Growing herbs in containers

From Gardener to Go (Sharyn Caudell) some pointers on growing herbs in containers.  For other gardening information you’ll find “Tip of the Month” at her website.

Herbs are wonderful addition to any garden.  They are beautiful plants and everyone knows that fresh herbs add so much to cooking.   Many of our herbs are Mediterranean in origin.  This means they grow in thin, often rocky soils in a hot summer climate with no rain in the summers.   Central North Carolina has the hot summers and one of the best ways to provide the other conditions is to grow them in containers.   Herbs will languish with ‘wet feet’ so good drainage is essential.

If you have sandy, well-drained soils in your garden, you can probably grow them directly in the ground.   For the rest of us, choose a large container. Some folks use flue tiles which are made of terra cotta. These are available from building supply stores.  Place the tiles upright on the ground and fill with a good soilless mix such as a high-quality potting mix. You want a potting soil that does not compress to a wet mix.   Several good brands are Fafard, MetroMix, Pro-Mix, Sunshine Mix and others (these are professional mixes).  If you can’t find those, look for a potting soil that does not contain moisture-retaining granules; this type is great for hanging baskets that you don’t want to water constantly but not herbs.  Try lifting the bag. It should feel light for its size.  Some potting soils are very heavy in the bag and will be too dense and wet for herbs.   You can mix perlite with the soil to improve the drainage. (Perlite improves aeration and drainage; vermiculite holds water so read the bags carefully!)   Do not add Styrofoam peanuts or pebbles or anything in the bottom of the pot to improve the drainage; it doesn’t work.  Soils drain by capillary action between the small pieces of the soil (think of a very thin straw).   Adding items in the bottom of the pot shortens the capillary ‘straw’ and holds more moisture in the pot.  To keep the soil from washing out of the pot, line with a sheet of newspaper, window screening, landscape fabric or several coffee filters. These will hold the soil in place while the roots form.   It is a good idea to mix in some dolomitic limestone with potting soil.

Herbs need 4 to 6 hours or more of sun per day.  Try to pick a spot that is easily accessible from the kitchen so you will use your herbs.   Herbs require moderate water so you don’t have to tend these daily.    Some good herbs to start with are parsley, chives, basil, thyme,  oregano, rosemary and sage.   Parsley is a biennial  plant—it sets seed its second year and then dies. Basil in an annual that needs replanted every year.   Chives, thyme, oregano and sage are perennials.   Rosemary is a shrub with lovely small blue flowers in the spring.  There are small varieties that will do better in a container.  Dill and cilantro will grow well in the spring and fall but will bolt, flower, set seed and die in our summer heat.   Pruning off the flowers or dead-heading will keep your herbs growing longer.   Herbs require little fertilizing.  It is better to be very sparing of fertilizer than to have lush growth that may be damaged in the winter.  You can always add a bit more fertilizer if you need it.   Most herbs will be fine with no fertilizer for the first year.

IMG_4073You can grow chives and parsley in a vegetable garden easily.    French tarragon is a wonderful herb that doesn’t do well in our summers.  You can substitute Mexican tarragon (Tagetes lucida) instead. This is actually a marigold that grows to 3-plus feet and has yellow flowers. Use the leaves as you would tarragon.   It is an annual.   There is a substitute for celery that is a perennial: cutting celery (Apium graveolens var. secalinum). It grows 12-15 inches and has a wonderful celery flavor but not the long stalks of regular celery.  It is an evergreen and will self seed.

In general, deer don’t like herbs because of their strong flavors or smells but a really hungry white-tail will eat almost anything.  Don’t use pesticides on your herbs.  The black and yellow caterpillars of the pipevine swallowtail butterfly will devour your parsley, dill and fennel plants but the leaves will grow back.

There are many other herbs that have been used medicinally or for dyes that are grown in our gardens for their beauty.   Browse the herb section at your garden center or find a book on the subject. You will enhance your garden and your table by growing herbs.

More on growing herbs

For those just starting gardening, and growing herbs is a great place to start, here’s an article from The Herb Companion that addresses the joys of having a kitchen garden of herbs (in containers), and how easy it can be.  You’ll probably find that it’s addictive!  Once you know how easily you can grow them almost any where, and how useful they are, you’ll not want to be without fresh herbs in season.

