I was wrong. Hard to admit, but there we have it. I passed on advice from those I deemed older and wiser than I am, and they were wrong too. But hey, none of us knew any better. Then.
It seems that the last thing you want to do when planning a new garden is dig.
Yes, we were all taught to plan out where the garden would be, then spread amendments, and likely fertilizer, and dig it all in—at least eight inches, and two feet is even better. Now we’ve learned that the only things we gain from all that work are sore muscles and aching backs.
Slowly, the light has dawned. First came fertilizers. Most soils have plenty of nutrients, and blindly adding fertilizer will just create an overabundance—as harmful as not having enough. Soil tests are essential to avoid polluting run-off and toxic levels of especially potassium and phosphorus. I’ve already warned you against using Epsom salts, but that’s just the beginning. Don’t add anything until you know what’s needed, and what isn’t.
But what about organic matter? Soils in Colorado tend to run around .5% organic particles, and the optimum is closer to 5%. Don’t we need to dig in compost?
Well, the experts have done studies, and the conclusion is that yes, compost is fine, but put it on top where nature does. Think of those layers of rotting leaves deposited every autumn. As they compose, the humus will work its way down into the soil. If you’re planting a landscaped area, rather than a garden that constantly changes, arborist’s wood chips are even better, and you can get them for free from most tree-trimming companies. They’ll even deliver, happily dumping a pile in your driveway and avoiding dump fees.
It turns out that Ruth Stout had the right idea all along. She was famous for her deep mulch approach to veggie gardening, simply dumping huge piles of straw on any weeds that dared arise, and scooping the piles out of the way to plant seeds. She is one of my gardening idols; I, too, want to garden into my 100s! If you haven’t read her books, I highly recommend them.
So what are the benefits of leaving the dirt where it lies? There are plenty. First and foremost, you preserve the soil structure. The particles in undisturbed soils tend to aggregate into clumps, leaving space for air, water, and hopefully roots. If you dig that up, or worse, rototill it into a uniform powder, that structure is destroyed. The particles pack down into a solid mass nothing can penetrate.
Furthermore, tilling increases soil erosion—all that fluffy dirt is just waiting to blow away (no wonder our recent 50 mph winds filled the air with grit!) or wash away in the next rainstorm. That rainwater run-off (because it can’t soak in) and, if you’re added fertilizer, it will carry that fertilizer with it, polluting streams.
While we till to incorporate compost, tilling actually decreases the amount of organic matter over time. That’s because the air we add in the process speeds up decomposition. This process also releases sequestered carbon into the atmosphere.
Untilled soils contain significantly higher levels of microorganisms, those little creatures that make nutrients available to plant roots. They live in the spaces between particles, and chow down on the higher levels of organic matter present. (Besides, how would you like it if someone ran a tiller through your neighborhood?)
So how do you prep your garden for spring planting? If you want to get going early, you can pre-warm the earth. Clear plastic works better for this than black plastic. I cover my raised beds with fiberglass panels to create temporary cold frames. You should remove any existing weeds. Deep mulch works well on areas you aren’t immediately planting, or simply pull them up. Then just plant.
Once the plants are up and growing, pile on the mulch. Straw is cheap but may contain a few seeds. Compost is excellent. Or use whatever you have available. Aim for a layer between eight and twelve inches deep.
If you’re starting in a new site with poor soil, build a raised bed. Add topsoil mixed with compost on top of the undisturbed dirt and plant in that. Don’t overdo the compost—too much organic matter creates its own problems. Then never walk on that bed again. Your deep mulch layer will deter most weeds.
I’m more than happy to put my little tiller in our next garage sale. Who would have guessed that lazy gardeners were the ones getting it right?
For more information, I recommend the Garden Professors’ blog post: A Raised Bed Rebuttal: In defense of a common garden practice and soil health.