When it comes to plant care, most people think of humidity and fertiliser as separate issues. But in reality, these two factors are tightly connected - and understanding how they interact is key to keeping your plants healthy.
In short:
🌿 High humidity? You can use more fertiliser.
🌵 Low humidity? Use less fertiliser, or risk burn.
Here’s why.
Plants Drink Based on Demand
Plants don’t just passively absorb water and nutrients - they pull them in based on how much water they're losing through their leaves, a process called transpiration.
Transpiration is heavily influenced by humidity:
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In low humidity, water evaporates quickly from the leaves, so the plant pulls in more water to replace it.
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In high humidity, the air is already saturated, so plants lose less moisture - and absorb water more slowly.
This is where fertiliser (and EC) comes into play.
Low Humidity = High Water Uptake = Higher Burn Risk
When the air is dry, plants drink faster. That sounds good - until you realise they’re also pulling in more nutrients per hour from the root zone.
If your fertiliser concentration (EC) is too high, all that rapid uptake means the plant might take in more salts than it can safely process. This can lead to:
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Tip burn
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Salt stress
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Root dehydration
So in low humidity, it’s often safer to dial back your fertiliser strength slightly. You’re not starving your plants - you’re simply reducing the risk of overwhelming their internal systems during high water demand.
High Humidity = Low Water Uptake = Higher Fertiliser Tolerance
In humid conditions, plants transpire less, so they drink less water. That means they’re taking in less fertiliser overall, even if your mix has a high EC.
Because uptake is slower, your plant can handle stronger fertiliser solutions without damage. This is why many growers use higher EC levels in greenhouses or high-humidity environments - plants simply don’t "chug" water the same way.
It’s also why your favourite tropicals can thrive in a steamy grow tent with a stronger feed, but burn easily if you use the same mix in dry, indoor air.
How to Adjust Your Feeding Based on Humidity
đź’§ If humidity is low (below ~40%)
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Use a gentler fertiliser mix (lower EC)
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Water more often to keep the mix evenly moist
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Avoid strong feeds that can spike salt levels between irrigations
🌫️ If humidity is high (above ~70%)
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You can slightly increase your fertiliser strength (higher EC)
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Be careful not to overwater, since uptake slows down
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Keep an eye on airflow and drainage to prevent rot
In Summary
Humidity doesn’t just affect your leaves - it changes how your plant interacts with everything in the root zone, especially fertiliser.
At HiGrow, we design our mixes to support strong, responsive root systems, but even the best mix can’t override basic plant physiology. Adjusting your feeding routine to match your environment - especially humidity - will help you avoid burning, stunting, or rot, and get the most out of your plants.
Your plants don't live in a vacuum - the air matters too.