Chervil & Savory

Chervil (Anthriscus cerefolium)

Chervil (Anthriscus cerefolium) is a wonderful herb, but unless you grow it yourself, you’re unlikely to every taste it.  It’s too delicate to be found in the grocery store in the little plastic boxes or in bunches.  I’ve not see it at the farmers’ market as a cut herb either.

As the plant is delicate, the flavor is too:  hints of anise/tarragon and parsley but subtle–which is not something you’d say about French tarragon.

Chervil seed is easy to germinate but the plant is difficult to transplant as it has a taproot. It likes rich, moist soil that is well drained, and would like to be in partial shade. You can sow outside several weeks before the last frost.  It is another herb that like cooler weather, but it may be prolonged by providing some shade, e.g. planting it under other plants. Like cilantro, it is a fast-growing annual that will flower quickly.  If you cut off the flowers you can prolong the foliage to some extent, but the old leaves will change color (from the lovely greet to yellow and purple) and become tough and lose flavor.  If it becomes one of your must-have herbs, you can sow successively (as with cilantro) throughout the growing season.

To harvest, cut sprigs about two inches above the ground, taking the older leaves from the outside of the plant, but be sure to leave the new center leaves as this is where the new growth is occurring.  As with most other herbs, you should not harvest more than one-third of the plant at a time since it needs the leaves for photosynthesis.

In cooking, use it where you want delicate flavors e.g. with mild fish or seafood.  It would do well with young poultry that has more delicate flavor than the older bird.  Chervil would be good with young vegetables–e.g. baby carrots, or fresh baby peas.   The leaves are mild enough to add to salads, and to use as a garnish in place of parsley.  It could be used with many of the same foods as tarragon, only where you’d like a more delicate touch–e.g. with eggs. It’s so mild that you will want to use lots of it–quite in contrast to tarragon.

I am not a fan of dried chervil–it seems to lose a lot of flavor and come across somewhat hay-like, even when I’m sure I’ve obtained it from a supplier with good turnover of their dried herbs.  So for me, it’s one of the signs of spring, right along with the new peas.


Image from Mountain Valley Growers

Winter savory (Satureja montana)

Savory is not going to be found in the grocery store shelves either.  Two savories, summer (Satureja hortensis) and winter savory (Satureja montana) have very distinctly different growth and appearance.

Summer savory is an annual about 12 to 18 inches tall that tends to be rather sparse, lanky looking with grayish green leaves that will last only until frost.  Winter savory is a perennial, evergreen or semi-evergreen, shrub with a bushy habit, usually not taller than about 12 inches.  It’s leaves are glossy, dark green and closely spaced.

While both have are spicy, rather than sweet flavor (like tarragon or chervil), the winter savory is spicier and hotter than the summer, but they can generally be used interchangeably, though the milder summer savory is best with fresh summer veggies.  I think that the savories are most commonly associated with northern European cooking than with American cooking.

Both winter and summer savory are sometimes known as the “bean herb” as they are particularly used with dishes made with dried beans;  the somewhat milder summer savory is great with fresh beans as well (fava, lima, or green beans).  Other uses include with cabbage, Brussels sprouts, and with summer squash, and roasted potatoes.  It’s potent enough to use in marinades for beef, lamb, as well as chicken and pork.

The summer savory is easily started from seed.  Summer savory is not fond of being transplanted (if starting indoors use peat pots so that you do not have to disturb its roots).  It does will is average soil that is well drained, but well watered.   It will want plenty of sun and does need to be well fertilized.  Blooms will appear between the leaves on the upper portion of the plant.  At that point you should cut the plant back by about one-third in order to prolong its culinary use by encouraging more foliage.

Winter savory can tolerate poorer soil than the summer, but it also must be well drained. It also wants plenty of sun.  It is hardy to about zone 5,  if the roots are not wet during the cold weather.  Wet roots in the winter may well mean no savory in the spring–really true of most perennial herbs!    After or as it blooms (I prefer not to let my herbs bloom), it should also be cut back to encourage it to be bushy and increase foliage, which is what you want for cooking.

