From our perspective as Crassula plants, the primary concern is not the method of watering itself, but the outcome it creates in our soil environment. Our roots have two fundamental, competing needs: consistent access to water and constant access to oxygen. We are succulents, adapted to store water in our leaves and stems, making us highly susceptible to root rot if our root zone remains saturated for too long. Therefore, the "better" method is the one that most effectively waters our entire root ball while allowing excess water to drain away quickly, preserving crucial air pockets within the soil. Both top and bottom watering can achieve this, but they do so in different ways with distinct advantages and risks from our point of view.
Bottom watering, where our pot is placed in a saucer of water and allowed to absorb moisture upwards, is highly beneficial for our root system. This method leverages capillary action, naturally pulling water to the areas that need it most. It encourages our roots to grow downward and outward, seeking the moisture source, which results in a stronger, more robust, and deeper root system. A strong root system makes us more resilient and better anchored. Crucially, bottom watering prevents water from pooling on our leaves or around our stem's base, a common cause of rot in succulents like us. It also ensures the entire soil mass becomes evenly moist, eliminating the frustrating problem of water running down the inside of the pot and straight out the drainage hole without ever wetting the core root ball.
However, bottom watering is not a perfect solution. The most significant issue for us is the long-term accumulation of mineral salts and fertilizers in the soil. Since water is moving upwards, it draws these soluble salts with it and deposits them as it evaporates from the surface. Over time, this creates a toxic concentration of salts in the upper soil layer, which can burn our delicate surface roots and alter soil pH, making it harder for us to absorb nutrients. This build-up appears as a white, crusty layer on the soil's surface and is detrimental to our health.
Top watering, when done correctly, directly addresses the main weakness of bottom watering. Pouring water evenly over the soil surface until it runs freely from the drainage holes provides a powerful flushing action. This leaching process washes excess mineral salts and leftover fertilizer residues out of the pot, preventing their toxic accumulation and keeping our soil environment healthier in the long term. Furthermore, a careful top watering that avoids splashing water onto our leaves and stem can effectively hydrate the root zone without promoting rot.
The primary risk of top watering from our perspective is soil compaction. The force of water can compact the soil surface over time, reducing the vital air pockets we need. It can also disturb and expose our finer surface roots. The greatest failure of top watering occurs when it is done too quickly or lightly. If water is applied rapidly, it often channels down the sides of the pot and out the drainage hole, leaving the core root ball bone dry. We are then left parched at our center while our caregiver believes we have been adequately watered, leading to chronic underwatering stress.
