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Redwood burl seeds

Poaching Redwood Burl Affects Tree’s Reproduction

Like other conifer trees, coast redwoods produce cones with seeds. However, their main reproductive strategy involves the lumpy burls that bulge from their base and roots, which sprout clones of the parent tree.

“It’s very difficult for a seed to drop on the forest floor and grow. There isn’t much light,” said Emily Burns, the science director of Save the Redwoods League. “The (burl) sprout is going to be able to benefit from the nutrients and water provided from the parent plant and the sugar from the canopy.”

When the parent tree dies, or space in the canopy opens up, the burl sprout is ready to shoot up quickly and claim the real estate.

“It’s a brilliant strategy,” said Burns. “To me it’s like an insurance policy for the plant — rebuild after disaster.”

A burl grows along the base of a redwood tree. Photo: Dale Beckett, Flickr.

Far from being merely misshapen growths, burls can be considered a key mechanism of survival of the world’s tallest trees. They also happen to be the prize of many a wood collector for the unusual shapes and ring patterns that form from the twisted and interlocked grain.

Along the northern California coast, burl poachers have become so pervasive that park officials have started closing the popular Newton B. Drury Scenic Parkway in Redwood National and State Parks at dusk. The poachers are apparently after the largest burls that grow in the remaining old growth redwood stands. Hacking off a burl not only destroys the redwood’s effectiveness at reproduction, but also opens the tree up to disease and other infections, and makes it susceptible to falling over, otherwise known as windthrow.

But Burns said burl removal doesn’t necessarily cause the tree to die.

“Redwoods are very hearty and very good at regrowing bark over their wounds,” she said. “There’s a lot of reason to think that these trees will be okay, but it’s weakening the tree. It takes a long time, but redwoods really do heal over wounds.”

Redwood burl boxes sold at the Muir Woods gift shop. The wood comes from old stumps from trees, fallen trees or waste wood lumber operations Photo: Austin, Flickr.

In theory, burl wood harvesting could be a sustainable resource, if done properly, Burns said. Burl wood bowls, furniture and other items can be found in shops in the Bay Area, but its source is rarely labeled, leaving open the question of whether the wood is legally harvested off private lands or whether it’s been poached from parks.

“The issue is, we can’t trace the source of it as a consumer, so given a sense of caution I would say don’t buy burl,” said Burns.

If you find redwood burl hard to resist (it is, indeed, beautiful), there is one palatable option. Search for burl wood products under the Forest Stewardship Council (FSC) label. The FSC certifies wood and wood products as sustainably harvested. Burl wood would likely fall under its “chain of custody” standards for secondary wood products, said FSC spokesperson Brad Kahn.

“If a forest is being harvested illegally (poaching implies this), then it cannot be FSC certified,” said Kahn in an email. “Legality is one of the first things the auditor checks. But assuming it is legal and part of an auditor approved management plan, a forest landowner could theoretically include burl as a product they produce from their certified forest.”

“In short, there is no reason that FSC certified burl could not be sold into the market, as long as the forest is managed to FSC standards.”

One fun fact about redwood burls: some of the trees sprout albino. They never turn green, and presumably cannot survive without the parent tree, because they do not produce chlorophyll.

“If we lose those burls, we lose those genetic anomalies,” said Burns.

Alison Hawkes is the online editor of Bay Nature.

About the Author

Alison Hawkes was a Bay Nature editor from 2011-2017. Before Bay Nature she worked in journalism for more than a decade as a former newspaper reporter turned radio producer turned web editor with each rendition bringing her closer to her dream of covering environmental issues. She co-founded Way Out West, a site dedicated to covering Bay Area environmental news.

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Let’s Rely on Each Other

Redwoods are monoecious, meaning both male (pollen-producing) and female (seed-bearing) cones are borne on the same tree but on different branches. The pollen is shed in winter or in spring, whereas the mature, fertilized ovulate cones ripen in early fall to shed their seeds in late fall and early winter. Cones are only produced after they reach the canopy and can use direct sunlight for energy. Redwood cones are only about one inch long. Each cone holds between 14 and 24 seeds. The seeds are so tiny that you would need over 100,000 seeds to weigh one pound! Redwoods start to bear their seeds when they are about five to fifteen years old. The cones dry under conditions of low humidity and release their seeds. Rains normally speed up seed dispersal. The seeds are normally ready to germinate soon after they have fallen to the ground, as long as the soil is moist and the weather is warm enough. Studies have shown that seed viability increases with the age of parent trees. Maximum seed viability was reached when trees were over the age of 250 years. On the other hand, seeds produced by trees under twenty years old were less than one percent viable. One tree can produce six million seeds in one year. However, less than 5% of these seeds germinate, and only a few of these end up growing into seedlings. Failure usually results from parasitic fungi, summer drought, or other causes.

