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August - 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:
We are buying a house with two multi-trunk crape myrtles around the front door. The trees are so beautiful and healthy but really hide the wonderful entry way to the house. We would love to transplant them to the back yard but don't know if that is possible. We have heard that we should not trim them back, not sure why, but we need some advice?
Answer:
Transplanting the crape myrtles is an option but I would not recommend that you try to do it yourselves. This would best be done by professionals with the proper equipment. Look in the Yellow Pages for tree moving or tree transplanting. There is no reason why crape myrtles should not be pruned. The common practice of pollarding (cutting back to a stump) is not a recommended method of pruning. Selectively cutting branches back to the main trunk can effectively reduce the size or thin out the canopy of the trees.

Question:
I want to use a plant to border an area of rock patio, to separate it from the planted beds that surround the patio area and to keep the cedar mulch from drifting out onto the rock patio. We had monkey grass along this border, but dug it up a couple of years ago. Do you have suggestions?
Answer:
I can only assume that you dug the monkey grass up because it did not do well in the full sun, thus burning on the tips. I do not know of another low, tight growing plant that will do what you wish (although cedar mulch shouldn't drift much). My recommendation would be to install some kind of edging such as the steel or black rubber.

Question:
My Mexican Bush Sage is not growing or flowering? What can I do to help it? It receives approximately 4 to 5 hours of morning sunlight.
Answer:
Mexican Bush Sage (Salvia leucantha) does its blooming in the fall (Sept - Nov). It also does best with more sunlight than yours is receiving.

Question:
I have five esperanza plants surrounding my back yard deck. Two of the plants are full of blooms and are absolutely beautiful. The other three have not bloomed and the plants are growing considerably larger than the ones that have bloomed. What could be wrong? Is there anything I can do to make them bloom?
Answer:
You can remove the three esperanza 'Yellow Bell' and replace them with the esperanza 'Gold Star. Make sure that the new ones you buy are labeled with the name 'Gold Star' and that they are blooming at the time of purchase.

Question:
I need to know about Thunbergia vine and where to purchase it. Also, does it grow well here?
Answer:
There are several species of the Thunbergia vines. The most common one for this area is Black-eyed Susan vine (Thunbergia alata). It is a tropical perennial that we grow as an annual from seed. Seeds are available from many of the mail order, online seed catalogs, and from your local nursery/garden center seed rack. The plant can be grown almost anywhere as long as it has a well drained soil and receives a sufficient amount of moisture.

Question:
Why do my zinnias have powdery mildew?
Answer:
Unfortunately, this occurs commonly on zinnias which have some type of a stress issue. Zinnias need to be planted in full sun and in an area with good air circulation. The powdery mildew can be controlled by spraying with a wide spectrum fungicide such as, Ortho Garden Disease Control, Ortho® Rose Pride® Disease Control Concentrate, Green Light Fung-Away® Fungicide and others.

Question:
My jalapeño plants are doing well and don't seem to have any bug problems but the blooms keep falling off. I have been told to water them twice a day instead of just in the morning. The plants are in a raised bed and have good drainage, but their blooms still keep dropping off! Someone suggested I use the Tomato Blossom Set for tomato blossoms. Should I try that? Is it too hot? What is the problem?
Answer:
Yes, it is too hot. Peppers set fruit best when the temperatures are above 60° F but below 90° F. Any fruit set when the temperatures are outside this range will, most likely, be small, thin-walled and misshapen.

Question:
I have some Lily of the Nile plants and need to know on how to grow them.
Answer:
Agapanthus (Lily of the Nile) should be planted in an area that gets morning sun but has some protection from the hot afternoon sun. They need a well drained soil too. Plant them so that the bulb is covered by about twice its height. They should be fertilized each spring with a good slow release fertilizer such as 19-5-9. If you plant them now, you must be very careful to keep the soil around them just moist (not saturated) and never let them dry out.

Question:
We have a compost bin from which we replenish compost into our flower beds. When distributing compost in flower beds, is it appropriate to place the compost directly on the root ball of the plant? Specifically, if compost is placed directly on the root ball of the plant, will the plant die?
Answer:
Compost is most effective when incorporated into the soil. When you use it as a mulch, as you describe, you give it a job that can just as well be done with rocks, leaves, newspapers or anything else that covers the surface of the ground. If this is the way you choose to use it, it will do a good job and could in no way kill your plants. It is always best to keep mulch from touching the trunks (stems) of the plants; otherwise it does not matter where you put it.

