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# 1 Hyperion and Helios

Disclaimer: This analysis is based on my own interpretation of published redwood study information, primarily from this source:

**How do tree structure and old age affect growth potential of California redwoods?**

**Stephen C. Sillett, Robert Van Pelt, Allyson L. Carroll, Russell D. Kramer, Anthony R. Ambrose, D’Arcy Trask**

*Ecological Monographs 2015 Vol: 85 (2) :181-212.
doi: 10.1890/14-1016.1*

So here we go ….

Hyperion and Helios are remarkably similar redwoods in some ways. They both grow on steep slopes above Redwood Creek tributaries. Their diameters and heights are very similar. But there is one big difference – Helios is 2040 years old versus Hyperion is a sprightly 1260 years old. Then also Helios has reiterations in its crown versus Hyperion does not. A reiteration is regrowth after breakage.

I started to think, I wonder what the height of Helios was before its top broke off and grew back. Was it once taller than its current height of 377 feet or so?

Well, I think it was taller, a little over 400 feet tall, and that was not so long ago.

# 2 Helios Height Estimate Before Reiteration

The idea is to review diameter at 80 meters in height for Helios and Hyperion, then for calculation purposes adjust Helios’ diameter at 80 meters downward a bit due to its greater age.

Then, take the amount of growth in Hyperion above 80 meters as a function of its trunk diameter at 80 meters. This is then applied to the Helios diameter at 80 meters to arrive at a Helios height before reiteration. Remember Hyperion has no reiteration in its crown.

Then to get the approximate date of the Helios reiteration take the Helios average change in height per year and apply this to the amount of height that is above the reiteration.

So we start with this table:

Tree Name | Age | Study Year | Height | Diameter cm at 80 meter height (est) | Ring Width cm at 80 meter height (est) | Diameter cm at 80 meter height age adjustment | cm growth above 80 / cm diam at 80 |

Hyperion | 1260 | 2010 | 115.62 | 163 | 0.065 | 0 | 21.9 |

Helios | 2040 | 2013 | 114.82 | 198 | 0.048 | -4 |

And from there do this set of calculations:

Hyperion cm growth above 80 m / cm diameter at 80 m | 21.9 |

Helios original growth above 80 m based on Hyperion | 4236 |

Helios height pre reiteration in meters (est) | 122.36 |

Helios height pre reiteration in feet (est) | 401.5 |

Helios reiteration point height meters | 106.5 |

Helios actual reiterated growth meters | 8.32 |

Helios growth rate per year centimeters (past 10 yrs) | 9.2 |

Helios estimated age of reiteration in years | 90.4 |

So it can be inferred there was at least one 400 foot redwood in the past, it was Helios. The top was probably blown out during a major windstorm between 1900 and 1925.

Helios may be a 400 foot redwood once more, but that will take another 70 years or so.

If there is a 400 foot redwood again it will probably be Helios, Hyperion, or some other redwood growing on a bench on a steep hillside with relative protection from high winds. Trees growing on flats along Bull Creek or Redwood Creek are probably too exposed to high winds to avoid breakage once they get a lot taller than the rest of the surrounding redwoods.

Then the other factor is the timing of the next Cascadia earthquake. That will snap off a lot of the tops.

Thanks for reading.