How thirsty are Haarlem trees?

How thirsty are Haarlem trees?

Young trees in Haarlem need to be watered ten times. They can't live without it for the first two years after they go into the ground. 

In dry, hot summers like this year, young trees in Haarlem need to be watered ten times. They can't live without it for the first two years after they go into the ground. Landscaping and the importance of managing irrigation in young trees are the topic of NHNieuws new article. 

As a game changer, this year the gigantic operation will be slightly less labor-intensive because ConnectedGreen and Sensoterra have implemented a solution to monitor the moisture of the soil around the young growth. The initial trial have been running now for four months in the municipality of Haarlem. This year, the dry spring and the recent heat wave didn't make it easy for the saplings or for the landscapers in charge. 

Dirk Hoogewerf and his team are currently driving through the city with four tractors and tanks full of water. About 2000 trees that have been planted in the past two years, receiving 100 liters of water at a time. That is an estimated cost of one and a half tons, money that can be spent more precisely thanks to the soil moisture sensors installed next to each tree. 

Sensoterra is a worldwide leader in landscaping and agricultural activities by helping customers to make wiser irrigation decisions. Wirelesses soil moisture sensors indicate real-time necessity of water at the active root zone, reducing uncertainties of manual management, because it can remotely control from individual plants to the whole area or field. 


Full video:


On his phone, data analyst Roy Kolk from Spaarnelanden is using the ConnectedGreen app to verify how much water the young holm oaks on De Bazellaan in Parkwijk have 'drunk' in the past week. Ten sensors have been placed throughout Haarlem on a trial basis. "The feelers measure the moisture content and with that we can see whether it is sufficient or not," says Kolk. 

No water for the big ones 

Another 700 trees are planned to be planted in the near future. The trees that stand for more than two years are then skipped by the water pullers of Spaarnelanden. According to Hoogewerf, they should be able to take care of themselves without too much water. "The great ones are already very deeply rooted, they can stand on their own two feet." With each growth, it is taken into account that 8-10% of the trees will fail. "That's normal", according to Dirk. 

"The tree protects itself by creating less leaf volume, and then it needs less water" 

Dirk Hoogewerf


With extreme heat, trees may drop leaves, such as the large oak in a small park on De Bazellaan. "And then people immediately shout 'oh, the trees are dying and they need water!' That's not true". Dirk explains. "The tree protects itself by creating less leaf volume and then it needs less water." 

When using Sensoterra soil moisture sensors, growers change their way to control the field. The old-manual techniques give space to a tech-controlled environment where over-irrigation is substituted for healthier plants. In the case of Dirk, even under-irrigation can be a scenario of happy plants, because it is 24/7 monitored by the sensors. In case plants require more water, as mentioned in the video, irrigation systems can be easily activated.

There are now 64,380 trees in the city and 700 more trees have to be added this year. More and more, municipalities are leaving the old techniques behind to move forward with Sensoterra sensors. The future will be based on smarter cities that can integrate smart devices to monitor quality, save water, save energy and costs, and the city of Haarlem is already making it happen. 

Year by year, cities are becoming 'smarter' and preparing themselves for a challenging future in terms of weather changes. Increased heat waves and tendency of droughts have been influencing landscapers to rethink on landscape management, reduce water costs and use adapted plant species for warmer climates.

Together with choosing the right plant species for each location, soil moisture sensors become crucial to promote a visible adaptation. The possibility to track individual trees, watering them correctly in accordance with the active root zone necessities, connected to an integrated irrigation system, promotes aesthetically healthier plants and increases the chances of survival from seedlings to older trees. 


About Sensoterra

Sensoterra is a leader in wireless soil moisture sensing, providing data-driven solutions for optimizing land and freshwater resources for agriculture, horticulture, landscaping, and Smart cities. LoRaWAN technology and wireless connectivity empower better decision making for land management through smart soil moisture measurements. With thousands of Sensoterra sensors in the ground, generating over 60 million data points globally, Sensoterra grows every year and have been supporting from small to big-ag growers. 

Sensoterra app is user-friendly, introducing a whole new world of technology to customers everyday - easily accessed by our web Monitor page or mobile phones. Curious to see how Sensoterra can help you today? Check our case studies!

For more information, send us an email to: [email protected] 


About ConnectedGreen

Founded in 2017, ConnectedGreen provides a smart system for remote monitoring of green projects. Making the world greener with smart technology. ConnectedGreen has deployed more than 1,200 sensors in The Netherlands and Belgium. 




Written by:

Caroline Arab
Soil Data Manager

Caroline Arab

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