The foliage of my river birch is yellow-green. Why?
In Iowa, the foliage of river birch (Betula nigra) often turns a sickly yellow-green. The yellow-green foliage is due to a deficiency of iron. The problem is referred to as iron chlorosis. Most soils in Iowa contain sufficient amounts of iron. However, in alkaline soils (those with a pH above 7.0), the river birch is unable to absorb adequate amounts of iron because much of it is in an insoluble form. Since many soils in Iowa are alkaline, chlorotic river birches are common in Iowa.
Correcting an iron chlorosis problem is difficult. One way to try to correct the problem is to lower the soil pH. Apply 1 to 2 pounds of elemental sulfur per 100 square feet in the area around the chlorotic tree. Broadcast the sulfur and then water it into the soil. Sulfur can be applied in both spring and fall. Lowering the soil pH is a slow and difficult process. It may take several years before the pH drops to desirable levels.
Another option is to apply iron to the soil. The best iron-containing materials are iron chelates. Iron chelates remain in a form available to trees for a longer period of time compared to other iron-containing materials. When using iron chelates, carefully follow label directions. Applications should be made in early spring.
Iron chlorosis is a difficult problem to correct. Efforts to treat iron chlorosis often are unsuccessful. Because of iron chlorosis problems, river birches are not recommended for alkaline soils in Iowa.
How often should I water my roses?
Modern roses, such as hybrid teas, floribundas and grandifloras, require watering during hot, dry weather. The frequency depends upon weather conditions and soil type. In most gardens, a deep soaking every seven to 10 days during dry weather is sufficient. Soak the soil to a depth of 8 to 12 inches. If possible, apply the water directly to the soil around each plant. Overhead watering wets the foliage and increases disease problems. If overhead watering is unavoidable, morning is the best time to water roses. Morning applications allow the foliage to dry quickly.
An excellent way to conserve soil moisture is by mulching. Possible mulches include wood chips, shredded bark, pine needles and cocoa bean hulls. Spread 2 to 4 inches of mulch around each rose or over the entire bed. Mulches also help to control weeds.
When should I harvest my beets?
Beets may be harvested when the roots are 1 inch in diameter. However, the main crop usually isn’t harvested until the roots are 1.5 to 3 inches in diameter. Beets larger than 3 inches in diameter are often tough and fibrous. Beets require approximately 50 to 70 days from planting until harvest.
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