Spring weather has caused many of us to turn our attention to our yards — or what’s left of them after winter, and in my case, lack of attention last fall.

Jack and Bailey have beaten a path that may never come back again around the circumference of my yard, and I don’t even want to talk about the flower garden part — both dogs have thought it was quite considerate of me to plant day lilies in their potty area.

A few recent discussions, though, have gotten me to thinking about what we actually put in our yards and whether these things could be harmful to our pets who have access to these living spaces.

This will be a cinch to write about, I thought. How much harmful stuff can there be?

My bad.

A quick visit to the ASPCA’s website taught me more than I could have imagined. From the homepage, just go to Pet Care, then Animal Poison Control and then Toxic and Non-Toxic Plants, and you’ll see a listing of 444 plants poisonous to cats, dogs and horses.

I had no idea, for example, that apple trees contain cyanide in their stems and leaves, which becomes more concentrated as these parts wilt. Those beautiful pink azaleas are toxic to all three groups of animals as well, producing symptoms that range from hypersalivation, vomiting and diarrhea all the way to coma and death. Geraniums and even those innocent-looking hostas can cause severe digestive upsets in cats and dogs.

Black walnuts, which many people collect and enjoy through the winter, don’t affect cats, but can cause all sorts of digestive disturbances in horses, and moldy nuts can cause tremors and seizures in dogs.

Both cats and dogs should avoid those stunning and graceful calla lilies: they cause mouth and lip irritations and difficulty swallowing. And while my abundant patch of day lilies may be fine for my dogs to prance among, they can cause kidney failure in cats (and cows can die from eating them as well).

The list seems endless, but www.aspca.org has it organized alphabetically. And for our technologically savvy friends, the site offers a link to a convenient “Pet Safe Application” that you can download to your handheld devices.

Beyond specific plants, another hot topic has been the mulch issue. Although mulching is a great way to keep plants moister and happier, it seems that some products can cause serious toxicity problems and are best avoided. Cocoa mulch in particular is not only attractive to look at, but it smells good. Unfortunately, also according to the ASPCA website, it contains high doses of theobromine. The study’s researchers recommend, “Pet owners should avoid use of cocoa bean mulch in landscaping around dogs with indiscriminate eating habits.” (In my experience, this statement is redundant: Isn’t “indiscriminate eating habits” part of the definition of “dog”?) Although some studies might argue otherwise, I’d say skip this type of mulch entirely.

As pet people, we also need to consider the chemicals we’re putting on our yards to keep weeds, grubs and garden pests at bay and to reduce fleas and ticks. “Green” living is becoming more popular, and the effects of the chemical processes we employ are now better understood. Remember that the things we spray on our lawns are still there when our animals go out and walk or roll in them. And our pets are inclined to lick their feet later, meaning that the chemical ends up not only in our environmental systems, but in our pets’ systems as well.

The same is true with the flea and tick medications we put on them to keep pests off them and out of our houses. One of the reasons some of this medication is applied between the shoulder blades is that it’s a place a dog’s or cat’s tongue can’t reach.

Finally, if you compost, be sure that either your pets can’t get to the contents or that what you throw out to compost is safe for animals to find. One of Bailey’s greatest treasures of the summer a few years ago was an old potato that she found and tried to bring back into the house to hide in the sofa (which, in retrospect, was much preferable to the enormous possum Jack carried in and deposited on the kitchen floor at 2 a.m. one day last week, but that’s another story). Foods that can be composted but are toxic to animals include avocado, coffee grounds, Macadamia nuts, onions and onion powder, raisins, grapes and garlic. Any moldy or spoiled foods can also make them sick.

Although these warnings might seem to make any yard an off-limits place, they’re really just a guide to remind you to take a few precautions with your best friends. Keep an eye on your pets, keep your vet’s phone number handy, and enjoy the summer!

— Sue Novak is vice president of the Lawrence Humane Society. She can be reached at SueN@lawrencehumane.org.