Mistletoe with Joshua Der

Note: This transcript was created by AI and has not been checked by a human. Please forgive any errors. 

Joshua Der  0:00  
And I think that's where mistletoe first became associated with Christmas decorations, because you have a sign of life in the dead of winter.

Michelle Fullner  0:10  
Hello and welcome to Golden State naturalist, a podcast for anyone who's ever wondered how many holiday traditions are actually based in natural patterns. I'm Michelle Fullner. And today we're talking mistletoe with Joshua dirt whose voice you just heard. There's so much festive and botanical goodness packed into this little tiny bonus episode including ancient mistletoe folklore, what kinds of critters rely on mistletoe druids botanical explosions, why the word parasite isn't as insulting as it might sound. And of course, why we bring a toxic plant into our homes during the holidays and kiss under it. A quick heads up to adults listening with young ones that later in the episode, there is a mention of one of the traditional medicinal uses of mistletoe that you may or may not deem appropriate for kids to hear. So I advise you to use your own discretion in this and all things and I'll pop in and let you know when we're about to get to that part. And if your heart is full of holiday cheer and the spirit of generosity, please consider supporting Golden State naturalist for as little as $4 a month on Patreon. Patrons of the show make this work possible. And I am so grateful to every single one of them, including Rosalyn Tory cliff and David who contributed questions for this episode. If you want to become a patron too, you can find me on Patreon at patreon.com/michelle Fullner. That's Michelle with two L's and Fullner is fu ll en er, if you want to see what my face looks like or see some cool videos I took of things like salmon and thistles and oak trees and then put my voice over you can find me at Golden State naturalist on both Instagram and Tiktok. I'm also going to be announcing a project on Instagram in a couple of weeks that I think has a good likelihood of disappearing very quickly. So make sure to check out my Instagram around the first week of January to find out more about that. Also a quick reminder that I'll be taking a mini break to spend time with my family over the holidays and I'll be back in January with an episode featuring naturalist and eco philosopher OB Kaufman. So make sure you're following the show wherever you listen so you know as soon as that's out. But now let's get to the episode. Joshua dirt earned his BS in botany and environmental biology from Cal Poly Humboldt MS in Plant Biology from Southern Illinois University Carbondale and PhD in Biology from Utah State University. He did his postdoctoral work at Penn State University as the Ambarella Genome Project Manager. Currently He's an associate professor of biology at California State University Fullerton and the director of the McFadden herbarium. He's also the president of the American firm society and the Vice President of the California botanical society. So slide on your Fuzzy Slippers Papa candy cane into your hot cocoa settled down by the fire. And without further ado, let's hear from Dr. Joshua dirt on Golden State naturalist.

I met up with Dr. Dirt not in a forest or urban park or even on top of a beaver dam, but in a location that was a first for the podcast on Zoom. So instead of lacing up my hiking boots, I put on cozy socks. Googled how to get good sound quality out of zoom plugged in my mic and hit record so many questions. So I'm going to fire them at you probably fast. Okay, great. That conversation after a quick break.

Welcome back today on Golden State naturalist. We're talking mistletoe with Joshua winter. First, let's dive into Josh's story. How did you get interested in mistletoe and parasitic plants and the like,

Joshua Der  4:30  
during my undergrad at Cal Poly Humboldt. Now, I got interested in plants and I was really fascinated with the ones that could make a living without photosynthesizing. And so I ended up pursuing a master's degree where I studied the evolution and classification of mistletoes and their relatives and I just got really excited about mistletoes and their life history their Khaleeji but also the their physiology and the evolutionary aspects of how mistletoes diversified and evolved.

