Northeast Florida Gardening Q & A: Cracking Tomatoes, Spiders, Sumac

Why are your tomatoes cracking? Name this pretty spider. Identifying poison sumac. Nassau County, Florida Extension expert answer questions.

Argiope Spider, Florida
Argiope Spider, Florida
EDITOR’S NOTE: A University of Florida faculty member and Nassau County Extension Horticultural Agent, Rebecca Jordi addresses some of the questions she receives about landscaping and gardening in northeast Florida. The Extension also offers helpful clinics throughout the year, providing assistance to local gardeners on Amelia Island and in the surrounding areas of Nassau County, Florida.

QUESTION: I have this very pretty spider in my garden. It has a very interesting pattern on its abdomen consisting of yellow, black, and white colors. The web has a zig-zag pattern which I have never seen before. Can you tell me what it is? SB

JORDI: This spider is called an argiope or common black and yellow argiope spider. The argiope group contains numerous spiders. Their large, conspicuous webs can often be seen along the edge of forests. The black and yellow argiope can reach a length of 25 mm. Its characteristic silver carapace and yellow-and-black markings make it easy to identify. Argiope spiders tend to hang head down in the middle of a medium-sized web that has thickened, zigzag bands of silk in the center. The photograph is actually from the UF/IFAS Demonstration garden at the James S. Page Governmental Complex. This spider has formed a web using one of the light poles in the median. I was pulling collecting trash and pulling weeds from the area and almost ran right into the web. Running into the web would have made both of us very unhappy.

Spiders serve an important role as predators feeding on insects and small animals. Argiopes, though large, are generally not aggressive spiders. However, every spider possesses venom and each of us may react differently if bitten, therefore it is best to observe them from afar. Bites from spiders on children often occur when a youth is curious about the creature. No reason to teach children to be fearful but rather respectful. If someone is bitten and the area becomes red and/or inflamed around the bite then it is best to consult a physician immediately.

Poison Sumac
Poison Sumac
QUESTION: How can I tell if I have the poisonous kind of sumac? CG

JORDI: The old adage, “three leaves let it be” does not apply to poison sumac, Toxicodendron vernix. Sumac leaves are classified as compound which means the petiole or stem arising from the bud has more than one leaf. Poison sumac has 7 to 13 leaflets. The edges of the leaflets are smooth and not toothed. Many plants put out new leaves in the spring which are pale green in color but poison sumac leaflets are bright orange making them easy to spot. These orange leaflets turn dark green and glossy as they mature. The underside of the leaflet becomes a pale green. The stem to which the leaflets attach is a red color which aides in identification once the poison sumac plant matures.

Poison sumac can grow into a large shrub or even become almost tree-like. Take great care if they need to be removed by wearing long sleeves, pants and gloves. Once shrubs have been removed be cautious about exposing skin to any part of the plant. Wash the clothing in a separate cycle from the rest of your laundry. Avoid exposure to burning brush as the smoke may irritate mouth, throat and lungs. Below is link to a publication from the University of Florida/IFAS which provides more information on sumac, poison ivy and poison oak. In addition, it provides an excellent drawing to help distinguish between other plants which may look similar to poison sumac. For those of you who camp and hike, this publication might be an important document to keep in your backpack. (Photo from Duke University).

QUESTION: My tomatoes are cracking in circles around the top. What causes this to happen? RD

Tomato Cracks
Tomato Cracks
JORDI: There are two different kinds of cracking commonly found on tomatoes. One of the cracks starts at the stem and flows downward toward the blossom end. This type of downward crack is called a radial crack. The other crack, which is the one you have, makes circles around the top of the fruit. It is possible to have both types on the same fruit.

Cracks are caused when the fruit internally grows more quickly than the outside. This fast internal growth spurt causes the external skin layer to split open forming a crack. There are varieties which have a resistance to cracking but that does not mean they cannot crack only that cracks will probably occur later in the maturing process. Environmental conditions such as huge temperature differences and/or inconsistent irrigation contribute to the formation of the cracks.

Not much can be done about the temperature variations especially when fruit is maturing during the spring however irrigation can be controlled by the home grower. Just be sure to water your tomatoes consistently but remember too much is not a good practice either. The vegetable is still safe to eat so there is no need to throw it away. (Photo from UF/IFAS).

Rebecca Jordi
Rebecca L. Jordi
University of Florida/IFAS
Nassau County Extension
Environmental Horticulture Agent III
543350 U. S. Highway #1
Callahan, FL 32011
904 548-1116 or 904 879-1019