Sub-Irrigated Planters

Tips on SIP's      Article by Pat Boyd and Bob Boyd.  We built the SIP in the spring of 2020.

Sub-Irrigated Planters make perfect sense for dry climates with little rainfall.  Think about it:  If you have plants growing in pots with drain holes in the middle of the bottom of the pots and/or raised beds filled with potting mix, and you water regularly, much of that precious water drains through and runs out the bottom.  If your pots sit on concrete, the water and nutrients that run out the bottoms of the pots onto the concrete are just WASTED!  I wish I had known more about such things when we started gardening in Temecula years ago (before Bob got addicted to buying large pots, filling them with potting mix and plants).  I would have insisted that he put a plastic liner in the bottom of each pot that retained water in the bottom 1" or 2" of each pot (depending on pot size and type of plant).

When Dave Freed, aka "Dave, the Tomato Guy", spoke to our garden club about how he raises tomatoes in SIP's and gets hundreds of tomatoes from each plant, I ordered two of the plastic totes he converts to sub-irrigated planters, although I was afraid the plastic would not last long in our intense sunlight.  

I was inspired to learn more about SIP's and watched several YouTube video's.  I chose the best tutorial that I saw on building a sub-irrigated, self-wicking, raised bed planter to show to my husband.  Al Gracian showed step-by-step how to build and gave do's and don'ts.  You can search YouTube for AlboPepper or go to:  and look in the column on the right for his YouTube playlist on SIP's.

We followed Al's instructions (with a few modifications) and built our planter 4' x 12' in our narrow side yard which wasn't being used for anything except a few weeds.  I surely wish that the space between our house and the wooden fence had been 2' wider.

If you are considering building a planter, be aware that it will take time, labor, and money, and someone with power tools who can use them.  That is a considerable investment initially, but if done correctly, the planter should last a long time.

If you want to proceed, you need to have a space and know about how big each planter will be.   The planter must be level. In our hot weather, I think it is an advantage to have shade part of the day.  If shade won't be provided by buildings, consider adding tall vertical 2x4's on both sides of the planter (we have 3 vertical 8' 2x4's on only one side).  My thought was to put something between the verticals and cover with shade cloth.  The problem is the peas and cherry tomato, cucumbers, pole beans, etc. grow taller than that. 


Here is how we built our planter:

First, Bob tried to get the ground in the side yard level.  Then he covered it with a tarp.  Then hauled a LOT (more than 50 bags) of small river stones and put on top of the plastic tarp.

If you have gophers, it might be wise to put down wire mesh, perhaps larger than the planter, so later the wire can be bent up the sides and stapled.  We haven't had gophers here, so we didn't do that.

Then he assembled the 4x12' rectangle, consisting of 3 layers of 2x6" lumber.  He wanted the bottom layer to be "treated" wood.  He bought three 2x6x12's that were treated and five 2x6x12's not treated.  As you can see from the photo below, he used square posts to hold the boards together.  He used a power nail gun to shoot nails through the 2x6's into the posts.  Along one side of the planter, he attached 4 treated 2x4x8's (vertically) intended to support netting that would serve as a trellis for peas, cukes, pole beans, etc.  

Remember that everything needs to be level.  The next step is to line the planter with Pond Liner to hold water.  Bob searched online and ordered a 5'x15' x 45 mil EPDM Firestone Pond Liner (recommended by Al Gracian), and also a 5'x15' Pond Underlayment.  Put the underlayment down first, then the Pond Liner.

Staple ONLY along the top edge of the Liner.  Fold the corners carefully.  Finish stapling and cut off excess liner material.

Because the Pond Liner was not wide enough to cover all of the top board, we used plastic tarp to do that.

The next step is to install the overflow drain tube, which is going to be located in the diagonally opposite corner as the water fill tube.  You need to determine the location vertically and horizontally to drill a hole through the bottom 2x6 so the overflow tube fits inside and near the top of the corrugated drainage tubing.  In order to do that, we placed one of the 7 corrugated, perforated pieces of drainage tubing that we had cut to length (and covered the ends with weed-block fabric secured with wire ties) into the planter and pushed it against the side of the planter and marked the spot for drilling the hole, which Bob cut using a hole saw.  (Note that we want the corrugated tubing to be straight, but it's not straight because it was coiled, so we will need to figure out how to deal with that.)

You are going to need some plumbing parts to make and secure the overflow tube.  The parts you see on the left are going to be inserted through the wall of the planter from the inside of the planter to the outside of the planter.  Then add the washer and screw on the remaining threaded metal piece.

Then you can add whatever other parts you need.  Our goal was to add a flexible hose to go under the wooden fence to drain overflow water to the front yard.  

On the inside of the planter, we used silicone caulk between the washers you saw above and the Pond Liner to make a waterproof seal.

Below is the finished tube that will be inside the corrugated tubing.

We placed all 7 corrugated tubes in the planter.  Bob made 3 spacer guides to help keep the tubes in place.  Note that he added a cedar board lined up with the top of the 2x6 to protect and secure the top edge of the plastic tarp. 

He cut a hole in the corrugated tube and placed a PVC pipe into it (vertically) to serve as the water fill tube.

I am beginning to add the wicking material.


The wicking material is a mixture of Sphagnum Peat Moss and Vermiculite.

It is not my intention to advertise for any particular companies or products, but just to give examples of some products I have tried.

Here is how I mixed them: with a mixing blade on a variable speed drill.

