Mittleider grow box maintenance
Mittleider grow box maintenance needs to be completed once or twice a year. Grow boxes in a Mittleider garden are filled with sand and sawdust. As the gardening season progresses the sawdust will decompose. As it decomposes the growing medium in the grow box drops. The lost material will need to be replaced.
How often to add more sawdust
Here on our little homestead we will do Mittleider grow box maintenance at before each gardening season right before planting. In grow boxes where we rotate in a new crop for our fall gardens the grow box will get topped off a second time. There are a couple things to consider when deciding how often to add more sawdust.
What to consider when deciding when top off a grow box
Performing mid season Mittleider grow box maintenance on crops like kale or tomatoes would be a problem because the fruit and growing tip wouldn’t get buried with the added sawdust. To try and top off a bed with crops such as cabbage or spinach you would end up partially burying your crop.
A common side effect of adding fresh sawdust is a drop in available nitrogen. Watch for nitrogen deficiencies if topping of the grow box during the growing season. If you see symptoms of a lack of nitrogen you will need to correct for nitrogen deficiency. Urea is a common nitrogen source that is widely available.
What sawdust will work
A common question I see asked is what type of sawdust is correct to use and what size it should be. The type is easy, anything but walnut sawdust will work. Walnut contains tannin that will kill seedlings and severally stunt the growth of established plants. Avoid any sawdust that could possibly contain walnut.
The size of the sawdust is important. Anything too large, or too small, can cause serious problems in your Mittleider grow box. See my blog entry on identifying the correct sawdust size. Another acceptable source of sawdust that can be bought is from equine pellets. Equine pellets cost around $6 per 40 pound bag and will roughly triple in volume once wet,
Mittleider grow box maintenance in our potato box
In this video you will see our potato and sweet potato grow box. Because of the length of the sweet potato growing season this box is only filled once a year. It gets topped off right before we transplant the sweet potatoes.