Michelle Fullner  5:06  
And mistletoes have a very interesting evolutionary history. So there

Joshua Der  5:11  
are five independent origins of mistletoes. And I guess to start off, I can explain what a mistletoe is, that would be fantastic. A mistletoe is a woody evergreen parasitic shrub that attacks and attaches to the branches of other plants. So mistletoes are a life history and a habit or in Plant Biology at the habit is the growth form. So it's a particular lifestyle and growth form of plants that make something of mistletoe,

Michelle Fullner  5:44  
that is fascinating. So just to clarify, does that mean that they're not necessarily all related, genetic,

Joshua Der  5:51  
they're all found within the same order of plants, but they're unrelated to each other, so they don't form an evolutionary group. Okay. And so mistletoes are found in five different families. But all of those families are found within the sandalwood order Santa les Lee's. Even

Michelle Fullner  6:09  
though mistletoes are all in the sandalwood order, their common ancestor is not a sandalwood you'd encounter in a smoky gift shop with beaded curtains in a college town today. Here's what Josh told me in a follow up email. The common ancestor of all mistletoes was an ancient species that gave rise to a wide range of other parasitic plants, and was not the sandal woods, we know from modern times. So you can't go find the species in a forest today. But you can find its distant descendants all over the place. And where are those found in the world where mistletoe is found in the world

Joshua Der  6:43  
mistletoes are found globally, they're most diverse in the tropics, and but they're also in in temperate regions. There are some mistletoes that are only found in Australia or South Asia or in South America. And other groups are found more broadly distributed.

Michelle Fullner  7:06  
Okay. And do we have some that are California endemic California native, we

Joshua Der  7:11  
do have some mistletoes that are California natives. Okay, so all of the mistletoes in California, belong to the family this case II, and we have two native genera of mistletoes. There are the dwarf mistletoes in the genus RC phobia, and the leafy mistletoes, which are in the genus for dendron. And we do have a non native mistletoe, one additional, it's viscum, which is the European mistletoe viscum album. And that's only found in a single population, and it was introduced maybe 100 years ago. Here, Santa Rosa.

Michelle Fullner  7:52  
Oh, and has it stayed geographically kind of confined to that area it has, interestingly, that's really interesting. And so if we're in the Santa Rosa area, there are some folks there who listen, how can you tell that mistletoe from the native mistletoes? Or is that getting challenging? It

Joshua Der  8:07  
might be hard to describe, but if you go to Sebastopol, it's right downtown. And you might be able to find it in some of the hardwood trees in the winter.

Michelle Fullner  8:18  
Okay, but generally, in California, most of the mistletoes you see in trees are going to be native mistletoes. Absolutely. Yep. Oh, okay, great. And you had kind of talked about, like the life histories of mistletoes. And I'm really curious how it is that they spread how it is that they grow, can you just give us a little bit of background on that? Sure,

Joshua Der  8:35  
since mistletoes, are parasitic plants and they're only found on branches, they have to first get to that branch. And mistletoes employ a lot of different strategies to get their seeds on branches. But the most predominant way, at least for most mistletoes is through animal dispersal. Animals eat the fruits, and then they poop the seeds out on branches. Birds are the main disperser of I think, the mistletoes that we are most familiar with here in North America. But the dwarf mistletoes, which are also here in California, actually use hydrostatic pressure in the fruits to launch their seeds out and kind of catapult them onto neighboring trees.

Michelle Fullner  9:23  
The general term for this explosive type of seed dispersal is called ballistic dispersal, which can work in a couple of different ways, including mechanical tension and water pressure as with the mistletoe, as Josh was talking about, there are many plants that use some kind of ballistic dispersal, including the Mediterranean native squirting cucumbers, which I just watched a lot of slow motion videos of. Then there's the South American dynamite tree with fruits that look like tiny adorable pumpkins until they dry out and explode with enough force to injure anyone standing nearby. And then of course we have the California Poppy with seed pa that burst in flames tiny poppy seeds in 100 different directions after they've had a chance to dry out a bit. My four year old had a lot of fun with this in my front yard this summer. And now I have 1 million Baby Poppy plants in about a 12 square foot area. And I know I should thin them, but I really don't have the heart to do it. But why would plants want to disperse their seeds by explosion? Well, there are advantages to every kind of seed dispersal. Oaks which use animals to disperse their acorns have the distinct advantage of being carried far away and planted by a squirrel or scrub J. But they're unlikely to get very far without the help of those animals or human helpers. plants that use ballistic dispersal, on the other hand, don't have to take the chance of relying on an animal to get the seeds far from the parent plant. The seeds are fired off and can spread away from the parent plant by themselves. Now mistletoes, if I can anthropomorphize them for a moment, are very smart plants because they use this ballistic strategy. And they get help from animals like birds who eat the seeds, digest them and put them out onto other branches. In fact, Smithsonian Magazine tells me that the Anglo Saxon origin of the word mistletoe is a mash up of the words dung and twig in a now defunct dialect. So maybe having more than one strategy for spreading out is part of why mistletoes are so successful around the world. But what happens after those mistletoe seeds have been flung by hydrostatic pressure or pooped out onto a suitable branch nearby, once the seeds get onto a branch of a suitable host, the seed germinates. And it has to germinate relatively quickly, because it doesn't have a lot of energy stores inside of the seed. And it needs to establish a connection with its host. And it borrows through the bark and connects to the vascular system of the host. Once it does that, the mistletoe will undergo a period of vegetative growth, some of which is inside of the host, and some of which may be outside of the host. Depending on the mistletoe species, it can send strands of plant material along the inner bark, or it may grow along the branch and then send another sinker or ha Storium into the vascular tissue, or it may just like, sort of stay there and grow up and look more like a typical plant. It's just instead of being rooted in the soil, it's rooted in another

