Web Builders and Pest Busters: Spiders in the Garden

In this episode, we join spider specialist Rod Crawford to dive into the fascinating world of spiders and their role in garden ecosystems. He covers common spider species in the Pacific Northwest and how they partner with gardeners by naturally controlling pest populations.

Rod addresses common fears and misconceptions and gives his expert insights to help unravel the mysteries of spider behavior, their impact on pollinators, and ways to create spider-friendly habitats in your garden.

He busts common spider myths and helps listeners gain a new appreciation for these eight-legged allies, embracing their role as key players in sustainable gardening and healthy ecosystems.

On his watch, the spider collection has risen from less than 2,000 specimens to well over 200,000; The spider species known from the state of Washington have increased from under 300 to 975 and counting.

In the process, Rod constantly tries to educate people to the realization that what they thought they knew about spiders is largely wrong.

• Website: Spider Myths
• Spider Collector’s Journal: Home
• Video: Spider Q&A with Rod Crawford
• Prey Control by an Assemblage of Generalist Predators: Spiders in Garden Test Systems
• Beneath the Blooms: Creepy Garden Critters with Todd Murray – Episode 007

[00:00:00] Erin Hoover: Welcome to The Evergreen Thumb, your go-to podcast for up-to-date research-based horticulture and environmental stewardship knowledge to help you grow and manage your garden. Produced by Washington State University Extension Master Gardener Volunteers and brought to you by the Master Gardener Foundation of Washington State.

[00:00:16] I’m your host, Erin Hoover, a WSU Extension Master Gardener since 2015 and a certified permaculture designer and modern homesteader.

WSU Master Gardener volunteers are university-trained community educators who have been cultivating plants, people, and communities since 1973. Are you ready to grow? Let’s dig into today’s episode.

[00:00:44] Welcome to episode 42 of The Evergreen Thumb.

My guest today is Rod Crawford and he’s here to talk to us about spiders in the garden. Rod has been working with spiders and adding to the research of the spider collection at the Burke Museum for over 50 years. He and his helpers still go out regularly on spider-collecting trips to document the spider diversity in previously unstudied parts of Washington.

[00:01:12] On his watch, the spider collection has risen from less than 2,000 specimens to well over 200,000. The spider species known from the state of Washington have increased from under 300 to 975 and counting.

In the process, Rod constantly tries to educate people to the realization that what they thought they knew about spiders is largely wrong.

Rod, thank you for joining me today. Welcome to the show.

[00:01:39] Rod Crawford: I’m glad to be here.

Guest Introduction

[00:01:41] Erin Hoover: So you’re here to talk to us about spiders, particularly ones we might find in our gardens. Before we jump into that, why don’t you tell us a little bit about yourself and the work that you do with spiders?

[00:01:54] Rod Crawford: Well, I came to the University of Washington as an undergrad in the early 1970s, and I’m still here.

I, uh, originally started volunteering as a Burke Museum volunteer in 1971, uh, and, uh, then in 1986 they gave me a position.

[00:02:19] Erin Hoover: So did you study spiders as part of your schooling?

[00:02:23] Rod Crawford: Well, I started out with a different career track in mind, but, uh, spiders pretty much took over my life.

Common Spider Species in the Pacific Northwest

[00:02:33] Erin Hoover: So what are some of the more common spider species that gardeners might find in the Pacific Northwest?

[00:02:40] Rod Crawford: Well, that depends on where in the Pacific Northwest you are. In, uh, western Washington, uh, you got one set, in eastern Washington, you got another set, and I don’t really have much data on, uh, Idaho or Oregon.

[00:02:59] But, uh, the most numerous spiders, uh, in any well-vegetated setting are going to be the micro spiders, which people don’t notice very much because they’re small and consequently less scary, but, uh, in a Seattle garden or in a Seattle yard, the most numerous spiders are probably micro spiders of the genus Erigone.

