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

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

Question:
David, I have a passion vine. Some kind of insect or worm has been eating the leaves. I have used insect sprays but it doesn't seem to help. How can I propagate the more passion vines from this one? I need your help, don't want to lose this one.
Answer:
The foliage of the Passionflower vines is the favored larval food for the Gulf Fritillary butterfly and they will find it and will eat it. You can control them with one of the Bacillus thuringiensis (Bt) pesticides. This is a safe pesticide that is harmless to everything except caterpillars. All good nurseries/garden centers carry it. It should be applied at the first sign of damage and then reapplied weekly. However, you must realize that you are killing the future beautiful butterflies. This plant is propagated by layering or by cuttings.

Question:
Mr. Rodriguez, I have had New Gold lantana that grew very tall, however, I've seen it in other beds where is was low and spreading. Is there more than one type of New Gold lantana? Also, would you give me the names of trailing lantanas and their colors?
Answer:
New Gold lantana can be kept low by cutting it back to the ground each year whether it freezes or not. Since it is vegetatively propagated, all the lantanas are the same. The common, native trailing lantana is Lantana montevidensis. This comes in purple (lilac) and white.

Question:
Sir, I have a small area in full sun with very sandy soil. Which grass (Bermuda, zoysia, etc.) with low water requirements is best suited for these conditions? How do I prepare the soil for planting and when is the best time to plant?
Answer:
I recommend one of the Bermudagrasses. First, I would incorporate into the sandy soil a generous amount of compost. Four inches tilled into the top eight inches of soil would be good. Then you can either establish the turf with sod or seed. Certainly the seed would be less expensive. However, you would need to wait until about mid April to sow the seed as it needs very warm soil to germinate. You will have to water it daily to get it up and growing but once established, it will be as low water as any of the turfgrasses, needing about an inch of moisture per week to keep it at its best but will get by on much less.

Question:
Mr. Rodriguez, I have a backyard with indirect light. St. Augustine will not grow and I tried JaMur Zoysia and it died as well. What do you suggest?
Answer:
If St. Augustine will not grow in the available light; there is no turf grass that will. Your alternatives are to do some tree trimming to allow more light or landscape with plants that will survive in the shade complimented with hardscape (mulch, flagstone & etc).

Question:
Dave, I am getting ready to completely till my whole yard, spread some dirt and plant pallets of grass (basically redo my whole yard). While pulling weeds this weekend, I noticed I have grubs. Should I treat them before or after I till and what is the best product to use to kill the grubs?
Answer:
Grubs, at this time of the year, are not harming anything and would be very difficult to kill. You should treat for the grubs about two weeks after the last of the June bugs disappear (mid June - early July). Any one of the products sold in nursery/garden centers for grubs will work fine. Just ask your favorite nursery for one. This year the application of pesticides might be a month early due to their appearance.

Question:
Mr. Rodriguez, how much potting soil will it take to fill a 10" hanging basket? They will have nine plants per basket. I plan on starting the flowers by seed then transferring them to the basket.
Answer:
Certainly all 10-inch hanging baskets are not the same volume, but I think that a good estimate would be one gallon or four quarts. I would think that nine are a bit much for a 10-inch pot. I would recommend five plants at most.

Question:
Dave, one of my Red Tip photinia bushes started losing its color, gradually fading from green to yellow to almost white. It's not losing leaves but the fading is spreading to my other photinia bushes. What's wrong? This has been happening over a long period of several years.
Answer:
This is the telltale sign of severe iron deficiency which many Red Tip photinias suffer from when grown in alkaline soil. There is little that can be done to correct it. I recommend that you replace the photinias with a better adapted plant.

Question:
Mr. Rodriguez, I recently put in a swimming pool and have been searching for appropriate trees to plant in my yard. One of the trees that I want to plant would be right by the pool to shade my air conditioner units. So, I am looking for a tree where both the limbs and roots are 20 ft in diameter or less and just as tall. It should have minimal litter and no berries. The tree would be located in an irrigated lawn in full sun.
Answer:
Such a tree doesn't exist. The roots of all trees extend well beyond the drip line and all trees drop something all the time. You might consider a Loquat (Eriobotrya japonica) or a large Indian Hawthorn (Rhaphiolepis indica) 'Majestic Beauty'.

Question:
Please tell me what would grow well in a window box that receives very little sun.
Answer:
Impatiens and begonias are very good plants for the shade and do great in containers. Be sure to incorporate some slow release fertilizer into the soil when you plant them and then reapply about once a month.

