September 2023 – The Garden Professors™

What a strong El Niño means for winter weather and our gardens

Earlier this spring, I posted an article about seasonal climate forecasting and noted that we expected to see the development of an El Niño after three years of La Niña conditions ended in March 2023. And sure enough, an El Niño was declared in August 2023 and has been strengthening ever since. It has a 71% chance of becoming a strong event by December or January before starting to weaken, as they usually do in spring or early summer. In today’s post, I will remind you all what El Niño is and how it is expected to affect our climate this (Northern Hemisphere) winter and spring. That will affect how our gardens survive the colder conditions and prepare for next year’s growing season.

Autumn season in Butanic Garden 33, Mostafameraji, Commons Wikimedia

Refresher: What is El Niño?

If you are a new reader of this blog, you may be wondering what El Niño is. El Niño and its companion, La Niña, are two opposite phases of an oscillation in atmospheric and oceanic weather patterns linked to the water temperature in the Eastern Pacific Ocean (EPO). When the ocean there is warmer than usual as it is now, rising air over the warm water creates thunderstorms which can affect the movement of global air currents that bring stormy weather to parts of the earth while leaving other areas high and dry. When the ocean there is cooler than normal in the La Niña phase of the pattern those currents shift, changing the expected weather pattern to something quite different resulting in a different pattern of temperature and precipitation than in El Niño . The maps below show how the climate changes globally in an El Niño in the December-February and June-August periods, corresponding to Northern and Southern Hemisphere winters, respectively. The El Niño pattern is linked to a variety of unusual weather phenomena around the globe. The variations in temperature and rainfall are what affect how our gardens grow or rest in preparation for the next growing season.

What is the current state of El Niño and how is it changing?

Right now, ocean temperatures in the EPO are from 1 to 3 degrees C ( 2-5 degrees F) warmer than normal all the way from the west coast of South America all the way west to the International Date Line. This is a large area of very warm conditions that are being heated even more by the trend towards warmer temperatures due to increases in greenhouse gases in the atmosphere. The heated water provides a lot of water vapor to the atmosphere that helps fuel thunderstorms and tropical systems. Normally in an El Niño year the number of tropical cyclones in the Eastern Pacific is larger than the number in the Atlantic because of that pool of warm water. This year the Atlantic has near record-setting sea surface temperatures which are helping to produce one named tropical storm after another (today we are have “Philippe” and “Rina” active in the Atlantic but only through the name “Kenneth” in the Eastern Pacific). Global warming has affected our climate patterns to such an extent that what used to be established El Niño and La Niña patterns are less likely than in previous decades, although there have always been variations from one event to the next.

Autumn in the botanical garden, Mostafameraji, Commons Wikimedia.

What will happen from N. H. winter through spring?

According to the predictions of how the current El Niño will evolve, we can expect the current pool of warm water and the associated global weather patterns to last through at least the April-June period. Since El Niño seldom lasts for longer than a year we are likely to go back into neutral conditions after that and neither El Niño nor La Niña will dominate. This means that over the next few months we can expect the southern part of the United States to be cooler and wetter than normal since in El Niño years the jet stream is positioned over that part of North America. As storms are pushed through the region rainy and cloudy conditions keep daytime temperatures cool as precipitation in the form of rain or sometimes snow or ice falls. In northern parts of the United States extending north into Canada, warm and dry conditions are likely to lead to a lack of snow cover and shorter ice coverage on what are usually frozen lakes. Warmer than normal conditions are also likely to occur in most of Southeast Asia stretching from India to Japan. Drier than normal conditions are likely in the Western Pacific Ocean and in southern Africa as well as South America, leading to the possibility of droughts in those areas.

Autumn garden 3, Jonathan Billinger, Commons Wikimedia

What does this all mean for our gardens the next few months?

