Illustration: Soup stock being made from backyard garden ingredients, including wild onion, parsley, oregano, and thyme, with a purchased bay leaf.
Soup stock, that deliciously flavored liquid we use as a basis for soups and sauces, is a natural for the gardener-cook. The beauty of it is that most of the ingredients can be scraps of vegetables, or over-produced ones we would otherwise probably not eat up. Let the cooks with no gardens go to the grocery and buy carrots, celery, onions, and other vegetables to flavor stock. We have it already if only we know what to use. No matter if the ingredients are a bit tough or strong-flavored, they are perfect for broth. They will be strained out and discarded anyway.
An important starting concept for the gardener who would make soup stock is that most stocks include plants from two different botanical plant families: the carrot and the onion families. Use at least one of each, add a few herbs, and you'll have a very nice stock.
In the carrot family are parsley, Japanese parsley (Mitsuba), celery, fennel, and, of course, carrot. The easiest plant of this group to grow in quantity in a small garden is parsley. Once you have it, you can let a couple of plants of it reseed and save as many seedlings as you want, transplanting some when the plants are still small to places you want it to grow. Japanese parsley is a perennial plant that grows best in shade. If you like its delicate flavor and have a shady, well-watered place for it, you can have it for harvest most of the year.
Celery is not as easy to grow as parsley, so most small space gardeners don't grow it. (If you buy celery, do save the leafy parts to use in stock.) Some gardeners do grow Chinese celery, which has narrower, less-tender stems. It is easier to grow and most useful in soup or other cooked dishes. If you are growing it, you will have plenty of leaves for use flavoring stock.
Fennel loses its anisy flavor when it is cooked, having instead a distinctive sweet flavor. It is not for every stock, but can be very nice in some. (I have used it as a second carrot family ingredient, with parsley or carrot tops as the main flavoring.) Most gardeners will not have fennel growing, but if you are growing even one plant for its tender, white bulbous leaf bases, you will have plenty of green stems and leaves that could be used in stock. (The fennel in vacant lots, a weedy variety, rarely has enough tender leaf base to be useful, but I imagine its stems and leaves would flavor a stock just as well as those of domestic Florence fennel varieties. And if they are tough, no matter, since stock ingredients will be strained out anyway.)
Carrot leaves are a fine addition to stock. If you grew too many carrots to eat up, of course you can add the root too, but most gardeners don't grow that many, so would prefer to save the roots for eating raw or adding to the soup later.
One of the best onion family crops for use in making stock is the leek. When you buy leeks, you may not realize that up to three of feet of leaves have been chopped off, leaving at most a foot of green leaf on the white lower stem that we think of as "the leek." All of that leafy part is great for making stock. If you had purchased the leeks, you'd just have a few inches of green leaf, but in the garden, there is plenty of it. And, should the leek sit in the garden over winter and you forget to use it up by late March, it will surely form a flower stalk, becoming tough in the process. If this happens, cut up the entire plant for stock.
Bulb onions are not the best crop for a small garden, and are not always successful in that if the timing is wrong, they will form poor bulbs or will flower before they bulb. If you do grow bulb onions, remember that any bulb, leaf, or flower stems you don't eat can flavor stock. That goes for onions you have purchased as well--any trimmings, even dry skins, will flavor stock. (if you do plan to grow bulb onions, the surest ways to do it are to plant onion "sets," small bulbs you get at a nursery, in February, or grow seed of "day neutral" varieties in early to mid spring.
Wild onions that grow in Bay Area gardens are a culinary secret worth learning. They are Allium triquetrum, a Mediterranean native that is a perennial plant. The bulbs are dormant in summer, grow in fall, and make useful greens and flowers all winter and early spring, dying back in April. If you have it as a weed, you may as well be eating it. The entire plant is tender and nicely flavored enough to use in salads and cooking, but if you have a lot of it (it tends to be weedy) you will find it flavors stock nicely as well. (Search for it by scientific name on this blog for a photo and more info on identifying it and managing it in you garden.)
Trimmings from a Grocery
While I am writing this primarily for gardeners, I should say that when produce workers put out vegetables, they often chop off the very parts you'd use for stock. I have come across workers removing leafy parts of celery, leaves of leeks, and carrot tops as they set out the vegetables, putting all the "scraps" in a box to discard. So even with no garden, one could frugally and deliciously make broth from these tasty discards.)
You will want to add some herbs to further flavor your stock. Add a bay leaf or two. I think the best idea for most of us is to buy some already dried. Bay trees get big and make a dense shade, so are not the best choice for most small gardens, but I have seen them kept small in a large pot or half barrel with some success. If you do have access to a larger bay tree, harvest by pruning to shape. Remove the leaves and press them in newspaper under books until flattened and dried, then store in a jar. (Be aware that the California bay is a different species than the Mediterranean one, with harsher-flavored, most think inferiorly-flavored leaves.)
A number of Mediterranean herbs are easy to grow in Bay Area gardens. The best to have handy in a small garden for stock are probably oregano and thyme. Grow them in the ground if at all possible, giving them room to spread their roots and make good plants. Add fresh sprigs to your stock.
Making the stock
To make your stock, add all of the ingredients to a large soup pot at once, adding plenty of water. You can also add salt and pepper, but I usually don't at this stage, leaving decisions about them until I am using the stock for making a soup or sauce. (If you eat meat, add soup bones too, marrow bones or boney parts of chicken.)
Boil all of the ingredients 30 minutes to 2 1/2 hours--use the longer time especially if you have included meat. If only vegetables and herbs were used, you can just strain them out in a fine-mesh strainer and you have your stock. (If bones were added, you will probably want to refrigerate the pot overnight, then use a spoon to skim off any fat before you strain.)
Once the stock is strained, you can use it immediately to make soup, or you can put it in containers in the refrigerator for use in up to a couple of days. Or, if you have too much to use fresh, put some in containers and store these in the freezer for later use. Write the kind of stock and the date on a label affixed to the containers.