[00:03:31] These are, uh, blackish-colored spiders with straw-colored legs that are about two millimeters long. Just big enough to see. They make a flat, postage-stamp-sized web at ground level, and in a really lush, moist lawn, there can be one of those webs between every two grass blades at the soil level. And, uh, you’ll get some of those in the garden as well, depending on how you, how much spider habitat you provide in your garden.

[00:04:09] You’ll also have, uh, small wolf spiders running into your garden. There is one species of wolf spider that’s predominant in Seattle. Uh, several others east of the Cascades.

Higher up in the vegetation you’ll get cobweb weavers of many species. Uh, later in the season you’ll get orb weavers.

[00:04:34] Spiders are a diverse group. Uh, your listeners would not thank me for just sitting here and naming species after species after species.

How Spider Species Adapt to Different Living Environments

[00:04:46] Erin Hoover: How do spiders adapt to changing conditions like in an urban environment versus a rural or in a native environment versus a constructed environment?

[00:04:56] Rod Crawford: Well, if you’re in an urban environment, uh, you already have primarily the spiders that are adapted for it.

[00:05:07] I mean, living things adapt. That’s part of being alive. And, uh, in a city, many of the species you see in spiders, as well as in other groups, are non-native species. But if they’re spiders, they’re still going to be, uh, beneficial to your garden plants. There are no spiders that are not beneficial to garden plants.

[00:05:35] Even if it’s something that you might not necessarily want to have around personally.

Spiders and Pest Control in the Garden

[00:05:43] Erin Hoover: So how do spiders contribute to pest control?

[00:05:47] Rod Crawford: Well, all spiders are predators. And with unimportant exceptions, all spiders are exclusively predators. They prey primarily on insects.

Where insects are the, uh, probably the chief, or at least among the chief enemies of garden plants, every insect has, uh, one or more spider species, usually many spider species, as enemies that can eat it. So, uh, that’s how spiders contribute there, as predators.

What Insects Do Spiders Eat?

[00:06:29] Erin Hoover: Are there, uh, certain types of insects that are a more predominant part of their diet?

[00:06:39] Rod Crawford: Uh, that depends on the spider species.

So it’s nice to have several spider species in a garden if you want them, all the insects, to be controlled. Like sheet web weavers tend to catch, weak flying and hopping insects, uh, orb weavers tend to catch, uh, strong flying insects, cobweb weavers tend to catch crawling insects, wolf biters will catch anything that lands on the ground and that they can see.

[00:07:18] Likewise, jumping spiders will go after anything they can see, whether it’s on the ground or on a plant.

How to Enhance Your Garden for Spiders

[00:07:29] Erin Hoover: So what are some ways that gardeners can enhance habitat for spiders in the garden?

[00:07:36] Rod Crawford: Well, the main thing to remember is that spiders are vulnerable to desiccation, particularly, and also to other adverse environmental conditions.

[00:07:52] If you’re a two-millimeter-long spider, one raindrop falling on you is sort of the equivalent of somebody dropping a giant-sized water balloon on you out of some tall building. So it helps spiders a lot and allows them to have a much higher population if you provide something for them to hide under.

[00:08:20] So your average garden or farm plot in which the plants that the gardener or the farmer is trying to grow have nothing between them but bare dirt, that’s not good for spiders.

An acquaintance of mine, uh, Susan Reichert of the University of Tennessee, did a study, uh, which was published in 1990, detailing an innovative way to enhance garden spider habitat.

[00:08:54] It simply involves covering that bare dirt with some kind of mulch that, uh, is thick enough that the spiders have something to hide under from the hot sun, or from the rain, or whatever. She used grass mulch. When I tried it in my own little vegetable plot at that time, I used leaf mulch.

[00:09:23] They both worked fine. Basically, you want to cover as much of the bare dirt surface as you can with something spiders can hide under. If it’s something that, uh, little decomposer insects like springtails, like to live on that provides some additional food for the spiders.

Sue Reichert’s study has some really, really, incredible results.