Both are harvested by cutting springs from the plant–remember not to cut more than one-third of the plant at a time so that it can keep growing and producing.  If you need to store savory,  wrap in a slightly damp paper towel and place in a zipper-lock back.  Summer savory should hold for about a week, and winter for about two weeks.

USDA hardiness zones

I’ve talked about growing your own herbs, and I’m sure I’ve mentioned that certain perennials are hardy in some zones and not in others.  If you are unfamiliar with these, here is a link  from the National Gardening Association which will answer some questions about hardiness zones, and will let you check out your zone.  Remember that drainage can affect hardiness, and it will make a difference if the plants are in pots, rather than in the ground.

It’s not only cold that affects your plants:  It’s thought that plants begin to suffer physiological damage at temperatures above 86 ° F.  From the American Horticultural Society, here is a link to a downloadable heat zone map; online this map may be viewed at the Southern Gardening website.  This gives the average number of days when the temperature is above 86 ° F

In using either of these (cold hardiness or heat zones) you have to consider where your plants are being grown–in the ground, in pots, the soil drainage, and water availability, among other things.

Harvesting & using herbs

Now that you have all those lovely herbs growing in your kitchen garden (or just in containers) you need to get them into the kitchen and use them.  There are some general things that apply to harvesting and using almost all herbs in order to get the best flavor in your dishes.

Even though there are “classic” combinations (e.g. basil and tomatoes) don’t be afraid to experiment…that’s the point of having this selection available at your kitchen door!  Smell and taste the leaves of your herbs.  Think about the dish you’re cooking, how you feel today….

Try something different–fresh oregano or marjoram with the pasta sauce today; or maybe even tarragon or fennel with tomatoes.  (Yes, the leaves of that Florence/bulb fennel can be used as seasoning too.)   Experiment!  Taste!  Smell!  That’s what herbs are all about.

In reading through cookbooks, you’ll find may different opinions about when to harvest, whether or not you want herbs to bloom.  Here are a few generalizations about growing, harvesting, and using those wonderful plants that come from my experience:

  • For best flavor you want to keep most of your herbs from blooming; once the plant starts blooming and making seed it is less flavorful.  (You can find all sorts of articles pro and con; this is my opinion.)  To do this you will want to pinch out forming flowers at the tips.  This is particularly true for basils.
  • You generally need to keep herbs trimmed or they can get very unruly, lanky and leggy and straggly.  If you’re not using enough to keep them bushy, and retard blooming, then give them a “butch” every once in a while to keep them bushy and full.
  • Rosemary is an exception it’s not “pinchable” as it blooms along the stems themselves.
  • If you have several plants or if you want to use the flowers (they are edible) then you may want to let part of them bloom–they are lovely, but you sacrifice flavor in exchange for the blooms.
  • Don’t harvest more than one-third of the plant at a time–the herb needs enough leaves to keep growing since it depends on the leaves for photosynthesis and growth.
  • Fresh herbs are best when harvested as needed–not to be stored in the refrigerator for days. That is the whole point of having those pots on the deck.  When I need to trim, I either find something to do with the trimmings (make an herb vinaigrette or put the leaves in salads), or give them to friends…I won’t store them in the fridge.
  •  You’ll be cutting springs rather than picking individual leaves for most herbs (e.g. thyme, tarragon, sage), and then stripping the leaves from the stems (if the stems are woody or tough).
  • Bay is an exception: harvest by picking individual leaves, not sprigs, and not the newest leaves on the plant.  To harvest bay leaves, take the individual leaf and pull downward sharply.
  • You may want to add herbs at several times during cooking:  early to allow flavors to “meld”, but also again near the end in order to have the fresh flavor as many herbs lose some flavor with heating; you can give you dish a “fresh” boost by adding a bit more of the fresh herbs at the end of cooking.
  • If your recipe calls for dried herbs and you are substituting fresh herbs, you’ll need to use about three or four times as much of the fresh as the dried:  e.g. one teaspoon of dried thyme = one tablespoon of fresh thyme.
  • The way that an herb is cut can affect the flavor of a dish.  The more finely it is cut, the more rapidly the essential oils will diffuse into your dish, and the faster the essential oils may dissipate with heating.  Coarsely chopped herbs will release flavor more slowly and “hang around” longer.
  • You can preserve herbs for off season use by freezing but just throwing them into the freezer in a bag doesn’t do well. You can freeze them in ice by coarsely chopping them, packing them in ice-cube trays, and then cover with cold water and freeze. Color may suffer, but flavor is preserved  though you have to consider the effect that the extra water will have on adding to a dish.
  • My favorite way of freezing is to make a “pesto”–an herb and oil purée–of the herbs and pack into zipper-lock freezer bags.  You can cut off what you need.  This has the advantage of not adding additional water, and I think that it keeps flavor better than water and is more versatile.  The approximate proportions for this would be 1/4 cup oil for each gently packed cup of fresh herbs.  This works with basil, tarragon, marjoram, oregano, dill and cilantro.

