Standing water in the saucer - harmless or risk of waterlogging?

Why is stagnant water so dangerous for the roots?

In normal, aerated soil, there are also air pores between the moist particles – roots need oxygen to breathe. However, if there is water in the pot, it displaces the air and the roots literally suffocate. The standing water blocks the uptake of oxygen and nutrients via the roots, which is vital for the plant. As a result, the plant shows signs of deficiency, even though it has actually been watered and perhaps even fertilized sufficiently. The symptoms (drooping, yellow leaves, stunted growth) are often mistaken for a lack of nutrients – but the cause is actually over-absorbed roots.

If the waterlogging lasts longer, the situation worsens: harmful fungi and bacteria can multiply rapidly in the airless, wet environment. Root rot develops quickly – the roots begin to turn brown, become slimy and die off. Permanently waterlogged soil is virtually a “paradise” for decay pathogens such as fungi. In addition, useful soil organisms die off, which further deteriorates the soil quality.

In short: Stagnant water leads to a vicious circle of oxygen deficiency, rotting and nutrient deficiency, which makes the plant seriously ill. As the saying goes, a waterlogged plant is “watered to death”.

Gardeners and experts therefore repeatedly emphasize how risky permanently wet feet are for almost all potted plants. One guide puts it like this: More houseplants die from waterlogging (because the water stands in the saucer for too long) than from dryness – you should never forget that a flower pot is not an aquarium and plant roots should never stand in water for too long(Pflanzen-Kölle Ratgeber). Even species that like a lot of moisture need air at the roots. The tropical Alocasia, for example, likes a constantly moist substrate, but cannot tolerate wetness in the long term(Palmenmann – Alocasia Pflege). Permanently moist soil should therefore be avoided.

Especially for cannabis plants: Avoid overwatering

Cannabis is particularly sensitive to waterlogging. The following principle applies to cannabis cultivation: the soil should be evenly moist, but never dripping wet. A frequently cited beginner’s mistake is to water cannabis too often and too much. The result is overwatered plants – and these react with the same problems: limp leaves, discoloration, growth arrest. Overwatering suffocates cannabis roots and prevents them from absorbing nutrients and oxygen(Watering cannabis: How to remedy overwatering and underwatering). If the root zone remains too wet for too long, there is a risk of root rot, fungal infestation and ultimately the loss of the plant. Cannabis growers know the rule well: the plant needs water, but avoid “wet feet” at all costs!

A practical example from a hemp guidebook illustrates this: It advises to always keep the soil moist (not soaking wet), because “if the roots are in water, the plant rots”(Planting hemp: tips and mistakes when growing). It is also said that there should be no more water in the saucer half an hour after watering – if there is, you have watered too much and there is a risk of waterlogging(Planting hemp: tips and mistakes when growing). These recommendations underline how important it is, especially with cannabis, to consistently drain excess water. Many experienced growers only use saucers to collect the drainage water and then dispose of it immediately. Some also work with fabric pots or clay shards in the bottom of the pot to minimize waterlogging right from the start.

Of course, there are special cases: In hydroponics or special irrigation systems (e.g. deep water culture), the roots are in water, but this is continuously supplied with oxygen (by pumps, aeration stones, etc.). Stagnant, oxygen-poor water, on the other hand, is deadly for cannabis roots. This is why you should not leave the stagnant drainage water in the saucer “for later” after watering in the hope that the plant will soak it up – without aeration it will do more harm than good.

How to avoid waterlogging: tips for healthy watering

The good news is: waterlogging can be prevented by correct watering behavior and a few simple measures. Here are the most important tips for avoiding stagnant water and root rot in potted plants:

• Ensure drainage: Always use pots with drainage holes in the bottom. Without a hole, water cannot drain away and waterlogging is inevitable(MDR Garten – Drainage in pots).
• Use a drainage layer: Add a layer of gravel, expanded clay or coarse sand to the bottom of the pot so that excess water can drain away more quickly and the drainage holes do not become blocked. This protects against water stagnation in the root area.
• Choose a high-quality substrate: Loose, permeable soil (possibly loosened with perlite) ensures that water is well distributed and excess moisture is released. Compacted, cheap soil tends to become waterlogged.
• Water correctly: Only water when the top layer of soil has dried out (finger test approx. 3 cm deep). Water thoroughly until some water runs off the bottom – but not excessively. The golden rule: keep the soil evenly moist, but never dripping wet.
• Remove excess water: Let the pot drain after watering. No more water should be left in the saucer for 15-30 minutes at the latest – pour it off!(Pflanzen-Kölle, hemp seed store). This will prevent the roots from standing in water for longer.
• Saucer with spacers: If your plant produces a lot of drainage water, you can use a saucer with elevations or a pot with feet. This way, the pot is not standing directly in the water. However, the following still applies: pour away the draining water promptly.

Conclusion: Stagnant water in the saucer is harmful in the long term, as it almost always leads to waterlogging. The plant is practically “drowned” – its roots suffer from a lack of oxygen and begin to rot. Particularly with sensitive plants such as cannabis, care should be taken to ensure that no residual water remains in the saucer after watering. If in doubt, it is better to water a little less and check more often. You can effectively prevent waterlogging with good pot drainage, the right watering rhythm and by consistently pouring off excess water. This allows your potted plants to grow healthily without “wet feet” causing them problems.