook here. There is a richness of diversity that has been lost. An entire People have been lost. I am also sad that a lot of our local land was destroyed by grazing, and now is colonized by plants that didn’t belong here, which destroyed our local ecosystems. Many of the plants and insects that thrive now came here as ballast on Gold Rush boats.

Of course, while I garden with a lot of plants native to this area, I also grow an awful lot of things that don’t belong here at all, and persist in keeping European honeybees which are non-native. I continue to wrestle with these issues and vacillate back and forth between championing this kind of growing, and vilifying it. We all need to make those decisions for ourselves. We need to know all the facts and acknowledge our actions, either way.

The same can be said for knowing who lived and worked on our land before we did. It is a way to honor them, to recognize them, to look them in the eye metaphorically and say “I see you.”