Question:
Is it wise to fertilize St. Augustine grass during this period of drought? We are due for our next application from our fertilizer company and I am just thinking that we should not do it.
Answer:
With our current (and expected even stricter) water restrictions I do not recommend that you do anything that is going to promote new growth. Just concentrate on giving the grass enough water to keep it alive but no fertilizer until mid-October.

Question:
As the heat and sun starts to take a toll on the garden, should I put a shade cloth over it, if so, how much? I have a 15 foot square garden with tomatoes, peppers, beans, beets, and carrots planted. It gets sun most of the day.
Answer:
No, I do not recommend the use of shade cloth in the vegetable garden. Next to adequate moisture and proper nutrition, sunlight is the most important ingredient for a vegetable garden. If you make sure that the garden gets the moisture it requires, those plants can and will handle the sunshine.

Question:
I planted a jalapeño plant in May and it hasn't really done anything. In fact, the leaves are a yellowish color and the bottom leaves have fallen off. I moved it to my square foot garden plot and it still has the yellow leaves and has only one small pepper. I never seem to have much luck with jalapeños. What should I do?
Answer:
It sounds like the plant is suffering from lack of necessary nutrients and excessive day and night temperatures. Jalapeños plants usually respond to our growing conditions much better than bell and other varieties of peppers. However, it will do best when planted early (March 15) so that it can grow and set fruit before the weather gets intolerably hot. I recommend fertilizing with high nitrogen, slow release fertilizer like 19-5-9. Just try to keep it alive and healthy until the weather cools enough to allow it to set fruit for the fall.

Question:
We are moving into a new home in the area and will be starting a new landscape with bermudagrass. The soil is rocky and there are not many trees on our lot. I want to plant a few trees for shade. I'm considering Cedar elm, Bur oak, and Lacey oak as choices to plant. I've never had bermuda grass and I want to make sure that grass will grow under the trees as they mature and provide more shade. I have areas in my current yard where St. Augustine grass will not grow under some of our trees. I'm not sure what type of trees they are and I don't want this to happen in my new yard. Are the trees I mentioned good choices or do you have other suggestions?
Answer:
Bermuda grass is a fine turf selection for home lawns. However, it is much less tolerant of shade than St. Augustine grass. If the trees provide enough shade, the shade will normally degrade and/or prohibit growth of the turfgrass. Your bermuda grass will be fine for a few years, but regardless of the tree you plant, the grass will suffer as the tree grows.

Question:
I have a two year old Mandevilla vine in a container on my patio. The leaves have started turning yellow. I check the water level regularly and keep the soil moist. The vine gets the afternoon sun. It did great last year and bloomed until frost. What am I doing wrong?
Answer:
It will naturally have some leaves turn yellow and drop off. However, since I am sure that you have had to water it very frequently, it may need to be fertilized. I recommend that you use a slow release fertilizer for containers, such as Osmocote 14-14-14 in the amount recommended on the label for the size container you are using. This will release some fertilizer each time you water it. The fertilizer will need to be replenished about every 30-60 days.

Question:
I have a three inch plumeria plant with three leaves on it, in a four inch pot. I would like to know what kind of soil it needs, the size of pot, and how much fertilizer to use. Where should I keep it for the summer and winter?
Answer:
Transplant from a four inch to at least a one gallon container. You can use any good quality potting mix heavy with enriched compost. Fertilize with Osmocote slow release 14-14-14 analysis in accordance with the instructions on the label. The one gallon container should be fine until next spring. Plumerias grow and blossom best in full sun. Bring the plant into a protected location when the temperature goes down to 45° F or below. An unheated garage is ideal. It will lose its leaves and will need enough water to keep the plant from desiccating, maybe a cup a month. When the temperatures return to above 50° F and no frosts or freezes are predicted, you can re-pot it into a five gal container to reside there for several years.

Question:
My question is about pruning my Pride of Barbados. After the bloom falls, should the branch be pruned?
Answer:
When all of the blossoms have fallen off the bloom spike, cut it off the branch to which it was attached.

Question:
What kind of apple can best be grown in San Antonio?
Answer:
None of the apples do well here as they do not like the high alkaline soil and the lack of cold weather. If you decide to plant, I would recommend Dorsett Golden, Ein Shemer or Anna for their low chill requirement.

Question:
I have some chili pequín seeds from one of my plants. What is the best way to start them?
Answer:
If you have fresh seed, still in the red pepper pod, just squeeze them out into some good potting soil or in the ground where you want them to grow. Cover them about 1/4 inch deep and keep the soil moist but not saturated. They should soon germinate. If the seeds are dry, put them between layers of moist paper towel and place in a Ziploc bag in a warm shady place. Check them frequently (after several days). As soon as they start sprouting, plant them in good potting mix or in the ground, again about 1/4 inch deep.

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