European White Birch Trees: Their Characteristics and Requirements

Questions from Theresa:
I have 7 birch trees in my yard and all get roughly the same amt of water & sunlight. Four are doing very well – 3 are not. In one area – there’s a cluster of 3 where one is doing beautifully, 2 have sparse leaves. In a different area shared with statice, one is doing quite poorly — limp branches & trunk, some green leaves but not many.

Any idea what I could do to help make them healthy?

Answer from Pat:
I gather from your email that you are having problems with birch trees but you fail to tell me what climate zone you live in. Nor do you give me the common or variety name for the birches you are growing. This makes it difficult for me to give you a precise answer. There are at least eight various species of birch trees (Betula) sold in the west. Two of them are not adapted to warm-winter climates. Some will only grow in the mountains. Two are native species; the others are exotic. At least two of the above species have several named varieties, numbering about twelve different selections in all. All of these birches vary in their appearance, characteristics, and problems, but most of them are native to stream banks where they can have their feet in water, their head in the sun, and their lower trunk in shade.

I am now going to don my Sherlock Holmes hat and consider first where you might live. You mention that there is some statice growing near some of the trees. This leads me to believe that you mean sea lavender (LImonium perezii). Sea lavender is a drought-resistant plant with masses of blue flowers that’s native to the Mediterranean region and thus grows well with little water in coastal Southern California where you probably live and might also have a drought-resistant garden, which would not be compatible with birch trees.

Since you have a clump of three birches together, I can guess that all your trees are probably European white birch (Betula pendula), since white birches (sometimes called silver birch) are often sold in clumps of three, and other birch trees are seldom sold that way. This is a truly beautiful tree, but I regret you have so many because silver birch is poorly adapted to growing in Southern California. European white birch trees or silver birch are extremely prone to an insect called the bronze bark borer and may be subject also to leaf miners. Take a close look at the bark of the trees that are doing poorly. If you see small round holes and frass, that is the problem. Look also at the leaves. Little wandering pathways of lighter color than the surrounding leaf show this pest has invaded the leaf.

Leaf miners weaken birch trees, but borers kill them. Once a tree shows serious decline from borer attack there is little one can do to cure the problem. They will always attack the weakest trees first and this includes drought-stressed trees, those suffering from a lack of nutrients, and those that are growing in shallow or poorly-drained soils. Trees that have an ample supply of water and fertilizer and are growing in ideal conditions and climate zones are better able to fight off borers, but these days it’s difficult or impossible to give birch trees what they want. Birch trees do not like hot, dry areas. They need rich, deep, well-drained soil and a constant supply of water. They simply cannot survive on a drip system or low impact sprinkler system. They grow best where the lower part of the trunk and the root run is cool and shaded with the top in sunlight, but in warmer regions they appreciate some afternoon shade.

The only yard I have ever seen with a grove of white birch trees that thrived in Southern California for many years was in Brentwood, California. About fifteen European white birches were planted on several mounds solidly covered in summer with impatiens and in winter with cinerarias. Around all these mounded flower beds with birches in them and snaking in and out between the mounds was an emerald-green lawn that looked like a perfect carpet, not a blade out of place. The gardeners fed the lawn at least once a month so the trees were benefitting from all that nutrition also. They looked happy and healthy. On the west side of the garden was another garden with a stream running through it and tall native sycamores that gave the birches some shade in the afternoon on hot days. This garden was at the foot of a canyon. The soil was extremely well-drained, friable decomposed granite. To keep it moist, a sprinkler system went on for half an hour every morning in warm weather before dawn. During the day the ground was continually moist but the grass-blades dry. The place looked like a stage set. If anyone gardened that way today they might be in danger of being prosecuted for wasting our precious imported water.

This above description of a healthy, pest-free grove of birches should illustrate the problem you are facing in a time of increasing drought and water cutbacks. You can do your best to feed, water, and protect your trees from hot sun, but I am really sorry to report that unless you live in a canyon where there is ample ground water, your chances for permanent success are slight.