Glass Jar Trick in March: Make Herbs Grow Faster

In many gardens, the end of winter still looks rather bleak. The beds are damp, the nights are cold, yet keen gardeners are already eager to get started. This is where a surprisingly straightforward tip can help: a simple glass jar can become a mini greenhouse, encouraging chives, parsley and other hardy herbs to grow noticeably faster as early as March - without high-tech equipment, electricity or costly specialist kit.

How the glass jar trick really works in March

The method sounds almost too easy: place a glass jar upside down over the young plant like a cloche. That is all it takes. Behind this simple approach, however, is a small piece of physics also used by large greenhouses.

“The glass creates a protected microclimate: warmer, more humid and sheltered from the wind - ideal for early herbs in March.”

When sunlight reaches the glass, the air beneath it becomes considerably warmer than the surrounding air. At the same time, moisture evaporates from the soil, condenses on the inside of the glass and drips back down. This creates a warm, humid environment that encourages plants to put on an earlier burst of growth.

• The air beneath the glass stays warm for slightly longer after sunset.
• Wind and cold draughts cannot reach the delicate shoots.
• The soil does not dry out as quickly because the moisture remains inside the glass.

There is one important point: once spring temperatures become consistently milder, or the herbs reach the base of the glass, the cloche must be removed. Otherwise, conditions inside can become too hot and the plants may literally scorch.

Which herbs benefit most?

This trick is particularly suitable for hardy herbs that produce fresh growth from the soil. In other words, plants that stay in the garden over winter rather than freezing completely.

Chives - the ideal candidate

Chives are among the first herbs to reappear in late winter. Their fine hollow stems emerge early from the soil, but are highly sensitive during cold nights. Under a glass jar, chives grow:

• taller more quickly,