Cilantro & coriander

Cilantro image

Cilantro (Coriandrum sativum)

Cilantro and coriander (Coriandrum sativum) are the same plant–just different parts used at different times–cilantro (herb) and the seeds (coriander–the spice).  I think cilantro (the herb) may be a love-it-or-hate-it flavor.  I like it, and even make a cilantro soup (no kidding).  It’s readily available in most grocery stores, but that large bunch does not keep well once you’ve used that little bit you need for single-serving cooking.  It’s a must-have for salsa, with chili, and Mexican and Asian dishes.

One way to have a continuing supply of cilantro when you want it is to grow your own, but that has its own problems, too.  It likes rich soil, plenty of  even moisture, and sun. Coriander seeds germinate easily. It can be direct sown in the garden or in a container and the foliage cut as you need it. It does best in spring and fall when the weather is cooler (even though it is a tropical plant).  Having a supply all summer (during tomato season) is going to take a bit of effort.

The difficulty with growing cilantro is that it’s not like  perennial herbs or parsley (a biennial) that just lasts all summer. Cilantro is a very quick-growing annual–it’s going to bloom and go to seed (bolt) as soon as it gets hot, perhaps even before it can develop a good crop of foliage, which is what you really want.  If you cut off the flower/seed head you can have the foliage for a bit longer. You can try giving it some shade in the hottest part of the day and perhaps prolong it a bit.

You can do succession planting…a little every two or three weeks depending on how much you use in conjunction with the above suggestions.  If you really love the stuff, then successive planting may help you keep a supply.

There is a benefit of growing your own: you can allow it to go to seed and you have coriander. The seeds, when not dried have some of the flavor of  cilantro and some of the flavor of coriander–so it’s fun to try using them in different ways too.

Frankly, I don’t think that even succession plantings works well  in the hot, humid, North Carolina summers–the small plants can bolt even before there is enough foliage for a single serving of something, and certainly NOT enough for cilantro soup. (This is a potato-based soup that I’ve made hot, but I think I’d like to try it as a cold summer soup too, garnished with some chopped tomatoes….that’s the fun of cooking for one.)

Culantro (Eryngium foetidum)

Another possible solution to get the cilantro flavor is to grow a substitute for it, such as culantro (Eryngium foetidum) sometimes found under the names of saw-tooth herb, or Mexican coriander, among many other names as well.  It is a native of South America and Mexico.  This is an herb which is widely used in Caribbean cooking, and in India, and East Asia as well.  It has the flavor of cilantro–but is a perennial plant (grown as annual in many climates).  The disadvantage of this herb is that the leaves are tough–not at all soft like cilantro leaves.  An advantage is that it’s tolerant of hot, humid climate.  Purportedly, it is increasing in use in industrial herb production as its leaves hold flavor when dried much better than Coriandrum sativum.  I’m trying a pot of it on my deck this summer.  Last summer I tried to germinate seeds and it was a total flop.  I was fortunate enough to find a plant at Stone Brothers & Byrd here in Durham this year so I’m going to try it again.

