It is possible to grow more than just tomatoes, cucumbers, and chilli in the greenhouse. Actually, there is a good reason to grow a lot more, for example plants from the sweet pea family, like beans. Quite simply because the beans and other members of the sweet pea family are great neighbours for other plants in the greenhouse.

Neighbouring plants 

The principle of neighbouring plants, also called “companion planting” or “plant partners” is a cultivation principle about plant composition. Originally, this is a farming principle, but it can easily be transferred to the greenhouse. It is about planting certain crops next to each other for different strategic reasons but primarily because certain plants benefit each other’s growth. This principle is not new at all and has been utilised for thousands of years by Native Americans before the arrival of the Europeans.  Maybe you are familiar with the term “The Three Sisters”. This term originates from indigenous American agriculture.

Good neighbouring plants are all about the following:

• One plant type keeps for example vermin away from its plant partner.
• One plant type attracts pollinating insect to its plant partner.
• One plant type attracts beneficial insects, that attack damaging insects on its plant partner.
• Exchange of nutrients between plant partners.

Beans are good neighbours

There are plenty of great plant partners. However, this article focuses on one group in particular – nitrogen fixing plants. A good example of this type of plant are beans.

The bean (phaseolus vulgaris) is an annual plant and belongs to the sweet pea family. It is a leguminous plant, just like peas and sweet peas. Plants from the sweet pea family have in common that they have the ability to fix nitrogen.  Beans originate from South- and Central America, where they are one of the most important nutrient sources, primarily because beans contain a high amount of protein.

Beans are a super food

Beans are brilliant for many reasons. Beans are healthy and a great choice on meat free days, because of the amount of protein they contain. Beans also contain magnesium, calcium, iron, and zinc.

Beans fix nitrogen

The bean plant is beneficial for the soil it grows in and is an excellent plant partner. The bean plant is, as mentioned above, a leguminous plant and all leguminous plants live in symbiosis with the nodule bacterium (Rhizobia) on their root net. The nodule bacterium catches nitrogen (N2) from the air and transforms it to ammonia (NH3). Nitrogen is one of the most important nutrients for most plants in the greenhouse.  By planting beans, a natural supply of nitrogen is secured. Don’t fertilize your bean plants in their growth period. During the summer months, the bean plants will share their stored nitrogen with the surrounding plants.

Beans and lice

You can’t avoid vermin in your greenhouse, but with good plant partners you are able to control where the vermin primarily are. Beans have a way of attracting lice when they live in the warm and protected climate of a greenhouse. That can be utilized strategically. By planting a couple of beans in the greenhouse, you can avoid plant lice attacking your pepper and chilli plants because the plant lice automatically will be drawn towards the bean plant.

Facts about beans as plant partners

In general, beans as plant partners are most effective in soil beds where the roots can freely exchange nutrients. In self-watering boxes or other plant boxes, you cannot be absolutely certain, that an exchange of nutrients happens in the same way.

• Plant beans between tomatoes and cucumbers.
• Plant the beans when the temperature in the greenhouse is above 12 °C both day and night.
• Both bush beans and runner beans can be cultivated in the greenhouse.
• Use beans as bate for plant lice.
• A runner bean plant provides a least a handful of beans daily during the summer.
• The bean flower is good for pollinating insects.

Other great plant partners

There are more great plant partners in the sweet pea family:

• Cromson clover, Trifolium incarnatum
• White clover, Trifolium repens
• Red clover, Trifolium pratense
• Beans, Phaseolus vulgaris
• Broad beans, Vicia faba 
• Soybeans, Glycine max 
• Pea flowers, Lathyrus odoratus
• Bird’s-foot trefoil, Lotus corniculatus
• Lupin, Lupinus angustifolius mm
• Common vetch, Vicia sativa
• Hop medic, Medicago lupulina
• Peas, Pisum sativum
• Liquorice root, Glycyrrhiza glabra
• Chickpeas, Cicer arietinum