by Stephen Kelly, regional editor

The famous Putterboy topiary and hedges of Ilex crenata ?EUR??,,????'??Stokes?EUR??,,????'??? holly at Pinehurst are fertilized each January with a slow-release balanced formula fertilizer (e.g., 10-10-10). 'Stokes' is a broad-leaf dwarf evergreen (a Japanese varietal) that is dense, slow-growing and, like many other shrubs, prefers acidic soils. Therefore, the fertilizer of choice is one that contains N in the ammonium or urea form, which helps to acidify the soil. Cottonseed meal, an organic fertilizer, can also be used, as it produces an acidic reaction in the soil.

Editor?EUR??,,????'???s note: A good deal of information for this article was gleaned from ?EUR??,,????'??Care of Ornamental Plants in the Landscape?EUR??,,????'?? by Gary Wade, horticulturist, and Beverly Sparks, entomologist, both from the Cooperative Extension Service of the University of Georgia College of Agricultural and Environmental Sciences. Additional information came from the North Carolina Dept. of Agriculture and interviews with landscape managers Chris Burrows (Pinehurst Resort, N.C.) and Jim Kaufmann (National Gallery Sculpture Garden, Washington, D.C.).

Mary Braden weeds a bed of reblooming Irises, which bloom May/June and again October/November. ?EUR??,,????'??The Irises are pruned and divided in the winter after going dormant and fertilized with a granular 5-10-5 throughout the growing season,?EUR??,,????'?? says Jim Kaufmann, horticulturist and grounds manager for the National Sculpture Garden in Washington, D.C. To prevent diseases no mulch goes around the Iris bases.

A good ornamental landscape management program requires regular fertilization, pruning, watering, mulching and pest control. Such a broad topic is difficult to cover in one feature, so we will concentrate on fertilizing ornamentals.

Clearly some plants (e.g., roses, English laurel) require more care and others are less worrisome (e.g., ornamental grasses, hollies, junipers). In short, you have to know about the particular plants on the property you are installing or maintaining. If installing plants, you?EUR??,,????'???ll need to know their sun and shade requirements. Azaleas, for one example, need moist soil and shade from the glare of the mid-afternoon sun. You don?EUR??,,????'???t have to be a horticulturist to know that azaleas also need good drainage. There are enough books on flora to fill a library and source material galore on the internet to answer about any question you might have about any plant or woody ornamental. Improper care and choice of ornamental plants breeds weak flora whose lack of vigor makes them more susceptible to insect damage and disease.

Members of the Pinehurst Resort greenhouse crew watering, fertilizing and pruning Boston ferns. Ferns are fertilized monthly with a 20-20-20 and water everyday if need be.

One though to keep in mind is low-maintenance landscape practices. It?EUR??,,????'???s a whole lot easier to care for plants native to a particular soil, terrain and climate than trying to nurse exotic plants to life. The low water needs of xeriscapes and employing integrated pest management (discriminating use of insecticides and encouraging friendly pests) are reaping not only attractive landscapes but saving landscape contractors time and money on T & O care.

The Soil Test

You?EUR??,,????'???ve heard this advice before, but let?EUR??,,????'???s reiterate. A soil test (through your county extension lab) is still the best means to know what fertilizer analysis is best for your soil, otherwise you are flying by the seat of your pants, not a tenable position for any garden pilot.

I?EUR??,,????'???ve recently interview two landscape managers: Chris Burrows, the superintendent for the Pinehurst Resort in North Carolina, and Jim Kaufmann, a horticulturist for the National Sculpture Garden in Washington, D.C.

A group of ornamentals in one area need a well prepared bed rather than individual holes. Till deep (12 to 15) and use about one pound (two cups) of an eight to 10 percent nitrogen fertilizer (e.g., 8-8-8 or 10-10-10) over each 100 square feet of bed area. Use lime for the bed but only if recommended by a soil analysis. Slow-release fertilizers, such as Osmocote or Agriform tablets, are excellent for flower beds because they give the plants an even supply of nutrients throughout the growing season. Several formulas are available, although one with at least an eight- to nine-month release duration is recommended.

Mr. Burrows at Pinehurst deals with maintaining 70 acres. His grounds crew plants 138,000 annuals (grown in Pinehurst?EUR??,,????'???s 17,280 square feet of greenhouses, cares for .7 acres of annual beds and some 10,600 bulbs. Mr. Kaufmann has only 6.1 acres to deal with, but the property is on the Washington Mall, better known as the ?EUR??,,????'??clay swamp.?EUR??,,????'?? When the garden was installed (opened in 1999) about three feet of soil (clay) was removed and replaced with a custom soil blend?EUR??,,????'??+about 77 percent sand and the rest organic matter. Some plant beds have required greater drainage mitigation.

