Volcanoes and climate: How will the eruption in Tonga affect our gardens?

If you have watched the news at all in the last two weeks, you know that there was a huge underwater volcanic eruption near Tonga in the South Pacific Ocean on January 15, 2022, that spewed ash and gases into the atmosphere. It blew with such force that the sound of the eruption was heard in Alaska thousands of miles away and the atmospheric pressure wave it set off has traveled around the earth as many as ten times according to satellite and ground-based sensors. With such a large signal, you might wonder what impact the eruption could have on our weather and climate for the next year. In this post, we will explore how volcanoes in general can affect the climate around the world and whether the Tonga eruption is likely to change our gardens’ climate this year.

What do volcanic eruptions emit into the atmosphere?

When volcanoes erupt they put out both ash and gases. The ash is made of tiny particles of rocky material from solidified lava and sometimes pieces of the volcano destroyed by the eruption. These particles are carried downwind in a direction determined by the winds at the heights to which the ash can rise. In a long eruption, the plume of ash can blow in a different direction each day, covering the ground when it falls back to earth. Usually ash does not rise very high in the atmosphere because it is quite heavy and so most of it falls out in just a few days.

Volcanoes also emit gases as they erupt. About 99 percent of all emissions are water vapor, carbon dioxide, and sulfur dioxide, with some trace amounts of hydrogen sulfide, carbon monoxide, and other minor gases. The gases are lighter than ash and so they can get lofted much higher up into the atmosphere than ash can. Because water vapor and carbon dioxide are greenhouse gases volcanic eruptions are often blamed for the recent rise in carbon dioxide in the atmosphere instead of human causes. A careful analysis of the relative amounts of carbon dioxide from the two sources easily shows that volcanic activity only contributes in a small way to greenhouse warming compared to fossil fuel burning and land-use changes. But the gases emitted do have a short-term effect on climate that can last several years in the largest tropical eruptions.

Sulfur dioxide (SO2) to sulfuric acid (H2SO4) has the most significant impact on climate. US Geological Survey.

What causes volcanic cooling?

Volcanic cooling of the climate is due mainly to the effects of sulfur dioxide and water vapor. As the gases rise, the water vapor condenses and joins with the sulfur dioxide to form tiny droplets of sulfuric acid that can rise to 50,000 feet or more, higher than most commercial jets fly. Those droplets are as shiny as the glass beads they use in stop-sign paint to make the signs reflective, and the droplets have the same effect on incoming sunlight. When they reflect sunlight back to space before it can reach the earth’s surface it reduces the energy we receive at the ground, and the earth gets cooler until those droplets fall out of the atmosphere. Because of their height and small size, that can take several years.

How does the cooling affect global climate?

We know that when you have a large volcanic eruption emitting a lot of sulfur dioxide, especially if it happens in the tropics where the sunlight is most direct, you can see cooling around the globe for the next 2-7 years depending on how much gas the eruption puts out. In the worst case, an eruption like Mount Tambora in 1815 in present-day Indonesia (along with some other eruptions around the same time) resulted in the “Year Without a Summer” in 1816. In the United States, frost was observed every month of the year in New England and eastern Canada, resulting in the loss of many crops. Even the crops that survived had low yields and poor quality that resulted in dramatic increases in food prices. Europe also saw very cold temperatures that resulted in food shortages there.

Other more recent eruptions have also had some impact on global climate, although none was as severe as the Tambora eruption. The most recent large eruption that affected global climate occurred in 1991 with the eruption of Philippine volcano Mount Pinatubo. As the volcanic emissions spread around the globe, the earth’s annual temperature dropped by almost 1 degree F in the years 1991–1993. Sunsets were also spectacular with the scattering of sunlight from the aerosols high in the atmosphere. Some scientists think painters like J. M. W. Turner were inspired by the spectacular sunsets that occurred after volcanic eruptions in the 1800’s.

Joseph Mallord William Turner (1775-1851) – Sunset – N01876 – National Gallery.jpg

Will the Tonga eruption affect the climate in our gardens in the next few years?

Since this is a blog for gardeners, you might want to know if the recent eruption will affect the climate in the same way that other eruptions like Tambora and Pinatubo did. If it is going to be much colder than average, then that could affect what you plant in your garden, especially if the plants you want to use are sensitive to frost. Or it could tell you that you might want to hold off on planting those tomato seedlings a little later than usual in spring. In this case, the amount of sulfur put out by the Tonga volcano was only about 60 kilotons compared to 20,000 for Pinatubo, so any cooling effects from the most recent eruption are so small that we will not be able to observe them. Gardeners can breathe a sign of relief this time! But when the next big eruption occurs, the climate may temporarily cool for a few years before it starts to warm again under the impacts of the “human volcano” emitting many more gases and pollutants than natural volcanoes into the atmosphere.

