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Sub-irrigated planters (SIPs) will save you time and money. They’ll also help you grow healthier plants than standard garden pots produce.
Do you have a patio or container garden? If you’re using traditional pots, you know that it can take a lot of work to keep the plants in them properly watered and fertilized – especially during the summer.
Growing plants in traditional pots/containers
In the summer, pots are being heated from all sides, as the potting soil inside wicks moisture up and out into the air. In the middle of the summer, the extreme heat makes daily or twice-daily watering a necessity when you’re growing plants in pots.
Meanwhile, your potted plants also require regular applications of liquid fertilizer or slow-release pelleted fertilizers because:
1. Limited space
The plants’ fast growth can only be fueled by whatever nutrition is in the pot. (Unlike in-ground plants whose roots and mycorrhizal partners can constantly grow outward, sourcing nutrition from greater distances.)
2. Nutrient loss
The constant flushes of water through the potting soil quickly washes the fertilizer/nutrients through the potting mix and out of the bottom of the pot. By the end of the growing season, your patio or deck has probably received as much fertilizer as your potted plant has!
Next thing you know, gardening goes from being a fun pastime that puts delicious food on your table to a burdensome chore. You can’t even go on vacation without recruiting a potted plant sitter!
Growing in Sub-Irrigated Planters
Thankfully, there are ways to do container gardening that drastically reduce the time, effort, and resources required.
One of our top recommendations? Use sub-irrigated planters (SIPs).
What is a sub-irrigated planter?
Sub-irrigated planters (SIPs) are planting containers designed so that irrigation is provided by a sub-surface water chamber, wherein water wicks up to the plant’s roots via capillary action (wicking) rather than being irrigated from the surface.
If you want to see the gravity-defying power of wicking, place the bottom of a towel in a bowl of water then come back a little while later. The whole towel will be soaked, despite the downward pressure of gravity.
In case you’re having trouble picturing a SIP, here’s a diagram we sketched showing how SIPs work:
Do SIPs Work?
Now you might be thinking: do SIPs actually work better than conventional pots and containers? The answer: YES!
That’s not just based on our opinion… A 2016 study on wicking bed irrigation (same process utilized by SIPs) conducted on tomatoes by the School of Natural and Built Environments, University of South Australia, found that:
“WBs (Wicking Beds) performed as well or better than precision surface irrigated pots, showing statistically significant improvement in WUE (water use efficiency), yield and fruit quality. The results also suggest an optimum design exists for soil depth (where 300 mm outperformed 600 mm) but not reservoir depth (no difference between 150 and 300 mm). The WBs were more labour efficient, requiring significantly less frequent watering to achieve the same or better WUE. WBs are inherently low-tech and scalable and appear well-suited to a variety of urban agriculture settings.”
Notice that the researchers mentioned “low-tech” in that last sentence. SIPs don’t have to be super fancy and expensive. In fact, many people make their own SIPs, and the internet abounds with DIY sub-irrigated planter guides.
However, if you’d prefer to get more aesthetically attractive, pre-made SIPs, here are a few options that we highly recommend:
We hope this article was helpful! Have questions about gardening in SIPs or other containers? Ask away in the comments below.