A while back, we did a post on growing hydroponic microgreens indoors. During the gardening season we also grow soil-based microgreens outdoors. We don’t do the soil-based ones indoors because it’s a mess and it’s inefficient—the greens only really work for one, maybe two, harvests and then you have to toss out the dirt in the tray and start over again. Not so with the method we use for outdoors. In fact, we will get several crops out of these and may only need to re-soil and re-seed maybe once during the season, depending on how the weather goes.
The decision to grow microgreens in flower boxes came slowly. At first, we tried growing cucumbers, then we tried beans, because we could just mount the flower boxes directly below the growing trellis we had built and mounted to the deck. But flower boxes don’t have nearly enough space in them to accommodate the root systems for these types of plants. Plus, because they’re not actually in the ground, these boxes have a tendency to get really hot which deep root systems don’t like. Ultimately, neither of those attempts worked at all. So, eventually, we realized we could grow microgreens in the boxes instead. Their root systems are shallow enough to thrive in such a small environment. Likewise, they aren’t as prone to succumbing to overheating because of said shallow roots.
All that being said, here’s how we do it. We got three flower boxes which have plastic inserts in them, so they are easy to maintain and clean. The boxes, and the inserts, have holes in the bottom to allow for drainage, but we also mix some small rocks and pieces of broken clay pots in there to aid the drainage. We fill the inserts with a mixture of seed starting soil and dirt from our garden.
We actually wound up not getting back to these boxes for several weeks so the soil had compacted a bit. So I loosened the soil up with the hand tool you see in the picture above. Then I skimmed a little bit of soil off the top.
I do this because last year I simply scattered the seed and then tried covering it by stirring the soil around by hand but I wound up with some bald spots. By setting some soil aside from the start I can be sure to have an even distribution of seed and soil when it’s all done.
Then it’s just a matter of spreading the seeds in a fairly thick—but not overbearing—layer. This year we’re growing beet greens, collards, and arugula, which is pictured here.
Then I give them a light covering of soil. I typically end up with leftover soil from the skimming so I just spread it somewhere else in the garden where it’s needed. Then I give them a good soaking with a watering can.
You can still see some of the arugula seed here, but that’s fine. It doesn’t need much cover anyway.
Mrs. Butcher mounted the boxes to the rail of the deck and I plopped the inserts in there.
The boxes themselves were initially painted a rust red color but we painted them white to make them more reflective and less prone to absorbing heat from the sun. These babies should be ready to harvest in a couple of weeks.