House Plant Basics

I love plants! I love gardens! I love nature! So why not bring it all inside the house? Who can resist those beautiful Calatheas (Prayer Plants) they sell at Home Depot? House plants afford us the opportunity to garden indoors when it’s hostile outside and they beautify a room like nothing else. There is an incredible selection of tropical, subtropical and succulent plants that we can cultivate indoors. Unfortunately house plants fade…waaa (sad). They lose leaves, they endure pests, they wilt, eventually they die. I am sure this is not the intended outcome when we purchased the beautiful plant in its six inch pot. However, since there are more to be had we can dispose of the tired ones and just buy more fresh ones. For lots of people, house plants are like cut flowers. Throw them away when they fade, especially true for orchids. This does not need to be the case if you understand the basic needs of container culture.

This Begonia is at the peak of its production cycle, the growing is done. To maintain this plant it will take nutrients, perhaps a different container and new soil.

Wise Choices Make Good House Plants

Not every plant you see in the nursery or box store is right for your location. Many tropical plants are grown in greenhouses under high humidity and carefully filtered water. For some plants like the previously mentioned prayer plants, this is a mimic of their natural growing conditions, moist, warm and humid. Many homes may have the warm part but not the humid. Heating systems often dry the air and increase the amount of water drawn from indoor plants. This can be damaging. Unfortunately, placing your plants on a tray of gravel filled with water will not cut it. Adding a humidifier in your plant room may be a solution if you are growing humidity loving plants, e.g., ferns, many orchids, Pipers, Philodendrons, Peperomias, Begonias etc. Another way around this is to cultivate humidity loving plants in terrariums (see blog on terrariums). If enough tolerant plants are grown in a room they will also increase the humidity in the room through transpiration. So add more plants! Always a good idea right?

Do some research on the house plant you want to purchase before you bring it home to find out where it grows in nature. This will give you hints on its needs. Also know when not to buy a plant, some are just too touchy without controlled environments. If you are new to house plants start off with the easy ones (Pothos, Syngonium, African violets and some Begonias). As you gain confidence move to more difficult or interesting types.

This Balfour Aralia is in trouble. Research shows that it prefers temperatures not less than 60F. It was in an unheated plant room that was seeing low temperatures of 45F. It also needs to be moved into new media and out of the nursery container.

Realize How Plants Are Produced

When you purchase a new plant it is already an old plant, production wise. The grower had a target size or bloom requirement and once the plant has achieved that it is sent out to the retail market. Often a plant has consumed its nutrient charge in the medium it may have filled that medium with roots and the medium may have begun the process of breaking down.

It is good to get plants as fresh from the grower as possible because once they enter the box store or even nursery or plant shoppe, they begin to be affected by the stress of being outside their cultivated environment. Retailers may skip irrigating or keep plants too wet, the air may be dry and the light levels not adequate to sustain growth. The longer plants are in poor growing conditions, the less able you will be to keep them going. Even when your plants look good they may be suffering already and need several things from you such as a soaking irrigation with pure water, fertilization, light, and new media.

First Things First: Repot

Remove your new toy from its container and inspect the roots. They should look white and healthy and should be throughout the medium. If they do not look this way take the plant back. Do not introduced diseased plants to your plant collection. Assuming everything looks good find a suitable container that has drain holes (very important: never use containers w/o drainage holes) larger than the one your plant came home in. Add container medium that you know grows plants well for you or make your own medium from known ingredients. Make sure your medium has a nutrient charge like a slow release coated fertilizer or add small amounts whenever you water your plants.

Next: Irrigate

Growers cultivate amazing house plants because they carefully control the purity of the water they irrigate with by using reverse osmosis filtration. Then they add back the nutrients the plants will need. Harmful salts like sodium, chloride, fluoride, and others are excluded or kept very low in concentration. After your plant is repotted saturate the soil with either distilled water or reverse osmosis purified water. Take careful note of how heavy the container is after irrigation and after all excess water has left the container. This is the weight of a just watered plant. As the plant dries out it will get lighter, simply pick up the plant to tell how dry it is. This is an art that works with smaller containers as well. You don’t have to get your fingers dirty to assess growing medium moisture. On large containers you can tip them to tell how heavy they are. You can also use moisture meters but they are often very inaccurate and will give variable results depending on the level of fertilizer salts in the medium. A last resort is to stick your finger in the pot. Very picky plants like the prayer plant are sensitive to salts in water and excess fertilizer, they will do best with distilled water with a very small amount of soluble fertilizer added back (1/8 of the recommended amount). In some areas tap water is very low salinity and grows good plants, in others it needs reverse osmosis filtration or buy it from the store.

Lifting a container after watering gives you an idea how much a well hydrated plant weighs. As it dries it will get lighter and you will know when to water it again.

