Bench and Soil Warming

Plants are made out of many different parts but can be broken down into 3 main areas.

1. Shoots – Stem, leaves, flower & fruit etc.
2. Roots – Stabilising, water & food collectors
3. Crown – The node joining the shoots to the roots

Although composed of similar material the roles of the roots and shoots are basically opposite. Roots pump water up and the stems push energy down. The crown serves as the switching centre that facilitates these important functions.

Incorporates all the parts of a plant that you can see. They can capture the energy from the sun, rotate their leaves towards or away from the sun and moderate their own internal temperature through respiration.

The shoot zone primary duty is energy absorption and propagation. Although they are the main source of plants energy the root structure is the main user.

Roots are a critical barrier for plants and are designed to find and absorb nutrients and keep water inside the plant. However they do not generate their own energy, instead, they make up the majority of the energy consumed by the plants. Collected nicely by the leaves and passed down.

Roots take in water and they do their best not to give it up and as such do not transpire to cool the tissue but instead transfer the excess heat generated in these reactions (latent heat) to the surrounding medium.

Dense mediums such as soil, sand, even water, have a large temperature buffer that makes the 24-hour swing in temperatures a root will see very minimal under natural conditions.

However, in many horticultural operations, these stable root temperatures are either not achieved or not even thought about, as they are the great unseen part of the plant. Lots of money is spent on controlling environmental spaces through the use of greenhouses without much thought to the root structures below.

The crown zone has a very important role. It works hard to control the water from the roots. Water in the roots is usually under pressure and in the stem, the zone is in a low-pressure condition. As the leaves perspire the crown has to control this flow.

The crown also has to handle all the chemical reactions required to pass energy from the leaves down to the roots.

The crown is the important junction between the roots and the stem of the plant, however, the roots and crown require ideal temperatures to perform their roles well.

Low root temperatures and high root temperatures retard the plant’s growth, but fluctuating root temperatures are known to cause higher mortality rates in plants.

Evolution over time has enabled plants to adapt to localised conditions and the roots, crown and stems have developed tricks to cope with this fluctuation. However, humans have developed their own range of plant variants as well as taken plants from their natural environments. We then grow these plants utilising many different methods from in soil to in water to hydroponics and greenhouse systems.

Fluctuating root zone temperatures increase plant stresses and as mentioned retard or kill a plants ability to pass water up or energy down to where it is needed. These additional stresses on the plant and the crown zones often cause stunted growth, no growth or a collection of dead or dying plants.

Maintaining root temperatures is so important as it removes these stresses and allows the roots and the crown to do their jobs in growing the plant.

The temperature will vary from plant to plant, but maintaining a stabilised temperature is more critical than the actual temperature requirement for success. However, root temperatures around 18 to 27 Celsius is considered ideal for most vegetable crops.

Ground temperatures also affect seed germination and is normally a little warmer than normal growing conditions.