Being outdoors is life: The life motto of Cora and Marcel of GildenGroen

03/04/2024 - 12:31

Cora and Marcel Achterberg are passionate gardeners from Zeewolde, the Netherlands. Together, they established GildenGroen, a family enterprise infused with a deep sense of social responsibility. Their unwavering dedication to sustainability and craftsmanship led them to be crowned as the “Most Sustainable Gardener of the Netherlands” in 2022. Engaging in a delightful conversation with this dynamic duo, we delved into topics ranging from sustainability practices to the invaluable benefits of TerraCottem and beyond.

Interviewer: Davy Ottevaere, Technical Manager TerraCottem BV

Hi Cora and Marcel! Exciting to have my first double interview – a refreshing change!
Could you share with us a bit more about both GildenGroen and yourselves?


GildenGroen is a company that actually started 23 years ago after a takeover from my previous employer.

We are a quintessential family business: my wife Cora, our eldest son and myself.

There is also a permanent team of eight. In the Netherlands, that’s a medium-sized company(laughs).

Where are you active?


We work mainly in Zeewolde, in the middle of the Netherlands.


Located in the polders region, Zeewolde boasts predominantly youthful sea clay soil. This unique composition presents challenges, with soil hardening during dry spells and becoming nearly unmanageable in wet conditions. Yet, despite these obstacles, the soil is remarkably rich in nutrients, ranking among the most fertile in all of Europe.


In truth, our operations are primarily localized, focusing predominantly on our immediate region. This deliberate choice stems from the abundance of opportunities present here.

However, expanding our reach has proven challenging, mainly due to the scarcity of skilled gardeners. Talented professionals in this field are few and far between, with many opting to establish their own businesses, further limiting the pool of available expertise.


But the business itself is running nicely (laughs). We mainly deal with private gardens. Sometimes we also do some government work.

You are also very socially engaged: in what ways does that manifest itself?


We take pride in our commitment to serving the community and consistently prioritize the collective good. Within our village, we actively engage with local associations and events, often providing sponsorship. One standout initiative is our annual potting soil campaign, a collaborative effort with the music society, which sees us sell upwards of 2,000 bags to support community endeavours.

Furthermore, our dedication extends to our employees, whom we consider integral members of our extended family. We prioritize open communication and actively support their needs, striving to foster a harmonious team environment where individual talents are nurtured alongside collective growth. As a wise individual once said:

“Alone you go faster, together you go further”. That really suits our company !


The current state of the potting soil market is incredibly delicate, driven by a growing demand for peat-free alternatives. Our focus lies in facilitating this sustainable transition. We diligently monitor market dynamics to ensure our offerings align with environmental concerns, benefiting both the climate and community organizations like the music association.

We also do local projects with schools and with the elderly, where our knowledge is called upon:

"While giving money is commendable, I believe that leveraging one’s expertise to make a meaningful social impact holds far greater significance."


Last year, we had the opportunity to revamp a small garden. Repurposing stones from another garden, we infused new life into this space. However, we discovered that the homeowner lacked the means to enlist our professional services.

After much deliberation, we initiated a “Heart in Action” campaign. Collaborating with her friends and leveraging her own efforts, we laid the groundwork for her garden.

It was heartwarming to receive a call from her a few months later, inviting us to revisit her transformed space. Through her dedication and resourcefulness, she had truly made the garden her own, showcasing her pride in what she had accomplished.

She expressed profound gratitude for the initial support that provided her with peace of mind.

Moments like these reaffirm our commitment to making a difference in people’s lives!

We also pride ourselves on working sustainably: through local engagement and using local products.

You also give training courses.


Indeed. Drawing from our own experiences, it’s a challenge to attract skilled gardeners to our company.

I believe this issue stems partly from an industry-wide trend where gardeners are expected to possess a diverse skill set encompassing everything from electrical work to masonry, woodworking, and paving.

In this process, we’ve somewhat lost sight of the core essence: fostering a deep connection with plants and soil. Consequently, our profession has lost some of its allure. While we may still be artisans at heart, do apprentices perceive it the same way?

The technical competencies required for gardening are now in demand across various fields, making it crucial to rekindle students’ enthusiasm for the fundamental reasons why horticulture is such a rewarding profession.


It’s becoming increasingly uncertain whether the students enrolled in the course are truly passionate about horticulture or are primarily interested in civil engineering aspects. The specialized training Marcel underwent in the past is no longer available in its original form.

"The depth of knowledge he possesses is increasingly rare (proud). "

Nowadays, reliance on smartphones and tools like Google Lens for instant information retrieval is widespread and often relied upon for knowledge acquisition (laughs). The individuals we recruit are largely influenced by our own training and guidance; if we can’t find candidates with the necessary skills, we must take on the responsibility of training them ourselves.