Vietnamese cilantro (Polygonum odoratum)

There is a second alternative for cilantro (Coriandrum sativum) flavor is  Vietnamese coriander or Polygonum odoratum. I have not been fortunate enough to find this one locally this year–it’s another that I want to explore the possibility of growing for the farmers’ market.  This herb is frequently used in Vietnamese cooking.  It has some “cilantro” flavor so is a possibile substitute.  The big advantage here is that it’s easy to grow.  It likes afternoon shade or even dappled shade all day, but needs to be evenly moist.  It’s fast enough growing that you may need to divide or transplant to a larger pot several times a season.  If it becomes root bound it will quit producing leaves.  It is a tropical plant that will die back at freezing (32 ° F/ 0 ° C).  Not all bad, as it can be kept indoors over the winter in a bright spot.  I had this on the deck last summer and was very pleased with it.  I just did not have enough light to maintain it indoors during the winter.   Now I need to find another plant.

(This image is from Mountain Valley Growers.  For some additional discussion of these herbs you can go to their website.  I’ve ordered from this supplier before and been very pleased with the quality and condition of the plants when they’ve arrived.  They also have some great recipes on that site too. There’s a lot of information on herbs and their use at this website.)

All things considered, I expect that I’ll buy cilantro from the grocery store when I need large quantities for the soup, but for single-serving amounts, I’ll  keep trying succession planting, culantro leaves, and hope to find Vietnamese cilantro locally rather than have to special order it.  (The problem with ordering for herb suppliers is that there is frequently a minimum order which needs to be met…I really don’t need six new herbs on my deck now–but I’m certainly considering it because I’d really like to have this one again.)  I’ll be letting some cilantro go to seed to try more of the green seeds as seasoning, too.

One additional solution to help you through the hot weather is to make “pesto” (leaving out the cheese and nuts) from cilantro leaves and keep it covered with a thin film of oil.  That holds remarkably well in the refrigerator (just like pesto)–about a week.   I’ve not tried freezing this as you can pesto, but I have used a frozen product during the winter.

There frozen cilantro available in the  Dorot (a company in Israel) line of frozen, chopped herbs.  I’ve used their cilantro/coriander during the winter when I need small quantities for things like adding fresh cilantro flavor to chili con carne, and been very pleased with it.  If you go to the Website you can find a store near you that carries the products.  (Image from Dorot.)

Bay, basil & oregano

Turkish (sweet) bay (Laurus nobilis)

New leaves on Laurus nobilis plant

Bay (Laurus nobilis)

This may be an herb that is associated more with winter cuisine because it is so frequently used in soups, stews, and braises which are typical of cool weather cooking.  Once you have used the fresh rather than dried leaves, it will be an all-season herb.

Culinary bay (Laurus nobilis) is often called bay laurel, sweet bay or Turkish bay.  The botanical name is important for this herb as there is another, California bay (Umbellularia californica), that is often found as “bay”.   The flavor of the California bay is more medicinal with a strong camphor smell that is much different from the complex flavors of  true bay laurel.   There is a whole new experience waiting when you use fresh bay laurel leaves in cooking.

This herb is “picky” to grow, but well worth the effort.  To grow bay laurel, you will need to buy a plant from a reputable source so that you can be sure that you are getting Laurus nobilis since the California bay lacks the “sweetness” of true bay.  True bay  is more expensive than most herbs because it’s difficult to propagate and is slow-growing.  You’ll likely (depending on climate where you live) want to grow your bay in a container in order to move it inside in the wintertime, at least until it is about 24 inches tall when the stems will be somewhat woody and better able to withstand cold.

Bay needs sun, but too intense sunlight will burn the leaves–so having it in a pot will let you move it around and discover the best site for it.   It also needs fertile soil, evenly moist but well-drained.  It should never be allowed to dry out completely or it’s likely to die. This is an herb that will need a container all to itself.  If you need to bring it indoors to winter over, you’ll need to put it where there is plenty of light and where it is well ventilated–best in a cooler area.  While indoors bay is susceptible to some pests like mealy bugs, scale, and aphids so you must watch it closely.

