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Flooding versus Topping Up

If you grow your plants in semi-hydroponics, I recommend that you fill the pot rapidly to the top at every watering, then letting it drain. That saturates the LECA, flushes the residues, and refreshes the chemistry of the reservoir.

Despite my recommendations, folks get lazy and merely “top up” the reservoir most of the time, and only flush infrequently. That will lead to a slow poisoning of your plants and their gradual degradation. I think a simple graph will demonstrate that.

In this, overly-simplified example, we are assuming that absorption of nutrients and secretion of wastes, as well as water use and evaporation are constant, and that we water after 5 days.

Both start out with “100% Quality” (whatever that means). The green line represents the degradation and replenishment of the reservoir quality if it is flushed and refilled at every watering. The red line represents what happens to the quality if it is merely topped-up at two waterings between a full fill-and-flush. Imagine if that was done less frequently!