Marcel, could you elaborate on your educational background?


Certainly. I pursued my vocational training in Frederiksoord, located in the Northern Netherlands. I was studying there in the late ‘80s, early ‘90s, when the school boasted a century-long legacy and served a significant regional role. Graduates from this esteemed institution were virtually assured of employment opportunities.

Regrettably, the school itself no longer operates, but the historic school garden, which spans a century of existence, still stands as a testament to its heritage.

And where did your passion for gardening stem from?


I realized quite early on that ‘a man cannot live without greenery.’ Gardening, therefore, seemed like a profession that would always remain. Even today, amidst automation advancements, the essence of nurturing greenery remains untouched. It’s a profession that continues to thrive. Personally, I find immense energy and satisfaction in my daily work. I’ve always had a desire to be outdoors, immersed in biology.

As you mentioned, I’ve truly embraced being a professional ‘idiot’ (laughs).

"Plants are my joy and my life. When we go for a walk, I walk with my nose to the ground."


My mother always said “do something with people”. So, by training, I’m actually a hospital nurse (laughs). And then I married a gardener (shouts).

In the process, I joined the company. First administration, but later I actually started working in the garden. Over time, we started building our business together.

Do you also provide educational services?


Yes. we do. We’re actively involved in NL Greenlabel, a national knowledge platform dedicated to promoting sustainable building and living practices for all stakeholders within the industry.


That’s actually where we got to know TerraCottem. Our supplier is also a member of that.

You have mentioned the word sustainable a few times now: it is very important to you, apparently?


Yes, indeed! At the start of 2023, we were honoured with the title of ‘Most Sustainable Gardener in the Netherlands’ for the year 2022.

It’s a source of immense pride for us as it validates our efforts and reaffirms the importance of landscaping green spaces.

This recognition only strengthens our commitment to promote and advocate for sustainable practices in our industry.

Why exactly do you think this need is there?


With the changing climate, green spaces are needed to provide cooling during high temperatures. And these green spaces also provide drainage and water storage during heavy rainfall.

Congratulations on winning that “Most Sustainable Gardener in the Netherlands” award: can you tell us more about that?


The recent election marked the 10th edition of this competition. It’s organized within the horticultural industry by two esteemed companies: Hortipoint and Innogreen, spearheaded by Ralfph Mens and Ruud Snijders.

To be considered for this competition, companies must be nominated. Subsequently, a thorough evaluation ensues, scrutinizing various aspects of sustainability such as procurement practices, personnel management, material usage and sourcing, project organization, and public presentation.


Following the assessment of all submissions, a longlist of candidates is compiled. A jury meticulously reviews these entries against the established criteria, ultimately narrowing down the selection to a shortlist of three companies. The finalists undergo site visits conducted by the jury.


And finally, the winner is announced at De Groene Sector Vakbeurs in Hardenberg.


Participating in the competition was an exhilarating and rewarding experience, especially considering it was our first time. Interestingly, both of the other finalists, who were also exceptional gardeners, had prior experience with the competition. One had clinched victory multiple times, while the other had been a runner-up on several occasions. However, to our delight, we emerged as the ultimate winner (laughs).

We received commendations for the sustainability of our workforce, which was truly gratifying. Our team is incredibly diverse, comprising individuals of varying ages, genders, and abilities, each of whom we value immensely and have fostered enduring relationships with as employers.

Congratulations, that’s fantastic news! Does this recognition also enhance your ability to attract new customers?


Absolutely. We observed a noticeable uptick in inquiries in the weeks following the award ceremony. Clients who place significant emphasis on sustainability were particularly drawn to our services, resulting in a surge of very specific requests.

"Our goal is not to be the most sustainable gardener, because that is temporary, but a sustainable one."

That is something we will propagate further in our branding.


We got a lot of attention. A number of interviews, some articles in trade magazines, ... It opened some new doors. I was even nominated businesswoman of the year. And we were nominated for NL Greenlabel’s “Outstanding Award".

Can you summarise in a few words what exactly “sustainable” means to you?


Sustainability is often regarded as a broad and ubiquitous term, especially in today’s discourse. However, for me, sustainability encompasses the entirety of your actions aimed at making outdoor spaces greener in a conscientious manner. It’s evident not just in the final outcome, but also in the methods employed during the process and the products utilized.

"Resulting in a better balance between green and grey."

You said got to know TerraCottem through the NL Greenlabel knowledge platform?


Indeed. That’s where we met Joffrey Van Rossum, our regular contact at Sana Flore Pro in Malden. Nice guy. And a good salesman (laughs).

Meanwhile, we have been using TerraCottem for several years.

It all started with a few bags. But over time we planted bigger and bigger, including for our solar park projects.

"In fact, nowadays we don’t plant anything without TerraCottem. It’s standard in our quotations."

