top of page
logo_Tulpenmanie2022 (2)_edited.png



Image by thomas heintz

Planter experiment @ Hortus

Planter project Hortus and Tulip Mania

In addition to the citizen science project, where tulips are planted in various gardens of Leiden's residents, Tulip Mania Leiden is working closely with the Hortus Botanicus and the Leiden Center for Applied Sciences on a more controlled experiment. On November 24, 2021, organic tulip grower and soil coach John Huiberts planted, together with Hortus employee Theo Houthoff, red organic Tulipa Masterpeace tulips in 11 planters, one of which is filled with just sand as a control, and the others with two different kinds of soil, i.e. soil from John's own tulips fields, or the "Leidse mix" soil that is used by the city of Leiden in green spaces. In the spring, when all tulips are growing and blooming, samples of the soil will be collected from each planter and analyzed using metagenomics. 


Theo Houthoff and John Huiberts fill the planters with different types of garden soil.


The growth of the Masterpeace tulips duriing one month, in one of the soils tested. 

IMG-0460 (1).jpg

Growth of the Tulipa Masterpeace tulips in April, 5 months after planting the bulbs.

Festive tulip planting in de Hortus!

2021-12-12 143143 tulpenbollen - ©Simone Both - P1383441.jpg

Behind the planters are people who are involved in the Tulip Mania project. On the right, initiator, Dr. Leonie Kaptein 

On December 14th, 2021, during the winter afternoon at the Hortus, the tulip bulbs with a different color were added to the planters with the previously planted red Tulipa Masterpeace tulips. This was done to show what that tulip will look like in the spring, because one in 25 sold tulip bulb bags contains one such a different tulip. Anyone who will see this tulip grow among the red Tulipa Masterpeace tulips can have their soil analyzed using metagenomics. The planting moment was a festive continuation of the earlier planting moments that took place in the fall. In addition to Tulip Mania initiator Leonie Kaptein, Arjen Speksnijder was present on behalf of the Leiden Centre for Applied Biosciences, Carla Teune and Theo Houthoff on behalf of the Hortus.  

2021-12-12 141013 tulpenbollen - ©Simone Both - P1383357.jpg

Carla Teune talks about the history of tulips and the role of the Hortus.

2021-12-12 143018 tulpenbollen - ©Simone Both - P1383415.jpg

De tulip bulbs with the deviating color are planted between the red Tulipa Masterpeace bulbs. In the spring everyone can see what color the tulip has! If you bought a bag with bulbs and this tulip shows up, you're the lucky winner to get your soil analyzed using metagenomics.

2021-12-12 143350 tulpenbollen - ©Simone Both - P1383461.jpg

Students of SV Nucleus selling the Tulip Mania bags at the Hortus.

2021-12-12 143420 tulpenbollen - ©Simone Both - P1383465.jpg

The goal of  the Tulip Mania project is to make the hidden life in the soil visible using metagenomics whereby the DNA of all the micro-organisms in the soil is analyzed.

Foto's: Simone Both

Sampling the soil after blooming

At the end of April 2022, after the bloomimg season, samples were taken of the soil around the  tulip bulbs from the winners' gardens of the citizen science project and from all the Tulip Mania tubs at the Hortus. All DNA is isolated from these samples and the micro-organisms are mapped using metagenomics. The analyses are performed by the LCAB (Leiden Center of Applied Sciences). The results will be announced in the fall.


Arjen Speksnijder and LCAB student Isa Wormsbecher take samples from the tubs in the Hortus.

1652783381970 (1).jpg

Samples were taken in the gardens of the winning participants.


The samples are placed in bags and the tulips are measured.

Read more about the analysis of the soil samples here.

Planter project 2023/2024

Mid November 2023 no tulip bulbs were planted in the planters, but daffodils. It's common practice in flower cultivation to change up the type of flower each season to maintain a more biodiverse soil. Tulip Mania Leiden chose the wonderfully scented Bio Narcissus Bridal Crown (courtesy of Huiberts Bio flower bulbs), and in sync with the 2024 theme of the Hortus which is "Scent"!


Initiator of Tulpenmanie Leiden, Dr Leonie Kaptein, plants daffodil vulbs in the planters at the Hortus.

One of the planters before planting the daffodil bulbs.


April 2024: In one of the planters a red Tulipa Masterpeace blossoms between the daffodils. After ending of the planter experiment and removal of the tulip bulbs apparently a tulip bulb was overlooked!


The planters with daffodils are spread out all over the Hortus Botanicus.

bottom of page