Joshua Der  12:31  
tree. Okay,

Michelle Fullner  12:32  
but typically, before you're ever seeing that kind of distinctive ball of mistletoe in a tree, there's a lot happening out of sight, there

Joshua Der  12:40  
is a lot happening out of sight, some of which happens inside of the host plant, and some of which happens outside of the plant. I've also

Michelle Fullner  12:48  
heard like, I know that mistletoe is a parasite. And so that's one of the things that I'm really curious about is because parasite and I would love your take on this has a very negative connotation, right? I think a lot of times we say parasite, and we're like, oh, it's bad. But when you think of parasite, and when we're talking about mistletoe, right, like how harmful actually is mistletoe to the host plant? Or is there variation there in that answer,

Joshua Der  13:12  
there is variation on how damaging the mistletoes can be. But most of the time mistletoes don't kill their hosts, they infect their host. And most of the time in most mistletoe species. It's a localized infection. So a seed germinates, and that's where the plant is going to be. That's where the mistletoe is going to grow. In some cases, the mistletoe can grow through through the branch and if it's occurring at a stem tip, it can cause sort of a systemic, localized infection, causing the host to branch and proliferate new side branches in a growth form we call a witch's broom. And that's going to be this big, obvious clump of hosts that doesn't look quite right.

Michelle Fullner  14:04  
I just looked up photos of witches brooms, and they generally look like tight bundles of twigs coming off of a tree branch, sometimes with leaves and sometimes without, but they seem to look different in different situations, maybe because I'm seeing them on different tree species or maybe because they can be caused by different things like mistletoes of course, but also by certain fungi and viruses. Some of the photos I'm seeing even look a little bit like clumps of mistletoe at first glance. So if you see something that you think is mistletoe, but looks sort of off, look again, it might be a witch's broom. Okay, back to Josh and the ways mistletoes impact their hosts

Joshua Der  14:43  
mistletoes generally don't want to kill their host because of their host dies, the parasites gonna die. Occasionally you can get hosts that are infected by many, many different individuals and that puts an exceptional stress on the host and in periods of drought, it can cause the host to die. But that's sort of an uncommon but serious level of infection. Okay,

Michelle Fullner  15:07  
so typically, the host plant has to be pretty stressed or compromised in some way, there has to be some factors that are outside factors that are impacting it that are going to cause there to be actual, big, big picture damage from them. Yeah,

Joshua Der  15:19  
so mistletoes can be sort of a symptom and an indicator that a plant distressed or a host distressed and then maybe it gets killed by drought or bark beetles or other things that are present that are actually dealing the final blow

Michelle Fullner  15:39  
and then sort of on the flip side of that potential harm or potential damage, we also see ecological benefits from mistletoe right, so absolutely, okay.

