The Unnatural Plant:
Do Potted Plants Have to Suffer from Hangovers?
Fred E. Knapp, Locust Valley, New York
Container grown plants are making a strong bid to drive field grown material off the market in many types of plants. This certainly includes rhododendrons and azaleas, except for very large specimen plants. The reasons are purely economic, and we must all adjust our thinking to go along with the trend.
Container plants are our future because of their great advantages in labor requirements, in weather control, in growth rate, and in growing space requirements. In pots, young plants can be lined out in a plastic house for protection from winter wind and cold in a minimum area, independent of the local soil quality, if planted in a "made" potting mixture. They can be fed and watered efficiently, and shipped at will - regardless of scarce digging labor, recalcitrant ground frost in a late spring, protracted rainy spells, etc. - with their foliage in perfect condition as if there had been no winter. The containerized nursery can thus deliver large quantity orders earlier and more reliably than any field nursery.
We, the plant buyers, must accept what is happening, but we need to know what it means to us. To discover this, we shall follow the life history of a plant from a high production rate nursery to one of our own homes. A good example is an Exbury azalea. At each point in its travels, there are alternates, a few of which will be considered, but in general the most extreme path will be followed since it ultimately requires the most care on our part.
The young Exbury is propagated from a cutting in early summer and forced into new growth before its dormant period begins in the fall. In late fall, potted in a suitably sized container, it is placed in an uncovered plastic house. Here is the first major choice, the potting mix. There are many mixes, from the home remedy type composed of sand and peat to such "unnatural" media as straight bark chips. The medium must hold moisture but have good drainage, permit lots of air around the roots so that they get oxygen, support the plant, preferably be light, and be as cheap as possible. It may or may not provide nutrients. The nurseryman may choose to fortify it with trace elements and slow release fertilizers or to do all his feeding in liquid form. Let us assume that our example is in an unnatural nonnutritive medium, and that it will be fed only by fertilizer included in the water it receives.
The young azalea goes dormant as winter comes on. With some experimentation, the nurseryman has found his right combination of sun, day length, and plants. At the right time, say mid-February in this case, he covers the plastic house with plastic and induces "spring" for the plants inside. Buds pop, and feeding and watering begin. They must never slacken. All the food comes from the water, and all that is not used leaches through in two to three days of plain watering, so fertilizer must be included in the water at regular close intervals. On this schedule, the plant grows the equivalent of three or four seasons by the time spring outside the plastic has caught up to that inside. It can now be moved out for retail, or repotted for fall sale. If repotted, we again have a choice of medium, and of feeding method. We can continue as is, or go to a mix more like soil; we can add slow release fertilizer to the new pot or not.
Assuming the plant is sold at the spring stage, observe who now gives it a home. In the worst case, this will be a garden center operator - and, let us assume he is an operator, not a nurseryman. As a businessman, his policy is to under - do everything except one - he does not under-price. (Remember, we are taking the extreme path at each point.) He is not up on Exbury azaleas in any case, and his knowledge of plants is just enough so that he will tell the hired help to water the plants if he sees them drooping. When we buy the plant, it has had not a bite to eat in some time, little to drink, and whatever drink it has had served to leach out the last vestiges of fertilizer from the root zone.
The plant now leaves its pot for our home ground, and is planted or plopped into a hole according to the methods of the particular buyer. At this point begin a number of standard comments about container plants. We hear that they die, they "don't move", they set no buds for 2 or 3 years. All of this is quite true - and none of it is true! The results are not a function of containerized plants but of how we plant them. Or - it's not the plantee, it's the plantor!
The word "unnatural" was applied correctly to the medium in which our plant is growing. Its growth rate has been unnatural, and its fertilization. Obviously, this must be the reason for our poor results. Mother Nature is paying us back for trying to fool her. This convenient conclusion just is not so. We cannot escape responsibility that easily. Unnatural is not the same as unhealthy, and containerized growing conditions do not "burn out" a plant so that it will die or must rest indefinitely. The problem is that we permit the unnatural elements of the situation to persist in the garden with out compensating for them as did the nurseryman when he had the plant in a container.
There are many conflicting opinions here, and no organized experimentation to guide us, but there are some obvious general principles. I recommend that everyone think about them and cautiously try his own experiments to find the best way to go. Consider the plant as we have described it so far: a full, healthy, leafy structure on a good root system completely contained in a foodless medium.
What does it need? If it is to grow, it needs food - so we must do two things. We must provide temporary food in the existing medium, and we must get the roots out into the new medium as soon as possible so that they can establish a permanent food source. Many people realize the first requirement, and kill the plant by over fertilization. If the new soil is heavy, then fertilizer will not leach through as it did in the pot - so be careful not to over-do it. If the soil is quite sandy, then leaching will occur (although not so rapidly as in the pot) and additional applications may be needed. Try to find out what material and rate of application was used by the nurseryman, and start your thinking there. Try half strength, twice as seldom. Be sure to emphasize phosphate, for that makes the roots grow and will get them into the surrounding soil. Fortunately, phosphate is also good for flower bud set. With fingers or hose, or as appropriate to the medium, expose some root ends before planting, so that they are in contact with the soil in the hole from the first.
Our new plant also needs water. If in a coarse fibrous medium in sandy soil it may dry out remarkably fast at first. Watch the water and do not stint on mulch. Here again, the primary need is to get out of the old medium into the new. Sometimes roots are reluctant to do this if textures vary greatly. Expose those roots before planting.
In some cases the new plant may have some slow release fertilizer in or on the mixture. It may be in a cake, or in little globules mixed in the medium. Look for it, and act accordingly. If the plant has fertilizer, put on by the nurseryman, do not add more. The nurseryman probably did it right. It is still a good idea, however, to lace the surrounding soil with super phosphate.
Examine the medium to see if its texture implies any special problem in freezing weather. It may retain less water than a soil mixture. Extra protection may be needed, since the roots will not have grown fully out of it before the first winter. Even in winter, a rhododendron must get water from its roots. Our deciduous Exbury, of course, has an advantage here.
The message in all this is that a container grown plant has exactly the same problems as any other, but with the emphasis shifted. Try to learn all you can by examining the plant. Ask the seller who grew it and how. He may know, and he can find out. Encourage the idea of some instructions on feeding on the back of those lurid name tags you see in nurseries. Make your request strong enough to get it back to the original grower. He is in the best position to make suggestions for feeding the plant. There is no reason why container grown stock should not enjoy perfectly good results - perhaps even better than those of field grown stock, in which bugs and pathogens are more difficult to control. Anyone who knows how to grow a plant he bought "B and B" can grow it just as well from a container once he evaluates the shifted emphasis in the same old familiar requirements. When a container grown plant dies, burns, does not bud, etc., the chances are the one agent most guilty is not the nurseryman, not the green dye in the container, but the gardener who planted it thoughtlessly. As has oft been said, "We have met the enemy, and he is us!"