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Q: Can I grow hazelnut trees or bushes here?

Q: Can I grow a walnut tree?

A: The problem with growing nut trees in this area is not keeping the tree alive. It is getting the tree to produce nuts. Walnut and hazelnut (filbert) trees are the most likely to succeed of the various possibilities. Some varieties certainly are more hardy than others, but it is possible to find varieties of either tree which are likely to stay alive in some areas of western Montana. However, we are at the extreme end of their growing range. That means that problems are inevitable in some years. Many trees never produce a nut, no matter how long they live.

The most common reason for a tree's failure to produce is that the nuts never get started. Nut trees in general bloom early in the spring. In all too many years the flowers are killed during one cold night. That ends the chance of a crop for that year. In other years when blossoms do not freeze and nuts develop through the summer, fall cold weather ends their growth before the nuts can fill out and mature. The frost-free season simply is not long enough to produce edible nuts with any consistency.

Of all the trees which can produce edible nuts, the ones most likely to succeed in western Montana are the European filbert (the commercial variety), the kind of English walnut called Carpathian (because it was introduced from the Carpathian Mountains of Poland), and the black walnut. The black walnut is the hardiest of the three, but its nuts—if they ever succeed in maturing—are an acquired taste. Black walnuts are grown mostly as timber trees, for their beautifully grained wood. Used in cabinet making, it is extremely valuable. There are horror stories of walnut tree rustlers operating with helicopter crews on dark nights.

Only if these trees can be planted in a protected microclimate is it worth trying to grow any of them for their nuts. I know, for example, of productive Carpathian walnut trees near Flathead Lake. I also know of hopeful walnut growers in the same area who have not succeeded. Montana nuts are a risky business at best.

Q: If I leave pieces of plants on the surface of my vegetable garden instead of first putting them into the compost pile to decay, what happens to the nutrients in the dead plants? Will they stay in the garden soil or evaporate into the air? Or is it necessary to break down plants in compost before the nutrients are available at all?

A: The chemicals in dead plants which feed new growth will be available in sheet compost, which is the term for the undigested pieces left on the top of garden beds. Horticulturists believe that nutrients will be released for about two years. They will be mixed into the top few inches of soil by those miracle workers of the garden, earthworms. Although compost is rich in organic matter and its growth-enhancing nutrients, its greatest benefit in a garden is probably its ability to improve soil structure and texture.

Q: I have had a patch of variegated snow on the mountain for several years. Recently I have noticed some plain green leaves among the ones with white edges. Is it from old age? Is there anything to do, to prevent the plants all turning to plain green?

A: Color variegation in leaves is a fascinating, complicated, and not always understood fact of plant life. Leaves are green because they contain chlorophyll, which is the source of energy for all life on earth. Because chlorophyll is so important, it would seem unlikely for plants to create leaves without chlorophyll, and that is true. Leaves with white or yellow edges, stripes, or spots seldom occur in nature. When leaf variegation does happen naturally, it is usually in the understory of tropical rainforests. Why? There are no answers, only speculations. Because house plants often originated in rain forests, though, house plants are among the most variegated kinds of plants on earth.

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Some plant variegation—striped tulips for example—is caused by a viral infection, and it may be that many naturally variegated leaves are infected by a virus. This is true of hostas with white and yellow in their leaves. As far as anyone knows, those light areas are all caused by a virus. Although viral variegation is rare, it is usually stable; i.e., it lasts a long time and reappears in new plants grown from cuttings and usually from seeds. Sometimes these virus-caused variegations make weak plants. Sometimes they do not.

There would be fewer variegated plants in the world if people did not find them beautiful. Nearly everyone likes variegated leaves and will work to keep their color patterns. In the case of your snow on the mountain, you can best preserve it by cutting off all the shoots with plain green leaves as soon as you notice them. Since they have more chlorophyll, the plain shoots are stronger. They would eventually push aside the variegated shoots if left alone. Removing all the competition often is the best way to preserve variegated shoots.

Even so, the variegation may vanish unexpectedly. Most leaf variegation is genetic, not virus caused. Most often the genetic change is a random one which soon disappears. It is nearly impossible to keep these random changes for long. Inherited genetic changes are uncommon, but they are stable and can be passed along to succeeding generations.

A seemingly stable genetic variegation is presumably the way your snow on the mountain occurred. Now it is illustrating the phenomenon called reversion, where some parts of a plant return to plain green. No one understands why this happens, so there is no way to protect the variegated leaves except by cutting off the stronger plain ones. Sometimes that works; sometimes it fails. There are plants which growers want to keep variegated; nurserymen do everything they can think of to continue the color pattern, and still the plant changes back to plain green after many years of being variegated.

Sometimes one or more shoots of a variegated plant change in the other direction, becoming all white. No one understands that phenomenon either, but it always is short-lived because it is fatal. No plant can live without some green leaves to make food.

There is also the kind of variegation where, instead of having no color, areas of leaves are striped or spotted with different colors—often red, purple, or orange. Coleus is an example. The fanciful colors are naturally in the leaves but are hidden underneath the green chlorophyll. When some of the chlorophyll vanishes, the underlying colors appear.