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Propagating Redwoods from Cuttings

We are deep into redwood season. Our efforts this month have been concentrated on redwood seed collection followed by seeding in our nursery greenhouse and in local classrooms. Each class is studying climate change and how planting redwoods is one way we can mitigate our impacts.

The mighty redwood begins from a tiny seed half the size of your pinky fingernail! Each tree will produce tens of thousands of seeds in its lifetime. This is because redwood seeds rarely find the essential conditions to germinate. The tree puts out a lot of seeds to guarantee that a few will find prime growth conditions.  In order for a redwood seed to grow, it needs to land somewhere on the forest floor where it will have access to light as well as direct contact with soil. Considering the soil of a forest floor is often covered in layers of pine duff and leaves, this is no small task. Redwood seeds require a natural disturbance such as heavy rain or fire to gain access to soil. Because of the gamble the trees make for their seeds finding ideal growth conditions, redwood trees have evolved a variety of routes for reproduction.

Redwoods are able to sprout new trees from the base of their trunk. Our nursery is experimenting with the possibility of growing trees from the new growth. Sprouts are carefully cut and propagated in our nursery. To maintain a strong redwood genetic bank in the region, our nursery tries to balances efforts between starting trees from seeds and cuttings.  Redwoods have 28 pairs of chromosomes, compared to humans 23.  Redwood cuttings will have less diverse genetics than trees that were started from seeds because cuttings make direct clones of the parent tree whereas seeds contain a new genetic map.

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Here is our nursery manager, Audrey, holding a fresh cutting taken from the base of the tree. Some sprouts can be divided into multiple cuttings.

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She removes current branchlets to expose at lease 2-3 nodes. A node is where a branchlet once grew. Once removed and dipped in plant growth hormone, roots will start to form from the exposed cells. This growth is encouraged by peeling off a bit of the cambium layer around each node and at the base of the cutting. This process is called scarring.

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Audrey dips exposed nodes in a rooting hormone for 5-7 seconds to help stimulate growth.

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We then use a dowel to create a hole in the soil, larger than the cutting. This ensures that when the plant is tucked into the soil, the rooting hormone does not rub off.

These redwoods plantings will be nurtured into maturity until they can be planted and thrive at a restoration site. Cuttings can take an entire year to start growing a root system, but some may start showing roots after six months. A redwood tree is planted at a restoration site when it is two or three years old. Older trees grow more each year, meaning older trees have the ability to take in more carbon. These are truly an investment into the future.

Each year we document our planting and propagating processes in the nursery and analyze our results to try and develop best practices. Currently, we see about a 50% survival rate from this process of propagating redwoods from cuttings. We hope to hone our knowledge and skills to improve our success rate in the future!

Through the progress of this project so far we have out planted 175, 4 year old redwoods. At year 4 they each hold 23.6 lbs. of carbon according to the forest service calculator estimation. This toals 4,130 lbs. of carbon.

When these trees are 100 years old they will each hold 24,876 lbs. of carbon. If we planted no more trees this would still total over 4,353,300 lbs. of carbon. At this point you would also want to add the value of carbon stored in healthy redwood soils by using calculators based on hectares of forest.

With thousands of seedlings in the nursery we hope to invest in a long lasting bank of carbon. We may never see the carbon storage benefits of these redwoods in our lifetime, but are doing our part to invest in the future.

Do you want to learn more about this or other native plants? Join us for a native plant nursery volunteer day, almost every Friday, from 10am to 2pm. Find our event calendar with up to date event listings here: https://seaturtles.org/take-action/event-calendar/