Weekly Home Horticulture Column
Rain Shutoff Device | Cucumbers (7/12/2014)
Snails | Sago Palm Flower (6/28/2014)
Citrus Scab | Philodendron Selloum (6/14/2014)
Magnolias | Thatch (5/31/2014)
Annuals | Lemon Grass (5/17/2014)
Plumbago | Boston Fern (5/3/2014)
Amaryllis | Sweet Potatoes (4/19/2014)
Azaleas | Cutworms (4/5/2014)
Q. I recently heard a radio ad saying that the law requires I have a rainfall shut-off device on my automatic irrigation system. Do I really need one, and why?
A. With all the wonderful summer rains we have been getting in North Central Florida, having a rain shut-off device is a great idea. Beyond a great idea, it also is the law.
Florida law requires that any person who purchases and installs an irrigation system must properly install and maintain a functioning rain shut-off device. These devices do just what their name suggests; they shut off the irrigation system when they detect rainfall.
This prevents your sprinklers from irrigating in the middle of a rainstorm or after we have had a heavy rainfall. It also is the right thing to do for the health of your landscape and for our environment.
These rain shut-off devices conserve water by preventing over irrigation when we have been getting enough rain. This prevents overwatering, which can promote diseases in the turf grass. These devices also help to protect surface and groundwater. Surface water runoff and water that percolates deep into the soil can transport excess fertilizers and pollutants into the groundwater and our ponds and creeks. The most common type of rain shut-off device is one that has absorbent discs that expand and contract with collected moisture.
When the discs expand to the preset limit, the irrigation system shuts off. Install the shut-off device where it will be exposed to straight rainfall — not under a tree or in the path of your sprinklers.
It is important to test the device because the one that was installed with your system may or may not be functioning anymore. Using a rain shut-off device saves water and money, and is healthier for your landscape. To learn more about these devices and how to test them, visit the University of Florida's IFAS Extension website at www.solutionsforyourlife.com.
I planted what I thought were green straight cucumber plants from a garden center this spring. They grew well, flowered, but the cucumbers they produced were yellow and shaped like a ball. Did they revert back to a different cucumber type, or did I do something wrong?
If you saved your label or tag, check to make sure you didn't buy lemon cucumber plants. This type has fruit that are round and yellow. If that is not the case, it could be from cultural problems. All vegetables need regular fertilizing as they grow; if the plants were nutrient deficient, it could cause odd-shaped cukes. Irregular watering or moisture stress also can cause fruit to be rounded or deformed. It happens when the plant is somewhat dry when the cucumber is developing, and then when we get a very heavy rain, the cukes blow up like a balloon. To prevent this in the future, maintain good soil moisture by using a drip system on a regular basis. For practical answers to gardening questions, contact the UF/IFAS Alachua County Master Gardeners at 352/955-2402.
Q. I think snails are eating my plants. I don't always see them eating, but there are holes in some of my plant leaves, especially on my margarita sweet potato vine. Is there anything I can do? They are about the size of a dime or a little smaller.
A. Florida is home to a number of terrestrial snails, many are native, and we have a few that have been introduced. The one that has a hearty appetite for our North Florida plants is the Asian tramp snail. They are mollusks and normally hide out in moist areas of your landscape.
Snails can cause a great deal of damage to the plants they feed on. You will see them on leaves, but they will feed on all plant parts.
First, you will notice irregular holes in the leaves or clipped off stems or tips. Not all feeding damage is snail-related, so look for the tell-tale snail calling card of slime trails on the leaves or surrounding surfaces.
A good management strategy to control snail damage relies on a combination of methods. The first thing to do is to eliminate their hiding places. They will hide under thick mulch, boards or debris. In areas like wooden decks or ledges, regularly remove the snails. Snails can be a sign of an overwatered landscape. Make sure you are only watering one-half to three-quarters of an inch when you water. With all the rain we have been getting this summer, evaluate whether you even need to be irrigating.