In the parts of the world that are under the jet stream, cooler and wetter than normal conditions should lead to high levels of humidity and increases in soil moisture over the winter since evaporation will be low in the cold winter months. That means gardens in those areas should be fairly wet going into spring. That means a spring or summer drought there will be less likely than after a La Niña winter, but it could be muddy working in your garden areas next planting season. Since El Niño is already strong and getting stronger this wet winter pattern may start early this year so don’t dawdle in preparing your fall garden for winter since it might be hard to work in those wet conditions. Soil temperatures may stay cool later in the spring, delaying planting of seeds and vegetables or flowers that require warm ground to germinate and grow.

If you are in northern parts of the United States and up into Canada, you can expect warmer and drier conditions than usual. That could mean a lack of snow cover and loss of some plants that need insulation provided by the snow to survive the winter. Even though temperatures will be overall warmer than in non-El Niño years, there are still going to be cold outbreaks that can cause damage to plants that are over-wintering. The lack of precipitation could also lead to dry soil conditions in spring that could require increased irrigation or hinder the growth of seeds or new seedlings you might plant. The lack of soil moisture could also contribute to the development of drought later in the growing season.

Lurie Garden in late fall, bradhoc, Commons Wikimedia.

Of course, even though El Niño and La Niña are the most reliable predictors for climate several months ahead, there are always other factors that can affect climate patterns too. There is no guarantee we will see these exact patterns this winter and there are sure to be some surprises that we don’t expect.

Electroculture – rediscovered science or same old CRAP?

I’ve been doing horticulture myth-busting for almost 25 years now – and what I’ve learned is that myths are zombies. Not only do myths not stay dead, but new zombie myths are also continually created. One of the newest bright-n-shiny distractions is electroculture. It’s EVERYWHERE.

What is electroculture, you might ask? Well, Jaccard (1939) described it as “the stimulation of growth in plants by means of electricity passed into the atmosphere surrounding them or into the soil in which they are growing.”

There was a surge in research in the late 1800s through the early 1900s, partially due to earlier observations which tied electrical storms to improved plant growth. (Further research determined that lightning fixes atmospheric nitrogen into a solid form (nitrate), which dissolves in raindrops and enters the soil system. This was undoubtedly responsible for the reported improvement in plant growth after electrical storms.)

Scientific interest in electroculture tapered off with advances in plant physiology and the development of commercial fertilizers. Furthermore, the few scientific publications that came from early studies showed no consistent benefit from electroculture:

“Favourable results in increased growth and yield have been obtained from time to time, but they are uncertain and largely dependent on weather conditions.”
“Plants on poor soil are little influenced, since electricity…does not provide either nutrients or energy.”
“A current of 10 milliamps inhibited growth in 5 plots, but in 10 others yields increased.”
“Electroculture experiments produced no differences in the treated trees in growth or yield.”

In the 21^st century, a desire to use fewer chemical fertilizers has spurred renewed interest in electroculture. There are vast numbers of websites proclaiming improved plant growth from sticking copper wires in the ground. None of these are backed with any reliable evidence, but proponents argue that new research (since 2000) supports this practice.

I did a search of the scientific literature through AGRICOLA, CABI, and Web of Science/BIOSIS. There were zero publications after 1968. However, Google Scholar lists several. Google Scholar searches for publications in any form on the internet that have been authored by scientists. Here’s an example of what you will find:

A 2021 conference report for the IEEE 13th International Conference on Humanoid, Nanotechnology, Information Technology, Communication and Control, Environment, and Management (HNICEM).”
A 2021 Research Centre Lab report from the Late Ramesh Warpudkar ACS College Sonpeth, India.

These are not peer-reviewed, scientific journal publications. Even earlier ones from the 1980s are in irrelevant journals such as Journal of Biological Physics. Plant scientists publish in plant science-related journals. Researchers outside the field of plant sciences really have no clue how plants function, nor do they have the expertise to design experiments which consider the variables that affect research in applied plant sciences.

Yet, proponents of permaculture push this concept without evidence, using anecdotes as equivalents to scientific data. Conspiracy theories abound, with accusations that chemical companies have forced scientists to cease electroculture research.

Proponents of electroculture “rely on theories of geobiology and use light devices, antennas, or magnets intended to act on the cosmo-telluric electromagnetic fields of the universe, as in dowsing (Wikipedia).”

