Darwin’s Orchid and the Wardian Case

There’s something very special about this orchid. Can you tell what it is?

PHOTO: Closeup of Angraecum sesquipedale bloom.
A native of Madagascar, Angraecum sesquipedale is an epiphyte that prefers the drier branches and trunks of trees as a host.

 

The nectar of this orchid resides almost entirely at the tip of the orchid's spur.
The nectar of this orchid resides almost entirely at the tip of the orchid’s spur.

If you guessed that it was the long tubular structure coming from the back of the flower, you are right! That spur contains energy-packed nectar and is the reason this plant has a place in history.

Discovery

Angraecum sesquipedale was first described in 1822 by French botanist Louis-Marie Aubert du Petit-Thouars and would be shrouded in mystery for decades after. It arrived in the United Kingdom 33 years later.

ILLUSTRATION: an illustrated plate of Angraecum sesquipedale from 1822.
An illustration of Angraecum sesquipedale from Histoire particulière des plantes orchidées recueillies sur les trois îles australes D’Afrique de France, de Bourbon et de Madagascar (1822) .

At the time  this orchid was discovered, transporting plants from one continent to another was extremely difficult and often unreasonable. The long sea journey, combined with polluted conditions in industrialized cities, made it difficult to collect and maintain specimen plants. This would all soon change.

It was in 1829 that Nathaniel Bagshaw Ward discovered the mechanism that revolutionized horticulture and botany forever. 

The Wardian Case

Nathaniel Bagshaw Ward was an English doctor who spent most of his life in eighteenth-century London. In his youth, he perused the writings of Linnaeus and spent some time in Jamaica, which fostered his love of entomology and botany. As an adult, Ward was inspired to create a wall of ferns and mosses in his own yard, but failed due to the polluted air of East London. He was distraught.

In the summer of 1829, Ward took a glass jar and placed a hawkmoth chrysalis inside, atop a bed of moist leaf mold. Ward regularly checked on the progress of the moth, finding that before it hatched, grasses and a fern emerged from the leaf mold. Ward observed that the glass jar retained moisture because as it warmed up, water evaporated, condensed on the glass, and returned to the base of the jar, never escaping. With this success he repeated his experiment and, to his delight, found that he could keep plants growing within the chamber for years. His discovery brought about the invention of the Wardian case, the predecessor to the modern terrarium. He wrote extensively about this in his book, On the Growth of Plants in Closely Glazed Cases. Soon the Wardian case became a popular feature of the parlor in Victorian society. These parlor versions, both tabletop and freestanding forms, often held one or more plants and could be rather ornate.

PHOTO: A large Wardian case, made of steel and glass—an individual greenhouse for an orchid.
One of four Wardian cases appearing in our Orchid Show this year. Wardian cases like this one could be found in parlors of wealthy Victorians.

In 1843, the Wardian case was used for the first time to bring plants from China by sea. The director of the Royal Botanic Gardens, Kew, observed that in 15 years, the Wardian case brought six times as many plants as had been imported in the last century. If you do the math, that means it made importing plants almost 40 times as efficient as regular ocean travel! This was of particular use to collectors like James Bateman, a wealthy landowner who sponsored several plant exploration trips through the Royal Horticultural Society. One such trip would bring several rare Angraecum sesquipedale from Madagascar to England, and in 1862, this plant would find its way to one of the prominent figures in history.

Charles Darwin

By 1862, Charles Darwin had already become a prominent figure internationally. Having published On the Origin of Species three years earlier, Darwin was already the subject of scrutiny by religious groups and scientists who disagreed with his theories on evolution and natural selection. In this same year that he received a number of orchids from Bateman, Darwin published his book The Various Contrivances by Which Orchids are Fertilised by Insects, which proposed that Angraecum sesquipedale must be pollinated by a “huge moth with a wonderfully long proboscis” (or straw-like tongue). He proposed that it might be a Sphingidae moth since these are typically large. No such moth was known to exist on Madagascar.

Though largely overlooked by the public, his proposal became a subject of controversy, particularly in the religious community. Critics attributed any existence of such a creature to be by divine will and not natural selection; most mocked the possibility of such a moth existing. Others viewed his prediction with skepticism since only smaller moths had been discovered in Madagascar.

PHOTO: Morgan's sphinx moth, with its 30-centimeter tongue unrolled to show its length.
Morgan’s Sphinx moth, the predicted pollinator. Photo by Esculapio (Own work) [GFDL or CC-BY-SA-3.0], via Wikimedia Commons

In 1903, 21 years following Darwin’s death, a subspecies of moth known as Xanthopan morgani praedicta, Morgan’s Sphinx moth, was found in Madagascar. This moth has a wingspan of 5 to 6 inches and a proboscis of 10 to 12 inches long. The subspecies name, praedicta, was intended as an homage to Darwin’s prediction that such an insect existed.

