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Question of the Week © 2017 Mike McGrath
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Can You Grow Rooted Supermarket Herbs?
Q. I'm an amateur gardener and cook. I buy live herbs at the grocery store for 2.99 each and repeatedly try—but fail—to keep them alive for more than two weeks in my kitchen. My house is on the water and gets a lot of light, but my kitchen faces North and West; and after just a few days cilantro, parsley, basil, sage, dill and everything but mint droop and then die. Please help; I set my alarm every Saturday to catch your show with my coffee!
---Michelle, "near Cape Cod, Massachusetts"
A. Thank you, Michelle! Now I have to say right up front that I have had the exact same experience. I must have bought a dozen of those big basil plants that still have their roots attached, but none of them survived when I potted them up or tried to plant them outside.
I soon came to realize that one cause of this failure was that I was giving them their first taste of dirt, and their roots just don't have the muscle to handle it. Those very popular basil plants sold in supermarkets with their roots still attached have been grown hydroponically—in water with regular applications of nutrient solution. The roots grow long and happy, but they don't face any kind of resistance and then don't have the strength to grow out into soil or even potting mix. Same with the gourmet lettuces sold this way; those roots are enticing, but they're not going to survive being moved into a more natural environment.
I've had a little bit of success growing these plants in a kind of continued hydroponic situation—standing them up with some kind of support so that the roots are under water but the plant is not. If you're going to try this, I'd advise using only rainwater, well water or distilled water—not city tap water; and I'd change the water every other day or so.
And I wouldn't bother with the 'bright window' in winter unless you live down South where the hours of daylight are longer. The further North you live, the less hours of daylight you have in the winter to begin with; and the angle of winter light in general just isn't good for photosynthesis.
Maybe you could use a South or East facing window for this in the summer, but in the summer it would probably make more sense to set it up outdoors. (Same with frost-free areas like San Diego, Phoenix and deep Southern Florida and Texas in the winter; go outside, you ice and snow cowards!) Otherwise, I'd turn to artificial light. As we've been suggesting on the show a lot lately, a couple of bright LEDs in normal light fixtures placed close to the plants should be great, and an indoor seed-starting system with adjustable lights would be just as good or better.
That brings us to food. Most hydroponic systems use chemical fertilizer. Homey don't play that. But I think that light applications of liquid kelp would be ideal in this kind of situation. Otherwise I'd experiment with a diluted tea made from compost or worm castings.
Now, Michelle says that she does better with mint…
Which may be because you can't kill mint!
Or it may be that the plants were raised differently. A few months ago, I look a really close look at the rack of 'living herb' plants in my grocery store. They were mostly the standard 'bare-root basil' but there were also a couple of mint plants in actual soil-filled pots inside that familiar plastic sleeve. So I took the mint plants home, potted them up into larger containers, and they're all still alive.
Yes, probably because they're mint and mint is hard to kill. But also credit the fact that they grew up with their roots in some sort of soil as opposed to being raised by Aquaman.
Now—several of the herbs our listener names are not long-lived to begin with. Basil, cilantro and dill are all famous for going to seed super-fast; that's why we tell people to sow successive runs of them in the garden to always have access to the best quality plants. And the size of the hydroponic basils you see in the market suggests to me that they were ready to go to seed and be done soon no matter what.
So I think the smart money says to forget about keeping bare-root herbs alive longer than a week or two and just use them as soon as possible after you buy them. And if you really want home-grown herbs over the winter in a cold clime, invest in a little system that includes lights that you can adjust and a platform that allows you to sow seeds in containers under the lights.
One extra nice thing about herbs is that they don't take months to ripen and mature; you can pick them at any time—even when they're just the size of micro-greens; that middle ground between sprouts and full-grown plants that's the hottest thing in market gardening right now. You can have baby plants ready to harvest in just a few weeks—and those tiny plants are packed with much more nutrition and flavor per gram than full-size plants.
(When I planted a container garden for a young woman battling leukemia this past summer, I sowed the seeds of the arugula she requested super-thick, and she really enjoyed 'eating the thinnings' early on.)
Your only real limit here is the amount of space you're willing to devote to your little micro-farm. If you can make room for three or four growing stations, you should be able to harvest a good amount of herbs—and actual micro-greens for salads!