Worldwide, scientists consider electroculture to be a pseudoscience, particularly because it does not propose any plausible scientific mechanism to explain how electricity would stimulate plant growth.

If and when this changes – when recognized plant science experts publish positive results that are confirmed by other plant researchers – those results will be in bona fide plant science journals and be worth discussing. Right now, don’t waste your time with another horticulture myth that refuses to die.

If you are interested in honing your BS detector, please take advantage of this peer-reviewed Extension Bulletin.
My thanks to Sylvia Hacker for finding great vintage photos to help illustrate this post.

Plant Disease Primer-Part 2: Fungus Among Us

In my last post, I talked about the factors leading to the development of plant diseases and some common signs and symptoms of fungal, bacterial, and viral diseases. In this installment of the series, I’m going to talk about some of the most common fungal plant diseases with some suggestions for treatment and prevention. This by no means will be an exhaustive list of diseases (there are so many!), but I hope to cover some of the most common ones that we see come into the extension office for diagnosis.

Common Fungal Diseases

Powdery Mildew
- Symptoms: White powdery spots on leaves and stems
- Common hosts: a wide range of plants, but peonies, lilacs, squashes, cucumbers, and roses are what we see most often

Downy Mildew
- Symptoms: yellowish or whitish spots on the tops of leaves with gray-ish fuzzy growth underneath
- Common hosts: downy mildew affects many plants, but basil, impatiens, cucurbits, and verbena constitute the most common questions.

Rusts
- Most rust lifecycles require two host plants: a primary and alternate host
- Common rusts:
  - Cedar-apple rust (Junipers– primary, Apple/pear – alternate)
  - White pine blister rust (white pine – primary, gooseberry/currant – alternate)
  - Hollyhock rust (no alternate host)
- Symptoms: rust colored (orange/yellow/red) pustules or blotches on leaves, stems, and fruit; may appear as gummy structures on primary host

Leaf Blights
- The most common blights we see are often for tomatoes and their relatives. There are many leaf spots and blights that affect these plants, but early blight seems to be one of the most common.
- Common leaf blights
  - Early Blight of tomato: irregularly shaped lesions on leaves, often with concentric rings and yellow halos. Eventual leaf curling, necrosis, or dropping. Severe cases can end up with lesions on stems and fruits.
  - Late Blight of Tomato and Potato: Starting as small water-soaked lesions and turning into large, purple-brown, oily looking blotches. Blotches appear on leaves, stems, and eventually fruit.

Early blight of tomato, Source: UMN Extension

Anthracnose (multiple species and target species)
- Anthracnose affects a wide range of plants, but we often see shade trees such as oak and sycamore, dogwoods, beans, peppers, and cucurbits as commonly affected plants.
- Symptoms: dark, sunken ulcer-like lesions on leaves, stems, fruits, and flowers.

Anthracnose on watermelon, Source: UMN Extension

Cankers
- Common cankers:
  - Cytospera – spruce, pine, poplar, willow
  - Phomopsis – juniper, Russian olive, Douglas-fir, arborvitae
  - Nectria – honey locust, oak, maple
- Symptoms: sunken necrotic lesions (cankers) on twigs, stems, and trunks of trees. Often leading to death of the plant beyond the canker location. This is especially problematic for trunk cankers which often lead to the death of the whole plant.

Nectria canker on young maple trunk Source: Missouri Botanic Garden

Root Rots
- Common rots:
  - Phytopthora – affects many species to cause root rot
  - Armaillaria – especially problematic for trees

Armillaria root rot (fruiting bodies), Source: UC ANR

Fruit rots
- Common rots:
  - Black rot – many species, but often apple and pear
  - Brown rot – peaches, plums, cherries, and related species

Fungus Treatment

Once a plant is infected with a fungus, it is difficult to eliminate the disease and treatment focus should be on slowing down the spread of the disease to the remaining plant. Treatment is important for annual plants, which may be killed entirely by fungal pathogens, and in woody perennials where symptoms include cankers or rots that affect perennial plant parts such as stems or trunks. Fungal diseases that affect only foliage on perennial plants are less of a threat and often the damage is limited to aesthetics.

