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How to Make a Self-Watering Planter

This easy DIY project allows you to go 1 to 2 weeks without watering your plants. With inexpensive materials you can get any at any hardware store, this planter turns any black thumb to bright green!

Build your own self-watering container for 70 percent off the retail price. Landscaping expert Beverly Welch from The Arbor Gate shows how to make these containers, which can run over $100 if you purchase them. While store-bought containers may be a little fancier, she says this DIY version is even better because it gives you better soil depth and larger reservoir for water.

Materials:
  • 18-gallon storage tote with lid
  • 1 1/2" PVC pipe
  • 4" or quart plastic nursery pots
  • 1-gal plastic nursery pot
  • organic soil
  • time-release fertilizer
  • 1 bag soilless planting mix
Tools:
  • Measuring tape
  • Utility knife/shears
  • Drill with 1/4" bit
  • Sharpie marker

Step 1: Cut the Lid

Take the lid of your storage tote, and using your utility knife, cut out the inside rectangle, leaving the outer edge that snaps to the top. Set the outer edge aside.

Step 2: Building the aeration shelf

The aeration shelf sits above the water reservoir, creating an air space between the root zone and the water. This air space provides oxygen to the root zone and prevents the media from becoming oversaturated or waterlogged.

1. Take the inner portion of the lid that you cut from the top and put it on a flat surface.

2. Place the 1-gal pot in the center of the lid, upside down.

3. Use the Sharpie to trace the top perimeter of the pot.

4. Turn the pot right side up and center it in your previously traced circle.

5. Use the Sharpie to trace the bottom perimeter of the pot.

6. Draw a dashed line between the two traced circles, creating a dashed circle.

7. Cut out the dashed circle using the utility knife or shears.

8. Using the drill and 1/4" bit, drill a grid of holes about 1" apart each way in the flat surface of the lid. Stay at least 1" away from the center hole and from the start of the rim of the lid.

9. Decide where you want to locate the Fill Tube (see below). Place the 1 1/2" PVC pipe in that location and cut that hole out. It should be just slightly larger than the PVC so the pipe slides easily and does not bind up.

Preparing the Water Reservoir and Soil Chamber

The bottom of the tote will be the water reservoir, the top portion of the tote will be the soil chamber, and the two will separated by an air space. Measure 4 inches from the bottom and drill a drainage hole.

For our project, we are using recycled nursery pots. There are lots of other options  short lengths of PVC, Solo cups with holes punched in them, or tin cans with both ends cut out (make sure they are not coasted with BPA). You will need enough of whatever you use to support the aeration shelf and the moist media. It is a good idea to plan to nearly cover the bottom of the reservoir with the exception of the holes we cut for the wicking pot and the fill tube.

Making the Wicking Pot

The wicking pot is the magic that makes everything work, so we will take time to make sure that we build it correctly. There is more than one way to construct the wicking pot, but the principles that make it work must be met. It must sit on the bottom of the water reservoir and reach through the aeration shelf into the soil chamber. It must have sufficient holes in the base to draw water into the wicking media. It must also have holes in the portion that will be in the air gap. These holes allow for the air in the media to be displaced during the capillary action that makes the wicking pot work.

A 5" Pond Basket meets all of these criteria. A Pond Basket is a square, perforated pot made to hold aquatic plants. They are available at many nurseries and big box stores that carry pond supplies. However, a very effective wicking pot can be made by recycling a plastic 1-gal nursery container.

10. Drill multiple 1/4" diameter holes 1" apart in all directions for the entire height of the pot and all around its circumference.

Preparing the Fill Tube

Water must be in the reservoir at all times. It does not have to be full, but it cannot be allowed to dry out completely at any time. The easiest way to keep the reservoir filled is with a tube that sits in the reservoir and is filled from the top. The fill tube should extend well above the top of the SWC so soil does not fall into the tube. The actual height can be anything that is convenient for the user. Beverly puts hers at about 2'. If you are only planning to build one or two self watering containers, most big box home improvement stores will sell cut lengths. They are a little more expensive than buying it in bulk lengths. The fill tube should be located on one of the outside edges of the watering container, but it does not matter if it is on the sides or the ends. The location should be the most convenient for watering access.

