Leaf-fall is a window, not a date. Warm nights >10 °C extend the window; one windy/cool night can compress it abruptly. Out Nov 5th Bonfire tradition here in Lewes, East Sussex captures where the window sits each year—this week it’s clearly later.
Each year, as November 5th approaches, bonfires are prepared, programmes sold, costumes readied and notices banning cars from the streets (including parked cars) go up. I consider the state of the trees, not least because most years I march underneath them carrying a burning torch or longer burning cross.
This year, much of the leaf fall has been delayed more than ever. It has been 16 degrees during the day, 13 overnight.
When we first moved here twenty-five years ago, we marched with burning torches through town beneath a bare canopy, both street trees and woodland trees were skeletal silhouettes by Bonfire Night.
Now, looking around me whilst some trees, horse chestnut stressed from a dry summer, may have lost all their leaves, even some ash, usually early to lose their leaves, still have a Green though thinning canopy. As for beech, though there is autumn colour, most still have most of their leaves.
Standing in Markstakes Common this morning, I found one veteran oak with a thick canopy of green leaves, barely a hint of colouring, and another, in a more challenging part of the wood, showing some orange and russet colours. The woodland floor is covered in leaves, though, as birch trees are stripped bare of their leaves, they create a bright yellow carpet, while beech leaves are a darker orange.
Why Trees Shed Their Leaves
Deciduous trees lose their leaves as the temperature drops, as the days grow shorter, or when autumn storms arrive. There has been little of that here in Sussex this year (so far).
As daylight shortens to roughly eleven hours (by late September) and nights cool (it’s barely dropped below double digits this year), then Chlorophyll breaks down, and its nutrients are withdrawn into twigs and roots. What remains are the yellows and browns of carotenoids and tannins, the pigments that have been there all along beneath the green.
At the base of each leaf stalk, a thin corky layer of cells—the abscission layer—forms like a line of perforation. Once complete, even a light gust or frost can sever it. A clean scar seals over, preventing water loss through winter. From above, we see colour; within the twig, it’s chemistry and timing.
Each species has its own rhythm.
Ash drops early, turning from green to black almost overnight. Most are things of leaves, but that could be dieback – there are some still with healthy-looking leaves. Birch flashes yellow, then falls in a single week; these are universally free of leaves by now. Beech and oak hold out the longest, their leaves toughened by tannins that resist decay. This staggered retreat once ended by late October. Now, warmth and soft rain delay the signals; the abscission layer forms slowly, sap still circulating when fireworks begin. There are beech trees with leaves, although not a dense canopy, while the oaks show few signs of preparing for winter.
Why It’s Later Now
Southern England today is roughly a degree warmer in autumn than it was twenty-five years ago. Average first frosts arrive ten to fourteen days later than they once did, and some years barely at all before December (if at all) we had no frost at all last year. Temperatures this week are running 6 to 8 degrees above the average.
Day length diminution remains the same, but warmth and soil moisture interfere with the trees’ internal calendar. Their hormones wait for two cues: shortening days and sustained cool nights. When the nights remain mild, the abscission signal falters.
The result is a seasonal delay.
Sap keeps flowing, leaves continue to photosynthesise a little longer, and the clean break never quite forms. Beech and oak—both late droppers by nature—cling even longer, their leaves crisping in place. Hornbeam holds parchment-brown right through winter, while birch and ash, less flexible, shed on time and stand bare.
The once-synchronised fall has become a patchwork: summer, autumn, and winter side by side between glades in the wood.
What We Can See and Measure
I chose Bonfire Night as a fixed ritual against which to measure the shifting seasons..
In Markstakes Common, the sequence now runs:
- Ash – usually bare by mid-October, leaves blacken quickly. Some still have leaves on 4th November.
- Birch – yellow and gold and parchment by late October have lost their leaves entirely, but not so Hornbeam (which is unusual).
- Beech and Oak – will hold colour into mid-November. The woodland floor has a covering of orange beech leaves but few oak with leaves likely to persist until Christmas in sheltered spots.
The Woodland Trust’s Nature’s Calendar data confirm what our eyes see: across southern counties, average leaf-fall now occurs one to three weeks later than in the late 1990s.
This year, note the date when around half the leaves have fallen from your chosen tree: record the weather, species, and location. Then, each year, do the same and see where the trend takes you.
Consequences of the Longer Autumn
Leaf-fall arriving weeks late means soil stays shaded and dry for longer; fungi work through warmer nights; worms and invertebrates feed deeper into winter. What feels gentle to us—a few more mild evenings—is a structural change for the land.
Water and soil.
Without the usual early-winter leaf mulch, rain runs off rather than soaking in. Heavy downpours then follow long dry spells, carving ruts and flooding hollows that once absorbed water slowly. The ground of Markstakes Common now swings between drought dust and standing pools—conditions our native flora were never shaped for.
