Ask Burton: Q: I’ve got a stringy pothos ivy, a peace lily whose leaf tips are blackened and browned, and the soil in many containers looks like mud and sticks. Most of the containers show a white ring around the base, and some of the soil shows what looks like white sandy bits on top. How do I fix these?

A: What you describe are common problems of older houseplants, mainly if they were watered and placed in saucers for extended periods.

Most common potting soils contain a mixture of sand, loam, peat, bark, and compost. The precise proportions vary, and most light, peat-based potting soils greatly support houseplants. Time and regular watering do take a toll on these soils, though! Compost and peat break down, fine soil particles wash out, and eventually, you’re left with soil as you described.

For the worst examples of worn-out soil, carefully pull the plants out of the container and wash as much of the soil out as possible, teasing roots apart to loosen them. Prune out dead chunks of the root, and if the plant’s badly root bound, cut down each quadrant with a box cutter to help with teasing the roots apart. Don’t be afraid to prune as necessary to fluff out the root ball, as it’d likely help the plant restore its vigor if you pruned off the bottom inch of the root ball entirely. Reset the roots in the container with fresh, peat-based potting soil, lightly watering as you go to help settle the soil around the interior roots. Do not bury the root system any deeper in the container than when you began! The houseplant should be replanted at the same grade.

For the ivy, cut it back dramatically. Pothos ivy is easily rooted from cuttings if you feel like starting some new plants, so feel free to start some new ones from the trimmings! Fertilize with a water-soluble fertilizer once a month during the spring, summer, and fall, and the plant will quickly regrow as a dense, healthier-looking houseplant.

Now, for every houseplant whose soil you do not change out entirely, you need to do some heavy flushing watering. The containers have built up salt from tap water over time. Too much salt makes it difficult for plant roots to pull moisture from the soil! Short of completely changing out the soil, you’ll need to water the plants slowly (in the sink, bathtub, or outside), allowing water to flush entirely through the container without washing the soil away. Repeat for the next few waterings each week until most of the salt has been dissolved and flushed out. It’s acceptable to water houseplants in saucers most of the time, but occasionally take them to the sink or the patio to give them a slow and thorough rinse.