TechNotes Jan. 27 - Florida Crabgrass, Ornamentals, Azaleas, Soil Temps

CRABGRASS COMMON TO FLORIDA. The five major species of crabgrass found in Florida are:
 
India crabgrass (Digitaria longiflora) – Summer annual or perennial (southern Florida) spreads by stolons.  Leaf blades are short.  Usually found on dry sites.
 
Southern crabgrass (Digitaria elliaris), also known as hairy crabgrass  – clumpy but spreads through rooting at notes Large leaves that are hairy. Found on dry areas.
 
Blanket crabgrass (Digitaria serotina) also known as rabbit or dwarf crabgrass – annual that can spread by stolons. The leaf blades are short. Differentiated from India by the presence of hairs on the leaves and sheath. Found on moist sites.
 
Tropical crabgrass (Digitaria bicornis) also known as Asian crabgrass – similar in appearance to southern crabgrass. Seedhead branches from the same point where smooth brances from several points. Found on dry sites.
 
Smooth crabgrass (Digitaria ischaemum) also known as small crabgrass – clumpy but will spread and root at nodes. The leaves are large. Found on dry sites.  In Florida, primarily found in the northern part of the State.

SUNLIGHT CAN BE TOUGH ON ORNAMENTALS. On cold winter days, sun scald can damage thin-barked trees like maple, plum, cherry and linden, and newly planted trees. Sun scald occurs when the sun heats up bark to the point where cambial activity occurs. If temperatures drop quickly from the sun being blocked by clouds, or building the tissue is killed. Symptoms of sun scald are characterized by sunken, dried or cracked areas of dead bark. The symptoms usually appear on the south or southwest side of a tree where the sun has warmed that portion of the trunk. To repair sun scald damage, cut the dead bark back to the live tissue, rounding off any sharp corners to facilitate healing.

Sunlight injury can also occur on evergreens during the winter months. Extended periods of bright sunlight causes the stomates on evergreens to open resulting in excessive moisture loss. Direct sunlight on the trunks and branches can cause freezing and thawing of the plant parts resulting in drying or cracking. Young deciduous trees may take several years before they develop enough canopy to protect the trunk and branches from freezing and thawing caused by direct sunlight. The trunks of the trees should be covered with plastic protector with burlap wrapping. Black plastic should be avoided because during the day heat can build up inside increasing the temperature fluctuation between day and night temperatures.

PLANTING AZALEAS. Azaleas growing in the southeastern United States can be planted anytime of the year. The most common time is in early spring when the plants are flowering. One advantage to this time of purchasing and planting is that the flower color is more easily matched. However, planting azaleas in the winter is a good time to get the plants established prior to the warm hot summer weather. When establishing azaleas be aware that planting them under shallow-rooted trees may deprive azaleas of water and nutrients. Evergreens and tall shrubs make good windbreaks and attractive backgrounds.