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Elisabeth C. Miller Library

Keyword: Nandina domestica

Nandina pruning and propagation

I have a Nandina (heavenly plum blossom) that is getting really top heavy and I need to find out how to divide it or cut it back and root the cuttings. I’ve been reading up on it and there is very little information about propagating them.

 

The book American Horticultural Society Plant Propagation by Alan Toogood (1999) recommends
taking nodal greenwood (similar to softwood) cuttings in the summer. The shrub
can also be propagated by division but this is recommended in the early spring
and not in summer due to the increased risk of wilting and scorching.

Rainy Side Gardeners in the Pacific Northwest notes that fresh seed (as soon as it is ripe) can be germinated in six to eight weeks. Old seed may take up to two years to germinate. Semi-ripe cuttings can be rooted in the summer.

As for pruning the Nandina, the American Horticultural Society Pruning and
Training: A Fully Illustrated Plant-by-Plant Manual by Christopher Brickell and
David Joyce (1996) suggests that plants can usually be renovated by cutting back
old canes to ground level in the early spring when the older leaves have turned
from red to green. Rainy Side Gardeners suggest cutting the oldest canes down to
the ground, discouraging the shrub from getting top heavy and falling over. The
pruning will keep it growing a denser growth lower down on the shrub.

A Practical Guide to Pruning: How and When to Prune for Better Shrubs, Trees,
Fruits and Climbers by Peter McHoy (1993) suggests cutting one out of every
three canes to the ground. His recommendation is not to do this each year.

Paghat’s Garden (a website maintained by a local gardener) had this to say:

“Nandina thrives in considerable shade, but has a tendency to become leafless underneath unless it can get sunlight around the lower part of the plant.
Before I transplanted this one, it was in a lot of shade, & needed to be staked
because it became top-heavy. This did not necessarily harm its looks, because
the species’ tendency to lose leaves at the bottom gives it the appearance of a
miniature tree with long trunk, & I used the “empty” space around its base for
small ferns. But when transplanted to a sunnier garden, it became more broadly
bushy & the trunk became stronger, no longer needing to be staked.”

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Toxicity of Nandina berries to birds

A rumor has been circulating among birders in our area (Puget Sound) regarding the toxicity of nandina berries to birds, specifically cedar waxwings. I use a fair amount of nandina in my landscape designs, so this is obviously a concern.

How toxic are nandina berries for wildlife? How often do birds or other critters eat enough of the fruit to be damaging?

 

I think that people are probably referring to this study:

Excerpt:
“Nandina domestica berries contain cyanide and other alkaloids. For most cultivars of N. domestica, cyanogenesis is the most important intoxication factor. Cyanide glycosides are substances present in many plants that can produce highly toxic hydrogen cyanide (HCN). At least 2000 plant species are known to contain cyanide glycosides with the potential to produce HCN poisoning. Generally, most parts of the plants contain cyanogenic glycocides [sic], the young rapidly growing portion of the plant and the seeds containing the highest concentration. At least 55 cyanogenic glycosides are known to occur in plants, many being synthesized from aminoacids as part of normal plant metabolism. Frost and drought conditions may increase cyanogenesis in some plant species. Cool moist growing conditions enhance the conversion of nitrate to aminoacids and cyanogenic glycosides instead of plant protein. Presumably, similar weather conditions during late winter and early spring in the study area might have favored increased cyanogenesis in N. domestica.”

Note that this is the first time a mass death of waxwings has been observed, studied, and related to Nandina. Also note that Nandina is invasive in southern states (which means there is probably a lot of it in Georgia, where the deaths were noticed). If there are diverse food sources for the birds in the landscapes you design, perhaps consumption of a few Nandina berries is less of an issue. Another thing to note is that there are a great many other plants whose fruit contains cyanogenic glycosides, and we are unlikely to be able to avoid planting every single genus with this characteristic.

You could aim to plant several plants in each landscape you create which are the preferred diet of local birds. Here is information about the cedar waxwing’s feeding habits.
Excerpt:

“Cedar Waxwings feed mainly on fruits year-round. In summer, they feed on fruits such as serviceberry, strawberry, mulberry, dogwood, and raspberries. The birds name derives from their appetite for cedar berries in winter; they also eat mistletoe, madrone, juniper, mountain ash, honeysuckle, crabapple, hawthorn, and Russian olive fruits. In summer Cedar Waxwings supplement their fruit diet with protein-rich insects including mayflies, dragonflies, and stoneflies, often caught on the wing. They also pick items such as scale insects, spruce budworm, and leaf beetles directly from vegetation.”

The rumor continues to arise from time to time, because of social media. This article by Mike Darcy, from the April 2014 issue of Digger, is helpful. In it, he quotes Nikkie West, the backyard habitat coordinator for Audubon in Portland, Oregon:
“We have not taken in any birds at the Wildlife Care Center that have displayed the symptoms associated with the Nandina berry, nor have our wildlife veterinarians heard about the issue within rehabilitation circles and professional affiliations in the Pacific Northwest. […] Of the approximately 3,000 birds we take in at the Audubon Wildlife Care Center each year, domestic house cats are by far the largest cause of injuries — about 40 percent. Due to the types of injuries sustained, these birds
have a low survival rate.”

