The Peat-Free Diet: Seedling development

When a seed sends out its first shoot and it rises above the soil level, germination is over and seedling development has begun. This is a particularly vulnerable time for the plant – it is running out of stored resources and needs to start collecting its own food. In this period of rapid growth it is also particularly at risk from pests and diseases.

As the plant continues to develop you will see stem growth and expansion of the ‘true’ leaves – they are smaller versions of the adult leaves, different for different species, and easily distinguishable from the plain ‘seed’ leaves that emerged first. Underground, the root system is branching and growing. The reason shoots go up and roots go down is that the plant is responding to gravity – it’s called geotropism or gravitropism. Tropos is the Greek word for ‘turn’, and it is used to describe the different ways that seedlings (and plants in general) respond to their environment.

At the tip of each stem and each root there is a growing point, called the apical meristem. These growing points need to be protected, as early on the plant doesn’t have many and damage to them can render it unable to continue growing. That’s why when you’re handling seedlings you should handle the leaves, rather than the stem. If you break the stem then the plant is unable to continue growing; damaged leaves are more easily replaced. When the plant gets larger it has more growing points, which is why it can respond to being pruned back by growing more bushy. (If you’ve ever seen an oddly shaped flower on a plant then you may have spotted an example of fasciation, which is where a damaged apical meristem causes growth to continue in a distorted way.)

What seedlings need

When you’re caring for seedlings