Weymouth, Mass. — About 10 years ago, an English cousin of mine introduced me to grow bags. We had just met for the very first time, and discovered that we shared a common interest in gardening, so he rushed me over to his tomato patch. He had 10 vines, about five feet tall, growing out of five plastic bags placed on a concrete slab. They were loaded with still-green fruit. I'd never seen anything like it and I was impressed that they could grow so well with such a confined root area. He said you could grow virtually anything in them, ``except potatoes,'' because the bags were too thin for that.
Since that time, what is sometimes called ``pillow culture'' (because the bags look like pillows) has spread from Europe to America. They're used mostly by commercial growers, but there is a place for them in the home garden, too. They make gardening possible where tree roots, concrete, or stone makes conventional growing impossible.
Commercial grow bags are available at some garden centers, but you can make your own using heavy-duty garbage bags. Half-fill the bag with a suitable container mix and tie the top. Now tip the bag onto its side and carefully work the growing medium into all corners until the bag has the desired pillow shape.
Planting these bags is simply a matter of cutting a hole wherever you want the plant to go. Rather than cutting a round hole, cut a cross in the plastic and fold under the corners. It's a good idea to cut another hole nearby for watering. If you plan to grow two large plants (tomatoes, for example) at each end of the bag, one watering hole in the center is all that you would need.
To plant seeds (i.e. beans) in a bag, cut out strips of plastic where the rows would go. Push a pencil through the plastic to make drainage holes around the base of the bag. Half a dozen on each side should do. If you find the bags aren't draining well, you can always make a few more holes later.
Grow bags are generally used for vegetables because plastic bags aren't considered attractive enough for a flower garden. But I once saw a piece of paved driveway turned into a colorful flower bed using grow bags. The gardener planted petunias, which soon draped themselves all over the bags, hiding them completely.
Heavy duty garbage bags can also be turned into effective tubs. Shovel some soil mix into the bottom of the bag to hold it in place, then fold the top half of the bag back over itself until it reaches the ground. Doing this strengthens the side and shapes the bag into a tub. Once filled with soil, the bag will hold its shape all season long. One major advantage of these garbage-bag tubs is that they can be made up in a few seconds.
Make your own growing mix
A commercial seed-starting medium is effective in grow bags. Or you can make your own from equal parts of peatmoss, garden soil, and sharp builder's sand available from hardware centers. If you have no garden soil, a straight peat-sand mix will work very well.
Except in areas where the garden soil is naturally very alkaline (ask your garden center about this), you will need to add a cup of ground limestone for every bushel basket of mix. If you are using a standard plastic bucket for measuring, add half a cup of limestone for every bucketful. At the same time, add a cupful of composted cow manure for every bucketful; twice that amount if there is no garden soil in the mix. This won't grow the plants through to maturity, though, and feeding with liquid fertilizers will be necessary later on. We'll deal with that in another article.
Next week: Growing carrots in a box.