Urban Herb Gardening Tips

Herb Garden

Most herbs are tolerant of harsh growing conditions—even those found in our urban centers, which are man-made heat wells. With a little direction and some perseverance, urban gardeners can grow plenty of herbs for the kitchen, bath, or cupboard.

It is a lucky urban gardener, indeed, who has access to a plot of land for gardening. Some cities provide access to community garden land.(Check with your local Cooperative Extension or city recreation department to see what is available in your area.) But if a little piece of land isn't available, the urban gardener often turns to container gardening. Fortunately, gardening in containers allows the grower to maximize limited space. Most culinary herbs will fill out a large pot, and any herb that trails across the ground can be encouraged to run up a trellis.

If you want to plant herbs and you have limited space, the first thing to do is survey what you have available and choose the most appropriate growing space. Even plants that are grown in containers will need adequate light. The best growing location is a southern exposure that gets sun throughout the day. A western exposure, where the sun hits the location from midday onward, is next best. Finally, an eastern exposure that sees sunlight from early morning until around noon will work well for many herb plants. While most herb plants need at least four hours of direct sunlight, it's possible to grow a selection of herbs that will survive in the shade. Your choices will be limited, though. Northern exposures that receive no sunlight will be very challenging!

Tips on Containers, Soil, and Planting
Let's work from the assumption that light will not be a problem, even if the available space is only a windowsill. The next step is to develop the "land." You need pots that are at least 12 inches deep to accommodate plant roots. Garden centers usually carry a variety of sizes, and the 10- to 15-gallon plastic pots are excellent. Don't forget those pickle buckets that restaurants go through by the dozens. Both of these types of containers are big enough to grow a variety of herbs, but they are not too big to move around once they are filled. As an added benefit, they tend to be free! If you do use pickle buckets, punch some holes in the bottom of the buckets before filling them with potting soil.

Of course, pretty containers can be purchased from a department store or garden center. Plastic pots are ideal, though, because they are durable and lightweight. Terra cotta pots are very attractive, but they can be heavy, and they must be protected from cold weather, as they are likely to break from freezing and thawing. The new foam pots that have become available more recently are, like plastic pots, durable and lightweight. Some are so well made that it's hard to tell them from a terra cotta pot—until you try to pick one up!

As a rule, it's hard to go wrong with a general-purpose potting soil. It will support most annual herbs, like basil, parsley, sage, coriander, and Clary sage. Ironically, if you are growing culinary herbs, you can save yourself some money by purchasing plain soil, because culinary herbs don't need a lot of fertilizer. Feeding them with a general-purpose fertilizer at the time of planting and then once more midway through the growing season is enough. (A general-purpose fertilizer has equal amounts of nitrogen, phosphorous, and potassium.) Fertilizing more often will result in lush growth that has little flavor. A great thing about herbs is that they are tough little fighters, and "roughing it" helps them to develop the right amount of essential oils.

This is especially true of the herbs (such as lavender, rosemary, thyme, oregano, and marjoram) that originated in the Mediterranean area. In this case, purchasing a soil mixed for succulents, which is formulated to drain well, would be a good idea. If you can't find this type of soil, it's easy to make. Just mix one part coarse builder's sand with two parts general purpose potting soil and you're all set!

Begin the setup of your containers by adding a one-inch layer of pebbles to the bottom of the pot. This will allow the container to drain and help prevent the soil from pouring out of the bottom of the pot. If you have access to old broken terra cotta pots, the shards make excellent material for covering the holes at the bottom of a container without totally blocking them.

Fill the containers up to two-thirds full with soil if you are using sets or plants from a garden center. If you plan to use a granular fertilizer, read the package directions and add the recommended amount of fertilizer now. Be sure to mix the fertilizer and soil together to avoid burning the root ball of your plants. If you use a liquid fertilizer, wait until planting is finished before adding fertilizer.

A 10-gallon container will hold up to three 15- to 18-inch tall plants. A 15-gallon pot can handle up to five such sets. A single plant that gets bigger, like rosemary, will quickly fill a 10-gallon container in two growing seasons. Check the plant tags that come with most nursery plants. They usually tell how big a plant will be at maturity.

When you plant each herb set in the container, the top of the root ball should come to roughly two inches below the rim of the container. If you don't have enough soil, add more now. Herbs that are set too low in the container will likely die from crown rot. Those that are set too high will dry out quickly and probably die from stress.

As you add plants, surround them with soil. Once all plants are in the pot, add more soil, firming as you go. Now, water the plants thoroughly to settle out any air pockets in the mixture.

If you are planting seeds, fill the pot to within two inches from the top of the pot. Read the directions on the back of the seed packet carefully. Some seeds are so "fine" they need to be distributed on top of the soil. Some need to be barely covered with soil and others can be buried one or two inches deep. The packet should also tell you when to expect your seeds to sprout.

Keeping soil moisture consistent is critical for seedlings. Watch tender, little plants carefully and if necessary, move the container out of the hot afternoon sunlight until the new plants develop a sufficient root system.

Once the plants are established, adding a layer of mulch will help control the moisture content of the soil. Mulch will also keep your herbs clean by prohibiting the soil from splashing up on the plants during rains or when you water.

As you plan your container garden, give some thought to the layout. You don't have to segregate your plants. In fact, mixing compatible herbs is a great way to add visual interest. Just be sure to mix those plants that have similar growing requirements. Thyme, oregano, garlic, chives, marjoram, artemisia, and pennyroyal need good drainage to grow well. They also appreciate that lean soil mixture of potting soil and sand mentioned earlier.

Anise, hyssops, calendulas, lemon balm, borage, santolina, sage, and tarragon are full plants that like average potting soil. Several of these plants come in a variety of colorful foliage that will give you plenty of design options as well as useful harvests for cooking or crafts.

Don’t forget to look up as you garden. A trellis in the back of a large pot will give passionflower vine and sweet peas something to grow on, or a place to support tall herbs such as cat mint, dill, and tansy. Some herbs work well in hanging baskets. Scented geraniums are naturals for hanging containers, as are nasturtiums.

Mixing annual and perennial herbs, especially in the first season, is a good way to adjust for robust plants later. For example, you can mix perennial lavender and annual calendulas in a 10-gallon pot the first year. But by the second year, the lavender will probably prefer to be left alone in its pot.

Container gardening is an adventure in learning. While books and Internet sources can get you started, nothing beats getting your hands in the soil and finding out what works for you. A golden rule in gardening is "You've got to grow it to know it." Find out for yourself if basil planted with thyme works for you. Will you be a mint lover? How many times will you have to plant oregano to get it to flourish for you?

Push your boundaries. Test your limits. Create your own little green spot wherever you live and thumb your nose at that concrete jungle that surrounds you.

From Llewellyn's 2012 Herbal Almanac. For current-year calendars, datebooks, and almanacs, click here.

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