For the most part, removal of the diseased plant parts is an important first step in treating the disease. This removes a great deal of the fungal organism from the plant that is likely still producing spores or hyphae to spread through the plant. Removal of affected foliage for foliar diseases is key.

In cankers, removal of whole branches or twigs starting at least a few inches below the canker location is necessary. Sometimes this may require removal of large parts of plants, at which point decisions should be made about removal of the entire plant. Cankers occurring on main stems or trunks are especially devastating.

Once affected plant parts are removed, a treatment with fungicides may be necessary to reduce spread of the disease further. Often repeated treatments through the season are needed once the disease is established in the nearby environment. Copper sulfate is a common organic option for treatment of fungal pathogens, but may not be effective for every disease. Care should be taken to not overuse copper sulfate, as it will not break down in the environment and can build up in the soil, causing damage to populations to good fungi and bacteria in the soil. Chlorothalonil is a widely used conventional fungicide and will help control many, but not all, fungal diseases. For specific fungicide recommendations for your area, contact your local extension expert.

Fungus Prevention through IPM

There are several Integrated Pest Management strategies that can be used to reduce the likelihood of fungal infection in your garden or landscape. Below are some strategies that can be used for general fungal prevention:

Use correct plant spacing and pruning to ensure airflow around plants. This can reduce humidity within the plant structure and moving air can reduce the number of fungal spores that land on the plant.
Use mulch to limit splashing of soil onto plants
Eliminate overhead watering to reduce foliar moisture
If overhead watering is necessary, water early in the day so plants dry out before the dew point drops in the evening
When possible, plant disease resistant cultivars
Reduce nearby weeds to eliminate potential secondary hosts
Remove rust alternate hosts (not always possible), such as junipers if you’re growing apples (or vice versa)
Utilize biofungicides as a preventative measure. Products containing different types of Bacillus bacteria can be competitive with disease-causing organisms and limit their ability to form on leaves.
Practice good hygiene in the garden by cleaning up any fallen or diseased leaves, fruits, etc.

Wrapping it up

There are lots of fungal diseases that can damage or kill plants in our gardens or landscapes. Prevention is key, as treatments only help slow the spread of disease. In the next installment, we’ll talk about bacterial diseases. Stay tuned!

The Fascinating Phenomenon of Fasciation

You may have seen it on the odd flower or plant here and there or you may be intentionally growing plants that show this unique and uncommon phenomenon. Fasciation (not fascination- though it certainly is pretty fascinating) is a malformation or abnormal pattern of growth in the apical meristem (growing tip) of plants. The apical meristem is undifferentiated tissue that triggers the growth of new cells (which extends roots and shoots, and gives rise to stems, leaves, and reproductive structures). In the case of fasciation (which originates from the Latin ‘fascia’ which means ‘band’ or ‘bundle’), this new growth is abnormal and often appears as flattening, ribboning, swelling, fusion, or elongation of plant parts. Sometimes referred to as ‘cresting’, this can occur anywhere on the plant but is more likely to be seen in stems, flowers, and fruit. You might encounter this as several stems growing together, a multi-headed or misshapen flower, perpendicular or irregular growth, dense tuft-like growth, or coiled, contorted, and twisted stems which can sometimes have an unusually high concentration of leaves and flower buds.

A fasciated hinoki false cypress ( *Chamaecyparis* *obtusa* ) (Photo: **Anton Baudoin, Virginia Polytechnic Institute and State University, Bugwood.org** )

There are multiple patterns of fasciation that can be observed, including: linear fasciation (which results in the more common flattened and ribbon-shaped stems), bifurcated fasciation (when a linear fasciation splits in two to form a “Y” shape), multiradiate fasciation (where the stems split into three or more short branches, referred to as a ‘witches’ broom’), or the rare ring fasciation (where the growing point folds over to form a hollow shoot) (Geneve, 1990).

