Overwatering? Underwatering?

If there's a choice between overwatering and underwatering?

Always choose to underwater.

Pretty much every single plant out there will bounce back from being underwatered far easier than it'll bounce back from being overwatered -- and here's why!

To understand, first you need to know what each term means, and why it can spell doom for your wonderful little plants! Overwatering isn't, strictly, actually about having too much water in the soil -- but instead, it's about having not enough oxygen in the soil. Roots need oxygen to operate properly, and there are anaerobic bacteria that cause root rot that thrive where there's no oxygen as well. Underwatering is exactly what it sounds like, though -- not having enough water! Water is truly the lifeforce of all living things, and it's the most important thing for plants; without it, they will shrivel up, brown, and die... some plants faster and more dramatically than others.

Overwatering can cause a plant's demise in two different ways. First, it can kill off the roots due to a lack of oxygen; ironically, this ends up making the plant die of thirst, because the roots can't take up enough water! The more common -- and more deadly -- issue, however, is root rot.

Root rot is, to some extent, exactly what it sounds like -- your roots are rotting! Instead of firm, light brown or white roots, you'll find weak, flimsy, dark brown or black roots, and you'll be able to smell the rot. This is caused by that anaerobic bacteria that was mentioned above -- bacteria that specifically thrives in low- or no-oxygen environments, such as a pot of waterlogged soil. Once it gets a hold, it's often hard to get rid of -- often requiring cutting away affected roots manually!

Meanwhile,underwatering just results in a slow, steady death -- the plant will slowly shrivel away, leaving lots of time for water to revive it! You'll often still see some leaf loss -- especially with certain plants like Ficus triangularis -- but the bulk of the plant will survive!

So: if you aren't sure about when to water, err on the side of underwatering!