Archive | July 2013

Mulch: the right thing to do

Mulch is as important to southern gardens and landscapes as sausage gravy is to biscuits or as corn bread is to pinto beans. Despite our record rainfall this spring and summer, mulch is still the right thing to do. A shallow layer of organic mulch conserves moisture, suppresses weeds, and supplies nutrients as it decomposes. Covering bare soil with mulch reduces erosion. Most importantly, mulch enhances the appearance of our plantings—it makes our plants pop.
A common question that arises is which mulch is best?  My answer: anything that looks good and is affordable.  During my travels throughout the South I’ve seen a wide variety of mulches used by gardeners.  They include newspapers, old carpeting, salt hay, cocoa and pecan hulls, and eucalyptus chips. Mulch, in my opinion, is a lot like barbecue sauces: there are regional differences. For example, pine straw is commonplace from the Midlands to the Carolina coast. Along the coast, besides pine straw, you’ll find seashells, white marble chips, and pea gravel. In the Piedmont shredded hard-and softwood mulches are commonplace.
Colored woody or rubber mulches are in vogue right now. Tired of earth tones, then consider mulches made of recycled tires in “Bright Blue” or “Real Teal”.
 
Whatever mulch you apply, apply it properly by following these simple guidelines:
 
Apply a shallow 2 to 4 inch layer of mulch.  For annuals and perennials, apply a mulch layer one to two inches thick.  Avoid the temptation to create a “mulch volcano” that’s a root-suffocating two to three feet high with sloped slides.  Volcano mulching will not impress passersby (“Hey, look everybody, Bob mulched his trees!”), but it can kill trees.  The bark of shrubs and trees needs to “breathe” and it needs to be dry. Keep the mulch at least 3 to 6 inches away from the trunk of young trees and shrubs and 8 to 12 inches away from the trunks of mature trees. Also, by keeping the trunk free of mulch discourages bark-feeding voles which like to be hidden from predators.
Mulch individual trees out to their outermost branches or drip lines, if at all possible. Because the root system can extend two to three times farther than the branches of a plant, mulch as large an area as possible.  To avoid Òslalom mowingÓ in and around individual plantings of trees, unite them with a single bed of mulch.
Every two or three years submit a soil sample from your mulched beds to have it tested for pH and fertility levels.  Mulches, such as pine straw or pine needles, are high in nitrogen and phosphorus, but they also acidify the soil as they decompose.  Florida researchers reported in the Journal of Arboriculture (March 1999) that a 3.5 inch layer of pine needles reduced the soil pH from 5 to 4.4 over the course of a year. While this makes pine straw an ideal mulch for acid-loving plants, other less acid-tolerant plants would benefit from the addition of calcitic or dolomitic limestone to increase the soil pH to the optimum level as recommended by the results of the soil test.  Also, adjusting the pH to the right level will avoid potential nutrient deficiencies caused by a low soil pH, especially nitrogen, phosphorus, potassium, calcium, and magnesium.
So, if you’re looking for something to do in the landscape, throw some mulch around.  And if you’re feeling really adventurous this year, toss out  a Caribbean Blue colored mulch with a sprinkling of last summer’s seashells on top.  Guaranteed, your neighbors will know that you’ve mulched your landscape .
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Euonymus scale: the “Achilles Heel” of euonymus

I received this emailed question the other day:  “I don’t know if you can help me, but I noticed that all of my euonymus shrubs were losing leaves.  It looks like something might be attacking them.  I took some pictures and have attached them. What’s eating them?”Euonymus scale1

Whodunit?  The culprit is euonymus scale (Unaspis euonymi), an armored scale from Asia that is the “Achilles Heel” of euonymus throughout the U.S. and Canada, especially the Japanese euonymus (E. japonicus) and European euonymus (E. europaeus); however, it also attacks American bittersweet (Celastrus scandens), Japanese pachysandra (Pachysandra terminalis), Paxistima canbyi, and other plants.