After many hours of mixing, carrying, dumping, and poking the material in between the corrugated tubes, it was time to test.  Add water down the fill tube.  

Will the water work its way through the entire bed?  And will water run out the overflow?  Yes and Yes.

The next step is to add the growing medium.  In early spring, Costco sold MiracleGro Organic Choice Potting Mix.  We bought 14 bags.  

Many, many more hours of mixing.  The above potting mix doesn't have Perlite in it, so I mixed the MG Organic Potting Mix with Sphagnum Moss, Vermiculite, and Perlite, and some fertilizer.  After I had used the 14 bags of Potting Mix, Costco was out, so I finished filling with MiracleGro Moisture Control Potting Mix and I didn't add anything to it.

Below are two kinds of fertilizers I used.  

The Garden-tone is for mixing with the planting material in the planter, e.g. after I pulled out one crop and before planting a new crop.

The fish and kelp fertilizer is to be mixed with water e.g. in a watering can, and poured down the PVC fill tube just before adding water with the hose.

I finally finished filling the planter with the planting mix and was eager to plant peas.  

I soaked the peas in water, then put them in a plastic bag with a piece of paper towel, and when the root sprouts emerged, I planted a nice, neat row of peas.  

I use a twig to poke a hole in the potting mix and carefully insert the pea with the root sprout pointing down.

A few days later, the peas had been unearthed, presumably by rats, so I set some rat traps and caught a few rats.

The rats did not eat the sprouts--I think they ate the pea seeds.

Although a sub-irrigated planter helps save water, it does not help with any of the usual problems you encounter in your garden.

I planted more peas and tried to protect the seedlings,

The plastic rat traps last a couple years and then they either can't be set or else can't be set off.  I prefer the wooden traps.

The best bait I have found is a piece of apple.

These Wando peas are off to a good start.

The peas grew taller than any I ever planted in the ground.  They reached the top of the support.

But they did get powdery mildew.

As usual, some things did very well and other plants did not.

In November of 2020 I noticed a little plant had come up in the center of the SIP.  

It was a tomato, but I did not know where it had come from or what kind of tomato it was.

It grew slowly through the winter and when warmer weather came, it grew faster.

Blossoms formed in a cluster--so clearly a cherry tomato of some sort.

Later we believed that it came from the heirloom black cherry tomato that Bob had planted in a pot nearby.

In the photo above, notice the addition of two 2x4's across the top of the planter--dividing the planter into three 4'x4' sections 

and hopefully preventing any spreading outward of the sides of the planter.

Also notice the netting trellis is ready to support peas, tomatoes, etc.

We ordered the netting through Amazon: 

At the same time, we also ordered plastic clips to clip onto the netting and encircle the stems of tomatoes, peas, cucumbers, etc. 

Notice along the fence at the back of the photo there is a pyramid-shaped support that in 2020 I placed in the planter to support cucumbers, which proved to be inadequate, so the following spring of 2021, I asked Bob to build a taller, more sturdy support that could be moved from the front section to the back section in alternate years for the purpose of crop rotation.

These Japanese cucumbers that I bought at Home Depot are doing great.

Notice the tan shade cloth--I tried to prevent the sun from burning the cukes.

This may have been the biggest cuke.  There are still blossoms and baby cukes forming.

In the photo above, the tomato has spread more.  We are getting into summer heat.  The pole bean leaves turned crispy and those plants died.  

The other beans produced a few beans, but it was too hot for them.

The vine growing up the center of the trellis and over the top thrived in the hot weather.  It is a Murasaki sweet potato.  I had a sweet potato with one end starting to spoil, so I cut off the end and put it in the center of the planter next to the tomato.  BIG MISTAKE.  It sent vines in all directions and grew and grew and grew, and the roots grew throughout the entire planter. 

 In the fall, I cut off all the vines and tried to take out all the roots.  There was not one root that could be considered a sweet potato. 

 Allegedly the vines and leaves can be eaten when young, but we did not like them.

The red roots you see above are the sweet potato roots.  The light-colored things are the tomato stems and vines which I was pruning.

In the summer of 2021, I picked tomatoes every other day for a total of 1300 tomatoes from that one plant. 

 (Most of them eaten by Bob.)

What I don't like about this plant is that as I pick the ripe tomatoes, I also remove dead leaves, which is time consuming 

and the pile of leaves is bigger than the pile of tomatoes. 

In the photos above, notice that there is one tomato on the right side of the colander with damage.  I believe that was caused by a hornworm.

Yes, we do have Tomato Hornworms.  Their camouflage is so great, it is hard to see them on tomato plants.

To find them, I go out after dark, wearing a headlamp.  When the light shines on them, they are much easier to see.

The tomato plant continued through 2022, then I cut off all the vines and pulled the roots out.

I started a couple new plants from cuttings.

Below is the cutting I put in the planter. Marigolds are coming up from seeds from last summer's plants.

 And purple potatoes are growing.  Photo taken in February 2023.

One night after it had been raining gently on and off, we suddenly had a downpour of sleet.

There was sleet and ice on all the outdoor furniture.  The little orange kumquats were coated in ice.

But there was no sleet or ice on the planter or around it.  

I assume that was because it is somewhat sheltered between the two houses.

I did pour about three or four gallons of hot water down the fill pipe, but I did not think that was enough to make much difference.

February 22, 2023:  Sugar Snap Peas are getting tall.

There are Wando peas at the other end of the planter.