Following are the highlights of a presentation I gave today for the University of Tennessee Gardens Fall Symposium. The theme of the symposium this year was "Incredible Edibles."
“You can’t grow that!” is the reaction I often get when I suggest to one of my gardening friends that I plan to try such-and-such next season. However, every time I look for information on a food crop that supposedly does not grow in Zone 7, I find plenty of suggestions and advice from gardeners who have done just that. In a minute, I will cite some examples of tropical and sub-tropical food plants that you certainly can grow.
I was appalled by an article I read recently that suggested producing the majority of our food locally is an impossible dream. I wonder how the Native Americans who occupied this Valley centuries before Europeans arrived would have reacted to that remark? Many of them were farmers as well as hunter-gatherers, and this region of the world is unusually lucky in having an abundance of edible wild plants. I have several examples of those to share with you today, also.
A third group of food plants includes some that lots of people apparently grow, but for some reason you never hear much about. I will offer two examples from this group.
First, however, let’s look at some plants you “can’t” grow here.
Tropical and Sub-tropical Plants:
Plants grown in large containers outside during the warm months will produce fruit. Dwarf and super-dwarf cultivars are available in the nursery trade. The one pictured, ‘Novak,’ fruits at only 4 feet tall.
The growing medium must be well-drained. Bananas do not tolerate wet feet. Fertilization with a balanced formula monthly is necessary. Bananas need about 1 ¼ ounces of nitrogen per month when young, and double that amount when mature. If your fertilizer is 8 percent nitrogen, that is, the NPK numbers are 8-x-x, you should apply a pound of this fertilizer around the base of the plant monthly, gradually increasing the application to two pounds over the course of the season. If the temperature at night is below 50°F, as during overwintering in a garage perhaps, don’t fertilize.
While bananas are generally tolerant of cold down to 28°F, they perform best when grown under constantly warm to cool conditions. If winter storage is a problem, however, you can take several steps to keep your banana plants growing. First, if you have a suitable sheltered spot exposed to southern sun, you can probably overwinter a banana plant outdoors as far north as Zone 4. This is accomplished by cutting it down, covering the base with a bushel basket, and piling leaves on top to protect the underground stem . Do this as soon as frost kills most of the top growth. Check such plants frequently in early spring and remove the covering as soon as shoots emerge. Be ready with a frost blanket in case of a late cold snap. A more reliable way of overwintering is to dig up small shoots and pot them in containers as houseplants for the winter. Grow in a bright, warm location and fertilize lightly until you are ready to move them outside again. Generally, you allow only two shoots to develop. The older one will fruit and the other will provide the subsequent crop.
This frost-tender shrub or small tree prefers rich, organic, well-drained soil. It grows best as a container plant, in full sun to partial shade. Do not allow plants to dry out, but do not allow soil to become soggy. Use a growing medium intended for citrus, if available. Can be successfully overwintered in Knoxville if grown in a sheltered location and the soil is prevented from freezing by deep mulch, an adjacent building foundation, or a water feature.
The photo is my Meyer lemon ‘Improved’ on a dwarf rootstock. This is a hardy citrus that will tolerate cold down to 34 degrees F. Kumquats, such as ‘Meiwa,’ can take it down in the 20s. The vast number of selections of grafted citrus means you must pay attention to rootstock and graft alike. Citrus prefers a gritty, well-drained growing mix and plenty of water and fertilizer when young. Drought tolerant as they get older. Water citrus when the top one inch of growing mix feels dry when you stick your finger into the soil. Feed once when the plants move outdoors, and again about three months later, using a good, balanced organic fertilizer. Formulas made just for citrus are recommended and available from garden centers or by mail order. Glossy, dark green leaves indicate that the plant is receiving adequate nutrition. When in doubt, err on the side of less food and less water. Too much of either one will result in leggy, unsightly growth and poor fruit production.
In the second year after transplanting nursery stock, you should expect a few fruits. Thereafter, fruit production will increase with the size of the tree. Lemons and limes can bear almost at any time of year, but most other varieties bear the best crop after their spring bloom. Leaving the fruit on the tree until you are ready to eat it is the best bet, as the fruit becomes larger and flavor improves with time. Don’t wait until the fruit begins to dry out, however, before picking. Among the numerous varieties of citrus available, consider one or more of the following. Meyer lemon is a small form with smooth, thin-skinned fruit and reasonable cold tolerance. Kumquats have good cold tolerance and adapt well to containers. Selections include ‘Nagami’ and ‘Meiwa,’ both of which bear during fall and winter. Mandarin oranges and tangerines also exhibit good cold tolerance, but with some varieties, such as the Clementine tangerine, you need two plants for successful pollination. Varieties to try include Satsuma, Owari, Clementine, Dancy and Changsha tangerines, and Minneola and Orlando tangelos.
Figs have been grown for centuries, and can be over-wintered outdoors in Knoxville in a sheltered spot. ‘Brown Turkey,’ ‘Celeste’ and ‘Chicago’ are popular cold-tolerant cultivars. Grow in any reasonable soil in a spot sheltered from winter winds. Keep root suckers pruned off and head back the tree to maintain shape. All are considered easy to grow, with water management being a more important consideration than soil fertility. Poorly drained, constantly wet soil will rot the roots, but trees should not dry out to the point that leaves begin to wilt. Since the tree should be sited in as much sun as possible, water needs during hot weather can be significant.
