Q. When is the correct time to prune a Japanese pine? Late February? March?
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A. You definitely do not want to prune any pines over winter unless they are very large and you are removing entire branches. If you are pruning to maintain a dense shape or a more compact habit, you will want to prune in spring as the new growth is emerging. New growth on pines is commonly called a candle. Prune those candles back a third or a half as they elongate. Remember that pines only have one flush of growth per year so for the most aesthetic pruning, don’t miss that growth. Pines can be sheared into early summer although this will sometimes lead to unsightly cuts and odd branch angles. Never prune your pine back beyond where there are green needles unless you are removing an entire branch.
Black peony buds
Q. I planted two peonies in pots last year. The plants are healthy, but the buds turned black. Any idea what is the problem?
A. It sounds as though your peonies are suffering from what is often termed bud-blast. Bud-blast occurs as a result of stress to your plants. Some of the most common reasons for bud-blast are late spring frosts, planting too deep, infertile soils, too much shade and drought stress. Sometimes young plants will form buds but are really too immature to support the energy-intense process of flowering and will instead abort the buds. Make sure you are providing an optimum environment for your peonies and they should be fine. The only similar affliction is caused by Botrytis, but if that were the case you would see other signs on the rest of your plants.
The Wrong Rose
Q. We planted a Joseph’s Coat climbing rose on the south side of the garage and created a wire trellis thinking it would branch out across the brick exterior. The rose is growing in height but very little laterally. My husband thinks we should take it out and plant a different rose. Are we doing something wrong or should we get a different rose?
A. Most modern climbing roses need some work in order to grow how and where we would like them. Climbing roses tend to grow long vertical woody shoots rather than twine like other vines. I would prune your roses back hard this winter. As new stalks grow, attach them while they are still young and flexible to the trellis in the direction you want them to grow. Prune out shoots which don’t grow where they should. Keep in mind that the heaviest flowering will be from horizontal shoots so encouraging more horizontal shoots will encourage more blooms. Each winter prune your vines back to mostly horizontal stems.
Mark Weathington is the director of the JC Raulston Arboretum at N.C. State University in Raleigh. Info: jcra.ncsu.edu. Please send your garden questions, including the city where you garden, to: email@example.com.
Common name: Japanese Black Pine
Botanical name: Pinus thunbergii
Family: Pine (Pinaceae)
Primary uses: Specimen, windbreak, bonsai
Dimensions: 25-40 feet tall in cultivation
Culture: Sun. This conifer is a relatively quick growing pine suitable for growing in most sunny conditions if given adequate drainage. Prune the emerging new growth (candles) by pinching them back a third to half as they emerge in spring to control size and keep dense. Japanese black pine is especially tolerant of sandy soils and salt spray making it very useful as an ocean side windbreak. Once established, it is quite drought tolerant. Expect it to be relatively short-lived in zones 7-8 if grown in heavy soils. Hardy to zone 5.
General attributes: This picturesque pine makes a lovely landscape specimen with dark green needles and a typically dense but irregular habit. The new growth is often a silvery white as it emerges for a lovely contrast against the older dark needles. A wide-spreading more compact form known as ‘Thunderhead’ is quite often grown.