Where’d it come from?  This critter has an interesting life cycle. Fertilized females overwinter on the stems and leaves of host plants.  In early spring when new leaves emerge, they lay yellow elliptical eggs and die. The eggs hatch over a two to three week period and the young scales or crawlers, which look like specks of yellow-orange dust, travel along the stems and leaves of the host plant or are windblown. They eventually settle down inserting their long, needlelike mouthparts into plant tissues to suck sap and develop a waxy protective covering. The brown oystershell-shaped females are typically found on stems, while the fuzzy white  elongated males are typically found on leaves. They reach adulthood within 40 to 60 days. Males mate with the immobile females to produce a second generation. Generally, there are two generations per year in the in northern and central areas of the U.S., and three or more in southern areas.

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Euonymus scale – white ones are male. Credit: Manigault, Edward L., Clemson Univ. Donated Collection. Image 1225115. http://www.ipmimages.org/. 4/13/04.

Do my euonymuses (perhaps “euonymi”) have euonymus scale?  Look for yellowish or whitish spots or halos on the upper surface of the leaves, which are caused by the feeding males. The gray to brown  females are often clustered on the leaf petioles and stems. Leaves of infested plants turn yellow and drop prematurely, often leaving tufts of foliage at the ends of stunted branches. Heavy infestations lead to plant death. Like other armored scales, euonymus scale does not excrete honeydew.

How do I control them?  Apply horticultural oils to dormant shrubs in late fall or early spring when temperatures will remain above freezing until the spray dries. During thegrowing season apply horticultural oil or  insecticidal soap when the mobile crawlers are present and when they have recently settled. To determine when the crawlers are active, attach double-sided sticky tape to twigs or branches and and examine the tape with a hand lens for the presence of orange-yellow crawlers.

Euonymus scale3Change the tape at weekly intervals.  Alternatively, shake a branch over a white sheet of paper and look for moving orange specks of dust. Certain systemic insecticides may help to reduce population of these pests such as imidacloprid (Bayer Advanced Garden® Tree and Shrub Insect Control). See “Euonymus Diseases & Insect Pests“, HGIC 2054, for more information.

Several natural predators have been introduced.  In 1984, the Agricultural Research Service (USDA/APHIS), imported and established two Korean predatory beetles, Chilocorus kuwanae and Cybocephalus nipponicus in the eastern U.S.

Instead of combatting the euonymus scale, consider shovel-pruning it (removing it completely at soil level) and replacing it with other more pest resistant shrubs. Consider Japanese anise tree (Illicium anisatumor Florida anise (Illicium floridanum), Mexican orange blossom (Choisya ternata ‘Sundance’), glossy abelia (Abeila x grandiflora), Soft Caress threadleaf mahonia (Mahonia ‘Soft Caress’), or variegated winter daphne (Daphne odora).

A routine check-up of trees saves lives and property

Trees provide significant benefits to our homes and communities, but they may also become liabilities when they fall or break apart, causing property damage, personal injuries, and power outages.  Although some tree failures are unpredictable and cannot be prevented, many failures can be prevented from occurring.  In fact, it is an owner’s responsibility to ensure that the tree on his or her property poses no risk to people or property.

Simply by inspecting your trees for common structural defects once or twice a year will help you find and correct potential failures before they cause damage or injury.

I created this “7 Point Check-up List” to teach tree owners in “cook book” fashion how to examine their trees for defects that are likely to lead to failure and possibly cause injury or damage.

codominant stems

First step: Stand far enough away from your tree so you can look up into its canopy.

1. Dead, hanging, or broken branches. Branches larger than 2 inches may cause damage if they fall and should be removed immediately.

2.  Leaning tree. See if your tree leans to one side or appears off-kilter.  If you see exposed roots or a mound of soil near its base, this tree may be an

 

imminent hazard that requires immediate action.

Second step:  Walk up to the tree and closely examine the branches and trunk for defects.

3.  Multiple trunks.  Look for cracks

 

or splits in codominant stems.  Wishbone-like trunks of equal diameter may separate during wind- and ice storms.  Also, closely examine trees with several branches that arise from the same point on the trunk; these branches may be weakly attached and tend to separate away from the trunk.

4.  Weak branch unions. Inspect large branches greater than 3 inches in diameter at a point where they attach to the trunk. A crack or split at the union indicates a high probability of failure and warrants action.  It’s best for you to remove the branch rather than a storm.