A ribbon of fasciated stems (Photo: **Joy Viola, Northeastern University, Bugwood.org** )

Fasciation is a symptom that can be caused by a variety of different factors including genetics, hormones, pathogens (including bacteria, viruses, and phytoplasmas), injury (including chemical, mechanical, and feeding damage), nutrient deficiency, or environmental causes (such as temperature extremes) though in many cases it is still not completely understood and the exact cause may not be apparent in a specific fasciated plant. The stability of this phenomenon is also pretty variable. Some plants can pass on this trait through their seeds (resulting in a genetic likelihood of expressing this symptom), while other plants can develop fasciation (through a variety of causes) and then resume normal growth from a fasciated point, or perennial plants that appear fasciated one year may be completely normal the next year. Scientists have even identified some of the specific genes in which mutation can cause fasciation and have experimentally reproduced this result in seedlings that were exposed to radiation, chemical mutagens, and high temperatures.

Fasciated Gaillardia showing unusual growth in the stems and flowers (Photo: **Department of Plant Pathology , North Carolina State University, Bugwood.org** )

Most often fasciation is just an aesthetic anomaly, is fairly uncommon, and rarely impacts the survival of affected plants (especially if they are established woody plants). In cases of fasciation due to infection by certain pathogens (such as the bacterium Rhodococcus fascians), it is possible for affected plant parts to die prematurely. Although infectious fasciation can spread to other susceptible plants, in the majority of cases fasciation is not infectious and will not spread.

Fasciated asparagus (Photo: **Mary Ann Hansen, Virginia Polytechnic Institute and State University, Bugwood.org** )

Although fasciation can occur on any plant (and has been documented in hundreds of plant species) it is more frequently seen in certain groups such as cacti, daisies, asters, legumes, willows, and plants in the rose family (Rosaceae). It is also more common in plants with indeterminate growth.

Crested saguaro cactus (*Carnegiea gigantea*) (Photo: **Joy Viola, Northeastern University, Bugwood.org** )

In some cases, distinct examples of fasciated plants are intentionally selected for their visual appeal and interest. Many times, plants that have a greater propensity for fasciation, or those that can be vegetatively propagated are developed into cultivars that can be sold (and are often a striking addition in any garden). Many of our dwarf conifers, for example, are propagated from witches’ broom cuttings. In addition, some of our large and uniquely shaped tomato varieties, such as beefsteaks, are selected for their fasciated fruit, and many strawberries that have a wider shape or appear to be ‘fused together’ are also fasciated and considered desirable.

Beefsteak tomatoes are a common example of desirable fasciated fruit. (Photo: Lufa Farms, Wikimedia Commons)

Examples of plants that frequently exhibit fasciation, including those with cultivars that you can purchase for your gardens, are ‘cockscomb’ celosia (Celosia argentea var. cristata), ‘fascination’ culver’s root (Veronicastrum virginicum or sibiricum ‘Fascination’), ‘crested’ hens and chicks (Sempervivum spp. var. cristata), and Japanese fantail willow (Salix sachalinensis ‘Sekka’), among others.

Fasciated cockscomb (*Celosia argentea* var. cristata) (Photo: **Julia Scher, Cut Flower Exports of Africa, USDA APHIS PPQ, Bugwood.org** )

If this strange growth is something you don’t enjoy, you can prune out the distorted tissue. Or if you’re like me – you can just marvel at the weird and the wonderful!

Fasciated Yucca flower stalk (Photo: **USDA Forest Service – Rocky Mountain Research Station – Forest Pathology , USDA Forest Service, Bugwood.org** )

Resources

Fascinating Fasciation (Wisconsin Master Gardeners):
https://mastergardener.extension.wisc.edu/files/2015/12/fasciation.pdf

Plant of the Week: Fasciated Plants (University of Arkansas):
https://www.uaex.uada.edu/yard-garden/resource-library/plant-week/fasciated-2-22-08.aspx

The Genetics of Fasciation:
https://trinityssr.files.wordpress.com/2016/06/4th-ape.pdf

Fasciation (University of California IPM)
https://ipm.ucanr.edu/PMG/GARDEN/FLOWERS/DISEASE/fasciation.html

