Re-imagining Mahonia

Mahonias are highly prized by gardeners as winter-flowering evergreen shrubs, but the majority of mahonias that most people know are the Mahonia x media (M. japonica x lomarifolia) selections, that originated in the UK. With age, these can reach 10-12′ tall, and are highly prized for their fragrant winter flowers, and ability to feed pollinators during the winter season.

Another well-known species is Mahonia bealei, which flowers slightly later than the Mahonia x media types and does tend to seed around a bit. It’s known to freak out non-native botanist, who pride themselves on botanical purity, and think nature is, or should be, static to a Camelot-like period prior to Christopher Columbus. Of course, they don’t advocate eliminating far more troublesome non-native species like honeybees, most earthworms, virtually all agronomic crops, and those pesky Homo sapiens.

Starting in 1982, and using what is now primitive DNA techniques, several taxonomists recommended merging Mahonia with their close relatives, Berberis (barberry) into a single genus, Berberis. Those who actually grew the plants strongly disagreed, as well as those who studied their work and found it riddled with problems such as “inadequate taxon sampling, problematic outgroup rooting, inclusion of poor-quality DNA sequences from GenBank, and taxon misidentification.”

Finally in 2017, Yu and Chung, using newer DNA techniques, a much more logical proposal emerged, to split the mahonia/berberis group into four genera, two of which are new, Alloberberis and Moranothamnus. It was shown that the two new genera resulted from ancient repeated hybridizations between Berberis and Mahonia. Sadly, many on-line reference sites, which quickly jump on any passing taxonomic bandwagon, still incorrectly list Mahonia as synonymous with Berberis.

As new Asian mahonia species slowly entered the US, we began to see the real potential for mahonias as garden shrubs. Our mentor, the late J.C. Raulston used to tell me about his desire to retire and breed mahonias, a chance that never presented itself due to his untimely death at 56 years old. The Chinese Mahonia eurybracteata first entered the US in the early 1990s, and was an ornamental game changer. The shorter habit to 3′ tall, and September/October flowering was something that US gardeners had never had access to before. The first named selection of the species, Mahonia ‘Soft Caress’, from Georgia plantsman Ozzie Johnson, hit the market around 2006. Propagation was painfully slow, since no one at the time had been able to master tissue culture of mahonia. The non-spiny foliage and compact size was loved by gardeners, although it turned out to be only reliably winter hardy without damage from Zone 8b and south.

An eight year old, compact seedling in full flower early October.

We dabbled with mahonias from seed after 2000, but took a deeper dive in 2012, as more and more new species became available. Now, we process through several thousand mahonia seedlings annually, with many having genes from a multitude of species. Our goal is to create a series of compact mahonias for the home garden with great foliage, great flowers, and great form. We’d like to think we could add better winter hardiness, but those genes to go north of Zone 6b/7a simply don’t exist outside of Mahonia aquifolium, a plant so distant from the Asian species, that crossing is all but impossible. We have been able to dramatically expand the flowering season to the point that March, April, and May, are the only months we don’t have a mahonia in flower. Only recently was word of the first successful tissue culture of mahonias, so the ability to market new introductions will expand dramatically.

Below is our 2024 seed crop. As you can see, the array of foliage types is quite amazing. We first trial all of our plants in nursery containers to evaluate disease resistance, which is critical to nursery industry acceptance. The next step is in ground trials, and to maximize plant stress, we perform our evaluations in a full sun field. Selecting plants for offsite trials and potential introduction usually takes at least 4-5 years.

Mahonia hybrid seedlings
Mahonia hybrid seedlings

One of our personal favorites is Mahonia x savilliana. Created in the UK and named for Savill Gardens, it is a cross of Mahonia eurybracteata and Mahonia gracillipes. Most UK clones are quite short, but our best seedling from our recreation of the cross is one below that we named Mahonia x savilliana ‘Unsavillized’. The orange color in the flowers comes from the Mahonia gracillipes parent. While the 4′ height and open form would not fit the ideally commercial form, it is a plant highly appealing to garden designers. These are just a few of the exciting things ahead from the world of mahonias.

Mahonia x savilliana ‘Unsavillized’
Mahonia x savilliana ‘Unsavillized’

8 thoughts on “Re-imagining Mahonia”

  1. I couple of years ago, I planted several Mahonia ‘Soft Caress’. It was just a matter of a few days before rabbits started seriously devouring them. I live in Wake County, NC.

    1. Very interesting. Fortunately, they are untouched by rabbits at JLBG. There are some delicious sounding rabbit recipes on-line. If you’re not so inclined, I’d encourage you to try the Trico Repellant, I blogged about earlier this year.

  2. Tony, thank you so much for articles as above providing information on the development of the plant we gardeners like and seek. Although I am no scientist I like to have up to date information when I go plant shopping. Just want you to know all your efforts to keep the public informed are much aporeciated

  3. Incredible read! Though hybridizing Mahonia aquifolium with Asian species is impossible, has anyone actually attempted to?

    Thank you!

  4. Cool hybrid and as ever a fun name. I think the Mahonia split might become widely accepted since there is a logical morphological key and one doesn’t need a $4 million laboratory and four doctoral students to do a field identification:

    Hsieh, C.L., Yu, C.C., Huang, Y.L. and Chung, K.F., 2022. Mahonia vs. Berberis unloaded: generic delimitation and infrafamilial classification of Berberidaceae based on plastid phylogenomics. Frontiers in plant science, 12, p.720171.

    3. Stem dimorphic………………………………………………………………….. 4
    3. Stem monomorphic……………………………………………………………. 5
    4. Stem spineless; leaves 3–9-foliolate…………………….. Alloberberis
    4. Stem almost always spiny; leaves unifoliolate…………….Berberis
    5. Leaves imparipinnate, 5–40-foliolate………………………. Mahonia
    5. Leaves uni- to 7-foliolate………………………………Moranothamnus

  5. Connor Mcgillion

    Amazing work. Hybridizing these Mahonias seems like it’d be great fun! I’d love to see a giant (narrow leaved) Mahonia eurybracteata x lomarifolia hybrid which grows over head height, almost like a palm tree…

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