5. Trunk and branch cracks. If you find cracks in the trunk or branches, measure its depth with a pencil or similar object.  If the crack extends beyond the bark and into the wood, contact an arborist to have it inspected.

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6.  Decayed wood.  Inspect the trunk and large branches for cavities, cankers, mushrooms and con

ks. Look for mushrooms and conks along the trunk and on exposed roots. These signs and symptoms are evidence of decay. A trained arborist should be contacted to conduct a risk assessment to evaluate the tree’s condition and its potential as a hazardous tree.

Third step:  Finally, look down and inspect the base of the tree.

7. Root problems.  Examine the base of the trunk for damage from rodents, string trimmers, etc.  Look for a soil mound, soil cracking near the root collar, or broken roots sticking out of the soil. Remove any soil or mulch away from the root collar and see if there is a flat side to the trunk.  If you find any encircling, constricting roots, consult a certified arborist (see http://www.isa-arbor.com) to address this problem.

This seven-point checklist may take less than 30 minutes to complete.  When conducted twice a year, this hour-long investment of time benefits our trees and everyone who dwells with them.

Seedless or seeded, warm or cold, just give me watermelon

No matter how you slice it, there is no summer without watermelon.  Royalwatermelon_USDA Sweet or Icebox, seeded or seedless, I’m not too finicky about watermelon. According to USDA estimates, each American consumes about 15 lbs. of watermelon a year.  By late July I’m way ahead of that mark.
While the interest in personal watermelons is warming up, the demand for seedless watermelons is red hot. Although several years have passed since seedless watermelons were first developed in 1939 at Kyoto University, Japan, they comprise about 70 percent of the watermelons grown in South Carolina.
Just the other day while eating a seedless watermelon with my kids, I lamented about their absence of seeds. Besides missing their crunchiness, I couldn’t showcase my prowess as a long distance watermelon seed spitter.
My kids, on the other hand, wondered where the seeds of seedless watermelons came from.  I told them that the parents are two seeded varieties. The male is a diploid variety, that is, a watermelon with the ordinary number of 22 chromosomes.  The female parent, however, is a tetraploid variety:  one that has been chemically treated to double the chromosome number to 44. (I believe it was at this point in my lecture when they tuned me out.)  The resulting hybrid seed is a triploid with a chromosome number of 33. Although these triploid seeds will sprout, the resulting watermelon plant is sterile. The vine flowers and makes fruit, but the fruit are seedless.
Growing seedless watermelons is more challenging than raising ordinary watermelons.  Seed of the latter will germinate at 75 degrees. Seedless watermelon seeds, by contrast, need at least 80 degrees and preferably 85 degrees to sprout. The thick seed coat sometimes sticks to the cotyledons on the emerged seedlings requiring them to be carefully removed by hand, although sowing the seed so that the pointed end is down reduces this seed coat-sticking problem. Seedless watermelon flowers must be pollinated to set fruit, but because the plants produce no pollen of their own, a seeded watermelon variety must be grown nearby. These seeded watermelons will set fruit of their own, but these are usually selected to have a different shape or rind color to make
it easy to distinguish the seeded and non-seeded fruits.
While many of you search for seedless watermelons–not me.  I¹m look for Charleston Gray watermelons that are too big for the refrigerator, but small enough to lie on a bed of ice in my daughter’s red Radio Flyer wagon.  I hope your summer is as sumptuous as mine.

Pineapple Guava

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Pineapple guava (8 ft. H x 8 ft. W) at the SC Botanic Garden, Clemson.

The pineapple guava (Acca sellowiana), formerly known as feijoa, is a small, subtropical evergreen tree that’s hardy to about 10 degrees F. In tropical regions it can reach a height of 10 to 15 feet with an equal spread, but in warm temperate areas like ours, expect it to grow 8 to 10 feet high and wide. It’s cultivated for its extraordinary flowers, which are about 2 inches wide and have white sepals arching downward to reveal bright red petals with white margins. In the center of each flower is a cluster of bright red stamens tipped with tipped with g

olden pollen. The green round to egg-shaped fruits, which mature into 2 to 4 inch long blue-green to grayish-green berries, can be harvested in late summer and fall.

