Why does my mint have small leaves?

Poor mint leaf size signifies the plant is under stress from environmental conditions. My first crop of mint started with dime-sized leaves until I raised the grow lights further above the plants. Plants, when given inadequate light, tend to stretch toward growing light sources, and this behavior results in sparse plant growth. Short compact leaves suggest that the plant does not have enough energy to expand cell growth in the proper amount, therefore you will want to address these three problems systematically.

Nighttime temperatures below 50°F (10°C) inhibit the development of the leaves. The mint plant on my balcony continued to fail until I added a thermal blanket. Use mulch or insulation in the pots to maintain soil temperature and warmth in the root zone. Day/night temperature swings greater than 25°F will shock the plants, and helping the plants to gradually adjust makes them less prone to breaking down their cells.

Plan your pruning to redirect energy effectively. In particular, remove flower buds as early as possible before they mature - I left my mint unpruned, and about 70% of its resources were diverted to flowers. Prune above the nodes of the leaves facing outward. This technique improved the size of my second growth cycle leaves by about twice their size, likewise to the energy distribution technique of cutting close to the base.

Read the full article: How to Grow Mint: Expert Tips for Thriving Plants