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June - 2009 Questions &Answers Compiled by David Rodriguez County Extension Agent-Horticulture Bexar County

Special thanks to Forrest W. Appleton and volunteers of the "Master Gardener Hotline" in support of the weekly gardening questions and answers.

Question:
My zucchini plants look beautiful, however in know time the fruit start withering and yellowing at the blossom end. Some of the summer squash fruit are also withering at about 2-3 inches in length. These shrivel and have brown spots on them. What is the problem and what can I do?
Answer:
This is the result of the lack of, or incomplete pollination. Either there are no male flowers open at the same time as the female flower or there are no pollinators (bees). You can assist by, on the day the flowers open, taking a male flower (the one with no immature fruit behind it), strip off the petals and rub it on the female parts of the open female flower (it will have a small fruit just behind it).

Question:
Are gold star Esperanzas poisonous to dogs and if you could, email me a list of poisons plants please.
Answer:
I can find nothing that indicates the Esperanza (Tecoma stans 'Gold Star') to be toxic to humans or animals. There is (to my knowledge) no list of ALL toxic plants. There are many lists on the internet. Just do a search using the plant name followed by the word toxic. Many animals and most people have the sense of not eating plants that have the potential of poisoning, especially when they are often bitter in taste.

Question:
How often do newly planted Vitex need to be watered? Despite all the rain we recently received, they were wilted when I came home today. They are approximately 2-3 feet tall.
Answer:
First of all, what rain are you referring to. We are still in an exceptional drought. You must remember that the plant is living within the small root ball that you planted until it can establish roots out into the surrounding soil. You should water that root ball whenever the soil in it feels dry to the touch when you stick your finger into in at least one inch deep.

Question:
My husband and I have been given conflicting advice on the benefits of aerating our St. Augustine lawn. He did it last year and he was very happy with the results. The landscaper today said that he recommends a liquid aeration of a chemical that will feed earth worms, make them move around and thus this moves the soil. What is your opinion? What is the best top dressing for a healthy lawn?
Answer:
Get another landscaper. However, anything that allows air, moisture and nutrients down into the root zone of the grass is beneficial. My preference is to do it with one of the plug pulling aerators that you can rent from any tool/machine rental place. For top dressing, I prefer fine compost with minimal amount of sand applied at a one inch layer. This process should occur every third year around late February through late April.

Question:
I have seen what looks to be a large red bottlebrush shrub growing in our area which is a heavy deer populated area. I tried to look on Yahoo to find what this variety of Bottlebrush might be, but have been unsuccessful. Is there a Red blooming Bottlebrush or something similar that is deer resistant?
Answer:
While I do not have first hand knowledge of this plant's resistance to deer, it is recommended to be so by many wholesale nurseries and even the city of Austin, and so I think it safe to assume that it is at least somewhat resistant. The plant in question is probably Callistemon citrinus.

Question:
I want to get rid of several large sago palms. How do I do it so that it is permanent?
Answer:
Cut them off at or just above ground level and immediately paint the exposed trunk with a concentrated herbicide containing Triclopyr such as Ortho® MAX Poison Ivy and Tough Brush Killer Concentrate or Green Light Cut Vine and Stump Killer. This will kill the roots.

Question:
I have a large bed of iris that I want to remove. What type of herbicide would kill out the plants? I want to replace them with dwarf Crape Myrtles.
Answer:
The bearded iris has such a shallow root system and the best manner would be to dig them out with a garden fork. A good solution might be to advertise "Free Iris - Dig your own." If you use a herbicide, the corms would still be in the ground, thus resulting in new growth.

Question:
I recently moved into a home where the previous residents used pecan shell mulch in all the beds. I now have been told that this mulch will attract mice and/or rats. Is this true? Obviously, I don't want either rodent around my home and need to know if I should replace all the mulch.
Answer:
The pecan mulch could have attracted rodents when it was first applied, especially if it is fresh from the shelling plant with any nut residual present. This mulch invariably has some nut meat left in it and this is the attraction. It should not be a problem now. However, many people use it as a deterrent for cats in the flowerbeds.