Finally: Location

Now that your new plant is settled in its container, its time to place it in a location where it will get adequate light. Some plants are from dark areas of the forest floor (ferns, begonia etc) and do best with north window light. Others require strong window light (Ficus, many bromeliads, and some succulents). It is also possible to grow plants under lights such as LED’s with great success. This is where your research into plant origins will be helpful. Try to irrigate with high quality water and dilute fertilizer when the plant’s media begins to lighten.

The ficus and coleus are in bright light in the garden room. The Syngonium is off and on closer inspection an infestation of scale was found.. It will be treated and moved.

A Note About Pests

As your collection grows there is no doubt that pests may become a problem. They come in on new acquisitions or seem to appear on their own without explanation. Many times new plants are quarantined before joining others. In any case it is best to watch for the common culprits of scale, mealy bugs, and occasionally aphids. If pests are detected there are many remedies available at nurseries. Make sure you identify your pest (Cooperative Extension offices can help) and that the pest is on the label of any product you chose to control it with. Take your plant outside to treat it and let the spray dry before bringing it back in. Quarantine treated plants away from others until you are sure the pest is controlled. Always follow pesticide label instructions precisely. Monitoring for pests can catch an infestation before it gets bad.

Simply paying attention to your plants, occasionally slipping off the container to look at the roots, re-potting when needed and keeping the fertility levels up will ensure good growth and performance. At some point you can move on to propagation of your favorites.

Something must eventually be done. A plant can’t live on wax alone.


Faber, B., J. Downer and L.Yates. 1993. Inexpensive, hand-held moisture meters. HortTechnology 3:195-196

People and Plants

In this People and Plants blog post we’re taking a look at the German botanist Adam Lonicer.

Theodor de Bry engraving, published 1652-1669

Adam Lonicer, also known as Lonitzer, Lonicerum, Lonicerus, or Loniceri, was born on October 10, 1528 in Marburg, Germany. He studied in Marburg and Mainz before becoming professor of mathematics at the Lutheran University of Marburg. In 1554 he received his medical degree and he later pursued a medical career as the city physician of Frankfurt. His true interest though was herbs and the study of botany. In 1554 he married Magdalena Egenolph and worked as a proofreader for his father-in-law, a German printer who specialized in producing herbals.

Adam Lonicer, Naturalis historiae opus novum (Frankfurt, 1551), fol. 258, Cyclaminus.

Lonicer soon decided to produce an herbal of his own, the Kreuterbuch, published in 1546. As the original full title makes clear, Naturalis historiae opus novum : in quo tractatur de natura et viribus arborum, fruticum, herbarum, Animantiumque terrestrium, uolatilium & aquatilium …  (Frankfurt, 1551), the herbal did not solely focus on plants but also included some descriptions of animals, birds, fish and metals. The emphasis throughout the book is on how one uses animal, vegetable, and mineral substances in the production of medicinal, gastronomical, and household preparations.

Adam Lonicer, Naturalis historiae opus novum (Frankfurt, 1551), fol. 184, Peony.

Although much of the work was not original to Lonicer it proved to be the greatest printing success of the Egenolph firm. It was one of the most enduring publications of its kind and was still being produced in Germany in 1783. The text covers much of the known natural world at the time and had a wide audience that included physicians, apothecaries, and both rural and urban householders. Lonicer provides us with one of the early descriptions of local flora and he is one of the first to distinguish deciduous trees from conifers. That seems obvious to us but at the time it was unconventional.

Adam Lonicer, Naturalis historiae opus novum (Frankfurt, 1551), fol. 56, Arbutus.

The most striking features of this book are its hundreds of hand-colored woodcuts. As you can imagine coloring in each image is an intensive task and would have greatly increased the cost of the book. Colored herbals were relatively rare since they were very costly to produce therefore many early printed herbals were unpainted. There’s the story of the coloring of a Flemish edition of L’Obel’s herbal for the Duke of Prussia, it took three months to color. By the time it was finished it was too expensive for hard-working botanists to buy. 

Lonicer took over the publishing firm after his father-in-law died in 1555. He went on to publish no fewer than four editions of his Kräuterbuch between 1557 and 1577. This Renaissance botanist died at Frankfurt-am-Main on May 29, 1586.

So, what plant genus is Lonicer’s name associated with?
A few hints:
It’s in the Caprifoliaceae family and native to North America and Eurasia.
There are about 180 species identified in North America and Eurasia.
It’s a widely cultivated ornamental garden plant.

If you guessed Lonicera, you’re correct!
Members of the genus are commonly known as honeysuckle, named for their sweet nectar. Lonicera are prized for their fragrant flowers with some bearing edible fruit. Many creatures, both day and night feeding, use them as a nectar source. While honeysuckle is a favorite landscaping plant many species can be invasive or grow so heavy they overpower their supports or trellis. Choose varieties wisely and monitor their growth.

Lonicera caprifolium, image used under CC license