Pencil in Some Privacy

By Scott Aker
Special to The Washington Post
Thursday, August 18, 2005

Q I live in a condo with a large balcony that gets lots of morning sun and afternoon shade. I would like to grow plants that would live in deep pots and grow tall and thick to act as a screen to the next balcony. I am looking for a plant that is fast growing, but not huge or high maintenance. The space I need to fill is three feet long, six feet tall and two feet deep. If bamboo is the answer, which variety should I choose? Do you have any other recommendations?

A A perfect solution would be a large trough or container planted with some upright evergreens. Sky Pencil Japanese holly comes to mind. It will do well in a container as long as you water it faithfully and the container has good drainage. Japanese hollies dislike extremes of wetness and drought. Sky Pencil will survive outdoors through the winter though any measures to minimize wild temperature swings will help avoid problems. It's worth wrapping the container in winter with fiberglass insulation placed snugly on all sides, to moderate soil temperatures, prevent rapid freezing and thawing and to keep moisture in the root zone.

You will need several plants for the space you describe because Sky Pencil grows no wider than about one foot.

Many bamboos can be grown in containers, but they tend to develop a fountain shape rather than a strictly upright form. They may end up taking up more space on your balcony than you are really willing to give up.

In the past couple of years I have had a few daffodil clumps grow well except that when the buds form, they turn brown and soft and don't bloom. I don't recall the varieties.

I amended the soil when I planted the bulbs but the soil is mostly clay. Could this be the cause, and how would I fix it?

Some of the double varieties of daffodils, such as the heirloom variety Rip van Winkle, are known for this problem. It is not caused by a disease but is the result of the large amount of petal tissue that must expand rapidly as the flowers bloom. If ample moisture is not available, if the humidity is low, or if the sun is a bit bright where the daffodils are planted, the petal tissue will be deprived of water and the whole flower will turn brown and wither.

It is best to plant double-flowered daffodils in a location where they will get some shade, particularly in the afternoon.

Another key requirement is that the roots can spread as widely and deeply as possible; perhaps your clay soil is having an effect. Make sure that the soil is generously amended with decayed organic matter. More importantly, the soil must have good internal drainage. If you improve the top six inches of soil, but there is an impervious layer below this, the roots will be saturated during wet weather and will die due to lack of oxygen. Raised beds or buried perforated drain pipes are a must if your soil is tight clay, even for daffodils, which will tolerate a bit of excess moisture from time to time.

A further cause, especially if yours are single-flowered varieties, is a pest named the narcissus bulb fly. This bee-like insect lays its eggs on the foliage, and the larvae find their way to the bulb. The larva then feeds on the bottom of the bulb, damaging the basal plate from which new roots and new top growth arise. One of the most striking symptoms is foliage that is weak and does not grow to normal size. You say the foliage is healthy, so perhaps we can eliminate this possibility.

Finally, it could be that your daffodils are in a location that is too shady. While exposed sites can cause problems for heavily double-flowered varieties, most daffodils need light to bloom best. That means a location in full sunlight, or in light shade provided by a high canopy of mature trees or a spot that gets sunlight for the morning hours.

Where daffodils don't get enough light, flowers will wither before they have a chance to open, and the bulbs will dwindle and disappear in time.

With bulb-buying season approaching, spare a thought then for good locations for your daffodils.

Scott Aker is a horticulturist at the U.S. National Arboretum.

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