Basil (Ocimum basilicum)

Sweet basil (Ocimum basilicum)

If there is a summer herb, as dried bay might be considered a winter herb,  it is most likely basil (Ocimum basilicum), especially the sweet, large-leaf, Italian basil.  Say tomato, and I’m sure a lot of  “foodies” would immediately say basil.  It is a tender annual that will not winter over–so it’s a spring event when you can plant basil and anxiously await that first harvest.   I suspect that basil would be at the top of a list of herbs grown by home gardeners–especially as it is so strongly associated with tomatoes.  There are many varieties of basil (purple, Thai, holy, cinnamon, lemon, and lime, globe for just a few) but we’ll start with the most common: sweet or Genovase basil.

To grow basil, you can start with seed or buy plants.  It is a heat-loving herb so you need to wait for warm weather to plant it outdoors (generally night-time temperatures need to stay above 50 ° F).  You can get a head start if you plant seeds indoors.  Once the weather is warm, you can gradually get your plants used to the outdoors, and finally plant them out. For your first time of growing basil, you should probably just buy plants.  Even so, if you plant your basil outdoors while the temperatures are too cool, you’re likely to have stunted plants that will never do really well.

Basil can be grown in the vegetable garden, herb garden, or in containers.  It needs average soil (so it will do well in that potting soil that you got from the garden center) but needs plenty of water (even moisture, not allowed to dry out between waterings) but must be well-drained.  It needs lots of  sun, but it does not like the drier, poorer soil conditions that some of the Mediterranean herbs will tolerate; however, basil will not do well in soil that is too rich either (don’t fertilize too much)–that will make it less fragrant since it will contain less of the essential oils.  This means that you should not plant basil in the same container as other Mediterranean herbs like sage.

As you start your basil plants, you want to pinch the growing tips so that the plants will branch sideways and be full and bushy.  Basil flowers readily, but after flowering the flavor declines so be rigorous in pinching the flowering tips.

There is one serious fungus disease (fusarium wilt) that can affect basil–it turns the leaves black and will kill plants in a short time.  This is a disease that is carried by seeds–so if you are starting your basil from seed, buy seeds that have been tested and are known to be disease free.  Should you get this disease in your plants, the only thing you can do is (literally) trash them–don’t throw the diseased plants in the compost or that will be contaminated too, and the disease can be transmitted to tomatoes and basil plants on which that compost is used.

Oregano (Origanum vulgare subsp. hirtum

Greek oregano (Origanum vulgare, subsp. hirtum)

There are many types of oregano which vary markedly in the intensity of flavor.  Likely the one most commonly found in the supermarket or in the garden center is common or wild oregano (Origanum vulgare subsp. vulgare).  I like to grow the true Greek oregano (subspecies hirtum) for my use as it is very spicy and has an intense flavor.  It is a less vigorous growing plant than the common, but still easy to grow.   While you can start oregano from seed, it takes a long time to germinate and is slow-growing so unless you have lots of patience, buy a plant to start your herb garden.   The best way to tell what you’re getting it to smell and/or taste a leaf from the plant that you’re going to buy.  If you have never tasted Greek oregano, you are in for a wonderful treat–it’s much more flavorful and more peppery than the common oregano (which is what is most likely in those supermarket packs and in the garden center).

The two basics for growing oregano are sun and well-drained soil; given these it is a vigorous grower.  It is a perennial so once you get it started, it will stay with you for quite some time and generally be quite carefree to grow.   As with most herbs, it benefits from being used frequently or having the growing tips pinched occasionally to encourage it to branch and be a bushy, rather than a leggy, lanky plant.

A word of warning:  if you are also growing common oregano (see also Marjoram), don’t put it near your other species of oregano–it spreads by underground off-shoots (stolons) and by seeding itself, and it can (and likely will) replace your prized Greek (or other) oregano.   You might plant your Greek oregano in a container with sage, but not with other species of oregano or with marjoram.

◊ ♦ ◊

These three herbs would have to be part of absolute bare necessities, along with parsley, sage, thyme, and rosemary, for my cooking.  The longer I cook, the more herbs I want to have available for spontaneous use:  I’ve added tarragon, epazote and shiso (perilla), and lavender to what I’ve come to consider the “necessities”.  Every growing season is likely to find me adding another herb–this year it’s lime basil.  I’m waiting rather impatiently for the plant to be large enough to harvest some leaves and do something more than nibble on a leaf and contemplate where I’ll use it!