THE USE OF SCREEN BOTTOM FLATS FOR SEEDLING PRODUCTION
Edward F. Frolich
Seedlings of many plants produce pronounced tap roots in their initial stage. This is especially characteristic of materials from arid and semi-arid areas such as the southwest of the United States and parts of Australia, South Africa, and the Mediterranean region. When transplanting from the seed flat to pots, it is necessary with these materials to drastically reduce the size of the root system in order to avoid bending of the roots. This very often results in loss of the seedling.
One way to overcome this problem is by root pruning the seedlings prior to the transplanting operation. In the past this was sometimes done by using a material toxic to roots in the bottom of the flat. Copper was most commonly used, either as a screen laid in the bottom of the flat, or by coating the flat heavily with copper naphthenate. This is effective in killing the growing point of the taproot, but there is a danger of getting an excess of copper into the seedlings, which could lead to various
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