Joshua Der  15:47  
Many mistletoes are important. Ecologically. They provide an important food source, especially when not many other foods are available so

Michelle Fullner  15:59  
they feed insects and birds and sometimes mammals with their fruits which are often available in the wintertime when not many other things are fruiting. It's mid December as I'm recording this and the mistletoe in my neighbor's tree has tiny white berries that still have a slightly green cast to them. So keep an eye out for mistletoes that are in low branches around you or bring some binoculars for the ones higher up in trees to see if you can spot mistletoe berries just know that some mistletoe like the leafless California desert mistletoe, which Josh will talk more about in just a second can have pink to red berries, so keep an eye out for those colors as well. They

Joshua Der  16:40  
also in changing the structure of the host, they can provide important nesting habitat. mistletoes are sometimes the preferred food plants for some insects. There are some psyllids and some butterflies that have caterpillars that are specialized on on mistletoes. And so mistletoes while having low biomass in some ecosystems, they can be really important Keystone players.

Michelle Fullner  17:10  
Dave Wyatt, a researcher who studies retails in the Sutter Buttes also found that mistletoes are an important food source for ring tails. And if you don't know what a ring tail is, please run don't walk to your nearest search engine to look them up because they look a little bit like lemurs, but they're actually related to raccoons and are a native species in California. And I adore them so thanks, mistletoe for helping those cuties out there's a

Joshua Der  17:34  
mistletoe the California desert mistletoe for dendron California come it's found throughout the desert regions of California, and it attacks mostly shrubs in the pea family and that mistletoe is really ecologically important as a habitat and food source in the desert. Okay,

Michelle Fullner  17:55  
and is it for many species or for a few particular species that it's important for.

Joshua Der  18:00  
It's actually really important for quite a number of species. Yeah, birds nest in it. There is one bird the fina papilla or the silky flycatcher is a bird that is often specialized and associated with the desert Mistletoe And so it'll guard a really infected host and use that as a perch for attracting a mate and they'll gorge themselves when the fruits are available and so there's a tight relationship there but they the mistletoe is it plays a really important role as a habitat and food source.

Michelle Fullner  18:36  
I think this is actually about the desert mistletoe. I had a question from David Cintron who heard about the desert mistletoe and said that maybe he heard they aren't toxic. And I'm wondering about the toxicity of different mistletoes and if there's variation there,

Joshua Der  18:52  
so most mistletoes are toxic to humans, though the berries are sometimes less toxic, and I have eaten desert mistletoe berries. They're kind of slimy and not very flavorful. So I wouldn't recommend it. But it is possible to eat for dinner in California come varies, but I would avoid mistletoe in general as a wild food source because it is relatively toxic and most species of mistletoes are are toxic. Okay,

Michelle Fullner  19:27  
don't put that on your foraging shortlist. Right. Okay, great. And speaking of the berries, are they actually berries, what are we what do we know about the berries?

Joshua Der  19:35  
They are berries. They are a fleshy fruit that has usually just one seed. We often think about berries as having many seeds, but but these are true berries that do have oftentimes just one seed but the flesh of the berry is well highly nutritious to many animals has a very sticky A carbohydrate called this skin that allows for the seeds to stick onto their hosts. It's like glue. And the seeds then have these hairs and strands of stickiness that glue them onto the hosts.

Michelle Fullner  20:14  
Okay, I had to check this out. So I just went back out to my neighbor's tree, plucked a berry from the lowest bunch of mistletoe and squashed it, which it turns out is exactly like having a booger stuck to your finger. I'm sorry for that image. But I promise I chose to mention the most polite bodily substance this seedy stuff has been compared to also the insides are composed largely of a clear, very sticky gel like substance surrounding the single seed Josh mentioned. So I got out my loop magnifier and took a close look at the seed, which turned out to have a thin layer of white, maybe fibrous material around the outside and a little green seed on the inside. I don't know if the seed changes color as the berries ripen, so I'll check on that again in a month or two. Okay, let's get into some human relationships with mistletoe. So I'm really curious about the origins of this cuttings of mistletoe bringing some mistletoe into the home. Where is that coming from?

Joshua Der  21:11  
So mistletoes are evergreen, and when they attack deciduous trees, they're up there in the tree looking all green and vibrant and lush, when there's not much else going on. And so they're conspicuous. And just like many other evergreen plants, pine trees or Hollies, we have a tradition of bringing those green vibrant plants indoors during the winter in order to sort of celebrate life and vitality. And I think that's where mistletoe first became associated with Christmas decorations. Because you have a sign of life in the dead of winter. Now, a lot of mistletoe Lord dates back to early European cultures. There's the druids that celebrated it as a symbol of fertility. And I think a lot of those European traditions and the mythology of mistletoe was brought over from Europe with colonization of North America.

