Our lawnmower is broken, and I’ve been stuck waiting a few weeks, held up by slow-to-arrive parts. Meanwhile the grass is growing quickly.

On a grazing farm, a lawn full of grass can be an opportunity. Rachel moved the cattle into the side yard today. They grazed the lawn: in among the red pine trees, along the kid’s zip line path, and all around the garden. Tomorrow we’ll have them come in behind the house, eating the grass right up to the back door.

President Woodrow Wilson is known for keeping a flock of sheep on the White House lawn. The idea was simple and straightforward: sheep eat grass, and the White House lawn is full of grass. And like so many simple ideas, it proved more complicated. The Washington Post ran a headline in 1918, “President Wilson is having no end of trouble with the flock of sheep he purchased recently to graze on the White House lawn.” A pasture and a lawn are similar, but only in an manner analogous to the correspondences between a lion and a housecat. Sheep and cattle can graze lawns, but maintaining a lawn may not be the best job for them.

We’ve learned that, while our cattle can graze the lawn in a pinch, there are times and places where a lawnmower is just better. I don’t let the cattle graze the edge of the pond, because I don’t want them trampling the banks and ruining the water quality. Similarly, we can’t allow the cattle to graze our orchard until the apples, peaches, and plums are harvested in the fall. They love eating the leaves off the trees, scratching their necks on the branches, and when the fruit is ripening they’ll gladly eat anything they can reach. And there’s the inevitable turd factor. As much as I am happy to allow the cattle to be themselves, I don’t want to step in manure on my way to the garden or to the mailbox, so we keep the cattle off our walking paths.

One challenge in grazing livestock in the yard is timing. Because we practice rotational grazing, our cattle are only in this corner of the farm for a couple of days, and then they’re on their way to new field, not to return here for another six weeks. Depending on where the cattle are in their rotation, it might not be convenient to move fifty cattle all across the farm to spend a few hours grazing the lawn. While a six week rotation is terrific for pasture management, the grass can certainly grow far beyond “normal” lawn length in that time.

Maybe the biggest challenge, and one that stumped Woodrow Wilson, is managing cattle or sheep to keep the grass clipped back to a uniform lawn-like appearance. Once grass is nibbled down to ankle height, it tends to be nutritionally compromised for the grazing animals. And, as a additive problem, when herbivores are continuously grazing the same plants over weeks and months, the soil and the plants begin to accumulate a load of harmful parasites, bacteria, and viruses that weaken and sicken the cattle or sheep. In our model, we rotate the animals off each particular patch of ground so they won’t be back for a month or more, breaking the disease cycles. But if the grass needs to be maintained cropped short, the consequences eventually manifest as sick, feeble, or infertile livestock.

So, we haven’t found it practical to mow the grass with cattle as a general practice. Sometimes it works out for us and for them. Whenever it can work out, we try to use the cows instead of the machines. A lawnmower imposes a neat, artificial uniformity on a lawn, while a cow participates in a landscape. The difference is important.