Fascinated with Fasciation (Dr. R. Geneve, 1990, American Horticulturist)
https://ahsgardening.org/wp-content/pdfs/1990-08r.pdf

Recognizing bad science by honing your B(ad) S(cience) detector

Last week there was much ballyhooing over a new article on the benefits of native plants in supporting insect populations. I’ve posted on the fallacy of native plant superiority before, pointing out that landscape biodiversity not plant provenance, is most important for supporting all types of beneficial wildlife. Despite robust, published evidence to the contrary, more people and governing bodies believe that native plants are the magic bullet for urban landscapes. (Never mind the fact that there are no plants native to urban environments.)

Using CRAP analysis to assess information:

C = credibility. Are the authors experts in the field of interest?
R = relevance. Is the information applicable to the field of interest (in this case, management of plants in urban landscapes)?
A = accuracy. Is the information grounded in current, relevant science?
P = purpose. What is the underlying reason that the information is being shared?

This most recent paper warrants a careful dissection as it has gone viral online. For me, the first red flag is that there are no plant or soil scientists on this team. The first two authors, who were responsible for developing the main ideas and designing methodologies, are both ecologists by training. The other authors are involved in insect collection and identification as well as ecological modeling. Not having plant and soil scientists on the team to ensure science-based practices are followed during landscape modification is a serious oversight.

**The pupose of this photo montage is apparently to show how healthy the site is after “greening.” A much better indicator would be street-level comparisons. Which you can see later in this post.**

The methods section regarding the study site is astonishingly vague, given this is essentially a landscape plant installation and management project (i.e., applied plant science, not ecology). A well-designed experimental project would include control plots, replication of treatments, site analyses (including soil type and texture as well as soil testing for nutrients and organic matter), and detailed explanations of how the site was prepared, how plants were selected, prepared, and installed, and what site management occurred post-installation.

Here is the section on how this “experiment” was designed:

“In mid- April 2016, 80% of the site was substantially transformed through weeding, the addition of new topsoil, soil decompaction and fertilisation, organic mulching and the addition of 12 indigenous plant species…Selected plant species met the criteria of being locally indigenous to the City of Melbourne and represented a range of growth forms— including graminoids, lilioids, forbs and trees— requiring no ongoing management such as watering and fertilisation.”

The purpose of the methods section is to provide detailed explanations on how the study was conducted so that it could be replicated by other scientists elsewhere in the world. There is no way to replicate this study properly, as the methods are vague and very possibly not based on applied plant and soil sciences:

“Addition of new topsoil” As we’ve pointed out in this blog numerous times over the past 14 years, you don’t add new topsoil to landscapes.
“Soil decompaction” What is this? Does it involve tllling, which would directly affect the health of the two existing trees?
“Fertilization” What is the fertilizer? When was it applied in the process? At what concentration and based on what data was it applied? You need to know baseline levels of nutrients before you can rationally add any fertilizer.
“Organic mulching” What material? Compost? Cardboard? Bark? How deeply was it applied?
“Addition of…plant species” Were these bare-rooted or simply popped out of the pot and dropped in the new topsoil?
“Requiring no ongoing management such as watering” News flash: newly installed plants REQUIRE irrigation during the establishment period regardless of their nativity. And this site now contains substantially more plants than before, meaning increased competition for water and other resources.

The problems with this nonscience-based approach to landscape plant management can be see by comparing the two spotted gum trees that were on site before this project began. Corymbia maculata is a threatened native species in Australia and the continued health of these trees should have been paramount before any site work was initiated.

*Exisiting spotted gum trees (Corymbia maculata) in December 2018*

Unfortunately, these sorts of projects, conducted by teams with no soil or plant scientists and published in journals that are not specific to urban plant and soil sciences, are neither well-designed nor useful. The mindset of many researchers outside the applied plant and soil sciences is that there’s no real science to preparing soil, installing plants, and maintaining the site. This current paper does not even meet the standard of being experimental: it is merely a report on what happens to insect populations when a landscape is altered. There is no basis for comparisons. Any conclusions drawn are anecdotal.

It’s bad science.