Handpicking snails can be effective if you do it often. Wear gloves whenever handling snails, and discard them in a bucket filled with salty water. You also can make a trap for snails by putting a piece of cardboard on the ground overnight near where the damage is occurring. The snails will move under the dew-moistened cardboard, and you will be able to remove them from the area. Beer traps can be used to get snails, too. Simply pour beer and a few slices of banana in a steep-sided bowl. The snails are drawn to the smell and crawl in, but they cannot crawl out. Barriers such as copper flashing or screen can keep snails out of plant beds.
Also, a barrier of diatomaceous earth, available at retail garden centers, can stop snails from moving into a landscaped bed. Diatomaceous earth needs to be reapplied after a heavy rain or irrigation because it washes away. There are a couple of pesticides such as metaldehyde that can kill them. Poisons should be used with caution around children and pets, so be sure to read the pesticide label carefully. An organic alternative to the poison is a product that contains iron phosphate. When the snails ingest the iron, they stop feeding.
For more information about garden snails, visit the University of Florida's Extension website www.solutionsforyourlife.com
My sago palm has sent up a giant cone from the center. Should I cut it out or leave it alone?
Sago palm is a common cycad that is used in our North Central Florida landscapes. Cycads are an ancient plant, and they are dioecious, meaning they will either be a male plant or a female plant. The male sago palm send up a 12- to 18-inch cone structure almost every year. This cone contains pollen that then is carried to a female sago floral spike. The female sago flower may only appear once every two years; only the female sago palms will make seeds. The flower spikes do not need to be removed. They will fade out after about a month or two.
For more information about palms and cycads, call the UF/IFAS Alachua County Master Gardener Volunteers at 352-955-2402.
Q. Most of my green grapefruits on my tree are covered in bumpy brown warts. The fruit are very young, and now it looks like they are all ruined. Is there anything I can do to save the fruit?
A. The problem you are describing is fungal disease of tangerines, tangelos and grapefruits called citrus scab. This disease is worse during springs that are rainy or particularly humid. People usually first notice the corky brown bumps or warty growths on the fruit, and then discover more wart-like projections on the leaves and young stems. Badly affected leaves can become distorted and stunted.
This year's crop will have the scab lesions on the rind, and won't win any beauty contest, but the fruit still is edible and you can enjoy the juice. The time to control this disease is early in the season of next year. You will need to apply three applications of a copper fungicide to control this disease.
The first spray should be applied at about one-quarter expansion of the spring flush leaves, the second at petal fall, and the third about three weeks later.
There are copper sprays that are labeled organic, but be sure to read all the label instructions for the tree's safety and yours.
For more information about citrus scab and other citrus diseases, visit the University of Florida's IFAS Extensions website at www.solutionsforyourlife.com
Q. There is a large fern-like plant in the shady wood line area of my backyard. One of my dogs broke off and chewed on one of the yellow-colored pods or flowers. This made the dog sick, but now he is fine. Can you please help me identify this particular plant? I do not mind its presence, since its huge shape creates a nice visual in the wood line. However, if it is toxic or at all dangerous to animals, I will gladly remove it.
A. The photos you sent me of the plant were of a common plant in North Central Florida called split-leaf philodendron or selloum. Its Latin name is Philodendron bipinnatifidum, and it is a member of the aroid family. All plants in this group contain calcium oxalate crystals in the leaves, stems and flowers.
The plant parts, if chewed and consumed, will result in oral irritation, burning of the mouth, lips and tongue. If enough is consumed, there will be excessive drooling and vomiting and difficulty swallowing. Some gardeners also complain that the sap will burn and cause dermatitis. Hopefully, the dog will leave it alone now, but, if not, they are easy enough to remove. Other plants in the group include caladiums and the houseplants dieffenbachia and aglaonema.
For more information about plants that are toxic to pets, contact the UF/IFAS Alachua County Master Gardeners at 352-955-2402.
Q. I am really enjoying all the blooming magnolias this year. I would like to plant a magnolia tree, but I don’t think my small lot can handle a huge tree. Are there smaller magnolias available?
A. The fragrance of magnolia blossoms is one of the joys of living in the South. The large white flowers emit an aroma of sweet citrus perfume; for me it is the scent of summer. As you have noticed the trees are big - huge in fact.