Question:
Mr. Rodriguez, please tell me what would grow well in a window box that receives very little sun.
Answer:
Impatiens and begonias are very good plants for the shade and do great in containers. Be sure to incorporate some slow release fertilizer (such as Osmocote 14-14-14) into the soil when you plant and then reapply about once a month.

Question:
David, we are in the process of building a home. The ground conditions are sand, sand, and more sand. While we plan to bring in some topsoil for a lawn - what would be the best type of grass for these conditions? There is no shade around the house at this point, although the surrounding area has black jack and post oaks in abundance - I am trying to choose grass that is easy to plant, grows rapidly, and is drought tolerant.
Answer:
The best grass for you is Bermuda (Tiff 419 sod or Sahara seed). It can be established either by seeding or laying sod. Certainly the seeding is less expensive but much more labor intensive in the beginning. The soil must be quite warm for the seed to germinate so I would not advise sowing it until after mid April. You can put down sod at any time.

Question:
Dave, I need to know the name of a fertilizer with a 19- 5- 9 ratio. I have also been told to make sure that it is 50% SCU. I am having a difficult time in finding it.
Answer:
Easy-Gro Premium Lawn Food (slow-release 19-5-9 with 2% iron) is the main one. However, this same fertilizer is packaged for many independent nurseries using their own name. The 50% SCU is the slow release part of the fertilizer meaning that 50% of the nitrogen is derived from Sulfur encapsulated Urea. This product is widely available in the San Antonio area.

Question:
We have numerous Mountain Laurel trees which are in excess of 12 feet tall & apparently have never been trimmed. They have many of the seed pods on them, but have not bloomed since we've lived there (we moved in around this time last year). Is there anything special we should be doing to them & should they be trimmed back at some point during the year?
Answer:
Several factors impact the bloom on Mountain Laurels. They set their bloom buds in the summer and fall, and a hard freeze can kill them. They also are affected by the lack of moisture during droughts like we have had. There is nothing that you need to do. They will be prettier if the old seed pods are clipped off, but that will not affect the bloom. If you do not see long snake-like gray bloom buds at the end of the branches, you are probably not going to get any blooms this year.

Question:
Our boxwoods are very healthy. They measure 46 inches high and 42 inches wide. If age is a factor, they are approximately 25 years old. We would like to trim about 10 inches on both height and width. When is a good time of year to do this? Can we cut this much at one time? How often can we trim them a year?
Answer:
You can cut them back this much now. You must be prepared for several months of 'ugly' as you will have cut off most of the vegetation. They should come back nicely. When you get them back to the size you want, they can be repeatedly sheared as often as you wish to keep them at that size.

Question:
Can celery be grown successfully in gardens?
Answer:
Yes, under the proper conditions. Celery does best in cool weather when nighttime temperatures are around 50º F. and average daytime temperatures stay between 60º to 70º F. Since celery requires these conditions for as long as five-to-six months, the optimum planting time is mid to late summer with harvesting in early winter. Prolonged periods of cold temperature during early growth or excessively high temperatures near maturity will start the formation of a seed stalk. In northern areas set out celery transplants early to avoid damage from low temperatures. In the southern regions seed or transplant in late fall for harvest during mid-winter.

Question:
Will freezing weather kill or damage celery?
Answer:
Yes. Young celery plants can be damaged by near freezing temperatures. At or near maturity celery plants can withstand frost or freezing weather although temperatures much below 30º F. can kill or damage them.

Question:
What causes the stout and often bitter flavor?
Answer:
Improper environmental conditions, primarily high temperatures at maturity along with stress conditions such as drought or low fertility can cause off-flavored celery. For maximum quality celery must be grown under suitable environmental conditions and a constant level of available moisture.

Question:
What is meant by blanching celery?
Answer:
Blanched celery lacks green color. Blanched celery is less popular and the self-blanching varieties are difficult to locate. Most gardeners prefer green celery because it is more nutritious. Green varieties can be blanched if light is blocked from the plant by placing strong paper or boards on each side of the plants or by loosely wrapping individual plants with paper two-to-three weeks before harvesting.

Question:
I plant celery seed and they won't grow. Then when it is too late in the season many of the seeds I planted come up. How can I get the seed to grow at the right time?
Answer:
Soil temperatures must be between 60º to 70º F. with a daily fluctuation to 60º or lower at night. Adequate and constant moisture is necessary for seed germination.