Q&A WITH BOB POLOMSKI 31

Extension Consumer Horticulturist, Clemson University

Hies are great plants, I don’t want stickery plants round my house. Can you suggest a few hollies that don’t have spiny leaves? –D.P., Saunderstown, R.J.

Answer: About 40 percent of holly species have spineless leaves. Included are deciduous hollies, such as possumhawholly (Ilex decidua), Japanese winterberry (I. serrata), winierberry (I. verticillata), and the hybrids of the latter two.

Evergreen hollies with smooth-margined leaves–in other words, without spiny points–include Highclere holly (I. xalta-derensis) ‘Belearica’, ‘Cherryberry’, ‘El-dridge’, and ‘Green Maid’, Japanese holly (I. crenata), inkberry holly (I. glabra), Nepal holly (I. iniegra), long-stalk holly (I. pedun-culosa), prostrate holly (I. rugosa), and I. wihonii.

Some Ilex species have leaves whose margins change from spiny to smooth as the plant ages. For example, juvenile leaves of I. aquifolium, I. cornuta, I. comllina, and I. dimorphophylla are spiny, but their mature leaves have smooth margins. Hollies are dioecious, which means that plants have either male or female flowers. For better fruit set, a male should be within 30 to 40 feet of the female holly.

Ants are swarming all over the buds of my peonies. Are they harming my plants? Should I spray something to get rid of them?

R.D., Moslnee, WI

Answer: Large black ants are a common sight on peony buds, but, far from harming the plants, the ants are actually providing protection. What attracts the ants is something called ex-tratloral nectar, which is made by special glands on the bud scales. These extrafloral nectaries differ from the more familiar nectar sources that are located within the flower and serve to attract pollinators. Extrafloral nectaries are quite common on tropical plants, less so on temperate ones. But peonies are a prime example. The ants gather on the peony buds (and even on the opened flowers) to collect sugar. The presence of these omnivorous hunters deters other insects, including herbivorous ones that might try to feed on the peony bud.

You don’t want to discourage these ants. Years ago it was demonstrated that banding peony stems with an ant-proof barrier resulted in a higher percentage of damaged flowers than on the peonies whose stems were not so banded. Interestingly, there is an old folk saying that ants help the peony flower open–and in a sense, they do.

Can you suggest some ground-hugging plants that can be planted between the stones of a walkway that’s used fairly often?

H.C., Atlanta, CA

Answer: Low groundcovers planted in the crevices of paths and walkways soften the edges of the paving. Some also offer the added benefits of flowers and fragrance.

Unlike the plants you choose to adorn rock walls, plants for walkways must both be prostrate and durable enough to withstand foot traffic.

Nurseries now offer an assortment of appropriate plants. One branded group of offerings are called Stepables (see www.stepables.com). These include blue star creeper (Isotoma fluviatilis), creeping wire vine (Muehlenbeckia axillaris ‘Nana’), miniature stonecrop (Sedum requiem), and Thymus serpyllum ‘Elfin’. Other plants that are moderately tolerant of foot traffic in sunny to partly shaded locations include Mazus rep-taus ‘Albus’ or ‘Purple’, Sedum spurium ‘John Creech’, and the speedwells Veronica repens ‘Sunshine’ and V: surculosa ‘Waterperry Blue’.

It’s best to prepare the planting bed before laying down the paving. Rototill the area to a depth of four to six inches, amend it with organic matter, and add any other nutrients as recommended by a soil test. Then, rake the soil smooth and pack it down lightly. Spread a three-inch layer of sand on top of the soil, pack it down, and then set the stone or other paving in place.

For an existing walkway, use a trowel and dig holes between the pavers to a depth of four to six inches. Set the root balls of plants into the openings and press soil around them. (It may be necessary to deform the rootball to fit the available space). Keep the new plants well watered until they become established and begin to fill in.

How can I prevent my sweetgum trees from producing gumballs?

D.G., Pea Ridge, AR

Answer: Sweetgum (Liquidantbar styraciflua) is a 60- to 100-foot-tall deciduous tree whose native range extends from Connecticut to Missouri and south from Florida to Texas and central Mexico. It’s adapted to a wide variety of sites that range from dry sandy soils to occasionally flooded bottomlands. Its glossy green star-shaped leaves turn fiery shades of red, orange, yellow, and purple in the fall. All of this makes sweetgum a tough, desirable shade tree for parks, campuses, or residential areas where its large size can be accommodated. It is best in USDA Zones 5-9.

The trees drawback, however, is its prickly seed balls, which resemble mace-like gumballs. Each one is composed of individual seed capsules fused together into a one-inch-diameter ball. Within each of these capsules is a pair of winged seeds, and arising from each capsule is a spiny hornlike projection. The gumballs mature in the fall, and the winged seeds are released and dispersed by the wind. Afterwards the gumballs drop from the tree to the ground where they lie in wait for unsuspecting people’s bare feet or other tender body parts to encounter them. Although Guy Sternberg and)im Wilson (authors of Native Trees for North American Landscapes, Timber Press 2004) suggest gathering the gumballs to use as a mulch to discourage cats, most people, like you, want to know how to get rid of them.

There is a chemical solution. Florel Brand Fruit Eliminator, which contains the growth-regulating substance ethephon, can be used to prevent trees from setting fruit. It needs to be applied right after the tiny balls begin to form. When sprayed on the tree, ethephon is converted to ethylene, which in turn causes the formation of an abscission layer that causes the developing fruit to abort. The tiny immature balls dry up and fall off. Depending on the size of the tree, commercial spray equipment may be necessary to treat the entire canopy. Florel works best when the daytime temperature is between 60o F and 95oF.

A more permanent solution is to replace your existing trees with the fruitless sweetgum cultivar ‘Rotundiloba’, which has more rounded lobes on its leaves. It grows only 30 to 50 feet high and 20 to 30 feet wide. Unfortunately, its autumn color is inferior to the species. While some specimens may turn reddish purple, others produce only a dull yellow.

In a hotel lobby, I encountered my first protea in a flower arrangement Is it possible for me to grow this huge bloom?

T.L., Ladue, MO

Answer: The flower you refer to is the king protea (Protea cynaroides). Although there are other protea species in the floral trade, this is the largest-flowered one. The artichoke-like flowers (hence the species name) of king protea vary in size but can be up to a foot across. The compound flower head is composed of a tight cluster of whitish tubular flowers surrounded by overlapping bracts that range from white to pink to deep red with a silvery sheen. King protea is the national flower of South Africa, where it can be found growing wild in the fynbos, a fire-prone environment with nutrient-poor soils.

The plant is an evergreen woody shrub with a spreading habit and round to oblong leathery leaves. Generally, it reaches a mature height of three to five feet. Flowers are produced at the tips of its branches on the current season’s growth. Six to ten flower heads in a season are common, although some selections may yield more. King protea does best in regions that have the Mediterranean climate of wet winters and dry summers. Minimum temperatures of 40-45oF and a maximum temperature of 80oF are best. Provide a sunny location and moderately acid soil (pH of 5) that is nutritionally poor. Proteas can tolerate light frosts, but nothing below 25 o F.

Heavy pruning is necessary to encourage the production of young, flowering shoots. Thin out the stems that bear spent flower heads. New shoots will emerge from the plant’s thick underground fire-proof rootstock. H

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