Michelle Fullner  22:16  
Okay, so these are European traditions. And are there any particular stories or myths that you know that kind of stand out about mistletoe?

Joshua Der  22:25  
I'm not much of an expert on stories. There are stories but I I don't know that I can tell you much about them. That's okay.

Michelle Fullner  22:35  
I'll Google it. I'll see if I can find any good ones. It turns out there are a lot of traditional European stories and myths about mistletoe. But I like Time Magazine's telling of one of the more popular ones. It says the origins of kissing under the mistletoe a plant that often bears white berries are often traced to a tale in Norse mythology about the God Balder in the story. Baldurs mother frig casts a powerful magic to make sure that no plant grown on earth could be used as a weapon against her son. The one plant the spell does not reach is the mistletoe as it does not grow out of the earth but out of a tree's branches, the scheming Loki upon learning this makes a spear out of mistletoe, the spear that would eventually kill Baldor. It goes on to say that in many tellings, Frigg declares the mistletoe to be a symbol of love after her son's death, and promises to kiss anyone who passed underneath it. But it's unclear if that's actually a way the story was traditionally told. Whether it is or not, though, I have to say that I like this story. Because even after a millennia or two, maybe especially now, it rings true that we overlook mistletoe and other pillars of biodiversity at our own peril. Okay, but what are some of the other myths about mistletoe? The University of Michigan extension has a great article bulleting a bunch of these traditional stories and uses. I'll link it in the show notes in case you want to read all of them, but here are a few of my favorites. Ancient Greeks thought it could help ensure eternal life. The Druids believed mistletoe provided protection from all evil and that the Oaks it was seen growing on were honored as well. Norseman believed the mistletoe was a plant of peace. When enemies met under mistletoe, they were obliged to stop fighting for at least a day. Traditionally, a bunch of mistletoe was hung over the doorway of one's home for peace and good luck. This was done around the new year and the previous year's mistletoe would be taken down. The new plant would then provide luck throughout the year. And it was in the 18th century that mistletoe became associated with Christmas from the tradition of hanging mistletoe in one's home to bring good luck and peace to those within the house. Now, there's a lot less information on the internet about mistletoe in cultures outside of Europe, I was only able to find a passing reference on Wikipedia to the fact that mistletoe was called the God Bush by Caribbean herbalist of African descent at least as far back as the mid 18th century and a mention of its traditional uses associated with broken bones. In Nepal, my guess is that with a global and ecologically important plant like this, there are lots of uses and stories from all over the world. But that either I'm searching with the wrong terms, or there's just less information or less English language information on the internet about it. Okay, but back to the tradition of bringing some mistletoe inside. Is that okay to do? And then I'm wondering to what are your feelings? Do you think it's it's good that people are cutting some mistletoe bringing it into their homes like is that something we should do or not do? Or is that neutral,

Joshua Der  25:31  
I think it's totally fine to harvest mistletoe and bring it in as long as you're not like totally decimating the populations. For more

Michelle Fullner  25:42  
on ethically harvesting wild plants, check out the foraging episode with me and antler,

Joshua Der  25:47  
there are some places where mistletoes are highly abundant. And taking some of these mistletoes is not really going to impact the populations and the trees will be fine, the mistletoes will be fine. Just be careful not to over harvest and take trash bags full of mistletoes.

Michelle Fullner  26:08  
So the best practice is to just take a little bit maybe for your home or to share for a holiday party from a place where mistletoe is abundant. And if people want to go and do this, or if they want to go and see mistletoe, what is it that they should be looking for when they're going outside.

Joshua Der  26:24  
So the mistletoes you might want to bring into your house for holiday decorations are going to be leafy mistletoes in the genus for dendron. And we've got a few different species in California, the most obvious ones that you'll be able to find are going to be some of the ones that attack broadleaf trees, because in the winter, there'll be deciduous. So here in Southern California, they might be on sycamores, or in other parts of California, you might find them on oaks and you can easily find those mistletoes and try collecting them but because they are up in trees, it can be tricky how to collect them. If you have pull pruners, you can do that. If you're really good with a rock, you can throw rocks up at them and knock pieces down. Most mistletoes are fairly brittle. And so they will just snap and the plant the mistletoe will will be fine. It'll send up some new shoots next year, but then you can collect the pieces of mistletoe from the ground. Fantastic. That sounds easy. There are some mistletoes that do in fact, evergreen trees, the dwarf mistletoes are not going to be very showy. And they're not going to look like what you expect a mistletoe to look like. So I don't think many people are using dwarf mistletoes for decoration. But there are a few species of four dendron that are specialized on conifers. Those will be harder to find, but you'll need to go up into the mountains to find them.

