Year of Pollination: Hand Pollinating Cucurbits

Because of their large, open, unisexual flowers, plants in the gourd family are perfect for practicing hand pollination. There are several species in this family that are commonly grown in gardens, and all can be hand pollinated. Hand pollination of cucurbits is most often done when there are problems with pollination (lack of pollinators, etc.) or for seed saving purposes (i.e. to ensure that a variety breeds true). It can also be done just for fun, and that’s mostly what this post is about.

But first, if your goal is to save seeds and maintain the integrity of the varieties you are growing, there are a few things to keep in mind. Cucumbers, melons, and watermelons are all different species (Cucumis sativus, Cucumis melo, and Citrullus lanatus respectively), so you won’t have to worry about crosses between these crops. You will, however, have to worry about crosses between different varieties within individual species. So, for example, if you are growing multiple varieties of cucumbers – or if your close neighbors are also growing cucumbers – you should hand pollinate. Summer squash, winter squash, pumpkins, and some gourds are members of at least four species in the genus Cucurbita (C. pepo, C. maxima, C. mixta, and C. moschata). There is a possibility of hybridization between some of these species as well as between varieties within the same species, so precautions should definitely be taken when saving seeds for these crops. This can mean, along with hand pollination, placing bags over flowers so that bees are unable to bring in pollen from “the wrong” plants.

There are plenty of great resources about saving seeds that offer much more detail than I have gone into here, one of which is a book by Marc Rogers called Saving Seeds. Consult such resources if you would like to try your hand at seed saving. It’s easier than you might think, and it’s very rewarding.

Regardless why you are hand pollinating your cucurbits, the first step in the process is differentiating a male flower from a female flower. This is simple. Female flowers in the family Cucurbitaceae have inferior ovaries, meaning that the ovary sits below the area where the petals and other flower parts are attached. The ovaries are quite pronounced and resemble a miniature fruit. The male flowers lack ovaries, so instead are simply attached to a slender stem. You can also observe the sex organs themselves – male flowers have stamens, female flowers have carpels. Male and female flowers may also be located on different areas of the plant and may open at different times of the day. All that being said, the most obvious indication is the “mini-fruit” at the base of the flower or lack thereof.

Cucurbit flowers: male (top) and female (bottom) - photo credit: wikimedia commons

Cucurbit flowers: male (top two photos) and female (bottom two photos) – image credit: wikimedia commons

Once you have identified your flowers, you have a limited amount of time to hand pollinate them. It’s best to find flowers that are just starting to open, as the female flowers may only be receptive for as little as 24 hours. You can use a cotton swab to gather pollen from the male flower, or you can simply pluck the flower from the plant, remove the petals, and touch the pollen-loaded anthers to the stigmas of a female flower. Either way, you must get the pollen from the male parts of a flower to the female parts of a flower as that is the essence of pollination. Simply put, it’s plant sex. Play some soft jazz while you do it if you want to.

A honeybee in a squash flower

A female squash flower with honeybee inside

A honeybee covered in pollen drinking the nectar of a female squash flower

Honeybee covered in pollen drinking the nectar of a female squash flower

As with saving seeds, there are a lot of resources out there explaining the details of hand pollinating cucurbit flowers, including this guide from Missouri Botanical Garden and the following You Tube Video.

 

While we are on the subject of cucurbit flowers, it should be noted that squash flowers are edible and can be prepared in a variety of ways, as described in this post at The Kitchn. Just another reason to be impressed by this amazing group of plants.

The Gourd Family

Pumpkins are practically synonymous with fall. Outside of every supermarket, bins overflow with pumpkins and other winter squash; inside, shelves are stocked with pumpkin flavored, pumpkin spiced, and pumpkin shaped everything. It’s the season of the almighty gourd – a family of plants that not only shares a long history with humans but also features some of the most diverse and unique-looking fruits on the planet. They are a symbol of the harvest season, a staple of the Halloween holiday, and certainly a family of plants worth celebrating.

Chinese lardplant (Hodgsonia heteroclita) - photo credit: wikimedia commons

Chinese lardplant (Hodgsonia heteroclita) – photo credit: wikimedia commons

The gourd family – Cucurbitaceae – includes at least 125 genera and around 975 species. It is a plant family confined mainly to tropical/subtropical regions, with a few species occurring in mild temperate areas. Most species are vining annuals. A few are shrubs or woody lianas. One species, Dendrosicyos socotranus, is a small tree commonly known as cucumber tree. Plants in this family have leaves that are alternately arranged and often palmately lobed. Climbing species are equipped with tendrils. Flowers are unisexual and are typically yellow, orange, or white and funnel shaped. They are generally composed of 5 petals that are fused together. Male flowers have 5 (sometimes 3) stamens; female flowers have 3 (sometimes 4) fused carpels. Depending on the species, male and female flowers can be found on the same plant (monoecious) or on different plants (dioecious). Pollination is most often carried out by bees or beetles.