Young trees are capable of sprouting from their parent’s roots, benefiting from the root system already present, along with the energy and nutrients contained inside. They could also sprout from dormant buds in the burls at the base of a tree or from fallen trees. Redwood burls are gnarled structures that form from axillary buds on seedling redwoods(left). In addition, if a tree is cut or burned, a family circle of trees may grow up from the stump(below). Stumps of small, young trees sprout more readily than those of large, old trees. Because the root systems are already established, these sprouts grow more vigorously than seedlings and therefore are the more common form of reproduction. This way of reproduction results in trees that are genetically identical to the previous tree.

In good living conditions with a lot of sunlight, redwood seedlings grow quickly, more than a foot per year in some trees. Trees that originate from seeds do not experience rapid height growth until they are over 10 years of age. Growth of young redwoods is best in full sunlight, but the trees are able to grow in dense shade as well. Photosynthesis rates are surprisingly high in redwoods, even at low light intensities.

The coast redwood lives incredibly long, grows taller than any other tree species in the world, and is exceeded in bulk by only the giant sequoia. Becoming sexually mature at the age of 10 years or less, the redwoods continue to grow in volume for hundreds and hundreds of years. The oldest redwood found so far, according to the growth ring counts, is almost 2,200 years old. Although, on average, redwoods seldom live more than 2,000 years, which is two-thirds as long as giant sequoias, and only half as long as bristlecone pines. Secondary growth of individual young trees can be extremely fast or very slow. Where competition is high, the annual diameter increase could be less than one millimeter. On the other hand, where competition is not a problem, the diameter could increase by more than 2.5 cm in one year.

The life cycle of a conifer.

Now that you’ve learned all about the reproduction of the coast redwood, it is time to discover the many connections this tree has with other organisms. If this sounds like something you’d be interested in, go to Interactions with Other Species.

How to Grow a Live Redwood Burl

At the base of a redwood tree (Sequoia sempervirens) are lumpy, gnarled growths called burls. Inside them are buds that sprout if the redwood dies. The shoots form new trees, preserving the genetic code of their parents. Important to forest regeneration, burls are at risk because the highly patterned wood they contain is valuable. As redwood forests disappear because of logging, poachers illegally harvest large burls from public lands, damaging redwood trees. Sometimes you find redwood souvenirs of small, legally harvested burls. These sprout in water. They might not root, but the shoots can live for several years.

Getting Started

A living but dormant redwood burl doesn’t look very viable. It has a flat side where it was cut from the tree and a lumpier, curved side that contains the buds that will sprout. Choose a low-sided container that will hold the burl with an inch or two of extra room along its sides. If you’re going to display your sprouted burl, consider using an ornamental plant saucer or decorative shallow bowl. Add about 2 inches of water and put the burl into the container, flat side down. Place the container and burl in bright light and add water as needed to maintain the level.

Sprouting the Burl

Usually the burl begins to sprout after a few weeks. Peter Del Tredici, director of Harvard’s Arnold Arboretum, had redwood burls sprout within a week or two after placing them in water. The new growth is rather ferny-looking because of the redwood’s fine needles, and a number of shoots usually emerge. You can allow all of them to develop or you can perform selective pruning to thin out the growth. The redwood shoots get taller as time goes on. The shoots can last for several years. Usually they eventually die because of over- and under-watering or from fungus disease.

Rooting the Burl

Sometimes burls will form roots, and then they should be treated as you would a redwood seedling, planting it in potting mix. To increase the chance of a burl forming roots, follow Del Tredici’s example. He put sprouted redwood burls inside a greenhouse with plenty of water and light, and the burls grew roots after six months to a year.

Potting a Rooted Burl

Choose a container with drainage holes slightly larger than the burl’s diameter. Use a well-draining mix such as a quality soilless potting mix. Make your own by combining 2 parts of peat moss with 1 part each of vermiculite, perlite and pine bark. Hold the burl in the pot at about the level you’d like it to be and fill in around the roots with the potting mix. Tap the pot occasionally to remove air pockets. Water the container until water comes through the drainage holes. Place the pot in partial shade. Keep the soil evenly moist. If you live within redwood’s U.S. Department of Agriculture plant hardiness zones 7 through 10a, you’ll eventually be able to plant the rooted burl outdoors. Redwood needs a large space and is capable of reaching 120 feet tall. If the burl must remain in limited space, consider training it to be a bonsai subject.