11. Cut the desired length of 1 1/2" PVC.

12. Cut the end that will sit in the reservoir at an angle so it will never become blocked.

Assembling the Components

13. Set the water reservoir and soil chamber in its permanent location (they are heavy once filled).

14. Set all of the aeration shelf supports into the bottom.

15. Set the aeration shelf on the supports.

16. Slide the fill tube into its hole.

17. Slide the wicking pot into the center hole and check it for fit  it should sit into the hole easily and the bottom should rest on the floor of the water reservoir. If it doesn't sit on the floor, use the utility knife to loosen the hole a bit. Remove the wicking pot after checking for fit.

18. Add the lid.

Fill the Wicking Pot

The media for the Wicking Pot is important  the wrong composition will fail. This is only for the Wicking Pot. Do not use this as your planting media.

19. Fill the pot with a soilless planting mix. You can find this pre-mixed at a garden store, or mix your own. Mix 1 part peat, coir, or peat-based potting mix, 1 part Perlite or Expanded Shale, and 1 part Vermiculite. You will not need large amounts - just enough to fill the wicking pot.

20. Moisten this mix thoroughly. You should be able to squeeze a few drops of water out of the mix.

21. Fill and pack the wicking pot with this media. It should be packed tightly. Leave 1 1/2" of headspace at the top.

22. Water the filled wicking pot until water drains from the bottom.

23. Fill the headspace with Vermiculite. This should be filled to the point of spillage.

24. Set the wicking pot into its space in the aeration shelf.

Fill the Soil Chamber

Fill the soil chamber with organic soil and time release fertilizer until it is 1/3 full. Water this thoroughly and lightly tamp it. We do not want to pack this because it is our root environment - we just want to make sure that there are no air pockets in the soil. Repeat with the second and last third, again watering thoroughly each time. This is a little more than recommended for this volume of soil, but it will be expected to last all season.

Plants

We used strawberries and spinach, but you can use any flowers or plants you like. Add water!

Price:

We spent about $50 for our container, but you could easily do it for a lot less if you only used one plant.
Strawberry Plants $3-$6
Spinach $2
Soil $20
Container $8
PVC pipe $5

Applying the Mulch Cover & Planting

The mulch cover is used to suppress weeds, to reduce evaporation, and to shed excess rainfall. You can use a black plastic garbage bag trimmed to fit. The mulch cover should extend past the rim of the container so it can be held in place with the mulch cover retainer which we made from the rim of the lid that remained after we built the aeration shelf. Using the binder clips to hold this all in place is convenient.

To plant through the mulch cover, cut X shaped slits in the plastic, pull the plastic back, and set the transplant in place or plant your seeds. If you are broadcasting a seed crop or planting closer than 3" spacing, do not use a mulch cover. You can mulch with pine straw or compost just as you would an in-ground garden.

Seasonal Maintenance

Taking care of an self-watering container during the growing season is easy. Just keep the water reservoir filled. The media in the self-watering container will remain damp even in hot weather. The top few inches may feel dry if you are not using a mulch cover, but you will find perfectly damp soil when you insert your finger into the media. If you use a mulch cover, even the top will feel damp.

If you have fertilized before planting, you will not have to side dress through a normal growing season. As always, keep an eye on your plants. They will tell you if they are not happy. If you are using a liquid fertilizer, just mix it in a 5-gallon bucket and use the mix to fill the water reservoir. They will self-feed as they draw the mix into the media.

Because you have not used garden soil, you will have few, if any weeds. Any that arrive on the wind or from birds will be easy to prick out from the loose, damp media. Planting can be very intensive in these containers. Close planting also decreases weeds  there is a saying that "where there is a plant there is not a weed".

After you have harvested a crop, just remove the spent plants, refresh the media with compost and fertilizer, and replant. The media will last for several plantings before it breaks down and needs replacement. How many plantings you get from the media will depend on several things including what type of plants you grow and the environmental conditions in your location. You will need to examine and assess the media from between plantings.

For more from Beverly, visit arborgate.com.
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