The flowers of balsam apple (Momordica balsamina) - photo credit: eol.org

Balsam apple (Momordica balsamina) – photo credit: eol.org

Vining habits and diverse shapes and sizes of leaves and flowers make plants in this family interesting; however, it is the fruits born by this group of plants that truly make it stand out. Known botanically as pepos – berries with hard or thick rinds –  their variability is impressive. Imagine just about any color, shape, size, or texture, and there is probably a cucurbit fruit that fits that description. Even the flesh of these fruits can be incredibly diverse. Some fruits are small and perfectly round; others are long, twisting, and snake-like or have curving neck-like structures. Some are striped, variegated, or mottled; others are warty, ribbed, or spiky. What’s more, the cultivated pumpkin holds the record for the biggest fruit in the world.

The spiky fruits of wild cucumber (Echinocystus lobata) - photo credit: wikimedia commons

The spiky fruits of wild cucumber (Echinocystus lobata) – photo credit: wikimedia commons

Having such unique fruits is probably what drew early humans to these plants. Bottle gourds (Lagenaria siceraria) were one of the first species of any plant family to be domesticated (more than 10,000 years ago). This occurred in several regions across the Old World and the New World even before agriculture was developed (more about that here). Today, numerous species in this family are cultivated either for their edible fruits and seeds or for seed oil and fiber production. Others are grown as ornamentals.

The genus Cucurbita is probably the most cultivated of any of the genera in the family Cucurbitaceae. Summer squash, winter squash, pumpkins  – all are members of various species in this genus. Cucumbers and melons are members of the genus Cucumis. Watermelon is Citrullus lanatus. Gourds are members of Cucurbita and Lagenaria. Luffa aegyptiaca and Luffa acutangula are grown as vegetable crops (the young fruit) and for making scrubbing sponges (the mature fruit). Chayote (Sechium edule) and bitter melon (Momordica charantia) are commonly cultivated in latin and asian countries respectively. And the list goes on…

Considering that there are so many edible species in this family, it is important to note that some are quite poisonous. The genus Bryonia is particularly toxic. Consumption can result in dizziness, vomiting, diarrhea, and ultimately, death. As Thomas Elpel states in his book Botany in a Day, “this plant is not for amateurs.”

White bryony (Bryonia dioica) - photo credit: wikimedia commons

White bryony (Bryonia dioica) – photo credit: wikimedia commons

Researching this family has been fun, and this post barely scratches the surface of this remarkable group of plants. One species in particular that stands out to me is Alsomitra macrocarpa, a liana from the tropical forests of Asia. Commonly known as Javan cucumber, this plant produces football-sized fruits packed with numerous seeds that are equipped with expansive, paper-thin “wings” that assist the seed in traveling many yards away from its parent plant in hopes of finding room to grow free from competition. Here is a video demonstrating this resourceful seed:

Year of Pollination: Bumblebees and Climate Change

Bumblebees, generally speaking, are having a rough time. In a world increasingly dominated by humans, some bumblebee species continue to thrive while many others are seriously struggling. Several are nearing extinction. A recent study involving 67 species of European and North American bumblebees concluded that climate change is having a major impact. Bumblebees do not appear to be migrating north in response to warming climates – a hesitation that could spell disaster.

There are over 250 species of bumblebees worldwide (46 are found in North America north of Mexico). Unlike other bees, whose diversity is greatest in Mediterranean climates, bumblebee diversity is highest in cool, temperate climates and montane regions. The majority of bumblebee species are native to the Northern Hemisphere; a few species are native to South America, and a handful of species from Europe have been introduced to New Zealand and Tasmania. Some species of bumblebees, such as the polar bumble bee (Bombus polaris) and the forest bumble bee (Bombus sylvicola), can be found in extreme cold climates and are among a select group of pollinators found in such areas.

The field guide, Bumble Bees of North America, by Paul Williams, et al. provides this description:

“Bumble bees are very hairy bees with combinations of contrasting bright colors, mostly black and yellow, sometimes with various combinations of red or white. They have two pairs of wings that are usually folded back over the abdomen while they are foraging on flowers, or hooked together as a single unit when in flight. Bumble bees also have slender elbowed antennae, and females of the pollen-collecting species have the hind tibia expanded, slightly concave, and fringed with long hairs to form a pollen basket or corbicula.”

Most bee species are solitary insects; bumblebees, like honeybees, are social insects. Unlike honeybees, bumblebee colonies begin with a new queen each year. New queens, after mating in late summer, overwinter in a protected area and emerge in the spring. They then search for food and a nesting site. Suitable nests include abandoned rodent dens,  the bases of bunchgrasses, hollow logs, and human-made structures. They build up a colony of workers which maintain the nest and forage for food and other resources. As the season comes to a close, the queen produces males and new queens. The new queens mate, go into hibernation, and the rest of the bumblebee colony dies off.

Brown-belted Bumblebee (Bombus griseocollis) - photo credit: wikimedia commons

Brown-belted Bumblebee (Bombus griseocollis) – photo credit: wikimedia commons

Bumblebees face numerous threats, both natural and human-caused. Despite their defensive sting, they are regularly eaten or attacked by various mammals, birds, and invertebrates. They are also host to a variety of pests, parasites, and pathogens, some of which have been introduced or exacerbated by human activities. The commercial bee industry is particularly at fault for the spread of certain maladies. Other major threats include loss of habitat and excessive and/or poorly timed use of insecticides. One looming threat that new research suggests is especially concerning is climate change.

A group of researchers from various institutions looked at the historical ranges of 67 species of bumblebees in Europe and North America over a 110 year period. They “measured differences in species’ northern and southern range limits, the warmest or coolest temperatures occupied, and their mean elevations in three periods relative to a baseline period.” They found that on both continents bumblebees are not tracking climate change by expanding their northern range limits and that their southern range limits are shrinking. They also observed that within the southern range limits, some bumblebee species have retreated to higher elevations. They investigated land use changes and pesticide applications (in the US only) to determine the effect they had on the results. While these things certainly affect populations on an individual level, climate change was determined to be the most important factor that lead to nearly universal range contractions of the bumblebees in this study.

The question then is why are they not tracking changing climates the same way that many other species of plants and animals have already been observed doing? Bumblebees evolved in cooler climates, so shrinking southern range limits is not as surprising as the bumblebees’ delay in moving north. Many factors may be contributing to this phenomenon including lack of specialized habitats beyond their historical ranges, daylength differences, and population dynamics. The researchers call for further investigation in order to better evaluate this observed “range compression.” They also suggest experimenting with assisted migration of certain bumblebee colonies, which in general is a controversial topic among conservation biologists. (Read more about this study here.)

Buff-tailed Bumblebee (Bombus terrestris) - photo credit: wikimedia commons

Buff-tailed Bumblebee (Bombus terrestris) – photo credit: wikimedia commons

The loss of bumblebees is concerning because they play a prominent role in the various ecosystems in which they live. They are prolific and highly effective pollinators of both agricultural crops and native plants, and they are also a major component in the food web. Some species of plants “prefer” the pollination services of bumblebees, such as those in the family Solanaceae. Many plants in this family benefit greatly from buzz pollination – a process in which a bumblebee (or occasionally bees of other species) grabs hold of the flower and vibrates its body, dislodging the pollen.

Participating in bumblebee conservation is simple. It’s similar to any other kind of pollinator conservation. Just learning about the pollinators in your region and being mindful of them can make a big difference. If you own or rent property and have space for a garden (even if its just a few containters on a patio), choose plants that provide food for bumblebees, including spring and summer bloomers. If you live in North America, this Xerces Society publication and the field guide mentioned above are great resources that can help you determine which plants are best for your region. Additionally, if you are working in your yard and happen upon a hibernating queen or a bumblebee nest, do your best not to disturb it. It may disrupt your gardening plans for a season, but the bumblebee sightings and the pollination service they provide will be worth it.

One family of plants in particular that you should consider representing in your yard is the legume family (Fabaceae). Bumblebees are commonly seen pollinating plants in this family, and because these plants have the ability to convert nitrogen in the air into fertilizer, their pollen is especially rich in protein. In his book, A Sting in the Tale, Dave Goulson describes the relationship between bumblebees and legumes:

“From a bumblebee’s perspective, legumes are among the most vital components of a wildflower meadow. Plants of this family include clovers, trefoils and vetches, as well as garden vegetables such as peas and beans, and they have an unusual trick that allows them to thrive in low-fertility soils. Their roots have nodules, small lumps inside which live Rhizobium, bacteria that can trap nitrogen from the air and turn it into a form usable by plants. … This relationship gave legumes a huge advantage in the days before artificial fertilizers were widely deployed. Ancient hay meadows are full of clovers, trefoils, vetches, meddicks and melilots, able to outcompete grasses because they alone have access to plentiful nutrients. Most of these plants are pollinated by bumblebees.”

