Why Spiders Are Beneficial in Our Gardens

Spiders in our gardens tend to evoke strong responses. We noticed this again when we posted our recent blog about Joro spiders—readers tended to have either extremely positive or adverse reactions. And we get it; there’s a lot of lore and cultural baggage around spiders in our gardens, homes, or elsewhere. However, in the United States and Canada most spiders are beneficial; there are places around the world with dangerous spiders but we don’t have many of those here. By learning a bit more about why spiders are beneficial in our gardens, we can dispel some myths about North America’s spiders and also have healthier, happier plants. Let’s dig in!

A Safety Note: We love our readers around the world, but some places really do have dangerously venomous spiders. Our advice is for the US and Canada unless stated otherwise, so please learn about your local spiders so you know which ones are safe and which ones you should avoid.

Gardzen Executive Summary:

· There are thousands and thousands  of spider species, most of which are safe for humans to be around.

· Spiders are helpful in homes and gardens, preying on unwanted insects and thus supporting our health and the health of our plants.

· By knowing about our local spiders, we can interact with them in a safe and healthy way.

· Some spiders are venomous to humans and we should learn to recognize them and treat them appropriately. Most of the spiders found in North America are safe.

· Spiders are interesting, fun, and generally good to have around!

What to Know About Spiders

Let’s start with a short breakdown of the basics about spiders. While spiders look like insects, they’re actually arachnids, meaning among other things that they have eight limbs instead of the six that insects have. They also have a centralized nervous system instead of antennae and their limbs move via a hydraulic pressure system instead of muscles. So the take home is that they’re not insects, and we can stick with that if we don’t want more details.

There are a lot of different types of spiders: over 50,000 unique species spread across 138 families found on every continent except Antarctica.  Most spiders are venomous, albeit to various degrees. The majority of spider species aren’t dangerous to humans, but some very much can be so international readers should learn about their local spiders and which they should avoid.

While spiders eat a variety of different food sources, many spiders thrive on small prey like insects, smaller arachnids, and even small birds and rodents. This is where the venom comes in by helping the spiders immobilize their prey before consuming it. Likewise web-weaving spiders use their sticky webs to help catch and immobilize prey, although not all spiders weave webs for this purpose.

Now that we’ve all refreshed our spider knowledge, let’s talk about what spiders do on our garden spaces!

How Spiders Help Our Gardens

As we touched on earlier, there are tens of thousands of species of spiders worldwide. With over 4,000 species of spider in North America, we can’t even really cover all the spiders found in our gardens. So instead we’ll explore some of the things that common spiders can do to help our gardens, our households, and our health:

· Spiders like the American house spider (Parasteatoda tepidariorum) that live in our houses eat the pests in our home. These include annoying bugs like mosquitoes but also the flies that spread food-borne diseases and destructive insects like termites.

· Large web-weaving spiders like the yellow garden spider (Argiope aurantia) and the orb weaver (Aradneidae spp) construct large webs so they can catch and eat plant pests like aphids, white flies, and the caterpillars and beetles that feed on many garden plants.

· Some spiders don’t weave webs to catch prey—they hunt for insects directly. These include grass spiders (Agelenopsis spp) who weave tunnel-like webs as nests and then trap pray that moves nearby. Wolf spiders (Lycosidae spp) are solidatry hunters, seeking their prey throughout their territory and eating unwanted garden pest insects.

· A variety of species of spider can inhabit the same garden space, fulfilling different niches and preying on different insects. This not only helps our gardens, but our overall biodiversity.

· Spiders are just fun to watch—they can be beautiful, they add something special to our gardens, and by learning more about them we can learn how to more appropriately interact with them.

When to be Cautious Around Spiders

While the vast majority of spiders aren’t any threat at all to humans, with most bites resulting in a mildly painful allergic reaction, some spiders are venomous to the point fo danger. Most dangerous spider bites come from either the window spiders of the genus Latrodectus or the recluse spiders of the genus Loxosceles. Both genera (the plural of “genus”) are found around the world, with hundreds of species that vary in severity of venom. In North America, however, we really only have two kinds to be cautious around:

· Latrodectus mactans, also known as the black widow, is found throughout North America. It’s a relatively easy spider to identify, being all black except for a red hourglass-shaped marking on its abdomen. Only the females are venomous—although sex identification can be difficult. While the bite is rarely fatal to adult humans, they can be painful and may require medical attention.

· Loxosceles reclusa, the brown recluse, is found throughout the central and southeastern United States. As the name suggests, these are brown spiders that vary in size between .25 and .80 of a inch/6 to 20 millimeters. Also as the name suggests, they are shy and tend to nest in out of the way places.  Their bites can result in necrosis, or tissue death. While not aggressive, bites can occur accidentally if a human reaches into a previously undisturbed place in which brown recluses are nesting. While bites are rarely life threatening, they can be painful and create necrotizing wounds so medical attention is recommended.

While there are spiders out there with life-threatening venom, neither the black widow nor the brown recluse are likely to be that dangerous for an adult. Medical attention is often advisable if a reaction to the bite occurs, but that’s a precaution. Children and pets should be treated with a bit more caution, as they’re smaller, but even then fatalities are rare if medical attention is prompt. So while we should be cautious around some North American spider species, they’re not dangerous per se.

The Wonderful Wild World of Spiders

Spiders are often seen as scary or spooky—how many Halloween decorations include spiders?—but the reality is that spiders are part of a healthy and functioning ecosystem while also being beneficial to our gardens and our plants. By learning a bit more about our local spiders we can interact with them in a safe and healthy way rather than reacting with fear. The spiders in our homes and gardens are likely helpful and we should recognize that.

Here at Gardzen we love spiders, so if you have a big web or a cool spider in your home or your garden space, let us know. Pics are appreciated so email them in!