Magnolia grandiflora trees are used in the landscape to frame a house or to be seen as a backdrop. Their mature height is 60 to 90 feet tall of straight trunk, and the branches form a pyramid-shaped crown. The leaves of magnolias are glossy green and sometimes have a rusty colored underside. Leaves are shed in the late spring just before the blooming time in May. That’s when the rakes come out. If a tree that is more than 60 feet tall won’t fit into your landscape, consider planting one of the dwarf cultivars that only reach 30 to 40 feet.
Little Gem is a dwarf cultivar (20 to 30 feet) that is the most common, but there are others to consider. Brackens Brown Beauty is known for the dark brown lower surfaces of its leaves and for its large flowers. Edith Bogue is a very tough form that is quick to bloom, and Hasse is a dense, compact cultivar that can be used as a large privacy screen.
Plant magnolia trees in an area that is in full sun and has well-drained soil. They will really take off if supplemental irrigation can be provided in the first three years. Once established, they will become drought- tolerant and tough trees in the landscape. Magnolia trees are native to Florida, and the seeds from the flower cones are a favorite with many birds and other wildlife. For more information about trees, visit the University of Florida Extension’s website at www.solutionsforyourlife.com.
Q. The person who mows my lawns says that I am getting thatch in my grass. I do not know what this is and how to deal with it. My lawn looks great to me and I would like to keep it that way.
A. Thatch is a layer of brown or dead grass between the roots of the turf and the healthy green grass. As is accumulates, grass runners grow over it and do not contact the soil. You know you have a thatch issue when you walk on the grass and it feels spongy, like you can bounce up and down on it a little. Thatch is a problem for several reasons; it is a haven for insects and diseases, and prevents irrigation water from getting to the soil. Also if the thatch layer is really thick, your lawn mower will sink into the grass resulting in too short of a cut.
If the problem is just beginning, you can remove the thatch with a good raking with a stiff metal rake. When the thatch problem is serious, consider a mechanical thatch removal with a vertical mower. This is considered necessary when the thatch thickness exceeds 1 inch. Vertical mower blades should be set at a spacing of 3 inches between blades for St. Augustine grass.
After dethatching, remove the dead material from the lawn. The lawn should then be thoroughly watered to encourage recovery of the turf.
Avoid thatch in the future by watering conservatively with ½ to ¾ inch of water one to two times per week, and fertilizing with a product that has water insoluble nitrogen.
For more lawn questions, call the UF/IFAS Alachua County Master Gardeners at 352- 955-2402.
Q. What are some good annuals to use for color during the summer? My petunias and pansies are long gone, and my annual beds and containers need help.
A. Finding annuals that can hold up to our summer heat and humidity can be a challenge until you get a few good plants in your corner. One of my favorites is the profusion zinnias. They come in a variety of colors and are great bloomers, only a foot tall and disease-resistant.
Another great annual for the summer is torenia, or wishbone flowers. They are about 9 to 12 inches tall and available in purple tones. They do well in full sun or in a partial shade.
Kalanchoe is a tough summer annual that is usually seen with red, yellow or orange flowers. The leaves are succulent and they are drought-tolerant once established.
Because of disease problems we really aren't growing impatiens anymore, but the disease-resistant and sun-tolerant New Guinea impatiens are a fantastic substitution. They come in vibrant colors of pink, orange and purple and grow to about 2 feet tall.
A local favorite that is grown more for its showy leaves than flowers is coleus. This annual comes in many different leaf forms and colors. Most coleus do well in partial shade, and some will perform in the full sun.
It is a good idea to improve the area of your annual bed with compost before planting. This increases the water and nutrient holding capacity of the soil. During the growing season water regularly and use a slow-release fertilizer to keep them looking green and blooming well.
Group your annuals to provide blocks of color for the biggest impact.
For more information about growing annuals and other landscape plants, contact the University of Florida/IFAS Alachua County Master Gardeners at email@example.com, or visit the UF/IFAS Extension website at www.solutionsforyourlife.com.
Q. Is it possible to grow lemongrass in Gainesville? Does it die back in the winter?
A. The popular Thai spice lemongrass is recommended for USDA cold hardiness zones 10 and 11. We are in zone 9 and 8b, but most lemongrass grows really well in zone 9 and comes back easily from the roots in zone 8b.