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Plants for privacy screens

Could you recommend some plants for a privacy screen that are also narrow? These would be planted in front of a fence in our backyard.

 

Here is some general information on plants for creating a screen.

Trees for Problem Landscape Sites — Screening from Virginia Cooperative Extension

Bet on Hedges by local garden writer Valerie Easton.

Landscaping for Privacy: Innovative Ways to Turn Your Outdoor Space into a Peaceful Retreat by PNW author Marty Wingate.

Here is a list of narrow plants for a screen from local garden designer Chris
Pfeiffer: “Fastigiate shrubs for naturally narrow hedges.” Compiled by Chris
Pfeiffer. 2005.

Zones 5-6:

American arborvitae ‘Rheingold’ (Thuja occidentalis ‘Rheingold’) 5’h x
3’w

Barberry ‘Helmond Pillar’ (Berberis thunbergii f. atropurpurea
‘Helmond Pillar’) 6’h x 2’w

Boxwood ‘Graham Blandy’ (Buxus sempervirens ‘Graham Blandy’) 8’h x 1-1/2′
w

English yew ‘Standishii’ (Taxus baccata ‘Standishii’) 4’h x 1-1/2′ w

Irish yew (Taxus baccata ‘Fastigiata’) 20′ h x 4′ w

Japanese holly Jersey pinnacle (Ilex crenata ‘Jersey Pinnacle’) 6′ h x
4′ w

Japanese holly Mariesii (Ilex crenata ‘Mariesii’) 3′ h x 1-1/2′ w

Zones 7-9, in addition to the above:

Dwarf yeddo rhaphiolepis (Rhaphiolepis umbellata Gulf GreenTM) 3-4′ h x
2′ w

Heavenly bamboo ‘Gulf Stream’ (Nandina domestica ‘Gulf Stream’) 4′ h x 2′ w

Japanese euonymus ‘Green Spire’ (Euonymus japonicus ‘Green Spire’) 15′ h x
6′ w

 

You might also consider installing a trellis to increase the height of
the fence, and then growing an evergreen vine such as Clematis armandii,
evergreen hydrangea (Hydrangea seemanii), or star jasmine
(Trachelospermum jasminoides).

This link is also helpful (scroll down to
“Evergreen Vines” and look for appropriate height and light requirements).

You could grow bamboo, but I would recommend growing it in a container,
or a series of containers, as you do not want the roots to spread. I have
seen an effective bamboo screen between two houses growing in a long
rectangular lined wooden trough (lined with bamboo barrier). Some species
of bamboo are more tolerant of partial shade than others. Look for a
clumping, rather than a running, bamboo (like Fargesia) to be on the safe
side.

Growing Bamboo
in Georgia

Running and Clumping Bamboos

Bamboos for hedges or
tall privacy screens

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removing a Nandina and planting a Grevillea victoriae

I had a Nandina that I decided to remove today after this winter’s freeze. While digging it up I noticed that the root tissue was bright yellow. The roots seemed fine otherwise–no odd smell, not mushy. Is this color normal for Nandina, or is this a sign of a virus? I lost another Nandina to a mysterious disease that looked like a mosaic virus, but that plant was nowhere near the one I just removed. I planted a Grevillea victoriae in that spot, assuming that diseases affecting Nandina would not affect it. Is this correct?

 

The yellow roots of your Nandina are normal. Nandina is in the family Berberidaceae, along with Mahonia and Berberis, which also have yellow, fleshy roots. Here is more information about Nandinas:
Clemson University page on Nandina

Nandina sometimes suffers from powdery mildew, which is usually not serious, and there is information about this plant occasionally suffering from a mosaic virus and from anthracnose. Here is information about the diseases occasionally affecting Nandina.
Image of Nandina leaf spotting from University of California, Davis Integrated Pest Management

Grevillea is in the Proteaceae family, and I have not found any information that suggests it would be either vulnerable or immune to the diseases which affect Nandina. Some plant diseases affect multiple plant families and others are more narrowly focused. In their native Australia, Grevilleas are not known to suffer from diseases. In our climate, I imagine that cultural and weather conditions would be of greater concern than diseases.
Gardening Australia factsheet
Oregon State University Landscape Plants database information about Grevillea victoriae, excerpted here:
“Sun to partial shade (best). Well-drained, sites, may need occasional summer water to prevent bud drop. Fertilize lightly, avoid fertilizers with a high content of phosphorus.”

on Cistus x purpureus and Nandina domestica

My landscaper has planted several Cistus marked Cistus x purpurea. He said it was a solid colored [pink/lavender] flower without spots at the base of petals. I have spent hours searching for a photo, all photos that refer to purpurea are spotted. They also are
referred to as orchid rock rose. Once there was a picture of a unspotted shrub, referred to as Cistus and next to it was a spotted one that had the purpurea label. Can you shed some light?

Also planted is Nandina domestica “Royal Princess.” There is hardly any information available on my search for this. It appears to be pretty, but I did read that outside of Seattle, some nurseries on the west coast stopped selling it. Should I anticipate a problem with this plant ? I also read that in some eastern states Nandina domestica is invasive.

