As you know, I am not one to dream up a lot of extra labor for gardeners; you never find me saying now is the time to swat the wisteria or dig a hole to China, merely because some books like to fill up space that way. But every year my heart sinks at the number of young clematis vines and tree peonies (to mention two conspicuous examples) that are consigned to slaughter merely for lack of a little (and it's not much) care in the planting.
Too often gardeners wait until the sun is warm on their backs before strolling forth to acquire a tree peony or clematis, and then they find young plants in full growth, wizened and chlorotic from lack of sun in the plant shop.
This growth is terribly soft, and since the store is usually hot -- instead of 48 degrees, say -- this new growth will be sadly injured if the plant is not given particular care.
A typical large-flowered clematis starts showing signs of leaves here in January, and often the leaf buds open somewhat in February. The individual leaves may be distinctly seen by that time, in some years, while in other years it will be March before these buds open. You will reflect that the weather is either cold or cool outdoors.
But in the hot climate of a shop the plant is inspired to grow very fast, and to elongate its stems far more rapidly than it would do outdoors. In the dim indoor light of the store it is trying to reach up to sun.
If a clematis (and most of them are sold in small cubes of cardboard, with one frail stem wavering forth) is planted outdoors in full soft growth the middle of March, this growth will be hurt by the inevitable cold winds, and almost always the growth will be killed to the ground and the plant will seem dead. (If this happens, leave it alone, and five times out of six there will be new growth the following spring and the plant will develop as if nothing had ever happened; but of course you lose a whole year.)
To prevent misery and death, all that's necessary is to check with the store and buy the plant as soon as it goes on sale, or within a week or two. Then, before it has developed all this soft nearly white pale growth, plant it in a pot and keep it on the back porch or a cool room. It will continue to grow, but do not plant it outdoors in its permanent position until mid-April. Be careful moving it from the pot to the garden; if you soak the dirt of the pot lavishly, you should be able to move the plant without the dirt's crumbling.
Give it some twigs or a stake or whatever you have, for it to start climbing on. It grows by twisting its leaf stems around a support, so the support should be thin. Do not expect it to loop itself firmly onto a post, but give it string or small twigs to get it started. In later months and years you will not need to worry much about it, since it will flop about contentedly and attach itself to whatever it finds handy.
In recent years tree peonies have been sold in cardboard boxes, and these are relatively quite cheap. Usually there is one bare stem, the size of a ring finger, with two or three fat red leaf buds ready to open. Again, in a shop, after some days the buds will open and the plant will start to grow, again reaching for the light and getting very soft and feeble.
I know from experience, however, that such plants will make excellent garden plants in two or three years, provided they are planted first in pots in the house, and set into their permanent garden places once the chance of bad freezes is past -- again, mid-April will do it.
Now if you are able to find the clematis or tree peony fully dormant, the leaves not yet expanded, you can plant directly into the garden, avoiding the intermediate step of the pot in the house. Give the still-dormant plant a bit of shelter from a few pine branches around it, not covering it to cut off the light, but around it rather as a shawl, and remove this once the weather warms up in late March.
Both these plants are easily damaged while young. They are worth a little trouble to ensure they get to mid-April without being damaged by premature planting out.
If, by the way, you can get your clematis in November or December, you plant them outdoors then and have no further problem, but most gardeners nowadays rely on the cardboard cartons in late February or March.