Okra Problems

Question: Why is my okra growing so slow this year and making so few fruit?

Answer: In the mid to deep south this has been an unusually cool spring (dang global warming - you never know how it will manifest itself ;) ). Okra is a heat loving plant that simply will not grow when the soil or the air temperature is cool. It is a hibiscus and cotton relative that loves the heat. Interestingly, the blooms are only open for a day and if not pollinated they will shrivel up and fall off without forming a pod.

Be patient and keep the plants watered and actively growing and when the weather really heats up and its too hot to be in the garden they will be bearing when other vegetables have bit the dust.

For a little more information and interesting history visit this UGA site.

Oak leaf blister

Question: Why would oak leaves start falling off the tree in the late spring or early summer?

Answer: Check the leaves closely for small spots that are often cup shaped. Some of these spots appear grayish while others are green, but all are characterized by small puckered areas. If this is what you are seeing it is likely a fungal disease called oak leaf blister. This particular disease affects many species of oaks and is a problem whenever our spring is wet and cool late into the season. Although it has been hot over the last month think back to early spring and you may recall we had a cool wet spring (in the mid-south US). Although infection took place much earlier you may only now be seeing leaf drop. On the plus side even heavy infestations are not a cause for concern.

Some of the infected leaves will not fall from the tree until the normal leaf drop period in early fall. When conditions are right and infected old leaves are preparing to drop for the winter, they will produce spores that infect the developing buds that will form the new spring leaves next year. This is the way the cycle repeats itself each year. If weather conditions are not right for infection next year you may not even see the disease. Again, the disease does not pose a serious threat to tree health so there is no need to spray with a pesticide. For information on other possible oak tree pest click here.

Mystery Muscadine

Last week I had what I thought was an easy question that forced me to dig deeper than I normally would have. A lady called with a question about her muscadine plant that she relocated to an arbor three years ago and she has never gotten any fruit off of it. I assumed she had a female flower type and no perfect flowered variety nearby. Typically you will find nurseries selling varieties that are either female or perfect flowered types. If you plant a female type alone you will not have fruit but many of the female varieties have desirable fruit. Therefore, they are planted with perfect flowered forms nearby to provide pollination.

This lady really wanted to know for sure so I asked her to bring a bloom sample in to get a closer look. After looking at the sample it was apparent she did not have a female variety as I originally assumed but a male plant that is totally incapable of fruiting (see photo above). Male plants are not uncommon in the wild but what really confused me was she said the plant was dug from an abandoned vineyard on her property. Why would anyone plant a male plant I wondered when a perfect flowered plant would produce pollen and fruit? When she told me the vineyard (she believed) had been planted in the 1940's that gave me a critical clue.

I pulled out an old textbook from my college days and found out that until 1948 there were no perfect flowered varieties available and growers were forced to plant male plants to act as pollinators for the female varieties. This lady had the bad luck of moving a male plant which were usually planted at a 1 to 8 ratio in these old vineyards. Of course in the wild you still find plenty of these male plants but they probably only exist in very old vineyards planted before perfect flowered forms became available.

Tomato Problems

Question: This year I decided to grow my own heirloom tomatoes because they are so expensive in the store but the lower leaves are dying and the problem is moving up the plant. Can you tell me what is going on and how can I stop the plant from dying? Also, I have heard a lot about tomatoes and salmonella lately – should I be concerned about my garden tomatoes?

Answer: Now you know why heirloom tomatoes are so expensive. Most of them have little or no disease resistance and they tend to make a lot of foliage compared to the amount of fruit produced. This is another reason for their expense plus a possible reason for increased disease. The large amount of foliage means the foliage stays wet longer after rain and dew. Wet foliage means increased foliar diseases like “early blight” which is the likely culprit on your plants. The relatively cool wet weather earlier this spring made for perfect conditions to spread early blight. Click here for other disease possibilites: http://www.aces.edu/pubs/docs/A/ANR-0895/

