Growing vegetables in containers

I have a dear old friend, Thomas, who raises organic vegetables in timber barrels. Several decades ago, well-used barrels were frequently discarded from the larger vineyards and distilleries or sold to gardening enthusiasts for a modest sum. Nowadays, the use of wooden barrels is greatly diminished as inexpensive alcoholic beverages are increasingly stored in stainless steel kegs. Consequently, the few wooden barrels currently available have become sought after items. They’re typically sold by outdoor design centers and antique dealers for upmarket prices. My friend recalls two men offering several thousand dollars for his collection of barrels. It was Easter Sunday and they were offering cash, he explains. They had their truck with them and they seemed pretty confident about purchasing his barrels. What’ll you do with them? inquired Thomas. Saw them in half, varnish them, and mount them on decorative stands. Sell them on the internet. On the internet? Thomas repeated. Yeah, they confirmed, decorative containers are popular on ebay.

The main challenge for the gardener interested in container grown vegetables is to select suitable varieties and to accommodate their individual requirements for space, water, sunlight, and nutrients. Container raised vegetables are susceptible to crowding, more so than those planted in open ground. Deep and spacious containers like those wooden barrels are ideal for growing small quantities of organic vegetables, particularly the green leafy varieties and compact growers like cherry tomatoes, and snow peas. Leafy vegetables like spinach or silverbeet grow surprisingly quick and even regenerate themselves after picking. Potatoes can be grown in troughs or drums which are simply emptied at harvest. There are miniature varieties of carrot and other root vegetables which have been refined for container growing. Containers are inappropriate for several classes of vegetable. Heavy feeding plants like corn are better served in open ground and the larger spreading vines like pumpkin, marrow, and aubergine will struggle to reach their potential when planted in containers.

When grown in open ground, vegetables can extend their roots over distances to obtain sufficient water in dry conditions. Because of their restricted root systems, container-grown plants require more frequent watering. At the peak of a dry summer, this may increase to several times each day. Automatic sprinkling systems can be programmed to deliver measured volumes of water at intervals throughout the day and evening. These units are extremely valuable in gardens supporting a large number of containers. The down side associated with frequent watering is the potential for drainage problems combined with a continual washing away of water-soluble nutrients. Providing regular replacement in the form of a liquid plant food can usually offset the loss of nutrients. The best organic products include seaweed extracts, liquid manures, and milder solutions brewed from nettle or comfrey leaves. While expensive, commercial organic supplements improve the overall quality and yield of container-raised produce. These should be carefully diluted according to each manufacturers recommendation. Excessive concentrations cannot be absorbed and will eventually damage root structure and function.

In the absence of good drainage, planting containers may eventually become waterlogged, damaging vegetables by restricting the uptake of oxygen from their roots. Drainage is determined by the availability of porous channels which absorb then direct water towards the base. Upon reaching the base, excess water is encouraged to drain externally from the container. Good drainage can be assisted by using quality organic potting mixtures, above a base layer of scoria or ceramic and by ensuring that pots and tubs have several drainage holes that are at least two centimeters in diameter. Most garden soils tend to compact with frequent watering so are not recommended for container planting. The best potting mixes contain fibrous organic materials that hold an even dispersion of moisture and air pockets plus nutrients to support plant growth. The mixture must also be sufficiently dense to support the vertical growth and weight of plants. For growing vegetables, my friend Thomas uses an organic potting mix combined with sandy loam in approximately equal quantities. He completely replaces this growing medium after each crop of root vegetables. For his tomatoes and leafy greens, he generally replaces this after harvesting a second or third crop.

The metabolic rate of all green plants is determined by the availability of light and heat. There is quite a bit of variation in the optimum sunlight requirement for the different types of vegetable which are commonly raised. Spinach, for example grows happily in restricted sun or partial shade whereas most tomatoes require direct sunlight for at least four or five hours on average per day. Most container-grown vegetables require good ventilation and at least several hours of sunshine each day. Their location must be carefully chosen to avoid difficult and extreme weather conditions. Enclosed patios are usually suitable but open and elevated apartment balconies are often subject to extremes of heat, cold, wind, and rain. While the Mediterranean or European tradition for growing vegetables and herbs on raised balconies is a cultural tradition, there is a potential safety hazard when heavy planting vessels are positioned on elevated surfaces. Call me anxious, but I cannot avoid checking upwards on visits to Spain and southern Italy. My friends laugh because I still grab every opportunity to browse around the fashionable terraces of Messina and Palermo.

Now those ebay entrepreneurs were pretty keen to purchase old Thomas’s barrel collection. They added an extra hundred to the original offer. Thomas admits being tempted. The barrels were pretty old, he says. He thought about raising vegetables in deep acrylic pots. In the end, I couldn’t, he reveals. You’d become attached to the natural timber? I ask. Yeah, I suppose so. Those barrels are the functional elements of my garden and they were planning to cut them longitudinally. Shallow trays for temporary flower displays? He scratches his head with disbelief. Their shape is kind of important to me, he asserts. I admire rounded things with pleasant curves. Like those old Buick passenger vehicles of the nineteen fifties. You don’t interfere with a brilliant design.