Angraecum sesquipedale, frequently referred to as Darwin’s Orchid, is currently being displayed in the Greenhouse Gallery of the Orchid Show (purchase tickets here) this year.

©2014 Chicago Botanic Garden and my.chicagobotanic.org

Let it Snow

If you’ve been around Chicago in the past month, you’ve probably noticed the sort of weather we’ve been having.

Snow covers the grass of the Elizabeth Hubert Malott Japanese Garden in 2013. This protected grass can expect good growth in spring.
Snow covers the grass of the Elizabeth Hubert Malott Japanese Garden in 2013. This protected grass can expect good growth in spring.

You may even be bitterly cursing the snow and hoping winter will end, cheering this week’s thaw and higher temperatures. What you might not know is that all this snow has a number of benefits that will help your garden and landscape later this spring.

PHOTO: Closeup of bright red, raisiny eastern wahoo berries.
The fruit of eastern wahoo (Euonymous atropurpureus) creates a striking contrast against the snow.

Snow is a great insulator!

As winter presses on, the ground freezes deeper and deeper. This prolonged cold soil can damage roots over time. Snow helps create a blanket that reduces freezing of the soil. Warmer soil keeps microbes more active, which helps break down any plant waste that is in the soil, releasing nutrients. As a result of this insulation, your plants will have a much better start in spring!

Snow brings an important nutrient into the soil: nitrogen.

There are not many ways for nitrogen to enter the soil. While planting legumes and adding fertilizer are the most common ways we add nitrogen to soil, the weather provides nitrogen as well! Nitrogen is abundant in the atmosphere and is most easily collected by falling snow. As the snow melts, it deposits the nitrogen into the ground. (Apple trees and other plants benefit greatly from nitrogen deposited by snow.) When the ground is soft, plowing the snow into the soil will give the greatest benefit. Snow is sometimes called the poor man’s fertilizer.

PHOTO: Bare, yellow willow branches against a blue sky.
The yellow whips of this willow make an excellent contrast to the snow in most landscapes.

Don’t forget, snow is water!

When snow melts, it provides moisture for evergreen trees and shrubs. This moisture helps keep these plants happy and healthy throughout the winter. You won’t see damage right away, but a few years of snow-free winters can cause health problems in your trees.

Last but not least, snow can be very attractive in a landscape.

Snow makes plants with ornamental fruit, flowers, and bark stand out in the winter landscape. Plants like holly, ornamental grasses, euonymus, crabapples, roses, birches, ghost bramble, striped maple, dogwoods, willows, hazels, winter hazels, and witch hazels are only a few of many very attractive plants for a winter landscape. Dogwoods and willow varieties often will have young growth that is orange, yellow, or red. These same colors appear in the fruit of euonymus, crabapples, roses, and holly. Look for varieties that will complement your landscape.

If you find that snow is weighing down branches in your landscape and disfiguring the appearance of your shrubs or young trees, brush off the snow regularly and prune in the spring to remove any dead or broken branches.

PHOTO: Boxwood and hemlock trees against a fence in winter.
Evergreen trees and shrubs like boxwoods and hemlock need water through the winter to stay healthy.
PHOTO: Boxwood in winter; its branches weighted down with snow.
Boxwoods are prone to damage from heavy snows. Minimize damage by removing snow as soon as possible from the branches.

When the snow melts, check your trees and shrubs for damage near the trunk of the plant. Rodents, particularly voles, take advantage of winter snow cover and feed more aggressively on tender bark of young trees. If your lawn has developed paths of dead grass from these garden pests, rake affected areas of the lawn, apply a light application of fertilizer and seed the affected areas if damage is severe.

While many of us are hoping for an end to this winter, this abundance of snow is promising us a great spring!

©2014 Chicago Botanic Garden and my.chicagobotanic.org

Seed Pools and Jacuzzis

Have you ever spent days tending to seeds only to find that they rot shortly after sprouting? If you want your seeds to grow into big healthy plants, you should take the precaution of treating them to prevent fungal and bacterial diseases.

Seeds can catch diseases from diseased parents or plants around them. Fungal infections are common because spores can travel on the wind or in water droplets and may land on seeds, sometimes penetrating the outer layers of the seed coat and remaining until germination. When the seed sprouts, the new soft tissue offers a welcome home for the fungus to grow. Bacterial pathogens sometimes will infect the embryo of the seed itself, so the tough outer seed coat protects the bacteria too! When the seed germinates, the bacteria grows and infects the young seedling.

Don’t worry! There is a way to save your seeds from this cruel fate! We use two methods to help prevent disease in seedlings: bleach treatment and heat treatment.