Early blight is the most common and widespread foliar disease on tomatoes in the southeast. If not controlled, this disease can severely damage fruit quality and lower yields. On young plants, dark brown, irregular spots form and completely encircle the stem, causing plants to quickly wither and die. On older plants like yours, the spots are restricted to one side of the stem. Leaf spots, which typically occur first on older leaves, begin as small (1/l6 to 1/8 inch in diameter), dark, irregular spots and enlarge to form larger spots up to ½ inch in diameter. Tissue surrounding these spots often will turn yellow, resulting in early defoliation. On severely infected plants, fruit may become sunscalded because of the lack of foliage for protection.
Once the disease becomes severe on individual plants control is unlikely. Removing infected leaves from the garden can help. Other cultural controls for this disease include; mulch to prevent soil splashing onto lower leaves, proper fertilization, don’t wet the foliage when watering, stake or cage the plants and prune off side shoots. Fungicides are also available and do a good job preventing disease but they don’t cure disease.
Let me elaborate on a couple of the cultural control options. Nitrogen fertilizer is a good thing for plants like tomatoes that grow fast but excessive fertility leads to growth that is often more susceptible to pest. There is a fine line between enough and too much fertilizer. If your plants are dark green and growing very fast you may have crossed the line. Along a related path you might want to prune excess growth off by removing side shoots called suckers. These suckers grow from the main shoot at an angle from leaf attachment points. In general they are less fruitful and the thick growth that results is more prone to disease because it is vigorous and causes the plant to dry slower after a rain or dew.
I have a couple thoughts about your salmonella question. First, salmonella is not a disease that tomatoes can contract but a contamination that can happen during harvest and/or packing. Second, it is possible to have salmonella contaminate even your garden tomatoes. As a precaution you should never apply fresh animal manure to the soil surface when vegetables are in the garden. Always compost animal manures well or till them into the soil before planting. Consider using a mulch around plants to reduce the risk of animal fecal matter splashing onto tomato fruit and other vegetables. Tomatoes that are home grown or vine ripened locally are very unlikely to pose a serious health risk. Nevertheless, even your own garden vegetables should be handled with clean hands and washed thoroughly before eating. You should take the same precautions you expect your favorite restaurants chef to take when handling vegetables to be eaten raw.

Squishy Squash

Question: My yellow summer squash is doing weird things this spring. Some are shriveling up on the ends, some have a fuzzy black growth on the ends, and others are just not growing but seem to get darker and tougher skins.

Answer: Congratulations, you have hit the squash problem jackpot or the squash disorder "perfect storm". In this case there are multiple reasons for the multiple problems. Let me take them in order:

First, poor pollination will cause poorly formed fruit and/or fruit end shriveling. Also, the dreaded calcium defeciency can cause similar symptoms as well. Cool soils can contributue to the lack of root growth and the lack of the plants ability to pick up the calcium.

Second, Choanephora fruit rot is favored by wet weather. Both blossoms and fruit are affected and fruit nearest the ground are more likely to become diseased. It is not unusual to find 30-40% of blossoms and/or fruit infected with the fungus. The growth looks like the picture above (from the The American Phytopathological Society website). On the plus side this disease is seldom long lived and will pass when weather conditions change.

Third, the very cool weather this spring (especially at night) has greatly slowed fruit enlargement and has led to slow growing fruit which matures (hence the darker color and tougher skin) without very much fruit enlargement. Pollination also affects fruit size and could be a contributing factor.

Warmer and drier weather will solve all the problems discussed and no treatments are needed.

Rhododendron Deadheading

I was out in the Birmingham Botanical Gardens admiring the last of the rhododendron blooms. The long and cooler than normal weather this spring has given us a long azalea and rhododendron bloom period. I think it is possible that the stress of last year may have also contributed to a big bloom show this spring. The plants looked stressed but they were filled with blooms. Sometimes when plants are under stress they will make a lot of bloom buds as a last ditch effort to reproduce itself. One way to reduce stress and to funnel energy into new growth is to dead-head old blooms. While out in the gardens we shot some video showing this task. Take a look here to see how this process is carried out.

The case of the missing tomato leaves.

One of my co-workers, David Hubbard had a question from a client who wanted to know what could have completely defoliated 36 tomato plants in a two night period. The damage was described as tomato stems and main branches remaining with no leaves or evidence left. My response was I felt it was too early for tomato hornworms or some other kind of caterpillar and it was likely a four legged rather than a six legged critter. (diagram from NCSU publication)

The client re-planted and decided to watch the garden the first night. He went out with a flash light and observed some bugs on the foliage. He treated the tomatoes with sevin dust and the next morning found large numbers of dead bugs at the base of the plants. He brought the bugs in for me to identify and they turned out to be vegetable weevils.

The interesting thing was the that these critters had never been a problem for this seasoned gardener of 30 years. When we discussed his recent gardening activities he reaveled one minor change in his normal modus operandi. Because of the drought of 2007 he had planted a large number of collards and turnips near his back porch where the water hose was available. Normally his greens were planted far away from his home. He recently destroyed the left over winter greens by tilling and then immediately planted tomato seedlings to the area. Upon investigation I noted that these greens were the host plants for the vegetable weevil larvae. My guess is when they became active the only food available were these tiny tomato plants and they completely stripped the foliage in short order.

The moral of the story is be careful to not jump to conclusion without a thorough investigation.