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I am trying to make a self watering planter, with a reservoir at the bottom. It has 4 polypropylene ropes (0.25 inch) which are supposed to wick water up toward the dirt.

The water is about 1 foot below the dirt, because I'm testing it to see if it'll carry water when the reservoir is low. It's definitely carrying the water up through the air that far.

My problem is that it seems to wick up to the dirt, but once it hits the dirt, the water doesn't go much further up. The area where it touches the dirt is vaguely wet, but that's about it. The rope actually goes to the top of the dirt, but the water stops following it once it hits the dirt. My hope was that the water would follow the rope and moisten the dirt as it goes up.

What can be causing this? Is the dirt sucking up the water faster than the rope can bring it up? Do people normally need to water from the top to jump start the capillary action?

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    Try using cotton, and a potting mix, not dirt – Graham Chiu Feb 15 '18 at 21:55
  • You mean a cotton rope? Won't a cotton rope decompose, requiring me to me to change it every few months? I was using a non biodegradable rope, so that it won't break. Also, yes, I meant potting mix. I'm new at this, so my terminology is bad. – NL3294 Feb 15 '18 at 23:35
  • Yes, cotton towel or similar. I tried polypropylene before and it doesn't wick – Graham Chiu Feb 16 '18 at 1:36
  • And yes they do deteriorate after a year – Graham Chiu Feb 16 '18 at 1:52
  • Thanks for the tip! Maybe I will get a couple of those cheap tshirts at my local dollar store next time i'm there! – NL3294 Feb 16 '18 at 6:57
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I tried using polyprolene rope some years ago and found that it was too tightly bound with no capillary action.

I was at the shops today and looked at what they use. It was a braided cotton string.

The other commercial wicking pot I have uses a tube of sponge but the roots grow into them as they must be open cellular sponge.

The larger pots don't use wicks but use columns of the potting mix which pulls the water up by capillary action.

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  • Thanks. I'm marking this as the answer. By the way, any thoughts on the size of the wick? I'm assuming that for a larger pot, a larger wick/dirt would be needed to pull more water. Also, is there a general rule of thumb on how deep to make the soil on top of the wick? I mean, if I pile on a huge amount of soil, the water probably won't wick all the way to the top of the container. But if I do too little soil, the bottom of the bucket might be too wet? I dunno. I've only done small tupperware self-watering pots so far, so no experience with larger ones yet. Thanks! – NL3294 Feb 16 '18 at 15:28
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    Polypropylene is hydrophobic. – Wayfaring Stranger Feb 16 '18 at 15:47
  • I've got some pictures but can't upload from behind the firewall so it'll have to wait a week – Graham Chiu Feb 16 '18 at 21:02
  • A wick can never be too large since the draw of water is governed by capillary action. – Graham Chiu Feb 17 '18 at 21:36
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Doesn't water follow the path of least resistance? Once it hits the edge of the dirt layer, why would it go any higher until that layer of dirt had the same amount of water as the rope? From there, it seems water would climb the rope at the same rate as the water would through the soil.

My understanding is that the pot should be watered thoroughly from the top after the rope/wick is positioned in the soil. That watering will evenly saturate both. Capillary action will take care of the rest as the soil/rope dry evenly dry out. Info from YouTube search.

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