 

Here is what I found on the web page of the Royal Horticultural Society.
The correct name is Cistus x purpureus. It has deep pink flowers with burgundy blotches at the base of the petals.

The Cistus website (a British site), in addition to its gallery of pictures of different species of Cistus, has some information about misnamed plants, which may be what you and your landscaper encountered.

Here is information from The National Gardening Association about Nandina domestica ‘Royal Princess.’

Here is an excerpt from San Marcos Growers site:

Nandina domestica ‘Royal Princess’ (Heavenly Bamboo) – This is an upright growing shrub to 6 to 8 feet tall has very lacy foliage. Pinkish white flowers bloom in clusters at the ends of branches in the late spring and summer followed by a heavy set of red berries ( notably heavier than most Nandina cultivars). The foliage turns to burgundy in spring and later a orange-red in fall. Branching stands stiffly upright unlike typical Nandina domestica and the foliage has a much finer texture. Plant in sun or shade. Tolerates fairly dry conditions but looks better when given water occasionally. It is hardy to about 10 degrees F.

Nandina is widely grown in our area, and so far has not exhibited the
invasive properties it has in the Southern U.S. Several cultivars are
listed on the Great Plant Picks website, which is created by local
gardening experts, so I am assuming there should not be a problem with
growing it here. If you are still concerned about it, the main way it
becomes invasive is from the berries setting seed and spreading. You
could plant native ornamentals in its place, if you wish. Here are links
to information about native plant landscaping:

Washington Native Plant Society
PlantNative.org
King County’s Native Plant Guide

purple-leafed shrubs

Can you give me some information on Weigela Midnight Wine and dwarf Nandina? Are there any plant lists of purple-leafed shrubs?

 

Following is a good description of Weigela ‘Midnight Wine.’ The information comes from the Missouri Botanical Garden, so it is tested and accurate.

WEIGELA

‘Elvera’ Midnight Wine is a dwarf version of the popular Weigela ‘Wine and Roses’ (W760). It is a dense, rounded, low-growing deciduous shrub that typically grows to only 1.5-2 feet tall and as wide. Features profuse reddish-pink flowers and burgundy-purple foliage. Reddish-pink, funnel-shaped flowers (to 1.25 inches long) appear singly or in clusters along the branches of the previous year’s growth in mid- to late spring, with sparse and scattered repeat bloom often occurring on new growth as the summer progresses. Elliptic to obovate, glossy, burgundy-purple leaves (to 3 inches long) turn very dark purple in autumn. Hummingbirds are attracted to the flowers. Original cultivar name is ‘Elvera’, but plants are being marketed under the registered trademark name of Midnight Wine. U. S. Plant Patent #12,217 issued November 20, 2001.

NANDINA

There are several varieties of dwarf Nandina, such as ‘Harbour Dwarf,’ ‘Firepower,’ ‘Nana,’ and ‘Nana purpurea.’ University of Florida Extension has a feature on dwarf Nandina on their website (now archived).  There are also plants available from nurseries such as Forestfarm Nursery in Oregon, and Whitney Gardens in Washington.

PLANT SUGGESTIONS

As far as lists of plants with purple foliage, you should find a wealth of information in the book Black Magic and Purple Passion, by Karen Platt, 2004. There are also lists online, such as this page from Iowa State University Extension, entitled “A Passion for Purple.” You can also search Royal Horticultural Society’s Plant Selector and other similar resources by leaf color.

treating powdery mildew on Nandina

Can you give me some suggestions on how to treat a Nandina infected with powdery mildew?

 

Apparently, powdery mildew on Nandina is becoming a common problem in our
area, as the article linked here indicates.

While this fungal disease is unsightly, it generally does not kill
affected plants. Sometimes improving air circulation around the plant (by
pruning congested growth) can help, and making sure to practice good
sanitation by picking up fallen leaves affected by the mildew is also
important.

There is an interesting idea in this Science News article on
using milk powder in water as a spray to control the disease.

Several organic gardening sources recommend a baking soda spray. The
Organic Gardener’s Handbook of Natural Insect and Disease Control by
Barbara Ellis (Rodale Press, 1996) recommends dissolving 1 teaspoon of
baking soda in 1 quart of warm water. You can add up to a teaspoon of
dish soap to make the solution stick to the leaves more effectively.
Here is another source with slightly different recommendations, from the
National Sustainable Agriculture Information Service.

More from University of California, Davis. Excerpt:

Shade and moderate temperatures favor most powdery mildews. Locate plants
in sunny areas as much as possible, provide good air circulation, and
avoid excess fertilizer. A good alternative is to use slow-release
fertilizer. Overhead sprinkling may actually reduce the spread of powdery
mildew because it washes spores off the plant; also, if spores land in
water, they die. The best time to irrigate is in mid-morning so that the
plants dry rapidly, reducing the likelihood of infections by other fungi,
such as the ones that cause rust or black spot infections on roses. As
new shoots begin to develop on perennial plants, watch closely for the
appearance of powdery mildew.