Agriculture.
Across Sussex, the ploughing calendar has shifted. Crops stay in the ground longer; cover crops thrive into December. Vineyards spread where barley once grew—beneficiaries of a climate one degree warmer and several weeks longer. The same warmth also invites southern pests, such as grapevine moths, oak processionary caterpillars, and the emerald ash borer, waiting in the wings. What arrives by accident often stays by advantage.
New species, new boundaries.
The trees themselves are migrating north. Holm oak and sweet chestnut already seed freely beyond gardens; wild service and field maple push into ground once dominated by ash and beech. Mediterranean bay hedges, once tender, now survive every winter in Lewes backyards. This year, I picked figs from a tree that should, by rights, be hibernating in a pot. It felt like a gift—and a warning.
Energy and water use.
A milder climate may seem benign until we consider the pumps and hoses. Longer growing seasons mean irrigation can be used later into autumn, and more chemical control is required for new insect infestations. The silent cost is groundwater: aquifers are drawn down faster than winter recharge can replace them. The forest senses this before we do; shallow-rooted beech and hornbeam already show summer scorch by July.
Markstakes Common as Witness
Markstakes Common is a rare patch of ancient wood. Within its 40 hectares, sixty-two trees have now been recognised as veterans — individuals that have stood through centuries of droughts and storms. They are not relics but participants: slow-moving witnesses to the warming world.
What a weather station measures in degrees, a veteran tree measures in growth and stress.
The younger trees in the common — birch, hornbeam, ash, and the self-sown oaks of the last century — react quickly. Warm autumn nights like these keep their sap circulating; leaf-drop drifts later each year. But the veteran appear to be less responsive, their systems buffered by sheer mass and age. A beech that began life when Queen Anne was a child is no longer easily persuaded that winter has arrived. Its canopy holds on even as the soil cools. The veterans are learning a slower rhythm, their dormancy lagging behind the rising mean temperature.
The contrast is visible in the wood today.
Veteran Oak (tree 13 on the Friends of Markstakes Common Map) deep in the interior, stands almost unchanged in colour — leaves still leathery and green on the fourth of November.
Veteran Oak (tree 14) older and more exposed on the north edge, has begun to thin and bronze. Their reactions differ not just by species or aspect, but by biography: the younger tree, more intact, keeps faith with the old calendar; the veteran, fractured and hollowed, is quicker to sense the shift in air and light.
Over time, this divergence will widen.
The veterans, with roots in cooler centuries, still draw on deep groundwater and stored sugars; the younger generations, raised in warmth, grow faster but live shorter. A century from now, Markstakes Common may hold fewer true ancients — not through neglect, but because climate itself curtails longevity. When winters are brief and soils seldom freeze, decay never pauses. The fungi that rest in cold months now work all year.
Yet these trees endure.
Many of the oldest have re-rooted from fallen trunks, the so-called “phoenix trees” that rose from the ashes after the 1987 storm. Others, like the hollow veteran Beech (Tree 12) continue to green each spring from what looks like ruin. They show that age can be adaptive, not fragile.
If we wish to understand climate change close to home, we need only stand beneath them. Their silence is a dataset; their scars are a timeline. By recording their behaviour — the timing of bud-burst, the lingering of leaves, the slow alteration in canopy form — we build a phenology not of abstractions but of individuals: trees with names, locations, and witnesses of their own.
A tree that has lived through three centuries knows more about climate than any model. We need only learn how to read it.
What Next for the South-East Landscape?
Sussex now has over fifty commercial vineyards, and the chalk downs suit them well. If warming continues at the present pace, trials of olive, almond, and pomegranate will follow; some of these species are already being grown experimentally in Kent and on the Isle of Wight. What was once fantasy horticulture is edging toward viable farming. Yet every new plantation is another negotiation with water, pollinators, and soil carbon.
For the woods, the choice is between adaptation and attrition.
Some species will migrate north through seed and bird dispersal; others, like ash, will fail before they can move. The survivors will not be purely “British” in any historical sense—they will be assemblages shaped by new temperature bands and our decisions about land use.
In Markstakes Common, the veterans stand as translators between past and future. Their rings record cold centuries and drought summers, the Little Ice Age and the 1976 heatwave. They are now writing a new script of mildness, storm, and uncertainty. Each November, I read the following line in bronze and brown.
Closing Reflection
“The forest has learned to wait; we must learn to listen.”
A late autumn once meant bounty and rest. Now it signals a world unwilling to sleep. If we can notice that—at the level of a leaf, a vineyard row, a frost that doesn’t form—then perhaps observation becomes our first act of care.
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