This instructable shows how I built a versatile and low maintenance above ground garden & greenhouse. This garden planter is self-watering, moisture regulating, self-filling, self-protected, and portable (with help or equipment). While not totally free, I kept my costs to a minimum by using roughly 90% reclaimed materials. The project should take 6-8 hrs per planter depending on tools available and finishing touches. This planter will result in 14 sq ft of garden space that can be protected from animals and children and can be converted to a greenhouse to extend growing seasons.
Time: 6-8 hours depending on experience and finishing preference.
Cost: Around $150 for soil and plumbing fittings.
Step 1: Features
1. Above Ground - The entire planter sits on or above the surface of the ground so it can be placed almost anywhere from urban to country. This feature is essential to allow you to grow plants where you can't otherwise due to things such as hard surfaces or underground utilities.
2. Large Scale - In the same ground area, this planter provides 14 sq ft of growing area with a soil depth of 14" for large and deep rooted plants. You can grow much larger crops of vegetables, herbs, fruits, or flowers than with smaller pots and containers.
3. Self-Watering - This feature is useful to just about everyone for a multitude of reasons. I no longer have to worry about remembering to water different plants on different schedules to get the best results, or worry about watering at all. This design can be adjusted for more or less, but my build has roughly a 75 Gal water capacity.
4. Self-Filling Reservoir - This is an awesome feature if you can connect the planter to a reliable water source. The reservoir is designed to keep a constant water level not only by filling as needed, but also by recovering excess rainwater from the planter's soil. I plan to connect my inlet to a rain water gathering system.
5. Moisture Regulating - With the right soil mixture, this planter will self-regulate the moisture in the soil based on the weather and plant requirements. It will help to prevent over-watering and under-watering including that caused by excessive or inadequate rain. The drains that remove excess water from the soil even capture that water in the reservoir for later use.
6. Protected - This planter has built in protection from animals and overly curious children. If desired, it can even be protected from insects. The best part is that the protective cage can be used full time (depending on plant size) and easily removed for maintenance and harvesting.
7. Greenhouse - The same cage that protects your plants can be covered with clear plastic to turn the entire planter into a greenhouse that will allow you to start plants outdoors earlier in the season, or even grow plants later in the year than conventional outdoor gardens can survive.
8. Portable - Without soil or water, this planter is light enough to be drug by a single person, or carried by 2-4 people. This planter is built on a pallet, therefore it can be moved (even fully loaded) to any location using equipment such as a pallet jack or fork lift.
9. Weed Limiting - Because of the potting soil mixture and the gardening method used, weeds are greatly limited compared to in-ground garden beds, even without additional mulching or tarping.
10. Customizable - You can tailor the final product to whatever style or function you would like. It can be utilitarian, eclectic, intricate, bare or finished wood, painted, wrapped in wallpaper, whatever you desire.
Step 2: Design
This planter combines two concepts to create a relatively small footprint yet high yielding garden. The first concept is that of Sub-Irrigation Planters (SIPs). The design behind SIPs uses the wicking abilities of different materials to pull water up from beneath the surface of the soil through the capillary action of water. I found most of the useful design information at Albo Pepper site written by Al Gracian. His site even shows some other ways of building similar containers that may work better depending on the materials you have available.
The second concept used in this design is the Square Foot Gardening method. When done properly, this method you to grow a very productive garden in a very space-efficient area. From my reading, it looks like this method was developed in the 1980s by Mel Bartholomew. I used a Garden Planner from The Old Farmer's Almanac to layout and plan my garden; it has SFG as a design parameter and even gives tips of what plants to plant next to each other for the best results. It is a great program that gives you printable layouts and even a list with planting and harvesting schedules. The web based program is free to try for a month, or there is a paid subscription as well.
I designed this planter to incorporate as many features into the smallest area possible while using the most efficient gardening and building methods as I could. I used as many reclaimed materials as I could get my hands on while reducing waste of materials as much as practical. I also tried my best to find the fastest and most effective ways to build these. (I built 5 of these planters concurrently; an undertaking I do NOT recommend for a first attempt.)
Step 3: Materials
Before obtaining your materials, read through the details of each component's use to be sure the supplies match your needs.