More information about bumblebees and bumblebee conservation:

Bumblebee Conservation Trust

Bumble Bee Watch

BugGuide (Bombus)

The Xerces Society – Project Bumble Bee

In Defense of Plants – A Podcast Review

I’m an avid podcast listener; however, the majority of the podcasts I listen to, while satisfying many of my varied interests, don’t speak to my interests in plants and plant science. Recently, when I went searching for such a podcast, I happened upon In Defense of Plants. Alas, my podcast queue felt complete.

indefenseofplants

In Defense of Plants began as a blog authored by a guy named Matt. The podcast emerged about 3 years later, and in the first episode (which was posted in January 2015), Matt explains why he started the blog. While searching the internet in an effort to learn more about plants, he discovered that people weren’t writing the stories that he really wanted to read – stories that went beyond mainly talking about the anthropogenic uses of plants. Rather, Matt was interested in the stories of the plants themselves, their biological and evolutionary histories and how they fit in with the ecological world around them. Unable to find such a blog, he decided to start one himself.

His passion for plants for plant’s sake continues in his podcast. It’s evidenced both in the topics he covers as well as in the way he speaks enthusiastically and affectionately about the plants involved in the stories he tells and their habitats. He finds people to interview that are as excited about plants as he is – some are friends, some are research scientists, and some are people otherwise involved in botany or horticulture. All have interesting things to say about the world of plants and plant ecology.

Ludisia discolor - the plant that inspired Matt to start the blog

Ludisia discolor – the plant that inspired Matt to start the blog (photo credit: www.eol.org)

Over the mere nine months that the podcast has been in existence, Matt has shared some of his personal botanical explorations. When he started the podcast he was living in Buffalo, NY. He completed a Master’s degree program there and has since moved to Illinois to pursue a PhD. His most recent episodes find him exploring the tallgrass prairie of the Midwest. He’s got my attention, since this is one of my favorite ecosystems in North America.

Standout episodes to me so far have been the two part episode with Russel Funderburk as they walk through the grounds of the Highlands Biological Station, the discussion with Dave Spiering about urban ecology, and the interview with Dr. Robert Warren about invasive species (“a refreshing take”). The episode about pack rat middens and the candid discussion with Matt’s friend Steve about why they botanize are also great. Matt and Steve also do an episode about plant poaching, a topic that deserves much more attention than it gets.

The love Matt has for plants is infectious, and it is hard not to feel his excitement as he helps tell their stories. So, if you find that your podcast queue is lacking something purely plant related, In Defense of Plants is a podcast you should definitely be following.

Yerba Mate (Ilex paraguariensis)

Yerba Mate (Ilex paraguariensis) is featured in two episodes of In Defense of Plants. Listen to part one and part two. (photo credit: wikimedia commons)

 

In Defense of Weeds – A Book Review

Weeds have been with us since the beginning of human civilization. We created them, really. We settled down, started growing food, urbanized, and in doing so we invited opportunistic plant species to join us – we created spaces for them to flourish and provided room for them to spread out and settle in. During our history together, our attitudes about weeds have swung dramatically from simply living with and accepting them, recognizing their usefulness, incorporating them into our religious myths and cultural traditions, to developing feelings of disgust and disdain and ultimately declaring outright war against them. In a sense, weeds are simultaneously as wild and as domestic as a thing can be. They remind us of ourselves perhaps, and so our feelings are mixed.

Considering our combined history and the fact that weeds have stuck with us all along, perhaps it’s time we give them a little respect. This seems to be the objective of Richard Mabey’s book, Weeds: In Defense of Nature’s Most Unloved Plants. In Mabey’s own words, “this book is a case for the defense, an argued suggestion that we look more dispassionately at these outlaw plants, at what they are, how they grow, and the reasons we regard them as trouble.” Additionally, we should recognize that we wrote the definition for weeds: “plants become weeds because people label them as such.” We introduce them, create conditions in which they can thrive, and then turn around and despise them for doing what they do best. “In a radical shift of perspective we now blame the weeds, rather than ourselves;” however, as Mabey ultimately concludes, “we get the weeds we deserve.”

weeds book

But before he arrives at that conclusion – and certainly Mabey has more to say than that pithy remark – Mabey takes readers on a remarkable journey. Starting with the origins of agriculture – and the origins of weeds – he recounts the story of how weeds followed civilization as it spread across the globe. He describes our diverse reactions to weeds, how we have dealt with them, and how they have infiltrated our myths, art, cultures, food, medicine, rituals, philosophies, and stories. Along the way, certain weeds are profiled using Mabey’s unique prose. Each weed has a story to tell – some more sordid than others.

