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Florida Torreya Assisted Migration Documentation by Torreya Guardians (Updates of this page: https://www.torreyaguardians.org/limits-northward-torreya.html) There is no doubt that global heating is underway, although there are some differences of opinion among the populace (less so among scientists) as to the most important causal factors. Long before any significant change in the global average temperature is experienced by individuals, the much larger amplification of weather extremes has already become impossible to ignore.
WHY EXPERIMENT with planting a Florida species a thousand or more miles poleward of its historical range? In part, it is to answer these questions: • HOW FAR NORTH does it make sense to officially begin "assisted migration" for a critically endangered plant that is already suffering from heat-induced diseases in its small, historical range in Florida?A quick look at the MAP BELOW suggests that if any of these experiments are too far north, it would be the one in northwestern Wisconsin. And what's going on in Illinois?
The rest of this page documents in photographs and text the degree of frost damage (or outright winterkill) at each of the starred locations.
• Hayward, Wisconsin is the bolded city in the center of the purple (COLDEST) temperature region. Mike Heim is the torreya planter there and he recorded -30F as the coldest temperature reached (January 21). These 3 torreya seedlings exhibit the full range of winter exposure: from zero damage to entire kill. 
CONCLUSION: Especially if snowcover is available, very short seedlings are not exposed to the worst temperature conditions. Therefore, until (and if!) the torreyas in this extreme climate zone survive well enough to grow much taller than they are now, it will be wise for torreya volunteers to participate in less extreme climate zones. Referring back to the USDA MAP at the top, it is wise to STAY IN THE GREEN ZONES!
• Visit the Hayward, Wisconsin torreya page for full documentation.
PHOTOS ABOVE were taken by Guy Sternberg on 27 April 2025. Not only is there apparently no winterkill, but the same tallest torreya (as above) is already bursting its apical buds. CONCLUSION: This site deserves a lot more scrutiny to determine why torreya can do so well here, despite a brief episode of -20F that was recorded in Springfield IL. Surely, planting on the lower slope was crucial. But are there other factors contributing to the success? On 5 May 2025 Guy Sternberg offered this analysis: "I know that the rating for our area is Zone 5 (meaning a -20 cold extreme). That rating has been the rule for many years. But in the past decade we have not gone nearly that low, and this past winter we didn't drop even to -10 (depending upon microclimate). Our weakness here seems to relate more to the timing and fluctuation of the ultimate low, but there is no standard to measure variations at that frame. I can claim that for us here over the past half-decade, there has been zero freeze damage in any part of any of our torreyas.• Visit the Starhill Forest Arboretum torreya page for full documentation.
ABOVE: The tender young tips of exposed branches on the windward side also sometimes experience frost damage during the New Hampshire winters, according to Daein. The low that affected these two plants was -9F on January 22, 2025.
• Visit the Grand Rapids, MI torreya page for full documentation.
The torreyas planted by Paul Camire are within his family's 45 acres of deciduous forest near Capac, MI. The forest is surrounded by vast acreages of flat farmlands — over which strong winds occasionally blow. Windchill during the coldest parts of winter is moderated but not completely blocked by the forest. Even so, over the past 8 years of his seedling plantings, winterkill has never been the cause of large injury or death. Rather, it is herbivory, including deer attempting to push over his wire cages, that pose the greatest peril for torreya.
ABOVE & BELOW: These photos were taken in April 2025 — after a winter that dropped down to -5F, as recorded at nearby Flint, MI on January 22. In this sample of 4 torreyas, Paul detected a slight amount of winter-kill only on the two seedlings below. (The yellow flower is trout lily in bloom.)
CONCLUSION: This far north, and especially in flatland settings where there are no ravines to preference plantings, it is wise to sacrifice the fast growth that is possible in open settings for the safety of forest windchill protection. Also important is that a fully deciduous canopy, such as depicted here, provides the proper soil conditions and opportunities to photosynthesize in the low-angle sun of late fall and early spring. • Visit the Capac, MI torreya page.
Loveland, Ohio is a northwest suburb of Cincinnati. The torreya plantings there offer the best photo-documentation of why ENVIRONMENTAL CONTEXT may matter more than latitude in handling below-zero temperatures. The low was -4F in Cincinnati, OH January 22.
Notice the drop-off at the near horizon. That goes steeply down into the ravine of a creek. PHOTOS BELOW show some frost-damage in high exposure areas of the upper ravine slope, but little or no damage elsewhere.
CONCLUSION: Especially in northern latitudes, planting on the lower portion of RAVINE slopes is ideal. • Visit the Loveland, OH torreya page, which combines the plantings of two neighbors: John Patterson (trees above) and also Bob Miller. The photos here were all taken by a beginning torreya planter in Cincinnati: Patrick Murphy.
Fred Bess has been experimenting with planting Florida torreya in his front yard in northeastern Ohio since 2011. The winter of 2025 was not a particularly harsh episode for the torreyas this far north, as the lowest temperature was just -5F Cleveland, OH on January 22, 2025. (Fred lives in Parma, a suburb to the south of Cleveland.) Fred took the PHOTOS BELOW in early May 2025. He wrote, "The windward southwest (and streetside) had some tip and needle damage. The northeast (leeward) side of the trees sustained no damage at all."
ABOVE: The orchard of Florida torreya trees on its northeastern side. Glimpses of the road are visible behind the torreyas. The left-most tree is male, the rightmost is female, and the center tree is a two-stemmed hermaprhodite (the main stem is male and a secondary is female).
ABOVE: This is the southwestern side of the grove, which is generally the windward side. Unlike the leeward side, here you can spot some noticeable browning. This side is also vulnerable to salt spray from the road during the winter. The two stems of the hermaphrodite extend beyond the top of the frame. Fred's house is visible above the right side of the grove.
ABOVE AND BELOW: Close-up views of the worst frost damage during the winter of 2025. This kind of branchlet die-off manifests as a kind of pruning. New growth makes the outer form denser, which can protect overwintering reproductive buds from windchill dessication.
Fred wrote, "All in all, the damage was not nearly as bad as the -17F they survived back in 2014."
ABOVE LEFT: Fred Bess in northeastern OHIO has been nurturing a NEEDLE PALM just as long as he has been tending torreyas. It always gets hit worse in the winter, as evidenced here in May 2025. ABOVE RIGHT: Paul Camire in southeastern MICHIGAN took this photo of his single FLORIDA YEW in April 2025. No winter kill. More surprising is that he had planted this potted seedling during a warm spell in January 2024 — and then, too, it came through with no injuries.
ABOVE: Most astounding is that a pair of FLORIDA YEW grown from cuttings survived a full week of below-zero nights in northwestern WISCONSIN during January 2025. Peak cold was a 3-day period of -22, -24, and -30 F. Mike Heim took these photos in late April. The photo with the shoes shows the left-most yew had topkill, but notice at far right a fully green yew cowering by the log. The photo at right is a close-up of its upper section.
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