[00:09:54] The mulch plots had 10 to 20 times the number of spiders as the control bare dirt plots, with nothing but the garden plants. The number of insect pests per plant was up to 13 times greater in the bare dirt plots, and the amount of insect damage to the leaves of the vegetable was up to 22 times higher in the bare dirt plots over the mulch plots.

[00:10:31] And not only worked for Sue, it worked for me because I tried it too.

Are Spiders a Risk to Pollinators?

[00:10:36] Erin Hoover: Well, and gardeners love mulch, so. So, is there a risk to pollinators?

[00:10:45] Rod Crawford: There are some spiders that will certainly eat pollinators. However, they’re not going to eat a huge number because the majority of spiders don’t live where the pollinators are going to land.

[00:11:06] And a flower crab spider that does live on the flowers is going to take probably two or three days to complete consuming one bumblebee, so it’s not going to really depopulate the local bumblebee colony or anything like that.

Are Spiders a Food Source for Other Garden Creatures?

[00:11:24] Erin Hoover: Thinking of higher on the food web a little bit, are spiders a food source for other creatures like birds or amphibians that might be in the garden?

[00:11:34] Rod Crawford: They’re a food source for other spiders. They’re a food source for predatory beetles and ants, birds, and toads. But of course, you don’t want your spiders to be eaten by too many things because they’re the ones that are eating your garden pests,

[00:11:53] Erin Hoover: Right! And that’s where that habitat comes in.

[00:11:58] Rod Crawford: Right.

[00:11:59] Erin Hoover: Besides habitat are there are there other ways to enhance spider predation on pests?

[00:12:07] Rod Crawford: That’s the main one that I know of. There probably are other ways, but again, you’re talking to a guy who mainly studies spiders in natural habitats, not in gardens. I just happened to know about this one study because, uh, I knew the author.

How Pesticide Use Effects Spiders

[00:12:26] Erin Hoover: OK. So, how can pesticide use affect spiders in an ecosystem?

[00:12:32] Rod Crawford: Negatively.

[00:12:33] Uh, it depends on the pesticides, but, uh, some pesticides kill more spiders than others, but there isn’t any that, uh, will have zero effect on spiders. Anyway, if you enhance your spider population sufficiently, you shouldn’t need any pesticides.

[00:12:55] Erin Hoover: Exactly. So, are there spider species that are particularly rare or endangered in Washington?

[00:13:04] Rod Crawford: Oh, probably. The trouble is, there’s just one guy in the entire state doing a full-time spider study, and I can’t keep track of everything and I don’t even revisit sites to see if a species is declining or not because there are so many thousands of sites that I haven’t even sampled yet and I’m not going to live forever, so I have to concentrate on those.

[00:13:29] And urban gardens are not exactly a major habitat for anything rare or endangered anyway.

The Biggest Spider Myths

[00:13:36] Erin Hoover: What are some of the biggest myths about spiders that you would like gardeners to know?

[00:13:42] Rod Crawford: The biggest myth, of course, I have an entire website about spider myths, which I trust you are going to link to…

[00:13:50] Erin Hoover: Absolutely.

[00:13:53] Rod Crawford: The biggest and probably the most harmful myth about spiders is the idea that if you didn’t see what bit you, it was a spider.

Spiders come up, uh, in a conversation at a lunch table or something, two or three people are going to say, “Oh, they’re terrible. They bite me all the time”. And if I were there, I would ask, well, excuse me, sir, but did you ever actually see a spider standing on you, biting you even once?

 “Well, no, but of course it’s spiders. What else could it be? Ha ha ha ha ha ha.”

Other Spider Myths

[00:14:33] Erin Hoover: Are there any other myths that you’d like to share? I know there are quite a few.

[00:14:36] Rod Crawford: In connection with that, there’s also, uh, people also get the idea that spiders are dangerous to humans. Uh, no, humans are dangerous to spiders as well as to other humans. Not the other way around.