?EUR??,,????'??We?EUR??,,????'???ve had to take everything out of some beds, put drainage in and replant it,?EUR??,,????'?? Dianne Cina, head horticulturist of the Sculpture Garden, told me. PVC pipe, soil amendments (gravel, organic matter, bark mulch) and tapping into drainage culverts have produced good results.

Ilex crenata ?EUR??,,????'??Stokes?EUR??,,????'??? holly (the insignia), and magnolia, holly and oak trees greet Carolina Hotel guests at the Pinehurst Resort, N.C. The annual beds at the entrance and circling the trees are impatiens with begonias (upper right). One application of a slow-release fertilizer suffices for the growing season. For just-planted ground covers, annuals, herbaceous perennials and roses, light applications of GPGs (12-4-8 or 10-10-10) are recommended at four to six week intervals. Peat moss, leaf mold or compost, perlite and bark make good drainage for the impatiens. Root-laden soil around the trees sometimes requires a fresh soil mix. Begonias do best in slightly acidic soil. Peat moss helps hold moisture and increase acidity.

The point is, these men are experts in their field with large responsibilities, but both rely on annual soil tests to guide them on fertilization and soil amendments. As a side note, Kaufmann, who employs integrated pest management practices (IPM), also relies on extension service recommendations for herbicide use and what other horticulturists in his area find works best.

Oakleaf hydrangea (Hydrangea quercifolia ?EUR??,,????'??Pee Wee?EUR??,,????'???) border many of the walkways in the National Gallery Sculpture Garden. In the background pink flowered Mandevilla (Mandevilla splendins ?EUR??,,????'??Alice Dupont) climb the fa??? 1/4 ade of the Pavilion Caf????(C). Fertilizer for the annual planting beds and container plants is done biweekly, normally a 20-20-20 liquid.

Lime, Lime, My Kingdom for Lime

Yes, a silly parody of King Richard III?EUR??,,????'???s plea, but before we dig into the topic of fertilizing ornamentals, a word on lime. According to note 4 in ?EUR??,,????'??Fertilization of Lawns, Gardens and Ornamentals?EUR??,,????'?? by the North Carolina Dept. of Agriculture (NCDA), lime contributes more benefits to soil than an other amendment. Lime is a primary ingredient for improving the soil environment. It neutralizes soil acidity, stimulates microbial activity, enhances the availability of nutrient elements and supplies essential calcium and magnesium and promotes plant growth.

While this article deals with ornamental care, here?EUR??,,????'???s is a turf fertilization tip. Lynda Bafile, assistant superintendent, at Pinehurst Resort, demonstrates the proper way to apply fertilizer (34-0-0 in this case) with the use of flags to ensure no skips or streaking of the fertilizer.

Most bagged lime sold by gardens centers is a finely ground, high-quality agricultural grade dolomitic lime (contains calcium and magnesium carbonates). Lime recommendations on soil test reports are expressed in units of M, the same as lb./1,000 sq. ft.

Lime, like fertilizer should be applied based on a current soil test. The suggested rate and application should raise the garden soil pH to 6.0-6.5, explains NCDA, and keep it within the desired range for two to three years on sandy coastal plain soils and for three to four years on silt and/or clay piedmont and mountain soils.

Jim Kaufmann (National Gallery Sculpture Garden) hedges a ring of little leaf lindens (Tillia cordata ?EUR??,,????'??Greenspire?EUR??,,????'???). The trees receive a soluble injectable fertilizer (PHZ) with mycorrhizal fungi, which has given good results. Mycorrhizal fungi (Gigaspora rosea) are white bushy fungi living in association with the cells of plant roots. The most common are endomycorrhizae, meaning they grow inside the root cells where they form tiny trees (arbuscules) and little sacs (vesicles) whose threads (hyphae) reach out into the soil to help plants gather water and nutrients (phosphorus and nitrogen). The plant, quid pro quo, gives the fungus sugar produced by photosynthesis. The other type of this fungi (ectomycorrhizae) grows between and outside the cells of roots, usually pine trees. Some ectomycorrhizal fungi associated with trees form mushrooms, such as Boletus, Aminita and truffles. All conifer trees have mycorrhizal associations.

For new gardens lime is broadcast over the surface and incorporated 4?EUR??,,????'???8 inches into the soil. For gardens and ornamental shrubs its broadcast then irrigated. The NCDA warns not to surface apply more than 50 pounds of lime per 1,000 sq. ft. at any given time. Overliming can reduce the availability of some micronutrients, a problem common on sandy coastal plain soils. Lime residue will not harm plants and can be removed easily by irrigation or rainfall.

