Is it better to top water or bottom water indoor plants?
Do you top or bottom water? My vote goes for top. Because, Science. The End. Just kidding. Here’s the ‘science’ (well, my simplified version), for why top watering’s the winner…
For indoor plants, minerals such as flouride build up in the soil over time (one cause of brown leaf tips by the way). Those excess mineral salts can’t go anywhere like they would outdoors and roots can’t escape. As water evaporates from soil, mineral salts get left behind. That’s also why terracotta pots go white, called efflorescence (that’s my Word of The Day).
Big words aside. So what? Brown leaf tips isn’t a biggie, right? Wrong. Excess mineral salts can also steal water from your plants, burn leaves, cause browning, increase wilt, cause leaf loss, stunt and slow down growth. That’s a whole lot of ‘No Thank You’.
Top watering uses gravity to flush mineral salts down and out. If you normally bottom water, or you top water but only lightly, at least once every 1 to 2 months, give your indoor jungle a good drench. Also called ‘flushing’ or ‘leaching’. If you do top water, but also leave excess in a saucer, that's a 'no no' too. Leaving leftover water in the saucer means those salts you washed out will just be reabsorbed. Nuh uh.
I usually drench water every time I water, until water really pours out the drainage holes. But if you don’t do that, do a double-drench at least every couple of months. A double drench is a top water, a short wait (a couple of minutes), then a second top water. Both times you want to water until it drains out the bottom. The first drench dissolves the salts. The second washes them down and out.
Oh, and if you do spot a crusty salt build-up forming on the surface, scrape it off. Don’t water through it! That layer is the mineral salts left behind when water evaporates up off the soil. Watering over it just dissolves those salts and puts them back in the soil all over again.
Another benefit of top watering is air. A good drench pushes out old stale air and pulls in fresh air for healthier roots. A light trickle won't do the job though. You want a good flush through of a decent amount of water.
After all that, that doesn’t mean bottom watering is bad. There are lots of good reasons to bottom water. BUT just add a top water drench every month or two to replace one of your bottom waters, and you’re good to go.