[00:14:49] And, uh, in western Washington the number of spider species you might find in your garden that would be any danger to you is, uh, zero. In eastern Washington, there’s a remote possibility you might come up with a black widow once in a while. Other than that, same deal, uh, nothing dangerous.

[00:15:11] Erin Hoover: Well, and I know for a long time there were a lot of people who thought that, was it the brown recluse?

[00:15:18] Rod Crawford: Well, I mean, everybody thinks that brown recluses are everywhere. Actually, the nearest brown recluse is in Nebraska.

[00:15:26] Erin Hoover: Uh, is there anything else you’d like to tell us about spiders?

[00:15:30] Rod Crawford: Well, uh, house spiders and outdoor spiders are not the same species.

[00:15:36] Therefore, if you find a spider in your house, it probably did not come in from outside. So, you can’t quote, put it back outside, unquote. Because it never was outside and probably would have a tough time surviving outside. And besides, there are pests to be consumed indoors as well. Clothes moths, carpet beetles, you name it.

More Thoughts about Spiders in the Garden

[00:16:01] Erin Hoover: Is there anything else that you’d like to add about spiders in the garden?

[00:16:05] Rod Crawford: Well, uh, there is one little tip I can mention. The major species that people notice in their yards and gardens are the large orb weavers that make large, circular spiral webs at the end of summer. If you have one of those making a web across a pathway and you don’t want to have it in your face, the thing to do is not bother to knock down the web because the spider can make a new one in 20 minutes.

The solution to that problem is to relocate the spider.

[00:16:47] Erin Hoover: And what would be a good habitat to replace it to?

[00:16:51] Rod Crawford: Well, any place where you, uh, want spider predation to occur, like, uh, for instance, in among your roses. Roses tend to be targeted by aphids a lot and, uh, dispersing winged aphids are among the main prey of orb weavers.

[00:17:11] Uh, a single one, can catch over a hundred a day.

[00:17:18] Erin Hoover: I was just thinking of a spider that I, the first time I saw one, I call it a garden spider, but I think it’s also known as a banana spider.

[00:17:28] Rod Crawford: There are no banana spiders in the Northwest.

[00:17:30] Erin Hoover: Okay, then that wasn’t what it is.

[00:17:32] Rod Crawford: Banana spiders are, the, uh, large tropical huntsman spiders that get imported on bunches of bananas.

[00:17:40] Erin Hoover: Okay, well this was a yellow and black spider that was probably an inch and a half to two inches.

[00:17:48] Rod Crawford: Okay, and uh, does it make an orb web that is the round spiral kind of web?

[00:17:54] Erin Hoover: Can’t remember.

[00:17:55] Rod Crawford: Okay, well where are you located?

[00:18:00] Erin Hoover: I’m in southwest Washington, south of Olympia.

[00:18:03] Rod Crawford: Okay, there is a black and yellow orb weaver that’s, uh, very large.

[00:18:09] Larger than most of the native orb weavers, uh, that could be found down there, but it’s still rather rare in western Washington, uh, up until now. It will be getting more common as the climate continues to warm.

[00:18:31] Brownish or orangish, uh, orb weaver species with white streaks on the back in the form of a cross is probably the dominant orb weaver you’re going to see. And, uh, that’s a non-native species, but it’s still perfectly okay for pest control.

Final Thoughts about Spiders in the Garden

[00:18:42] Erin Hoover: Okay. Any final thoughts on spiders or myths about spiders?

[00:18:50] Rod Crawford: Well, I mean, I, there are, uh, 75 or 80 myths debunked on my website. I go through them one by one, but, uh, we don’t have time.

[00:19:00] Erin Hoover: Well, you shared some of the bigger ones, so I think that covers it then. Thank you so much for joining me today.

[00:19:07] Rod Crawford: You’re very welcome.

[00:19:09] Erin Hoover: Thank you for joining us on this episode of The Evergreen Thumb, brought to you by the WSU Extension Master Gardener Program volunteers and sponsored by the Master Gardener Foundation of Washington State.

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