This week, a question for the indoors!
Q: I have a peace lily at home that’s done well for me for years… until lately. Now, I’m getting black tips to the leaves, and the plant looks like it’s drying out, but it isn’t! I’ve watered it like clockwork, once per week, for a long time. It’s been in the same spot for most of that time, too. It’s too big to easily move – I bring water to the plant, I don’t take it to the sink.
A: Check the top of the soil for white crystalline material, or an excess of salty residue on the inside of the pot rim. Because salt buildup over time is one of the most likely answers to your problem.
Tap water – heck, most water – contains a modest amount of salty mineral residue. This isn’t bad! Plants need these minerals, and the most common way that plants get some of these minerals is through your water supply. But in a container sitting in a saucer (to catch run off) starts to concentrate these salts! Too much salt in the soil makes it difficult for plant roots to take in water from the soil, leading to a plant that dries out or is continually drought stressed even when the soil is quite moist.
Fortunately, the solution isn’t all that hard. The next three weeks you water, pull the plants out on the patio, take them out of any saucers, and give each of them a leisurely drenching. Water the plants, let them drain out, dunk them again… take your time with it. It will take several such drenching waterings to bring soil salt levels back down where they belong, and if you try to wash it all out at once, it’s just too much. For plants with a very salt encrusted soil, you might consider teasing the moistened roots apart, rinsing away the existing soil, and replanting with fresh potting mixture.
Once you have rinsed the majority of the excess saltiness out, give your houseplant water soluble fertilizer to label directions once per month. Your plant should improve.