Mabey is a British author, and so the book has a strong Anglocentric slant. But this seems fitting considering that the explorations and migrations of early Europeans are probably responsible for moving more plant species around than any other group in history – at least up until the modern era. Mabey describes the myriad ways these plants were introduced: “Some simply rode piggy-back on crop and garden plants…others were welcomed as food plants or glamorous ornaments, but escaped or were thrown out and became weeds as a consequence of unforeseen bad behavior.” The seeds of many species hitched rides with numerous agricultural and industrial products, while others attached themselves to clothing, shoes, and animal fur. Everywhere humans traveled, weeds followed.

Weeds are one of the great legacies Europeans brought with them as they settled the American continent. A veritable wave of new plant species entered the Americas as the Europeans trickled in, some were purposeful introductions and some accidental. Ever the opportunists, Europe’s weeds traversed across the continent as settlers tilled and altered the land. Mabey details the introduction of “invasive European weeds” to the western United States, claiming that “by the twentieth century two-thirds of the vegetation of the western grasslands was composed of introduced species, mostly European.

One of these European species in particular has been wholeheartedly embraced by American culture; it was even given an American name. Kentucky bluegrass, Poa pratensis, “is a common, widespread but unexceptional species of grassy places in Europe…but in uncontested new grazing lands of North America it could color whole sweeps of grassland.” It has since become a preferred turfgrass species, and it’s innate ability to thrive here makes it partly responsible for Americans’ obsession with the perfect lawn. Oddly, other European invaders infiltrating a pristine, green lawn are unwelcome and derided as “weeds.” In actuality, considering its relentless, expansive, and spreading nature and its reliance on humans to perpetuate its behavior, turfgrass is much more fit for the label “weed” than any other species that invades it. As Mabey asserts, “a lawn dictates its own standards…the demands made by its singular, unblemished identity, its mute insistence that if you do not help it to continue along the velvet path you have established for it, you are guilty of a kind of betrayal.”

Kentucky bluegrass (Poa pratensis) also known as smooth meadow-grass - photo credit: wikimedia commons

Kentucky bluegrass (Poa pratensis), also known as smooth meadow-grass – photo credit: wikimedia commons

Reading along it becomes clear that Mabey is infatuated with weeds. You can see it in sentences like, “the outlandish enterprise of weeds – such sharp and fast indices of change – can truly lift your heart.” This doesn’t mean that in his own garden he doesn’t “hoick them up when they get in [his] way.” It just means that his “capricious assault” is “tinged with respect and often deflected by a romantic mood.” Does Mabey wish his readers to swoon the way he does over these enterprising and opportunistic aliens? Perhaps. More than that he seems to want to instill an awe and admiration for what they can do. In many cases they serve important ecological functions, including being a sort of “first responder” after a disturbance due to their fast acting and ephemeral nature. In this way, weeds “give something back” by “holding the bruised parts of the planet from falling apart.” They also “insinuate the idea of wild nature into places otherwise quite shorn of it,” and so despite their dependence on human activities, they could be considered “the very essence of wildness.”

For all the love Mabey has for weeds, he remains convinced that some absolutely need to be kept in check. He calls out Japanese knotweed specifically – an “invader with which a truly serious reckoning has to be made.” In speaking of naturalized plant species – introduced species that propagate themselves and “spread without deliberate human assistance” – he makes the comparison to humans becoming naturalized citizens in countries where they were not born. In this sense he argues for more acceptance of such species, while simultaneously warning that “there are invasive species that ought never to get their naturalization papers.”

Japanese knotweed (Fallopia japonica) is listed as one the 100 Worst Invasive Species - photo credit: wikimedia commons

Japanese knotweed (Fallopia japonica) is listed as one the 100 Worst Invasive Species – photo credit: wikimedia commons

This is an engrossing read, and regardless of how you feel about weeds going in, Mabey will – if nothing else – instill in you a sort of reverence for them. You may still want to reach for the hoe or the herbicide at the sight of them – and you may be justified in doing that – but perhaps you’ll do so with a little more understanding. After all, humans and weeds are kindred species.

As a type they are mobile, prolific, genetically diverse. They are unfussy about where they live, adapt quickly to environmental stress, use multiple strategies for getting their own way. It’s curious that it took so long to realize that the species they most resemble is us.

Listen to Mabey talk about his book and his interest in weeds on these past episodes of Science Friday and All Things Considered.