Fertilization

Fertilization is key to landscape maintenance, particularly true where development has scraped away native topsoil and exposed the less nutrient rich subsoils. Generally, most ornamentals benefit from 3-1-2 or 4-1-2 ratios of nitrogen, phosphorus and potassium (N-P-K). Phosphorus, the middle number in an analysis, does not leach with rains or irrigation as does N and P, thus the lower ratio requirement for P. Still, on ground where phosphorus has never been applied, a balanced ratio (8-8-8 or 10-10-10) is sometimes recommended.

The huge variety and forms of fertilizer can be confusing. There are general-purpose garden fertilizers sold as pre-mixed liquid concentrates, water-soluble crystals, slow-release fertilizers and ones identified for certain plants. Base your choices on cost, types of plants being fertilized, the soil type and the desired growth response. Liquid or water-soluble fertilizers are good choices for just planted annuals and herbaceous perennials as they need to quickly take in nutrients. Woody ornamentals, on the other hand, store food reserves in their roots and benefit from slow-release fertilizers. Some granular slow-release fertilizers last six to eight months after application. Nitrogen listed as ammoniacal has slow-release properties; nitrogen listed as derived from urea, urea-formaldehyde, isobutylenediurea, or sulfur-coated urea increases the release duration. Common slow-release fertilizers include Osmocote granules, Osmocote tablets, Jobe?EUR??,,????'???s Spikes, Once, Woodace briquettes, Agriform tablets and Milorganite. These fertilizers generally cost more per pound than general-purpose granular fertilizers (e.g., 10-10-10 or 12-4-8) but last longer.

You may prefer composting or organic fertilizers (bone meal, cottonseed meal, manures). Table 1 lists the average nutrient content of several organic fertilizer sources.

Table 1

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When to Fertilize

Research published in the Journal of American Horticulture Science on nonbearing prune trees and their growth cycle revealed the tree begins actively absorbing nitrogen from the soil beginning in April, with the peak levels of nitrogen absorption between May and Sept. This is the most critical fertilization period. The rule of thumb is to apply fertilizer as soon as the plants begin to bud and stop fertilizing after the first fall frost.

Frequency of Fertilization

One application of a slow-release fertilizer should suffice for the growing season, however, two or three applications are necessary for general-purpose granular (GPG) fertilizers, depending on the slow-release properties. For just-planted ground covers, annuals, herbaceous perennials and roses, light applications of GPGs (12-4-8 or 10-10-10) are recommended at four to six week intervals. During periods of little rainfall or drought or in nonirrigated areas, reduce the amount and frequency of fertilizer, as it can injure ornamental roots under drought stress.

Newly-planted ornamental trees and shrubs benefit from light applications of fertilizer made during the first growing season after transplanting (Table 2). Broadcast the fertilizer uniformly along the perimeter of the planting hole. Newly planted ornamentals are under stress and can be easily injured by overfertilization. Also, don?EUR??,,????'???t use weed-and-feed fertilizers in the vicinity as the herbicide may do damage.

Table 2

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Nitrogen controls plant growth, so application rates are based on this primary nutrient. Table 3 lists suggested application rates for several general-purpose fertilizers.

Table 3

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Do not exceed the application rate in Table 3, though you can increase the frequency of application. The recommendation of fertilization rates is 3-5 applications on annuals, herbaceous perennials, roses and newly established ground covers; otherwise, low rates are recommended, particularly if you desire a lower maintenance landscape.

?EUR??,,????'?? The low water needs of xeriscapes and employing integrated pest management (discriminating use of insecticides and encouraging friendly pests) are reaping not only attractive landscapes but saving landscape contractors time and money on T & O care.?EUR??,,????'??

Fertilizing Guidelines/Precautions

The following are some do?EUR??,,????'???s and don?EUR??,,????'???ts prescribed by Gary Wade, horticulturist, and Beverly Sparks, entomologist, both from the Cooperative Extension Service of the University of Georgia College of Agricultural and Environmental Sciences, in ?EUR??,,????'??Care of Ornamental Plants in the Landscape.?EUR??,,????'??

Anthony Ferrell completes planting a winter display bed of Atlas pansies at the National Sculpture Garden. Atlas pansies are suited to colder climates, although if planted after soil temperatures go below 45 degrees F they exhibit stunted, pale green leaves and little or no flowering. Gary Wade, an Extension Horticulturists at the Universityof Georgia College of Agricultural and Environmental Sciences has recommended at transplant a 150 ppm of a soluble greenhouse fertilizer of 20-10-20 for the first weeks of September and October and warns agains high rates of nitrogen during September and later in April and May, because the plants grow fast and can stretch in warm weather under high nutrition.

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