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how to build organic planter boxes

So now our farm hand, Hunter, is back from his medical leave and ready to go on our projects list. He and I started on our planter boxes yesterday after he worked hard on the barn manure job. And whoa, was it overdue! I had been simply adding bales of the old scrubby hay to give Lilah a more tolerable clean bed to lay on at night.


The planter boxes are being constructed from sawmill lumber we harvested over twenty years ago here on RGM Farms property. If you ever worked with oak sawmill rough cut lumber you will better understand our challenges. We will be adding more of our experiences and photos as this project comes to completion.


Here is a little bit from our research on how to deal with the inconsistencies of working with rough-cut sawmill lumber..


Filling cracks in your homemade planter boxes built with rough sawmill lumber is crucial for plant health and water management. While several natural products exist, the best choice depends on the size and depth of the cracks, your budget, and your desired aesthetics. Here are some options to consider:

For small cracks (less than 1/4 inch):

  • Beeswax: A natural sealant that repels water and is safe for plants and humans. Melt beeswax and fill the cracks with a putty knife, smoothing the surface. Reapply as needed.

  • Tree sap: Similar to beeswax, but may darken the wood. Collect sap from healthy trees and apply like beeswax. Test on a hidden area first as sap can be sticky.

  • Clay: Mix dry clay with water to a thick paste and press it into the cracks. Smooth the surface and allow it to dry completely. This option may not be as waterproof as others.

For medium cracks (1/4 to 1/2 inch):

  • Rope caulk: Made from natural fibers and waxes, it's safe for plants and provides good water resistance. Press the caulk into the cracks and smooth the surface.

  • Wood flour putty: Mix wood flour with glue and water to create a paste. Fill the cracks and wipe away excess. Sand smooth after drying. This option offers good strength and water resistance.

For larger cracks (over 1/2 inch):

  • Wooden wedges: Cut small wedges from scrap wood and tap them into the cracks to create a tight fit. Seal the gaps with a natural sealant like beeswax or caulk.

  • Landscape fabric: Cut a piece of fabric slightly larger than the crack and staple it to the underside of the planter box. This prevents soil from leaking but may not be aesthetically pleasing.

Additional tips:

  • Before filling the cracks, ensure the wood is clean and dry.

  • Consider the potential impact of the chosen material on the appearance of your planter boxes.

  • Test any product on a small, inconspicuous area before applying it to the entire planter.

  • Regularly monitor the cracks and reapply sealant or repair methods as needed.


Remember, natural materials may not offer the same level of durability as synthetic sealants (which we definitely do no want to use). If your planter boxes are exposed to harsh weather or require frequent watering, you might consider consulting a professional for long-term solutions.


For consulting I will engage our local Missouri Extension Service. They have great resources!

And I will be getting Hunter right to work on these crack fixes.




Build the sections then assemble with the corner braces.
Different approach to building this second planter box.

Two planter boxes for a mini garden behind the guesthouse.
One down and one more in process!


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