(1) 275 Gal IBC (Cage Optional)
(5) 48" x 40" Hardwood Pallets
(25 ft) Poly Rope
(1) 4' x 20' roll of poly Landscape Fabric
(50") of 15" Diameter Plastic Culvert Pipe *See alternatives in "Before Building"
Framing Nails or Screws
PVC Fittings for fill and/or overflow ports
(1) Universal Replacement Toilet Float Valve
PVC Fittings to plumb valve to desired Inlet Location
IBC Cage for Greenhouse and Protective structure
Chicken Wire, Bug Screen, And/or Transparent Plastic
I was able to obtain the IBC and pallets and even some culvert scraps that were discarded at work. These can be found many places for low cost or even free. Try Craigslist, Ebay, etc.
When looking for reusable items, research and know what you are getting and how to handle and use the items safely. Ideally, look for IBCs that are food grade and that have been properly cleaned (These are hard to find as they are usually reused). No matter what IBC you find, be sure that they are safe and will not have any harmful residues (These containers are required to have MSDS labels). Since you will be cutting the plastic liners open, you can easily clean the inner surfaces with the appropriate cleaners. *Because of the range of uses for these containers, I can't give any advice on whether a certain container is safe, that will be your responsibility to research and use these at your on risk.
Choose pallets that are heat treated rather than chemically treated, and look for good solid hardwood. The pallets I got were open slats with three vertical beams. Pallets with additional beams may require design modification and/or removing unnecessary beams. Pallets with close slats (although not as common) would make for a much cleaner looking final product. Pallets have markings that tell what treatments they have undergone. For more information on choosing pallets, I used the guidelines found in the following Instructables:
Step 4: Tools
Hammer or Screwdriver
Allen or Torx Wrenches
Pry Bar (Long Demo Bars are nice)
Knife (serrated cuts rope more easily)
Staple Gun & Staples
Nail Gun or Impact Driver
Ratchet and Allen or Torx Tip Sockets
Jigsaw & Blades (While cutting pallets, you are very likely to hit a nail or two, so extra blades are a must)
Step 5: Before Building
Before building this planter, do your research to find the best aspects for your application. I wish I had done a little more testing before I began building my setup. Spend some time planning your setup, especially the components that will be underneath the soil pan, as any later modifications will require removing all of the soil. You will need to determine the following requirements:
Soil Depth: Plan your soil depth to accommodate the plants your intend to use. Also be sure that you use a soil blend that will be able to wick water high enough to reach the roots of your plants. There are many websites that give information on different blends. You can even test your own blend to see how it performs.
*To test the wicking abilities of soil blends, you will need to make a column of soil. You can use either a plastic cylinder or bottle, or a fabric that will NOT wick water. If using a plastic bottle, use something tall and poke several small holes around the bottom. Fill it with soil and sit it in a pan of water. Be sure to keep the pan full so the column can pull as much water as it can. After a day or two, measure from the top of the water in the pan to the top of the wet soil in the bottle. If it is hard to see a wet line in the soil, use a soil moisture meter ($10 at Lowe's) starting at the top and moving deeper into the soil by 1/2" at a time until you see a noticeable increase in moisture. That point will be the height your soil can wick, and should be greater than the depth of your soil pan in this planter.
Rope & Landscape Fabric: Be sure to test the fabric and rope you intend to use. Fine thread synthetic fibers are the best choice as they usually have good wicking properties and are resistant to rot and mold. I used a version of poly rope and found that the outer sheathing wicks water very well, but the core material doesn't wick at all. It may also be beneficial to get rope that doesn't float, or to use small weights or rocks, although even a rope that floats can still wick water. (Don't use lead weights as they could leech into the water and into your plants.)
*To setup a material wicking test, hang a long piece of rope and/or fabric above a pan of water with the bottom inch or two in the water. Be sure to keep the pan full so the column can pull as much water as it can. After a day or two, measure how far above the water surface the material is wet. This should be the maximum height that the material can wick water. You should design your water reservoir to be less than this height.
Culvert Alternatives: The culvert pipe in this design is used as a spacer and support to hold the weight of the soil and plants up above the water reservoir. These supports can be anything that is strong enough and can resist rot or deterioration while submerged under water. Wood is not a good choice; plastic is the best as it will last a long time. Concrete blocks are another option but they will weaken and begin to crumble after a few years.
Step 6: IBC Dismantling
The outer cage is attached to the base with 6-8 bolts, then the top of the container has two crossbars that are attached with a bolt on each end. I have seen these bolts as either allen head, or security torx. If you don't have these, you can always try a strong pair of vise grips. A small set of allen or torx bits that attach to a ratchet are very handy and are relatively cheap for an off brand. These can be readily found at most hardware or automotive stores.
The distance measured from the bottom up will determine your water reservoir capacity. (Most of these containers have a guage on the side that shows the volume at heights.) I chose 10" as my reservoir height which will give me roughly 50+ gals of capacity. A permanent marker works well to mark the height; I marked a few points around the corners and used a straight edge to fill the lines.
*If you choose to use the toilet valve for the self-filling feature, be sure to leave room for the valve and note that the float will shut the valve off before water reaches the top of the valve which will affect your final capacity.
Measuring from the top down will determine the depth of the soil in your planter. I used 14" as my soil depth to allow plenty of room for all types of plants. Be sure to choose a depth that works best for the types of plants you will be growing; a shallower soil pan will wick water more easily, but will limit the types and sizes of plants that will succeed. (Also take into consideration your soil blend as different blends will have different wicking characteristics.)
Once you determine your desired depths, I found it easiest to leave the plastic liner sitting on the base. The outer edge of the base makes a good reference point to measure from the true bottom of the liner. Measure up to the height of your water reservoir (10" for me) and mark (Sharpie works well). I marked a few places around the corners and then used a straight edge to fill in the lines. Measure down from the highest flat of the top of the liner and mark the depth of your soil pan (14" for mine). Now, if you measure up from the base to the mark for the top soil pan, this distance makes it easier to mark the remainder of the marks by using the bottom edge as a reference point. Once again, I then filled in the lines using a straight edge.
Cut apart the plastic liner at your lines. I laid the liner on it's side and used a jigsaw with a fast cut wood blade. Once you cut apart the sections, it is much easier to reach and clean the inside surfaces of the container. If your container has any remnants or residue, be sure to dispose of chemicals properly. Luckily for me, I used large quantities of the substances in my containers on a daily basis at work, so I disposed of the contents along with those.
*If there are a few gallons of fluid left in the container when you cut it open, I found that a wet/dry vac does very well to speed cleanup. Be sure that if you must dispose of these in a special manner that you use either a liner for the vac tank, or an intermediate catch tank to collect the fluid.
#BONUS# : The middle section of the plastic liner isn't used for this project, but can be useful for other projects such as a protective workbench top, a painting palette, or hundreds of other things that would use a thick sheet plastic. I plan to try some of my leftovers as a bamboo root barrier.
Step 7: Pallet Dismantling
Pulling apart pallets board by board is a long, tedious, frustrating, and wasteful task. Dry hardwood that most pallets are made of tends to split when pulled on with a pry bar, and the nails are hard to remove without breaking off the heads. Then, when you go to build something, you're just putting more nails back into the boards you just removed them from. Although not completely avoidable, I tried to minimize the use of a pry bar by making strategically placed cuts with a jigsaw.
4 of the 5 pallets for the planter will be cut as the side walls. The dimensions will depend on the size of the pallets and IBC you can get; my pallets were all 40" x 48" as were my IBCs. The cut placement will depend on the depths of your water reservoir and soil pan; mine where 10" and 14" respectively.
(1) 48" x 40" Base Pallet: This pallet will not be cut down in dimension; however, you will need to notch out one end to accommodate the valve in the base of the IBC liner. The dimensions of the notch will vary depending on your IBC. The notch for mine was roughly 6" x 6" and was centered on the center beam of the pallet and cut in from one edge. (Can be seen in photo in next step.)
(2) 48" Long Walls: Starting from the center beam on the top side of the pallet, measure out 14" and mark the planks. (This is the Water Reservoir Depth + the Beam Thickness + 2-3"). From the center beam, measure out the other side of the pallet and mark 14" on the planks (This side is equal to the depth of the soil pan). Using a saw, (Jigsaw works best IMO), cut each of the planks on both side of the center beam.
*There is no need to pry the top planks from the center beam as it will be part of the final structure. I plan to finish my planters in a Board & Batten style. I will be using the planks from the bottom of the pallets that I cut for walls as the battens. Therefore, it will save time to go ahead and mark and cut the bottom planks to the same dimensions as the top now rather than handling them again later. You will need to remove the bottom planks from the center beam either way.
#BONUS#: Although you will use some of them in a later step for the planter, the side beams with the cut ends of the planks still attached can be used to make other pallet projects such as window box planters, utility shelves, book shelves, and more that I haven't thought of yet.
(2) 40" End Walls: Start by measuring along the beams of the pallet and mark them at 40" (The width of the base pallet). Cut the three beams first to remove the end of the pallet. Starting at the center beam, measure and mark the top planks at 13" (Soil Pan Depth - Center Beam Thickness) from center on one side and 15" on the other (Water Reservoir Depth + 2x Beam Thickness + 2-3").
*By adding a beam thickness to one side and subtracting the same thickness from the other, I am effectively offsetting where the center beam will be when I assemble the walls to the base in the assembly step.
#BONUS#: The end of the pallet that was removed from these end walls is well on its way to becoming a pallet project in itself. I have seen Instructables using this exact part of the pallet for book shelves.
Take two of the side beams that we cut off of the 2 long wall pallets and strip them of the plank remnants. I found that the claw side of a hammer is effective at splitting the plank pieces from the nails that hold them on the beam. The remaining nails can then easily be removed using a pair of locking pliers. This method is easier than handling these small pieces with a pry bar, and doing this step after cutting the walls will help prevent splitting the wall planks.
Step 8: Basic Frame
To build the basic frame for the planter, you will use the four walls that were just made by dismantling the pallets. Taking the two long walls, attach each one to each long side of the base pallet that was notched. Allow the planks to overlap the sides of the base pallet by 2" and nail each plank to the base. To make this easier, I used a couple pieces of my culvert supports to hold the side wall at the right height.
Using the two side beams that you stripped in the last step, cut each to 40" long and attach strips to the top of the base pallet on each end. This will give a strong attachment point for the end walls.
Next, attach the end walls to the side walls. Lay the center beam on top of each end of the center beams of the long walls. Holding the walls together, (a rope, or long clamp, or even a ratchet strap can help with this) nail the beams of the walls to one another. Nail the bottom of each plank of the end wall to the strip you just nailed to the base pallet.
On the notched end of the base pallet, use the ends of the side beams that you just cut to reinforce the plank of the base pallet that was cut to make room for IBC valve. If a plank of the end wall falls within the notch, cut it up from the bottom by a height that will allow you to reach in to access the valve (this can be done after the water reservoir is installed in a later step), mine require a cut 9" up from the bottom edge of the plank.
Step 9: Install the Water Reservoir
Take the bottom section of the IBC that you dismantled and insert it into the frame you just completed being sure to line up the valve in the IBS with the notch in the pallet. Check to see that the pan sits evenly in the frame and that the valve has enough clearance in the notch.
Soil Pan Supports:
Take the culvert pipe and cut it to pieces that are a length equal to your water reservoir depth, 10" for my design. Five pieces of 15" culvert fit well into the water pan of my planter without allowing excess movement.
(If you chose another option for your supports, you will want to be sure that the supports will not shift while under load.)
If you chose not to install the self-filling valve, you will want to make a port to allow you to fill the reservoir with water. You can either leave a slot to slip a hose through, or plumb a connection of your choice to the side of the planter.
The water pan will also need an overflow. I chose not to plumb or cut a special port for overflow; instead I will allow excess water to flow over through the air gap I leave between the soil and water pans. For me, even when water overflows, it will not reach the bottom of the soil pan. This will ensure that, even with water overflowing, air will still be able to reach the bottom of the soil pan.
Step 10: UPGRADE: Self-Filling Valve
Toilet Float Valve Replacement Kit
3/4" Pipe Thread to 3/4" PVC Adapter
3/4" PVC Pipe
3/4" PVC Elbow, either F-F or M-F
3/4" PVC to 3/4" Garden Hose Adapter
3/4" PVC Mounting Straps
If you wish to install the self filling valve, you will need to install it now, before you being installing the soil pan. Through trial and error, I found that the water pan needs to be rigidly held in place if you are going to plumb a float valve through the bottom. This can be done by stapling the top edge of the water pan to the planks of the walls. You can also staple or screw the pan to the base pallet through the bottom, but this will require covering each fastener with silicone to prevent leaks.
Once the pan is secure, you will drill a hole through the pan and between the planks of the base pallet. This hole should be big enough for the connection on the bottom of the float valve to slip through.
Next, take the float valve and slip the rubber washer on the stem as indicated by the valve's instruction. There should be a nut that threads onto the stem as well. Slip the valve stem through the hole in the bottom of the water pan. From the bottom of the pan, apply a small bead of silicone around the stem as it meets the pan, then thread on and hand tighten the nut.
