DIY Sub-Irrigated (Self Watering) Raised Cedar Garden Planter Woodworking Plan

This has been by far my favorite build to date and is going to completely transform the way I garden moving forward. This Do It Yourself Sub Irrigated (or Self Watering) Raised Cedar Garden Bed is designed to not only be functional but absolutely gorgeous to look at! And who doesn’t love when style and function come together perfectly?

What is a SIP & How Does This Garden Bed Work?

SIP stands for Sub-Irrigated Planter. This is a generic term that covers container gardening where the water is given to your plants from underneath instead of above. This allows your plant to gain their water needs through capillary action. While there are many commercial uses for SIP systems, home gardeners can also enjoy the benefits of lower maintenance gardening! Since water is being stored underneath the plant, not only are you watering less (by simply filling the water reservoir) but less water is getting wasted trying to ensure your plant’s soil is evenly moist¹. Some call it self watering because the rain water is collected into the reservoir to reduce needing to hand fill it.

There are 3 main ways a SIP system can work to deliver the necessary water to your plants. Some systems use battery operated drip systems that pull from a water reservoir, wicking where water is pulled through some type of “wick”, commonly a cotton rope, to deliver the necessary water, or through air & water². This bed uses air and water to make sure the plants get the water they need. The overflow tubes are installed to leave about 1″ of air in the drain pipes, allowing a barrier between the water and the soil. Just surrounding the drain pipes there is a special soil mixture that allows extra water absorption that allows the water to easily be absorbed up to the plants. This will provide a consistent level of moisture to the plants, which honestly is impossible to achieve when watering by hand. Pretty cool, right?

So Why Make This Bed?

So what makes me love this specific elevated planter so much compared to other beds? Here’s just a couple reasons:

1. It’s made of cedar boards and sealed with spar-urethane, making it have the potential to last for 20 or more years. Just make sure to get a high quality pond liner with a long warranty like the one I used here that has a 20-year limited manufacturer’s warranty. So while you will be spending a little more upfront for materials compared to pine or white-wood, the finished product will last you years and years, making the annual cost minimal.
2. It is build with a sub-irrigated system that you refill with a hands free PVC fill tube. What does this mean? Instead of watering your garden constantly, this bed holds about 3.5″ of water at the bottom that gets pulled up into the soil as the plants need it. So if it rains in your area, the water reservoir will collect that water since the top isn’t sealed and if not then all you need to do is put the hose in the fill tube and let it run while you admire your garden or spend some time pruning and weeding. This bed also has 2 drain tubes so if you do get heavy rain or distracted while filling up the reservoir, you don’t need to worry about your plants getting root rot because the excess water will drain out!
3. This bed is the perfect height not not have to bend down to plant or weed (though weeds will be minimal since it is raised) or strain to prune taller plants. It’s also raised off the ground enough that you don’t need to worry about animals interfering with your crops (here I have terrible problems with rabbits in my garden but they are too cute to get upset with).
4. I’ve designed the perfect fold down side shelf for this bed to use while harvesting or planting, or just to put your coffee down while you work on your garden. The perfect way to save space but still have a resting place for all your tools when you need them.
5. This plan is completely customizable for you! I built a 2’x6′ bed for my tomatoes, but you can easily modify this to your liking.
6. You don’t need a ton of tools to complete this bed or a professional workspace. In this plan I will walk you through the tools I used to build mine but also give you alternatives where applicable so you aren’t breaking the bank on this build. So in the tools section if you see the word optional next to it, make sure to check the instructions before running out to buy anything.

The DIY Sub-Irrigated (Self Watering) Raised Cedar Garden Planter Woodworking Plan:

At first glance this woodworking plan may seem a little overwhelming but I promise it will come together quickly and you will love the end result. This bed is broken into 3 main components: building the bed, installing the sub-irrigation system, and adding the soil/planting. The first component by far takes the longest, but once it’s done you’ll be so happy you invested the time up front for years of low maintenance gardening!

Non-Wood Materials List (Updated):

Please note the wood cut list is in the free woodworking plan listed above.

Materials:	Quantity:	Notes:
Pond Liner	1	At least 115″ x 70″
Butt Hinge	6
Perforated Pipe	16 ft	4″ wide
Drain Cover Sleeve	16 ft	4″ wide
1/2″ PVC Pipe	1	6″ in length
1 1/2″ PVC Pipe	1	21″ in length
1 1/2″ to 3″ Pipe Increaser	1
Exterior Wood Screws
Silicone
Wood Sealant

Soil Materials

Materials:	Quantity:	Notes:
Peat Moss	1.5 cu ft	You can substitute with Coco Coir
Vermiculite	.5 cu ft
Perlite	.75 cu ft
Moisture Control Potting Soil	2 cu ft
Potting Soil	2 cu ft
Pine Bark Mulch	1 1/2 cu ft	plus additional for top of the bed
Fertilizer		Optional – Mix in based on specific fertilizer directions

Disclosure: I am an affiliate seller and may receive a commission if you click through this link and make a purchase on Amazon.

Self Watering Bed Soil Mixture:

This bed uses 2 different soil mixtures to make it work: 1 for around the drain pipes for wicking power and 1 for above the drain pipes. While I give exact amounts in the woodworking plan, I think it’s important to know the ratios and rational to each soil component so you can build a bed with different dimensions³.

Drain Pipe Soil Mixture:

• 3 Parts Peat Moss: Highly absorbent material that can hold it’s weight in moisture several times over. Be careful not to overdue it with this since it does have an acidic pH.
• 1 Part Vermiculite: The perfect soil amendment to help with aeration. It is light weight, non-toxic, and will not rot or deteriorate. Vermiculite helps increase water and nutrient retention.
• 1 Part Perlite: Allows water retention like vermiculite, but also allows water to drain more easily. It helps with improving soil aeration and prevents soil compaction⁴.

Above Drain Pipe:

• 2 cu ft Moisture Control Potting Soil
• 2 cu ft Potting Soil
• 1 1/2 cu ft Pine Bark Mulch (plus extra for top of garden bed if wanted)
• 2 gallons Perlite
• Fertilizer if desired

(Please note: The ratios for the above drain pipe soil mixture is 1 part moisture control potting soil, 1 part potting soil, .75 parts pine bark mulch, and .13 parts perlite.)

Huge shout out to Albopepper for their insane knowledge of SIP raised beds. I went through hours and hours of videos and articles when designing this bed and I found their information not only informative, but also easy to understand. Al was great at helping me get the perfect combination of soils for around the drain pipes to make this bed a huge success! Check them out if you want some more in depth knowledge of SIP beds prior to building this one: http://albopepper.com

References:

1. Sub-irrigated planter. (2019, July 20). Retrieved from https://en.wikipedia.org/wiki/Sub-irrigated_planter
2. Clayton, T. (2019, July 9). S.I.P. Gardening: Self Irrigating Planters. Retrieved from https://gardenculturemagazine.com/s-p-gardening-self-irrigating-planters/
3. Self-watering SIP Sub-irrigated Raised Bed Construction. Retrieved from http://albopepper.com/SIP-raised-bed.php
4. Information About Soil, Fixes & Fertilizers. (n.d.). Retrieved from https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers