Palmkas (palm house) of Hortus Overzee

The site grew out of Den Helder's municipal nursery. In 1939 the town set up a new one on the Soembastraat, with a distinctive palm house in which the potted plants that adorned the streets in summer were kept over winter. The municipal monuments list also gives 1939 for this "Palmenkas oranjerie", whereas OpenStreetMap dates both glasshouse blocks to 1931.

The Oranjerie De Groene Parel foundation was established on 9 March 1993, the year the botanic garden came into being. During the 1990s the palm house was designated a municipal monument. A major restoration and renovation between 1995 and 2000 replaced most of the original iron structures in steel while keeping the Palmkas's most characteristic parts. The Japanese garden, designed by Wybe Kuitert with Japanese colleagues, was laid out in 2000; the succulent house has held a large cactus collection since 2006, and the butterfly house opened in May 2016.

On 22 April 2017 Oranjerie De Groene Parel became Hortus Overzee. The garden has since taken in salvaged pieces of the town centre: in the 2010s the canopy of a shopping street, the Kroonstraat, found a second life here, and in 2024 the hortus planned a glasshouse built from parts of the demolished Kroonpassage. The Wereldkas, a themed glasshouse, was pulled down in 2026 and its parts reused to create a shelter for potted plants.

The complex is a row of adjoining glasshouses grouped around the Palmkas, listed as number 0400/WN039 among Den Helder's municipal monuments. During the 1995–2000 works most of the original iron structures were replaced by a steel frame, but the palm house's most representative parts were kept, including pieces that still carry the name of the maker, Krupp. None of the sources consulted names the 1939 builder or gives the buildings' dimensions.

The orchid house is attached to the Palmkas, and the garden presents the pair as "the maritime glasshouse". The succulent house is staged as a ruin in a desert landscape, the butterfly house as a world of metamorphosis. The Wereldkas, dismantled in 2026, supplied the materials for a new space for potted plants. Since April 2026 the restored lantern dome of the old Lange Jaap lighthouse, which previously stood at the Willemsoord site, has stood in the garden beside the Japanese pond.

True to its original role as a wintering house, the Palmkas holds tropical and subtropical plants such as orange trees, bananas and agaves. The adjoining house is devoted to orchids. Since 2006 the succulent house has shown a large collection of cacti, and the butterfly house, opened in 2016, is dedicated to their metamorphosis.

Until it was demolished in 2026, the Wereldkas displayed carnivorous and edible plants; it was also used for events and for overwintering the potted plants that stand outdoors in summer.

Outside, the Japanese garden, with its stream, waterfall, rapids, rocks and island, brings together plants from Japan, South Korea and China, among them camellias, paper mulberry, Abeliophyllum and bamboo. Koi carp and turtles live in its large pond, crossed by stone bridges.

Hortus Overzee is at Soembastraat 83, in Den Helder's Indies quarter (Indische buurt), about five minutes' walk from the railway station. The Japanese garden, billed as the main attraction, pairs naturally with the glasshouse route, and the old Lange Jaap lighthouse dome beside the pond adds a local curiosity.

The official site announced a closure to visitors until March 2026, so it is wise to check opening periods before travelling. The garden also has a social mission: for more than thirty years it has offered meaningful work, in the garden and in welcoming visitors, to people for whom regular employment is not straightforward. It is a member of the Dutch Association of Botanic Gardens.