A wonderful addition to your edible landscape or even to your perennial border, lemongrass is a versatile grass that can be used as an ornamental or as an herb. It will grow up to 6 feet tall and at least 4 feet wide at maturity.
Plant in full sun to partial shade and water when it shows signs of drought stress. The long grass blades are bluish-green in color and have a graceful droop. The wonderful scent of the leaves is described as lemony or citrus-like. It can be used for tea making, cooking and for essential oils. Some gardeners just use lemongrass as aroma therapy to keep them charged through their landscaping chores.
The leaf edges can be sharp, so position the plant far enough away from walkways and entries to avoid an unpleasant encounter.
Q. My plumbago bushes around my new pool are looking really sad. They have yellowing leaves and some of the leaves have brown edges.
A. Plumbagos are flowering shrubs that usually do well in North Central Florida. They are favored for their sky-blue flowers and dwarf growth habit. Normally plumbagos (Plumbago capensis) are used as a foundation plant or in mass planting where you need summer-long color.
Plant in full, hot sun and in well-drained soils for maximum growth and the best flower show. If we have freezing temperatures, the plant can be killed back to the ground, but well-established shrubs will return from the roots and bloom within a few months. Many gardeners plant plumbago in their butterfly gardens because they are a favorite of the beautiful Cassius Blue butterfly.
Plumbagos do appreciate regular fertilization with a balanced fertilizer. If they are growing on unimproved or in soil that is made up of “fill dirt” like what might be around your pool area, you will need to be on the lookout for nutrient deficiencies. Correct this deficiency with a fertilizer that contains micronutrients and work in a light layer of composted manure on top of the root balls of the shrubs. For more information about plant health, visit the University of Florida IFAS website at www.solutionsforyourlife.com.
Q. Please advise as to how I can get rid of or at least minimize the invasion of Boston fern Nephrolepis cordifolia spreading rapidly into shaded wooded areas of our yard. I am manually harvesting, but with 2.5 acres, I am only making a dent. The roots have round tubers so I know it is the invasive type. I would prefer not to spray.
A. Boston fern, or Nephrolepsis cordifolia, is an aggressive invasive plant in many Gainesville landscapes. People used this plant when they were looking for a vigorous groundcover for shady areas, and they certainly got the vigorous part.
This sword fern is a threat to our native species, it is able to form dense stands and it quickly displaces the native vegetation. It is often the same Boston fern that is sold in hanging baskets. As a fern it reproduces by spores and spreads by rhizomes and tubers. The dime-sized tubers are what distinguish this fern as the invasive species.
The best way to deal with this problem is to not purposely plant the fern. If you already have it, pulling it by hand or hoeing is a good way to remove it mechanically. I know you do not want to spray, but an herbicide would provide the most effective control for this weed. Plants can be killed with herbicides containing glyphosate. A foliar application of a 1.5 percent solution provides good control. Follow-up applications are necessary to control plants regrowing from rhizomes and tubers. For more information, contact the Alachua County Master Gardener office at 352/955-2402.
Q. Some of my amaryllis are blooming beautifully this year and others are not. Also, a few of the flowers that I thought were deep red have faded to an orangey-red. Is there anything I can do to get better flowers?
A. Amaryllis are a subtropical bulb that thrives in Florida. They are tough and reliable bulbs that require almost no maintenance if they are planted correctly. Every spring the bulbs will throw up two to three leaves, and produce large trumpet flowers in bold colors like red, pink, white and orange.
Use them in the landscape with sunny to partial shade conditions. When planted in groups of five to seven of the same color, you can make a striking display.
Amaryllis bulbs will perform best in well-drained soils that have been enriched with organic matter such as 3 to 4 inches of peat or compost.
Plant the bulbs 12 to 15 inches apart, with the neck of the bulb protruding above the ground. The bulbs can be left in the ground for years, but if they are getting really crowded, you can dig the bulbs up in the fall and reset them. This encourages overall health of the plant, and helps to keep the plant flowering. Even though I said you can almost neglect them, fertilizing once or twice a year with a balanced slow-release fertilizer like 10-10-10 will keep the plant green and blooming.