Question:
My red oleander is flowering now but the leaves closest to the top are turning yellow and dropping off. What could cause this to a normally healthy plant of two years?
Answer:
Oleanders are subject to a 'leaf scorch' which will cause the leaves to turn yellow/light brown and drop off. This disease is similar to the "Pierce's Disease" that has killed so many grape plants. There is no known cure at this time. Keep the dead leaves raked up and disposed of. Next spring cut the plants to the ground and dispose of the residue. They will come back from the roots and may (or may not) have the disease return.

Question:
There's a vine with orange daisy size and shape blooms. They bloomed all winter. They are not in the trumpet category. Any ideas?
Answer:
It is probably a Mexican Flame Vine (Senecio confusus). An added benefit of this vine is its resistance to the deer.

Question:
When is the best time to trim back the Lady Bank's rose?
Answer:
It should be pruned immediately following the spring bloom.

Question:
How do I eliminate a large patch of clover in my Bermuda grass?
Answer:
I doubt that you have clover and would probably bet that it is Oxalis. This plant is difficult to kill. I recommend that you use a herbicide containing 2-4D for broadleaf weed control. This product can be purchased in most nurseries/garden centers. Be sure to apply in accordance with the label instructions.

Question:
I was at the San Antonio Botanical Garden and came across an Indian Coral tree. It is beautiful! Can a person without a lot of horticultural knowledge grow this in north Bexar County?
Answer:
The Coral Bean tree/Indian Coral tree (Erythrina X bidwillii) does quite well throughout the San Antonio and surrounding areas. It requires no special treatment and is quite drought tolerant once established. However, it does have some detractors; freeze damage, borer problems, and wicked thorns.

Question:
How can one "over summer" geraniums in our area? Can they be put in deep shade where they would receive rainfall (if it ever rains again) but not be watered?
Answer:
The best way to do this is to purchase a variety that will bloom and can be enjoyed all summer. The Fantasia series 'Violet' and 'Strawberry Sizzle' will do this. It is not worthwhile to try to keep the common geraniums through the summer.

Question:
Does it harm plants to water with an over head sprinkler in the heat of the day?
Answer:
No. However, overhead sprinkling results in water loss due to evaporation. If you do water by a sprinkler, it is best to use it in early morning to reduce evaporation. Add water slowly so it will soak deeply into the soil. Always water early enough in the day to allow foliage to dry out before night to reduce disease problems. Consider trickle irrigation and mulches to conserve water. Also, if your water provider is SAWS, we are currently in Stage II restrictions. Within this stage, you can only water your lawn once a week, between 3-8 a.m. or 8-10 p.m. Your watering day is based on the last number of your address. Hand watering is OK any time, any day.

Question:
I use the mulch from the Bitters road brush site. I have been told that there is a possibility of spreading Oak Wilt to my trees. Is this true? If the mulch can spread Oak Wilt, is it advisable to use the mulch at all (as on my vegetables).
Answer:
You cannot spread Oak Wilt from tree trimmings. I would not use the mulch on the vegetable garden since it is too course; use it around trees and shrubs. Use shredded leaves and grass clippings in the garden and add extra (4 pounds rather than 3 pounds of 19-5-9 per 100 square feet) fertilizer when adding non-decomposed organic matter.

Question:
I've got some wonderful Crawford lettuce that has bolted and is flowering. What do I do to capture the lettuce seeds?
Answer:
When the flowers have finished and the tops of the flower stem looks like balls of fuzz cut them off into a brown paper bag and put in a hot, dry place. Let them sit and dry. Later you can shake them vigorously and the tiny black seed will fall to the bottom of the sack. You can separate them from the fuzz and store in an air tight container, such as a Ziploc bag and keep them in the refrigerator for the next desired planting.

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