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A hawthorn that has not flowered

Berries on a Washington hawthorn.
Berries on a Washington hawthorn. Courtesy of JC Raulston Arboretum

I received a sapling from the Arbor Day Foundation a number of years ago that was identified as a Washington hawthorn. It is now about 14 to 18 feet tall. I have read that it should have small white flowers during a certain period of the year, but the tree has not produced any flowers. Is this due to it being still too young? Is there anything I can do to stimulate it to grow flowers?

Anders Flodin

Holly Springs

A 14-foot Washington hawthorn should definitely be flowering by now. Clusters of small white flowers in spring will be followed by bright red to red-orange fruits in late summer and fall. Washington hawthorn (Crataegus phaenopyrum) makes a 25- to 35- foot-tall tree. It grows fairly quickly when young but slows down with age and is a useful plant for wildlife gardens since both birds and squirrels will eat the fruit. It is quite tough and will adapt to less than ideal landscape situations. It is susceptible to a variety of fungal and bacterial problems in our area, including fire blight, which will blacken entire stems; and an assortment of leaf spot diseases.

Occasionally trees may be misidentified, your plant should have serrate edged leaves with three lobes. The branches will have some long, vicious thorns as well, and the overall tree is typically quite twiggy and dense. If you think misidentification is a possibility, bring a branch or send a photo to your local extension agent or to the JC Raulston Arboretum.

Lack of flowering on a Washington hawthorn is likely due to it growing in a spot that is too shady. It prefers full sun and will require a good four hours of bright light to produce flowers. Pruning your tree in fall or winter also will prevent flowering, because it develops its flower buds toward the end of the previous growing season. The last reason for not flowering could be excess nitrogen fertilizer. If you do a lot of lawn fertilizing, you could be stimulating the vegetative growth of your tree at the expense of flowers.

Will elderflower grow here?

Please can you advise as to whether elderflower is native to this area or if it can be cultivated here? I’ve missed it since moving here from the British Isles and I would also like to use it in cooking.

Micheàl Lynch

Cary

European elderflower or elderberry, Sambucus nigra, is not native to North America. While it can be grown here in North Carolina, it really prefers a somewhat cooler climate. Our native elder, Sambucus canadensis, is very similar and can be used for cooking as well. There are likely fewer selections of our native species, but the cultivars Adams and York are especially good fruiting forms. Both the European and American elders make somewhat rangy multi-stemmed shrubs with pinnate leaves and white, late spring flowers followed by glossy black fruits.

Best fertilizer for perennials

What is the best type of fertilizer to use and when should I fertilize various perennials, such as camellias, rhododendron and hostas? Would a liquid fertilizer be better than a granular fertilizer, and what ratio of NPK?

Sylvia McCollum

Nashville

I am not a big proponent of utilizing lots of fertilizers in the garden for trees, shrubs and herbaceous perennials. Instead, I recommend utilizing compost and organic mulches, which will not only provide nutrients but will also help build soil structure over time. In general, our red clay is very high in fertility, although in some areas which have historically been intensely cultivated as farmland will need some supplemental fertilizer. The first step is always to take a soil sample to your local extension agent for analysis. Quite often a soil may be low in one nutrient but not need others and in that case, you are throwing money away by putting down fertilizer which will not be used. The main nutrients – nitrogen, phosphorus and potassium (or N-P-K as they are listed on fertilizer packages) – are the primary concern. Nitrogen is mobile in the soil, so soils often are lacking in nitrogen. If you overfertilize with nitrogen, it will simply leach away. Phosphorus and potassium are much more stable in the soil and overfertilizing with them will lead to huge build-ups over time.

Once you have a soil test done and know what nutrients, if any, are needed, you can decide on a fertilizer. I usually only use a liquid feed on flowering annuals, which are heavy feeders. For almost everything else, I use a granular fertilizer if I use anything. My preference is to use either a slow-release fertilizer in spring or to split my application in two. I will apply at half rate in spring between Easter and Mother’s Day and the other half around the Fourth of July.

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: askthegardener@newsobserver.com.

Plant Spotlight

Common name: Japanese Woodland Peony

Botanical name: Paeonia japonica

Family: Peony (Paeoniaceae)

Category: Herbaceous perennial

Primary uses: Shade gardens, woodlands

Dimensions: 1.5-2 feet tall by 2 feet wide

Culture: Part sun to shade; moist, well-drained, organic soil.

Bloom time: April to May

Bloom color: White

Hardiness: 15 below zero (USDA hardiness zone 5)

General attributes: While most peonies prefer full sun and an open spot in the garden, the Japanese woodland peony prefers a shaded garden spot, where it makes a low mound of deep green leaves topped by cupped, white flowers in spring. The mass of yellow-tipped stamens and central burgundy blotch shine against the pristine white background. By mid to late summer the seed pods split open to reveal metallic blue seeds held on scarlet red stalks. Japanese woodland peony does not tolerate heavy clay soils or lean sandy ones well. It should be planted in a loose, humus-rich spot. If your plant produces red seeds instead of blue, you likely have the white form of Paeonia obovata, another woodland peony which is often sold under the wrong name.

Win a Gardening Book

We’re seeking more questions from gardeners for this monthly column. Please send your gardening questions, including the city where you garden, to: askthegardener@newsobserver.com by May 31. You will be entered to win one of these lovely gardening books: either “Shakespeare’s Gardens,” by Jackie Bennett or “The New York Botanical Garden,” by Gregory Long and Todd A. Forrest. We’ll choose two winners at random.

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