Michelle Fullner  27:54  
I was gonna say I don't think I've ever noticed those before. Once you

Joshua Der  27:57  
learn what to look for. You will spot them all over

Michelle Fullner  28:01  
the place. Okay, okay, I gotta start looking. That's great. I'll look up some pictures of them. Dwarf mistletoes are a leafless mistletoe. And in the photos I just looked up, they look like little yellowish green or even yellowish red bundles of twigs sticking out of a conifer. Keep an eye out for them next time you're in the hills or mountains, but maybe choose a leafy mistletoe for your holiday party, as I somehow think the leafless ones would be less persuasive in the kissing department. Any mistletoe myths you would like to debunk?

Joshua Der  28:30  
Well, so I love parasites. Parasites are exciting, they're ecologically relevant. And so not all parasites are bad. I think. Another interesting thing that your listeners might like to know is that some mistletoes have been used to create medicines, and some mistletoes have been used to treat various different diseases. But you do need to be careful because in high amounts are used improperly, they can be really bad. So some mistletoes have been used to develop cancer treatments.

Michelle Fullner  29:04  
Hey, adults with kids around this is the part I mentioned earlier, you can jump forward by 15 seconds if you want to skip this part. And some

Joshua Der  29:11  
mistletoes have been used as a folkloric remedy for to induce abortion as an abort efficient. You can drink a tea but I wouldn't recommend any of these as as home remedies, but they are cultural uses that they back a long time. Wow, that's

Michelle Fullner  29:28  
really interesting. Thank you. I might have mentioned just once or twice in past episodes that nothing on this podcast is medical advice. And I would like to reiterate that here. Always talk to your doctor about your health and medical treatments. Alright, last thing I want to ask you is just what amazes you what blows your mind what takes your breath away about mistletoe?

Joshua Der  29:47  
I love the diversity of mistletoes and I'm fascinated with the potential for coevolution with the mistletoes and there hosts as a mistletoe adapts to become a better parasite and to more efficiently infect their hosts, the hosts are also evolving resistance to becoming infected by the mistletoes. And that can lead to this CO evolutionary arms race that may promote diversification of mistletoes. Whoo. And that's one of the things that's really exciting to me.

Michelle Fullner  30:28  
That's fascinating and follow up question to that. I don't think you said this exact number before if there is an exact number, but about how many mistletoe species are there?

Joshua Der  30:36  
I think there's maybe 1700 species of mistletoes worldwide. In California. Depending on whose classification you use, there might be between seven and 25 species. Wow, you refer to the Jepson manual, which is the technical reference for botany and California. There are seven species Okay, and and a few subspecies.

Michelle Fullner  31:04  
All right, Josh, thank you so much for being here for making the time on short notice. And I appreciate it. It was really nice talking to you.

Joshua Der  31:11  
Thank you so much, Michelle.

Michelle Fullner  31:13  
So the next time you see mistletoe hanging in a doorway, I hope you feel a little more connected with the living world. This plant supports the insects, the birds, the ring tails, and maybe even see it as an evergreen symbol of hope in the winter. That if we don't overlook beings like mistletoe, we can still live in a world that hums with life. I want to give a big thank you, of course to Josh ster for taking the time to talk with me in the midst of his busy botanical life. And to Naomi Fraga, the guest from the California native plants episode for pointing me toward Josh for this episode. Something interesting from my week is that I have just a wee bit of last minute shopping to do so. I'm going to go do that now. Happy holidays. Merry Christmas if you celebrate thanks for listening and I'll see you on the next episode of Golden State naturalist bye.

The song is called a no buy grapes and you can find a link to the song as well as the Creative Commons license in the show notes

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