Next, you will need to plumb the valve to an exterior point on the planter where you will be able to attach a water source. The plumbing requirements will depend on your setup. I built my planters to connect to a garden hose. While looking for fittings to adapt from the toilet valve to a garden hose, I couldn't find anything other than the expensive stainless flex lines that would thread onto the toilet valve. However, I did find that 3/4" female pipe thread was a very close fit. I used a two-part epoxy between the threads of the toilet valve and the 3/4" Pipe Thread to 3/4" PVC Adapter to seal and attach the rest of the PVC run. It is easiest to allow the epoxy to reach the consistency of thick peanut butter and then spread it onto the male threads. Be sure that the epoxy doesn't get into the inside of the toilet valves or PVC fittings. From the adapter, I then ran an elbow and a length of pipe to the outer edge of the planter base. Unfortunately for me, the only garden hose to PVC fitting I could find at the time was a male garden hose connection, so I also had to make a Female to Female change-over for the end of my garden hose.
When using rigid plumbing, it is all but required to attach it to the base pallet to prevent movement and damage. You can buy several variations of mounting straps for this purpose. I also used wood scraps from my dismantled pallets to install blocking around the plumbing in order to protect it if I ever want to move the planter with a forklift or pallet jack.
GREAT IDEA: Make sure you test your valve and check plumbing for leaks BEFORE moving on to the next step.
Step 11: Build the Soil Pan
First, you will need to drill the drain/wick holes in the pan. Drill 16 holes that are twice the diameter of your rope wick; space them evenly in four rows of four. Leave space around the 6" top port as it will serve as your primary wick. Also space your holes so they will not be obstructed by your supports in the water pan.
Next, cut lengths of rope that are 32" (2x your water pan depth + the distance between drain holes). With the pan facing inside up, insert the ends of the rope through two adjacent holes so the rope hangs evenly from the bottom of the pan. Staple the rope in place. (Be sure to wear gloves as the staples will protrude from the other side of the pan. You can use a hammer to bend over the sharp ends of the staples to make them safer.)
Next, you will line the soil pan with landscape fabric. Cut a length of fabric 68" (Length of Soil Pan + 2x Water Reservoir Depth). Lay the fabric in the soil pan, centering it on the 6" Fill Port. (If you haven't already done so, remove the fill cap. A strap wrench or large pipe wrench may help with this.) Using either an open hand, or a pipe of close diameter to the port, push the fabric down until it is through the port far enough to touch the bottom of the water reservoir. (This is easiest if the soil pan is setting on the supports, either in the frame or on the ground.) Staple the fabric to the soil pan around the fill port and the outer edges of the fabric.
Now, cut two lengths of fabric 76" (Length of Soil Pan + 2x Soil Pan Depth). Lay one length of fabric in the soil pan so that the inner edge is on the opposite side of the fill port. Do the same with the second length of fabric. This should create a fabric overlap of at least 6" (or the size of the fill port). Staple the fabric along the center overlap and along the base of the soil pan walls. Then, wrap the fabric over the top edge of the wall sand staple at the top edge. Using a knife or one side of scissors, cut slits in the top two layers of fabric across the fill port opening. Be careful NOT to cut through the bottom layer that you pushed through the opening.
Step 12: Install the Soil Pan
With the water reservoir, supports, and any optional plumbing in place, insert the soil pan into the frame until in sits on top of the supports.
The curve of the soil pan should allow an air gap between the top of the water pan and the bottom of the soil pan. If it does not, then it will be necessary to cut a few notches in the top edge of the water pan to allow air movement.
Be sure that your wicks are hanging down to the bottom of the water pan and have not been obstructed by your supports.
Step 13: Mix Your Soil
WARNING: Be sure your planter is in its final position and is level before filling with soil as it will quickly become too heavy to move.
This is the step where you need to know which soil blend you will be using. If you are going to be using a blend other than the one I have used, you will need a total volume of 108 gals of soil to fill the soil pan that is 40" x 48" x 14" deep plus the primary wick.
Materials: Total for the volume, around $125.
12 Gal Coarse Perlite
12 Gal Coarse Vermiculite
60 Gal, or 8 Cu FT Miracle Gro Moisture Control
20 Gal Pine Bark
4 Gal Peat Moss
The soil recipe I used called for two layers:
Layer 1: Wicking Layer
Mix 4 Gal of Perlite, 4 Gal of Vermiculite, and 4 Gal of Peat Moss. Pour this mixture into the soil pan, filling the primary wick chamber first. Spread an even layer over the bottom of the soil pan being careful not the push the wicking mixture under the layers of fabric.
Layer 2: Growing Layer
Mix 60 Gal of Miracle Gro Moisture Control, 8 Gal of Perlite, 8 Gal of Vermiculite, and 20 Gal Pine Bark. Pour or shovel this mixture into the soil pan spreading it evenly. You may want to wet the soil a little as you mix and shovel to help reduce dust.