Bleach treatment

PHOTO: Pumpkin and tomato seeds.
Pumpkin seeds (left) require bleach treatment, while tomato seeds (right) will require heat treatment.

If you’re working with squash or melon family members, asparagus, or zinnia seeds, you will want to give them the bleach treatment. These plants are rarely—if ever—infected from within the seed coat. Use heat treatment for seeds of the tomato family, (tomato, eggplant, pepper), carrot family (carrot, celery, parsley, cilantro), cabbage family (see here for a long list of those vegetables), spinach, and lettuce.

Bleach treatment is easy! Your first step is to collect your materials. You will need a work space with bleach, water, measuring cups or spoons, dish soap, seeds appropriate for this treatment (the list above), a bowl, a strainer, and a mesh screen or newspaper.

PHOTO: Measuring cups full of supplies, including seeds, bleach, and water.
A few common household supplies make this an easy task.

Create a bleach solution of 80 percent water and 20 percent bleach. An easy way to do this is to combine 1 cup (8 oz.) of water with 1/4 cup (2 oz.) of bleach in a bowl. Add a drop of dish soap to the solution to break the surface tension, add the seeds, and allow them to sink. Mix the solution for one minute. Next, pour the contents of your bowl through a strainer, and rinse your seeds well in cold water for about 5 minutes. Finally, place your seeds on a screen or newspaper and allow them to dry before putting them in bags or containers for next spring.

Heat treatment, or the “seed jacuzzi” method

If you’re concerned about your seeds carrying a bacterial disease inside their coat, do for them what our bodies do for us when we are sick: heat them up! Bacteria don’t respond well to higher temperatures, which is why you develop a fever when you become ill. Since seeds can’t get fevers, we put them in a seed jacuzzi.

For this treatment, you will need water, a warming plate, thermometer, nylon bags (I use coffee filters instead), a glass container, and a screen or newspaper.

PHOTO: Tomato seeds, wrapped in a coffee filter and rubber-banded, are soaking in a glass of water.
Allowing seeds to pre-warm will prevent the embryos from being shocked by the heat. If you don’t pre-warm your seeds, fewer seeds will survive the treatment.

First, place your seeds in a bag or filter that will allow water to flow through. Next, pre-warm the seeds by placing the bag in a glass container of 100-degree-Fahrenheit water for 10 minutes. Make sure the temperature stays within a few degrees of this range.

Next, place the seeds in water heated to between 118 and 125 degrees Fahrenheit. Use the chart below to identify the proper temperature for your seeds and maintain this temperature within a few degrees for the time listed on the chart.

 

Chart of Seed Treatment
Chart of Seed Treatment via Ohio State Univeristy Extension Program

PHOTO: Pumpkin seeds sprouting on a dampened paper towel.
Healthy, sprouting seeds will be back before you know it!

Finally, place the bag of seeds in cool water for 5 minutes before putting them on newspaper or a screen to dry.

Whether you take the seeds to the pool (bleach treatment) or the jacuzzi (heat treatment), treating your seeds to prevent disease is very important. When spring returns, you’ll be very happy that you did.

Mark your calendars for our annual Seed Swap on Sunday, February 23, 2014.


©2013 Chicago Botanic Garden and my.chicagobotanic.org

Living Fossils

I have been waiting weeks for my favorite moment in fall. It’s almost here! My ginkgo is turning golden and is getting ready to drop its leaves!

It might not be an exciting prospect for some people but the fall leaf drop of Ginkgo biloba is something I find amazing and wonderful. Before I get into why, let me tell you about this fantastic tree.

PHOTO: Ginkgo tree in spring and summer green color.
Also known as maidenhair tree, Ginkgo biloba has unusual leaves in that they do not have a branching network of veins; single veins run from the base of the leaf in a straight line to the edge.

Ginkgo biloba is a living fossil—fossils of Ginkgo biloba date back 270 million years, predating even the dinosaurs. This tree is truly durable and long lasting. They make excellent street trees, tolerating restricted soil space and pollution. Several even managed to survive the detonation of the atomic bomb over Hiroshima, Japan!

PHOTO: Ginkgo trees planted along a street.
A row of ginkgo trees planted along a street demonstrates the difference in growth habits.

Though ginkgo tree habits tend to vary between cultivars, they can grow anywhere from 50-100 feet high and 30-40 feet in diameter. When left to grow naturally, these trees will grow slowly, but growth can be accelerated with the help of fertilizer and watering. Young ginkgoes can often be very open and awkward-looking when left unpruned, and this is clearly visible with some street trees. Their habit, however, will improve with age as these young, long branches will become massive and reminiscent of old oaks over time.

