Heartwood Forest.

Six hundred thousand planted trees, five fragments of ancient woodland, and the only wood in this series I have watched grow from open fields.

In 2010, shortly after the first trees went in, I stood in the Magical Wood and photographed the sunrise over open fields. There was nothing to block the view. The horizon ran clear across the frame, hedgerows and farmland all the way to the sky.

Stand in the same spot today and you cannot see the horizon at all. It is dense woodland now, young but closing, and somewhere in the last sixteen years the fields I photographed became a wood. I have never watched that happen anywhere else.

This was mainly arable farmland until the Woodland Trust acquired it in 2008. From 2009, thousands of volunteers planted more than 600,000 native trees across 858 acres, making Heartwood the largest continuous new native forest in England. Five pockets of ancient woodland survive inside it: Langley Wood and, at the far end of the site, Well Wood, Round Wood, Pismire Spring and Pudler's Wood. The mix is the point. Nowhere else in this series do brand-new and ancient woodland sit side by side like this, and they ask for different photographs.

I visit a couple of times a month, and I was privileged to walk the site with the Woodland Trust's site manager. What stayed with me was the sheer scale of the change, and its direct effect on wildlife: the monitoring record now lists 27 butterfly species and 87 bird species, with rare visitors recorded that include Hen Harrier. The place is free to visit and costs the Trust around £200,000 a year to keep. Both halves of that sentence deserve to be known.

The main Woodland Trust car park (AL4 9DQ) serves the heart of the site, but it is gated overnight, so it does not work for sunrise. For first light I use one of the two Nomansland Common car parks on Ferrers Lane, both at AL4 8EG. Laybys on Coleman Green Lane and Hammonds Lane give access to the newer planted sections.

There is no station close by; the nearest are around 2.7 miles away, so this is a wood you drive to.

The ancient woods, and Langley Wood especially, have roped paths. Stick to them without exception: Heartwood lost over an acre of bluebells in Langley Wood in just a couple of years to trampling, more than half a Wembley pitch of flowers gone under feet. The ropes are not decoration.

Dogs should be on leads, with signed exceptions in a few areas; check the boards, and expect staff to ask for leads in protected places, particularly around the wildflower meadows where skylarks nest on the ground. Drones need a permit, as everywhere in this series. A public footpath and two bridleways cross the site, with three way-marked trails for everyone else.

Fog, frost, stormy conditions and golden light are all great tools here. And Heartwood has something no other wood in this series offers: the sky is part of the image. The young plantations are still open enough that weather and light arrive in the frame, not just on it.

My routine from the Nomansland end: wander the four small ancient woods at the far end of the site, then work down through the plantations to Langley Wood. Parts of the new woodland are now forming a canopy, so for the first time there are enclosed woodland images to be made in the newly created areas, and that option grows every year.

If you are still working out which conditions suit which subject, start with the best time for woodland photography.

Two kinds of pictures live here, and telling them apart is the craft of the place.

In the ancient pockets you make the enclosed, interior images: bluebells under old hornbeams in Langley Wood, gnarled trunks and soft light, all of it from the roped paths.

In the young plantations you make the other kind: conditions-led, open, with the sky in the frame. Frost on the sapling rows, fog lying between the young birches, storm light and golden light over ground that was farmland sixteen years ago. As the canopies close, the first interior images are arriving there too, and photographing that change is the project only Heartwood offers.

Between the two sit the wildflower meadows, at their best in high summer, with the pollinators the monitoring record celebrates and the skylarks the lead rules protect.

Hornbeam. Found in all five ancient woods, and the reason Langley feels the way it does. These are veteran coppiced trees, multiple stems rising from broad old bases that have been cut and regrown over centuries, and in winter their twisted branches make the strongest silhouettes on the site. The ridged leaves carry texture deep into autumn. Photograph them as the ancient counterpoint to everything planted since 2009.

Silver birch. White bark that stands out in every season, often in groups that suit wide frames, with peeling bark for the detail work. In the young sections the birches are often the first trees tall enough to hold a frame on their own. In frost, with the sky behind them, they carry the signature Heartwood winter picture.

Hawthorn. Gnarled forms that read older than they are, blossom in spring, and berries that bring the birds in autumn. In the old hedgerows that survive from the farmland years, the hawthorns mark where the field boundaries used to run. Work them as small portraits: one twisted tree against the young plantation behind it.

Field maple. The smaller tree that owns October here, rich gold arriving against the greens around it. Because so much of the planting is young, the field maples sit at eye level rather than overhead, which makes their colour unusually workable for intimate frames. A reliable subject for the seasonal close work.

Rowan. Red berries from late summer into autumn, delicate feathered leaves, and a habit of standing out from whatever surrounds it. The berries earn their keep twice, as colour for the camera and as food for the birds the monitoring record counts. Close-up friendly at every stage, from spring flower to fruit to bare winter buds.

And the arboretum: the only one known in the UK to contain all 60 native British tree species in one place. If you want to learn your trees, there is nowhere in the country more efficient to do it. Photograph a leaf you cannot name anywhere on the site, then walk here and name it.

Spring. Bluebells in Langley Wood from roughly the 20th of April to the 7th of May, the same window as the rest of Hertfordshire, though it moves with the early spring weather, so check how the season is running a couple of weeks ahead. From the roped paths only. Hawthorn blossom follows across the young sections.

Summer. The wildflower meadows are beautiful from the end of May through to early July, the bee orchids appear in late spring and early summer, and the pollinator numbers that the monitoring record documents are visible to anyone standing still for five minutes.

Autumn. The young trees are starting to give proper autumn colour as they mature, a patchwork that improves every year, with mist over the open ground on the right mornings.

Winter. Frost over the young plantations is the signature Heartwood picture, with fog and big skies. The openness that will one day disappear under canopy is, for now, the gift.

The largest of the ancient fragments and the famous one: bluebells in spring under old hornbeams, gnarled trunks, and soft interior light. The paths are roped, and after an acre of flowers was lost to feet in two years, the ropes are the deal.

Well Wood, Round Wood, Pismire Spring and Pudler's Wood sit at the far end of the site from the main car park, and they are where my first-light circuit begins before I work down to Langley. I photograph the veteran coppiced hornbeams here, the bluebells, the autumn colour and the fungi, with the woodland floor and the deadwood carrying the intimate frames.

The Magical Wood is where this guide began: I photographed the 2010 sunrise from inside it when the horizon was still visible, and today the same spot is enclosed by dense young woodland. Across the plantations the photography is conditions-led, frost and fog and storm light with the sky in the frame, and the first canopy-closed interiors are now arriving.

The end of May through to early July is their season, with colour for the wide frames and pollinators for the close ones. There is a bee orchid area, and the orchids appear in late spring and early summer. Skylarks nest on the ground here, which is why the lead rules are strict and worth honouring.

For the wood that taught me the craft I bring here, read my guide to Ashridge Estate. All six guides live at the location guides index.