Saving a Genus
Brooklyn Botanic Garden's magnolia collection is in full swing right now. The loveliness of these trees may be unmatched but the enjoyment of these timeless beauties goes deeper than their primitive-like blossoms, glossy leaves, graceful forms, and artful arrangement.
A walk through Judith D. Zuk Magnolia Plaza brings the visitor a comfort of the ages, a harkening back to perhaps the beginning of flowering botanical time.
With its collection of 17 varieties of magnolia species and hybrids, many bred at BBG, the Garden steps forth in its role as plant collector and breeder, living museum, seed bank and maybe savior - a bastion against the demise of wild magnolias.
Over half of wild magnolia species face extinction, according to The Red List of the Magnoliaceae, a report by Botanic Gardens Conservation International (BGCI), a British organization involved in worldwide plant diversity conservation with US headquarters at BBG, and Fauna & Flora International, a British-based organization dedicated to conserving threatened species and ecosystems.
They say, of 245 species of magnolias, globally, 131 are imperiled, mostly in Asia and South and Central America. Northeastern U.S. species appear not to be in danger. A trip to Magnolia Plaza brings assurance that public gardens such as BBG are dedicated to the survival of this magnificent, beetle-pollinated family.
“Gardens endemic to an area preserve, protect, and hold plants that would otherwise have gone away,” says Patrick Cullina, BBG vice president of horticulture and facilities.
The BBG collection has three kinds of magnolias:
1. Early - saucers, star, and Yulan
2. Species - North American natives
3. Late bloomers - the heart of BBG plant breeding.
BBG began their Magnolia breeding program in 1978 with M. acuminata (cucumbertree) to anchor crosses, such as the cross with Yulan Magnolia, M. denudata, that produced fragrant ‘Elizabeth.’
They crossed Elizabeth with M. liliiflora, the anchor of Little Girl Hybrids developed at the U.S. National Arboretum, to produce Judy Zuk.
Uphill, the fragrant M. sieboldii ‘Oyama’ opens with stunning white flowers with deep magenta stamens. M. lennei blooms pale inside with a pink exterior. Southern magnolia, M. grandiflora ‘Edith Bogue,’ exhibits a gardenia-like rich, drenched, whiteness.
Sweet Bay, the most prominent native magnolia in DIG IT! territory, is an indicator species of forest quality, growing on forest edges and in wet habitats. This June bloomer is secure within northeastern forests and does not face extinction. “There are more forests now than anytime in the last 200 years,” says Steven Clemants, vice president of science. He has been working in New York forests for 25 years.
But what, exactly, does “face extinction” mean? “It means they survive in gardens but won’t survive in the wild,” Clemants says.
It’s no news that as human populations grow, their need for land for habitation and the materials it provides causes habitat destruction and loss. Of China, Clemants says, “The pressure for land use is ever-increasing. Forests are being cut down. The loss of the forests these trees are in is a prime problem. It’s not just human habitation; it’s human use. They’re growing in forests and forests are used for wood, for fuel, for any number of things.”
And, yes, population size really does matter. “In Hawaii, there are plants known from three individuals. Any random event could destroy that species. With a sizeable but single population, like on a mountainside, there’s risk of chance events, like Asian Longhorn Beetle, coming in that could destroy that population and the species is lost.
“Some areas where you have mountains and each mountain top is distinct from the next one down the line, you often get species that have evolved for that one small habitat and you won’t find it anywhere else. It can be a natural part of that species that it’s just a small population, but that doesn’t mean it’s not at risk.”
Not to mention that tropical forests are at high risk with slash and burn agriculture.
Even if the forest remains intact, other things may be happening that are not good – insect damage, drought or other things that impact a forest that may not be visible immediately.
“The forest is still there; it’s got big trees; it’s green; everybody thinks it’s great. But there are certain species that are more sensitive to changes, like the canary in the mine shaft. If you start to see these species struggling or dieing, that’s an indication you’re having trouble with that forest. Magnolias are one of those indicators,” says Clemants.
So what can be done?
1.) Preservation in its natural habitat. Many species co-occur. When removing one magnolia from a landscape, those other species may not come with it.
2.) Creating seed banks. Seed can be grown to restore decimated or reduced populations in their habitats or used elsewhere.
Types of seed:
1.) Orthodox: species from dry areas. Dried seed is put into liquid nitrogen and kept for hundreds of years.
2.) Recalcitrant: seeds like acorns that germinate and cannot dry down. Tissue culture is an option: bits of embryo are grown at low temperatures in test tubes and preserved.
“Growing collections of magnolias in botanic gardens and arboreta go hand-in-hand with seed storage – “ex situ” – preserving the species outside its habitat,” says Clemants.
But one or two magnolias growing in a garden contain a very small amount of the original gene pool, while large populations in the wild have a variety of genes.
“One way that gardens try to get around that is to have different genetic make-up plants at different gardens so that, as a totality, if we have one magnolia and the National Arboretum in Washington has one, and San Francisco has one then we’ve increased the gene pool that’s in the living collections in the Gardens of North America,” says Clemants.
What can a homeowner do?
If you want to grow native magnolias, Clemants recommends getting plants that came from the genetic make-up of this area rather than elsewhere. Why?
- To improve the local gene pool
- Plants evolve for a specific habitat. The chances of a southern-grown plant doing well compared to ones that have been here for thousands of years is less likely.
“As homeowners want to grow more exotic magnolias, there’s a double-edged sword. People may be going out and cutting it down to bring it into cultivation, but more than likely they would be using seed. That’s a problem conservationists have is how do you make that decision. Is it better to develop a demand for something with the potential threat that people will go out and over-collect it? Or is it better not to build up that demand but then there’s nobody caring whether that species gets lost,” says Clemants.
“These are species that generally grow lower in the forest. If you see them in a forest, it’s a healthy forest generally. If you start to see them dieing out, then that’s a sign the forest is becoming unhealthy.”
So take a walk around Magnolia Plaza and fall in love with these relatives of ancient, regal plants. They may just be the ultimate flowering plant – primitive, fragrant, sleek bark, super limbs, and blossoms that make you smile.
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published May 24, 2008