Ginkgoes can be male or female, and identification is easiest at this time of year. Your nose can tell you if a ginkgo is male or female before you even see it. The female typically produces an abundance of fruit with a bad odor. In fact, the University of Illinois has a female ginkgo tree near the center of campus where students frequently walk, and it is not uncommon to see people checking their shoes, thinking they “stepped in something.” This fruit frequently makes a mess on lawns, paths, and sidewalks. That is why males are usually preferred for landscapes.

PHOTO: Gingko fruit and leaves on the grass underneath a tree.
Yes, they are edible, but the fruits of the female ginkgo tree have a distinctive, unfriendly smell. Female trees are often single plantings, rather than a series of trees.

In spite of the fruit odor, and beyond their ornamental value, some research suggests that the leaves can be used to improve memory and concentration. The leaves also increase the body’s production of norepinephrine, which can increase heart rate. The seeds of the female tree can also be used in cooking and are sometimes considered an aphrodisiac. If you are interested in picking the fruit, however, make sure to pick fallen fruit and wear gloves, because some people will have an allergic reaction from contact with the fleshy coating.

My favorite thing about ginkgoes, however, is their dramatic fall color and leaf drop. The leaves of ginkgo turn a beautiful golden yellow that rivals the fall color of birches. Beyond their fall color, the real drama happens after the first few golden leaves fall. After this, you can expect the rest to fall within the next 48-72 hours, carpeting the ground beneath it in golden yellow leaves.

PHOTO: Ginkgo tree in fall color.
A ginkgo tree in full fall glory. Male trees bear catkins in early spring; female trees flower, but very inconspicuously.

If you’re thinking about growing a ginkgo, it is important to always consult with a nursery about the varieties they have, and the gender of the trees. Buying an unnamed cultivar grown from seed is a big risk if you don’t want to be cleaning up the fruit later. (It takes 20-50 years for a ginkgo to produce fruit, so you may suffer the consequences if you don’t attend to the details when you make your initial purchase.)

As part of our specialized collection, the Chicago Botanic Garden has 28 different varieties of Ginkgo biloba, all of which can be located via our website and GardenGuide plant finder app.

I hope you can find your way to the Garden and check out all our wonderful ginkgoes!


©2013 Chicago Botanic Garden and my.chicagobotanic.org

Willow Pruning in the Malott Japanese Garden

If you took advantage of the warm weather last Tuesday and decided to visit the Chicago Botanic Garden, you may have noticed something unusual, especially if you wandered over to the Elizabeth Hubert Malott Japanese Garden.

IMG_8860
The Zigzag Bridge was closed for public safety until we could finish pruning.

The sight of horticulturists walking on water was not a hallucination.
In spite of the 60-degree weather, the lake was still frozen and we took advantage of the situation to finish some winter pruning.

IMG_8868
The arborists, equipped with the proper safety equipment, are busy pruning the small willow branches.

 Though this willow pruning appears very intense, even harsh, it provides airflow into the tree and gives young branches more room to grow. Some of the large, more upright branches are left to provide height. From an aesthetic point of view, this pruning gives the tree significantly more texture, creating clumps that flow into thin weeping branches. As willows can become quite large, pruning also prevents the tree from becoming disproportionately so.

IMG_8845
Benjamin Carroll stands on the ice to prune and provide direction to the arborists.

For the past four years, Benjamin Carroll, the senior horticulturist who maintains the Japanese Garden, has been working with arborists from the area to shape up his trees to give them a more traditional appearance. This style first emerged in Japan.

Seba on the Kisokaido by Utagawa Hiroshige shows the style we are trying to emulate.

Before this style of pruning was implemented, the willows were pruned to appear mounded. For the first three years of this pruning style, many large branches were cut to drastically change the appearance of the trees. This past year we were able to focus on smaller branches.

A willow prior to pruning this year.
A willow looks different before it was pruned this year.

January is the best time for us to do this because the trees are dormant and the sheet of ice on the lake is fairly thick. Tree dormancy is very important when pruning because nutrient flow is minimal and the wounds made by winter pruning will heal quickly in the spring.

Cleanliness is very important to us, it looks good and reduces debris that could promote disease.
While the arborists cut branches with pole saws and chainsaws, I moved branches off the ice.

 The thickness of the ice is also helpful to us because it simplifies cleanup.

IMG_8858
After the branches are moved to shore, they’re loaded onto a club car and taken to the mulch pile.

Cleanliness is very important to us because it not only keeps the Garden looking its best but it also reduces debris that could cause disease problems in the future.

Though we look fairly confident walking on the ice, it is important to remember that ice is always dangerous. We always have seasoned professionals and the proper safety equipment nearby.


©2013 Chicago Botanic Garden and my.chicagobotanic.org