If your plants aren't blooming this year, it could be that they are growing in too much shade. Consider moving them to a sunnier locale. Or, that they were over-fertilized; too much nitrogen will cause the plant to produce leaves at the expense of bulb growth and flowers.
For your plants that have changed flower color, sometimes amaryllis hybrids will change color over time, often back to the orangey-red or a similar shade.
For help with your landscape, visit the UF/IFAS website, www.solutionsforyourlife.com, or call the Alachua County Master Gardener office at 352/955-2402.
Q. Is this a good time to plant sweet potatoes?
A. This is a great time to get those delicious sweet potatoes in the ground. You can plant them as early as March, and as late as June. They do really well in the summer garden long after some of our other veggies have petered out.
Plant varieties like Porto Rico, Georgia Red, Jewel and Vardaman. Normally, you will purchase slips from the garden centers. These are small, live offshoots that should be set in the soil about an inch deep. Set them 12 inches apart, with 4 feet between rows.
Sweet potato plants are vines and will scramble all over the garden if you let them. Water as you would the rest of the vegetable garden, and fertilize with a balanced fertilizer every three weeks. It will take anywhere from four to five months before you can harvest the tubers. So you will have to plan and plant accordingly.
Call the Alachua County Master Gardener office at 352/955-2402 for advice on your vegetable garden.
Q. This year, my azaleas weren't as beautiful as in years past. The flowers didn't all bloom at the same time, and, when they did, there were brown spots on the flowers and they sort of melted. What happened?
A. Azaleas are a Southern favorite and standard in most North Central Florida gardens.
The old-fashioned Southern indica azaleas are "one-hit wonders" and normally put on a beautiful show in late February to early March.
This year, the weather delayed the bloom by about two weeks, and many of the cultivars, like Formosa, George L. Taber, Mrs. G. G. Gerbing and Southern Charm, didn't bloom in unison. More consistent temperatures next year should get them to flower at the same time.
The spots on the blooms are another problem called petal blight. It is caused by a fungus, and also is referred to as Ovulinia petal blight. It only damages the flowers. It is worse in years we have wet, cool weather during the flowering period.
The symptoms start as pale or white spots on the flower petals. The spots enlarge quickly and then the blossom collapses and is slimy. The fungal spore germination occurs when temperatures are in the mid-60s with mist and fog.
The pathogen can persist through the rest of the year as a small, compact mass of the fungal strands (sclerotia) in the fallen diseased flowers, or lying on the mulch below. When the flowers start to form in the spring, spores germinate and infect the flower. The best thing you can do to break the cycle is to rake up the spent flowers from under the shrub, and consider replacing the mulch, if possible.
Use of fungicides is not normally recommended because you can control the disease by removing the flowers and replacing the mulch. Hopefully, the weather will cooperate for a more beautiful azalea bloom for you next year.
For more information on growing azaleas, visit the University of Florida/IFAS Extension website at www.solutionsforyourlife.com.
Q. My new eggplant and pepper seedlings that I just planted have been snapped off 1 to 2 inches above the ground. What is doing this, and how can I stop it?
A. It is more than likely a cutworm caterpillar that is nibbling and snipping off the tops of your young seedlings.
These are brown or green plump caterpillars that hide in the garden soil. If you touch one, it would curl into a "C" shape. Normally, we don't see them because they eat at night.
They mow down seedlings at about soil level. On older plants, you might see channels or scars on the stems.
The best way to deal with them is to make a cutworm collar. Take a cardboard tube from a paper towel roll and cut it into 2-inch tall rings. Place these cylinders around each small seedling directly on the ground with the seedling in the center. Cutworms usually won't climb over these barriers.
Also, crop rotation will help to keep populations down. Some of my farming friends say that letting the chickens scratch through the garden at the end of the season helps to keep caterpillar populations down.
For more information about vegetable gardening, contact the UF/IFAS Extension Alachua County Master Gardeners volunteers at 352-955-2402.
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Rain Shutoff Device
Snail Damaged Leaves
Sago Palm Cone