Besides the flowers, I’m also enamored with its dense rounded habit and lustrous, almost bluish-green leaves. When breezes lift and turn the leaves over, admire their fuzzy-white pubescent undersides.

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Close-up of pineapple guava berries the first week of July at the SC Botanic Garden.

Besides the flowers, I’m also enamored with its dense rounded habit and lustrous, almost bluish-green leaves. When breezes lift and turn the leaves over, admire their fuzzy-white pubescent undersides.

Besides purchasing it from a reputable nursery, you can also root cuttings of self-fertile cultivars, such as ‘Coolidge’ or ‘Nazemetz.’  ‘NCSU Hardy‘ is a more cold hardy species introduced by NC State University. Expect rooted cuttings to bear fruit in two or three years, whereas seedlings may take four years or more to bear.

Pineapple guava needs a well-drained soil, with a pH between 6 to 6.5.  It also needs to be mulched and watered during dry spells to prevent fruit drop.  They have few, if any, pest problems.  For more information about pineapple guavas, see “Fruit Facts” at the California Rare Fruit Growers web site (www.crfg.org/pubs/frtfacts.html).

Pomegranates are good for you and your landscape

Although pomegranates have been cultivated since ancient times, few southern gardeners include this deciduous to semi-evergreen large shrub or small tree (height and width of 12 to 15 feet or more) in their landscapes.  Besides its glossy green leaves, pomegranates produce gorgeous carnationlike flowers during June and July.  They are about an inch wide and comprised of 5 to 8 crumpled petals.  They occur singly or in groups of twos and threes at the ends of the branches.

Pomegranate tolerates acid or alkaline soils and can be sited in full sun to part shade.  However, best growth occurs in regions with hot summers and cool winters.  The pomegranate can be grown as far north as Washington County, Utah, and Washington, D.C., but not expected to bear fruit.  Domant pomegranates can tolerate temperatures down to 12 degrees F; however, severe damage can occur from late spring frosts when new growth emerges in the spring.  Commercial pomegranate fruit production is centered in the Bakersfield-Fresno area of California.DSC_0040pomegranate_BP

There are basically two kinds of pomegranates:  cultivars that produce sweet- or tart-flavored fruits and those that do not bear fruits.  Many ornamental pomegranates have been selected for their showy flowers, especially those with double flowers that look like carnations.  The fail to set fruit due to the abnormal structure of their flower parts.  Although pomegranate flowers are typically hermaphroditic containing both male and female stamens an pistils, some nonfruiting cultivars have unisexual flowers or have flowers whose pistils degenerate or are nonfunctional.  A few double-flowering pomegranates include ‘Alba’ (double white), ‘Mme. Legrelle’ (coral-red with white variegation), ‘Nochi Shibari'(dark red), and Tayosho (apricot).

Fruiting cultivars bear round reddish-green to violet fruit about 3 to 5 inches wide that have a leathery rind.  The fleshy seeds are enveloped in a juicy pulp, which may be sweet or tart-flavored depending on the cultivar.  These healthy fruits provide potassium and vitamin C and are chock-full of antioxidants. Cultivars grown for their fruit include ‘Wonderful’, in cultivation since 1896, which bears double orangish-red flowers and greenish-red to reddish-orange fruit.  The juice is mixed with sugar and water to make grenadine syrup.  ‘Grenada’, is a close relative of ‘Wonderful’ with sweeter, darker fruit.  ‘Ambrosia’ has gold rind with a red blush, while the rind of ‘Sweet’ remains slightly greenish with a red blush when ripe.

While folks may either like or dislike this unusual fruit, there’s no disagreement about the flowers.  Granted, it may be an acquired taste.  But there’s no disagreement about the flowers:  they’ve been captivating civilizations for centuries.

For more information on growing pomegranates in South Carolina, see  “Pomegranate”, HGIC 1359 (http://www.clemson.edu/extension/hgic/plants/vegetables/tree_fruits_nuts/hgic1359.html