*If mixing large amounts of material, using a compost tumbler / soil mixer can save time and work. I built one just for this project, and I will be posting the Instructable for it soon.
Step 14: Add Water
Next, you can fill the water reservoir with water either through the self filling valve (if installed) or through your water fill port.
Step 15: Plant Your Garden
This part is entirely up to you. If you chose to use the Square Foot Gardening Method, follow the guidelines you found during your research. If you want to plant based on your own methods, good luck with whatever you choose.
Please let me know what works best for you.
Step 16: UPGRADE: Board & Batten Finish
If you already cut additional planks to length while dismantling pallets, start by placing planks where they best cover the gaps in the walls. The planks should match the height of your planter walls; I even made sure to cut the planks so that the nail holes from the center beam lined up with those on the planter walls. Some gaps may be larger or smaller than others, so it's best to have them sorted before attaching; the planks should slightly overlap each other. Start by attaching the planks to the center beams on the walls. Then nail each of the plank bottoms to the base pallet. You can use brad nails to attach the planks to one another along the top edge or anywhere you don't want to see nails.
*If you prefer a cleaner, smoother look, you can take the time to cut the planks to fit in the gaps between the other planks.
For the planter corners, using two planks arranged at a 90 degree lap joint, attach the planks to one another before attaching them to the frame. This will improve the look and be easier to fit.
As you finish the planter, you will want to be sure to cut out around the drain valve where the pallet is notched, and around the water fill port.
If you have never worked with mitered joints, you can use square joints at the corners of the to trim. Because the final planter is wider and longer than the original pallets, each side takes more than a single plank to create the top trim.
I measured the length of each side to the outermost plank and added 1/2" to each end. Then I took one long plank and cut a 45 degree miter at each end. Line up one end at the corner of the planter with the long point of the miter hanging 1/2" over the end of the planter, and the outside edge of the trim board hanging 1/2" over the outer edge. I attached the top trim with brad nails to make them less noticeable and to prevent splitting the wall planks to which the trim is attached.
The miter on the other end of this plank is to create a cleaner looking butt joint. Measure from the short side of the miter to 1/2" past the outermost end wall plank. Cut a short plank with two 45 degree miters that will butt up to the existing miter and will have a long corner that hangs 1/2" over the end of the planter wall. Match this board up to the previous top trim and attach it to both the wall and the other trim.
Continue this process one board at a time around the top of the planter. Marking each joint while holding it to the previous cut will give you the best chance of getting the miters cut correctly with the fewest mistakes.
*If the planks you are using vary in width, you may need to rip them all to the same size to get a good fitting mitered joint.
**If you plan to use the IBC cage as explained in the next step, be sure that the inner dimensions of your top trim will be small enough to prove a supports platform for the cage.
Step 17: UPGRADE: Protective Cage / Greenhouse
You can reuse the cage from the IBC to create a protective cage / greenhouse / partial trellis for your planter. Here's how I did it for mine:
**First, for this to work, you must have installed some type of top trim like that described in the last step. The dimensions of the cage are smaller than the inner dimension of the planter walls, so without a top trim the cage would fall into the planter.
Unbolt the cage from the base plate; there should be 9 bolts attaching the cage to the base if you haven't done this previously. You have the choice of wrapping the cage in chicken wire, bug screen, or transparent plastic. Chicken wire will help protect against small rodents and children; a heavy bug screen will help protect against both insect and rodents.
As it sits, the cage is light weight, so you will want to find a method to securely attach it to the planter. I am going to attach it on one end using conduit straps to make hinges. Then I will be able to tilt the cage up and away from the plants to maintain and harvest as needed. This will require placing the hinges close enough to the edge that, when tilted, the top of the cage will rest on the ground. Otherwise, you can leave the cage centered and use a pallet remnant to make a stand to hold the weight of the cage when it is tilted.
*If you have plants that need trellised, you can use the cage as a trellis. However, the only way to use the cage as a trellis and still be able to remove or open it is to place your trellised plants ONLY along the hinged edge of the cage. And most importantly, to prevent breaking the vines when opening the cage, you will need to be sure you train the vines so that there is a small coil of vine at the base of the cage that will allow it to hinge.
GREENHOUSE: Wrapping the cage in transparent plastic will create a greenhouse that will allow you to extend your growing season. Since the top of the cage is flat, you will either need to add a beam across the center to create a ridge, or pierce a few holes to allow water to drain into the planter. A future upgrade for me will be to build a venting panel for the top of the cage that will open automatically to control and maintain a proper temperature.