The Dirt on Bagged Dirt…

Memorial Day weekend I was determined to get all my container plants in. I have about 16 of them I do on an annual basis; some big and prominent and some smaller and just tucked in here and there. As you well know, the weather hasn't been overly cooperative this year so I was happy that I'd at least gotten the bulk of my plants in advance so I could just focus on my favorite part… planting! I started with four large concrete/resin hybrid planters on the pool deck. They're brand new and about 24" in diameter. With no soil from previous years to simply add to, it was going to take a lot of dirt to fill them. First, I loaded them with dried leaves to fill them about halfway. It's an old Martha Stewart hack I learned years ago. Saves money on bagged soil, provides great drainage and is a bonanza of nutrients as the leaves break down. Then I headed to my local garden center for bagged potting mix. You might think soil is just good old dirt but there's a reason why those Miracle Gro bags specifically say "potting mix." In general, you don't really want to use actual dirt from the garden or elsewhere on your property for container gardening. It might be wonderfully rich soil, but it's got lots of clay and other mineral material which would drain poorly when contained in pots, leading to root rot. It's also very heavy (another reason potting mix doesn't contain real soil.) Potting mix is typically made up of peat moss, perlite or vermiculite and composted forest by-products. Oftentimes there's a synthetic slow-release fertilizer also added. Those are those tiny fluid-filled balls you see. If the bag also says it contains worm casings (poop) or bat guano (again poop), all the better. These last two are a natural form of fertilizer. I bought three bags of Miracle Gro Moisture Control potting mix. The moisture control component means a surfactant, or wetting agent, is added which helps the mix absorb and distribute water more evenly. While lots of folks have negative feelings about Miracle Gro and its parent company for lots of legitimate ecological reasons (chemical synthetics can adversely affect our environment,) I'm ok with using it in controlled situations such as container gardening. My containers are primarily annuals that bloom all summer long and need a constant feeding to keep producing and Miracle Gro does this well. Two things, though, have started bugging me about bagged soil mixtures. While aged/composted tree bark is indeed a wonderful element for planting mixtures, I believe more and more producers are using non-composted shredded wood. I did a double take when opening a bag to make sure I hadn't mistakenly opened a bag of "bark" mulch. Bagged mulch has long had a significant portion of wood chips and shreds and now it seems it's also being used as a filler in potting mixes. While I can see a small portion of raw wood chips might help with drainage, there's a downside to wood chips. They can overly acidify the potting soil and can also carry bacterial and fungal pathogens that don't get broken down as they would if composted. If you've ever experienced that orange foamy fungus on your bark mulch, that's likely caused by the non-composted raw wood content in it. The other bee in my bonnet about bagged dirt is simply the price. I got three 2-cubic-ft bags of Miracle Gro Moisture Control Potting Mix. Granted, these are large bags, but when I got to the cash register, I was appalled that they were $26.95 each. For dirt! I know… it's not really dirt but still. The store had a wonderful selection of all-organic potting mixtures that have the really good stuff like emulsified fish, seaweed and bat guano but they're even more expensive. There's really only one good answer to my potting mix dilemma and it's to simply make my own. I've written before about a wonderful nursery in Bellows Falls, Vt. called Morning Star Perennials and years ago he showed me that he makes all his own potting mixtures from compost. To do it, though, I think I'd need to convince my partner that it's time we get a Kubota tractor. I've got a huge compost pile but it's impossible to turn it by hand and compost piles really need to be turned regularly. I just keep adding to it but over the years, weeds and briars have taken over. It would probably take a lifetime's worth of commercial potting mix to make up for the cost of a tractor but, hey, it would be handy for so many other tasks on the property. Right?