From our perspective, water is life, but its balance is everything. You often worry about under-watering, and yes, if our soil becomes bone dry for too long, our roots cannot uptake the moisture and nutrients we need. This causes our leaves to dry out, become brittle, and turn brown, starting at the tips. However, the more common issue is over-watering. Our roots need to breathe oxygen from the air pockets in the soil. When we are constantly sitting in soggy, waterlogged soil, our roots suffocate and begin to rot. This root rot prevents us from absorbing any water at all, leading to a paradox where we exhibit signs of thirst (yellowing and wilting leaves) while actually drowning. The first sign is often a general yellowing of the lower, older leaves.
This issue is directly tied to your watering habits. We thyme plants hail from dry, rocky Mediterranean hillsides. We absolutely demand a home with exceptional drainage. If you have planted us in heavy, clay-based, or overly moisture-retentive potting mix, you have placed us in an environment we are not adapted to survive. This poor drainage creates chronically wet conditions around our root zone, inevitably leading to the root rot described above. Our preference is for a gritty, sandy, fast-draining soil that mimics our native habitat. A pot without adequate drainage holes is essentially a death sentence for us, as it traps any excess water with no means of escape.
We are sun-worshippers. We require a minimum of six to eight hours of direct, bright sunlight daily to thrive. When light is insufficient, our growth becomes weak and leggy as we stretch desperately for more sun. This weak growth is more susceptible to stress and can lead to yellowing and leaf drop. Conversely, while we love sun, a sudden drastic increase in temperature or intensity (such as moving us abruptly from indoors to a blazing hot patio) can scorch our leaves, causing brown, burnt patches. We need a period of acclimatization to adjust to such intense changes.
While we are not heavy feeders, a complete lack of nutrients in depleted soil can eventually lead to yellowing leaves, as we lack the essential minerals like nitrogen needed to produce chlorophyll. However, it is more likely that over-fertilizing is the problem. Too much fertilizer can cause a rapid, weak burst of growth and can actually chemically burn our roots, damaging the very system we use to feed and hydrate ourselves. Furthermore, though we are naturally pest-resistant, stressed plants are vulnerable. Sap-sucking pests like spider mites can infest our leaves, causing a stippled yellowing or browning as they drain our vital fluids.
Finally, it is important to recognize that some browning is a natural part of our life cycle. As we grow and mature, our older, woody stems will naturally lose their lower leaves, which may brown and fall off. This is part of our natural habit of becoming more shrub-like. Furthermore, if you are harvesting from us, it is normal for the cut stems to brown slightly at the tips as they callous over. This is not a cause for alarm if the rest of the plant remains vibrant and healthy.
