Lars Lund

08 Sep 2020 14:34

The ants are coming


A sure sign that the ants are here is when there is loose sand by the joints in the tiles.

Photo: Grøn Kommunikation


Now it is nice and warm in the greenhouse and for ants, that is the ideal home.

Ants love lice, including scales. They eat the lice’s excrements that is sweet and for an ant delicious. At the same time, the ants protect the scales from other insects that might be the lice's enemies. They do this by simply eating them. So, beware.

Therefore, you should check all your plants for scales or common lice so that they are not the reason why you have ants in your greenhouse. Even if that project succeeds, the ants are likely to go great lengths to find food, as long as the home is ideal.

Ants are especially fond of tiles in the greenhouse. The tiles absorb heat and are laid on gravel or tile sand. Tile sand has the ideal structure for their path systems. It does not collapse so their paths are destroyed.


Beach sand is sliding

If you have tiles in your greenhouse - or like me brick floors - and want to get rid of the ants, it is my experience that beach sand keeps the ants away. Beach sand is not meant for tiles. In my greenhouse, the brick floor is laid according to all the rules, but if the brick floor on the walkway is covered with a layer of beach sand, the ants simply disappear. I use two to three bags per. 64.5 square feet.

Now you might be wondering if it was not meant to be a brick floor.

Yes, and it is for parts of the year. When I can’t see the bricks, it's just a solid floor with beach sand 

In late autumn I cover the floor with beach sand. It suddenly creates a completely different atmosphere in the house, and then it shuts off all the algae that will otherwise settle on the stones.

In spring, already in March, ants are looking for housing. They come to the open house, look at the floor, but do not choose my greenhouse because of the sand. In June, I sweep all the sand together, and store it for the fall. Now I suddenly have a nice clean brick floor without ants and algae.


The ants do not like beach sand, and beach sand gives your tile floor a nice look.   

Photo: Grøn Kommunikation


Cloth under the tiles

Something else you could do is to lay a cloth under the tiles. This is something people have stopped doing on driveways because the tiles can slip easily, and weeds still come up between the joints. But in the greenhouse, it does work.

When the ants no longer pose a danger because they have found another home, you may want to remove the beach sand.

Photo: Grøn Kommunikation



Finally, there is a grand opportunity, which is affordable. Make the floor completely level and lay flamingo floorboards. The kind one can walk on, e.g. 4 inches thick. Then lay tiles directly on top of the floorboards. Now you have an insulated "cast" floor in an easy way, and the ants have no opportunity to make path systems under the tiles. This is how I made my plant hotel and my floor in the tool shed. I did not do it to avoid the ants, but more because, it is an easy and quick way to make an insulated floor.


If it goes wrong anyway

Tiles or not, if you have ants and cannot get rid of them, do not use poison that is dangerous to other animals and humans. Use the old and most effective house advice. It is made from natural products that ants just cannot stand. The trick is potato flour, powdered sugar and baking powder. Mix 50% icing sugar, 45% potato flour and 5% baking powder (no water). Sprinkle the mixture near the areas where the ants live, for example along the house wall. The ants go for the sweet (icing sugar) and drag the mixture down into their nest, where they share it with the other ants. They get a stomachache. Their digestive system cannot tolerate the potato flour/baking powder and they die.


Ant water

Another novelty has just arrived on the market. It's called ant water. It is a "ketchup bottle" containing a special clay mixed with water. The bottle is made so the spout fits in the hole where you see the ants go in between the tiles. There will typically be some sand they have dug up. The ant water then flows out into their path systems and blocks the access to the queen. The result is that she dies of starvation and the nest is lost.

Ant water is a new organic product that closes the ants' paths so that the queen cannot get food. Here the tiles are removed to show how the clay water penetrates the pathways.

Om Lars Lund

Lars Lund
Danish horticulturist and journalist
Lars Lund has for many years engaged in the garden and greenhouse. Lars has published many books about greenhouses, and he has participated in many Danish horticultural TV shows. He is a walking garden encyclopaedia, and he has answers for most basic cultivation questions – also the more ambitious ones.  

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