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.

That’s because the pots are being heated from all sides, and the potting soil inside is wicking the moisture up and out into the air. In the middle of the summer, the extreme heat makes daily or twice-daily watering a necessity.

Meanwhile, your potted plants also require regular applications of liquid or even slow-release pelleted fertilizers because:

  1. limited space – their 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); and
  2. nutrient loss – the constant flushes of water quickly wash the fertilizer/nutrients through the potting mix and out of the bottom of the pot.

Next thing you know, gardening goes from being a fun pastime that puts delicious food on your table to a chore. You can’t even go on vacation without recruiting a potted plant sitter!

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 the heck is a sub-irrigated planter? Simply put, 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 towel in a bowl of water then come back a little while later: the towel will be soaked, despite the downward pressure of gravity.

In case you’re having trouble picturing a SIP, here’s a quick diagram we sketched for you:

Sub-irrigated planter diagram.


Do SIPs Work?

So, do SIPs actually work better than conventional pots/containers? Yes! 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 SIP DIY guides.

However, if you’d prefer to get more aesthetically attractive, pre-made SIPs, here are a few options that we highly recommend:

Organic Tomato Success Kit

If you want to easily grow your own organic tomatoes, peppers, etc. in a planter, this SIP kit will do it. Includes a self-watering planter, cage supports for your plants, and organic soil mix with all the nutrition and beneficial microorganisms your plants need to stay healthy, well-fed, and productive. Also has a steel trolley (extra) to raise it up.

Sizes: 26″ L x 19 3/4″ W x 10 1/2″ H

Price: $79.95

Organic EarthBoxes

EarthBoxes are another great option for growing organic veggies in a small space. We’ve been amazed by some of the patio garden photos sent to us by GrowJourney members who use EarthBoxes to grow everything from large tomatoes, to squash, to corn. Designed to drastically reduce irrigation and make growing organic food on a patio easy.

Size: 29″ L x 14″ W x 11″ H

Price: $71.14

Terrazza Trough Planter

This SIP planter is used throughout Italy and is much deeper (16″) than most American planters of a similar style. A dual action watering system that can hold up to 4 gallons of water means you’ll only need to water once or twice a week. You can also get rollers/casters to make it super easy to move around on your deck or patio.

Size: 16 1/2″ W x 39 1/4″ L x 16″ H

Price: $125.00

We hope this article was helpful! Have questions? Ask in the comments below.

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