More even:

"We only give a guarantee if TerraCottem is used!"

What prompted the decision to start using TerraCottem?


Well, Joffrey had quite the convincing pitch (laughs). He not only shared an engaging story but also demonstrated the product’s effectiveness. You know, the classic glass of water test, where the gel granules swell significantly. We often replicate this demonstration with our own clients to showcase the product’s impressive water-holding capabilities.


"Indeed, for us, this served as tangible proof of TerraCottem’s sustainability. Its long-lasting efficacy means there’s no need to constantly switch to other products."

Plus, it reduces reliance on costly drinking water for initial plant establishment and ongoing maintenance.

There is also a lot going on about climate change at the moment: are you noticing the effects of that too?


We are planting more and more in autumn instead of spring. We notice that climate-wise the seasons are shifting. With more warmer periods in spring. We respond to that by simply saying that we no longer plant in such periods. We do add the materials to the soil, but if necessary, we leave the soil fallow for a bit and then plant in the autumn.

What do you use TerraCottem for?


Primarily for perennials and lawns. And also when planting hedges. To ensure a high water buffering capacity.


We’ve noticed a significant reduction in plant mortality when planting hedges with TerraCottem, which is a considerable benefit.


So far, we’ve exclusively used the “blue” TerraCottem, the TerraCottem universal.

We’re aware of the “orange” TerraCottem specifically designed for trees and shrubs, the TerraCottem arbor but we haven’t had the opportunity to incorporate it into our practices yet.

Having a universal product like TerraCottem universal readily available on-site simplifies our operations, allowing us to use it for all our plantings and sowings.

While we’re always open to exploring new products, we’re excited to consider adding this variant to our repertoire.

You mention that TerraCottem is consistently included in your quotations. Is it then relatively easy to persuade customers of the benefits of this soil conditioner?


We operate with transparent quotations, detailing labour, materials, and associated costs. TerraCottem is always listed, along with a link to a YouTube video demonstrating its effectiveness.

"Interestingly, we’ve never encountered resistance due to cost; customers view it as an added value."

Those who choose our services already prioritize sustainability in their gardens, making them receptive to TerraCottem. For instance, in a recent sizable project which consisted in an extensive lawn and plantings, TerraCottem was a necessity, and we’ve observed improved turf establishment.

Customers today are more discerning about the products they use, considering factors like quality labels, circularity, and sustainability.

Read here the blog article “Water scarcity is a hot topic across the world”

What other products do you use?


For groundwork, we use a mixture of Lava Oxygen, TerraCottem and Worm Soil.


Yes, a top layer of 25-30 cm, which allows good rooting, that is nutritious and has an active soil life. This is how we optimise the top soil.

Let’s talk about some of your projects. You mentioned solar parks earlier: what exactly are they?


By nature, solar parks present a paradoxical concept. They entail converting agricultural land into vast fields of solar panels, eliciting both praise and resistance.

There’s significant opposition, as the Netherlands is perceived as densely populated, and repurposing land for solar projects is seen as a loss.

On the other hand, we are looking at how to maximize the utility and aesthetic integration of these parks within the landscape.

We have completed a 7-hectare solar park with an additional 8.5-hectare project in the pipeline. We’re committed to strategically landscaping these areas with diverse plantings to promote biodiversity.


We look at suitable seed mixes and adequate plants. We also take care of maintenance.

We actually got in touch through your Instagram post about the project in France. Can you tell us a bit more about that?


Our first visit to Merlanes was in 2005, initially for camping, and again in 2011. Over time, our visits became an annual tradition, fostering a strong rapport with the owners. Merlanes offers not only camping but also accommodation in beautiful villas, making it a delightful destination.

We were approached to enhance the greenery and add more vibrancy to the surroundings. Without hesitation, we embarked on this project, incorporating TerraCottem for optimal results. We provided the owner insights into the product’s effectiveness, particularly in France’s climate.

In addition to new plantings, we also transplanted several shrubs, ensuring TerraCottem was utilized for their successful establishment.


One of the reasons for using TerraCottem there was because the soil was basically similar to ours in Zeewolde. Through TerraCottem, we want to level out those extremes a bit.


And of course because of the increasing water scarcity, we wanted the best possible water buffering for our plants.

Are there any other projects you would like to highlight?


We did a project in the Schelpenbuurt, a new, green and water-rich neighbourhood in Zeewolde. We planted beautiful borders in the spring, among other things.


Last year, we had the opportunity to undertake three projects in support of the Natural Pavillion, a prominent feature during the last Floriade Expo in Almere.

These projects were executed in collaboration with Nico Wissing, a renowned Dutch landscape architect, and all were completed using TerraCottem.

Cora and Marcel: thank you very much for your time and this nice chat.

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