Purchase nursery-grown stock of a known cultivar, or root a cutting from a tree of known provenance. Cuttings taken in August will root readily and can be transferred to their permanent location the following year. Plant the tree a little deeper than it was growing in the nursery container, using a well-drained mix such as has been previously recommended for growing avocado and citrus. Add a little bone meal to the mix at planting time. Figs are not heavy feeders and phosphorus is more important for them than nitrogen. You will need a container holding fifteen to twenty gallons of potting mix to accommodate a mature fig tree. Trees can be kept in bounds by thinning the main stems and by root pruning every three years.
Overwintering a container fig is relatively easy. When leaves fall, move the tree indoors to a cool spot. Light is unnecessary while the tree is dormant, so even a closet will do. Water about once a month. As the weather begins to warm up, gradually acclimate the tree to outdoor conditions, and new buds should begin to swell. Thereafter, resume your normal schedule of watering. Work a few tablespoons of bone meal into the top layer of soil when the plants are growing well again.
A fig tree planted in the ground in a sheltered spot can be successfully overwintered if the roots are protected from freezing. When dormant, the tree can be wrapped in a frost blanket until warm weather returns. Gardeners as far north as Zone 5 report success with this technique. Some drape the tree with Christmas lights connected to a timer, thus providing extra warmth on cold nights.
Olives typically do not do well in the humid South, but the Spanish Arbequina cultivar does perform well here. I saw olives fruiting in small pots at the Farmers Market this summer. They are decorative plants that adapt well to container culture. Use a well-drained mix, such as intended for citrus or palms, and keep well-watered and fertilized during the growing season. Hold back on water during the winter, but do not allow to dry out completely, and keep the plant in a sunny window.
Unusual ornamental edibles:
Tolerant of poor soils, drought and shade, the native elderberry is a reliable and easy edible shrub. Two plants are needed for pollination, except in the cultivated varieties ‘Nova’ and ‘York.’ European elderberry is also available; ‘Black Lace’ is a particularly decorative selection.
This Native American tree is under-appreciated. Usually found in rich, moist, organic soil near rivers and streams. Once established, the trees are rarely bothered by pests or disease. Selections available in the trade. Choose two different varieties to insure pollination. The tree is the host plant for the zebra swallowtail butterfly, and chilled pawpaw is said to have been George Washington’s favorite dessert.
A sturdy native American tree, persimmon is self-fertile. Several cultivated varieties are available, along with a hybrid between the American and Asian persimmon species. Attractive checked bark and fruits remaining after leaf fall create year round interest in the landscape. Tolerates a wide variety of conditions, but prefers rich, well-drained soil high in organic matter.
Native to the desert Southwest, but naturalized in some places around here, this cactus can grow to an impressive size, provided it has plenty of sun and well-drained soil. Handle with extreme care. Tiny spines come loose and work themselves into your skin if touched. Fruits are used for juice, jam and wine-making. Leaf pads are de-spined and eaten as a vegetable, nopalitos, available canned in the Latin section of the grocery store.
A fruiting tree with four season interest: spring flowers, summer fruits, fall foliage and winter bark and buds. Fall foliage color is often spectacular. Numerous cultivares are widely available, and tolerant of just about anything but wet feet.
Often called “bear grass” this desert native is naturalized throughout the Southeast. Flowers are edible raw or in stir fries and omelets. (Some people may have a reaction, but this is rare. Eat only one flower the first time.) Trim out the centers and chop them separately, using the petals whole.
You can easily produce a year’s supply from a couple of purchased roots. Look for those with attached green stems, and use the best-looking ones to start your plants. Select a container at least four times larger than the piece of rhizome you are planting. A 12 to 14 inch azalea pot works well. This will allow for the development of an extensive root system. Fill the container three quarters full with a good, well-drained potting mix containing plenty of compost. Place the rhizome on top of the mix with the eyes pointing upward. Cover with more potting mix and water well. Place the container in a plastic bag in indirect light until green shoots appear. (This can take a month.) Then remove the bag and water well. Keep the plant in bright, indirect light and never allow the soil to dry out. Growing plants need protection from wind and should be brought indoors any time the temperature is headed below 50°F. The ideal growing temperature is 75°F to 85°F. Water and feed regularly, like most houseplants.
Saffron crocus grows like any other crocus, but blooms in fall, not spring. It grows well in Zones 6 through 9, and prefers good, well-drained soil in full sun. A patch of ten square feet, enough to accommodate about 50 bulbs, will provide an increasing abundance of spice as the plants mature and multiply. Set them out in summer, while they are dormant, six inches apart and three inches deep. Drainage is essential. Avoid keeping the soil too wet when the plants are dormant. You can overplant, if you wish, with annuals, but take care not to irrigate too much. Pull up the annuals when you see the new green shoots of saffron poking through the soil in autumn. When the lovely lavender-blue flowers open a few weeks later, harvest by picking the bright red stigmas by hand. You can use them immediately in such Mediterranean dishes as paella, bouillabaisse, and risotto, or dry them for a few days before storing in an airtight container for later use.
With just a little planning, your yard can become more beautiful and productive. Just be sure not to listen to anyone who says, “You can’t grow that!”