Module 8: Thinning of Indoor and Outdoor Plants

Module Overview

In this module you will learn about techniques for correct thinning and spacing of vegetable, fruit, and herb varieties used in experiential learning through GTS. Thinning techniques for optimal plant spacing with minimal plant damage will be discussed.

After this module, learners will be able to: 

• Properly thin and space vegetable, fruit and herb seedlings 
• Determine how many seedlings are needed for each garden size to avoid overplanting
• Explain the importance of and technique for watering prior to thinning

Roadmap

These items will all appear, in order, in the module.

• WATCH: The Importance of Thinning
• READ: Thinning in a Seed Starting Kit
• READ: Thinning in a Raised Bed
• REVIEW: GTS Seed Guide

Please click NEXT at the bottom of this page to advance through the module. To return to the list of modules, PC users click “Modules” in the top left corner, App users click the back arrow in the top left header.

The Importance of Thinning

Watch this video to learn why you will want to thin your seedlings after they begin growing, as well as a couple tips and tricks to help you thin effectively. 

(1 minute, 22 seconds)
Video Transcript: Thinning Indoor and Outdoor Plants

Please click NEXT at the bottom of this page to advance through the module. To return to the list of modules, PC users click “Modules” in the top left corner, App users click the back arrow in the top left header.

Thinning in a Seed-Starting Kit 

When planting seeds in a seed-starting kit you always want to plant the recommended number of seeds per pot — determined by the instructions on the back of the seed packet — to foster a high germination rate. You also want to make sure to plant directly in the center of each pot.

Once seeds have germinated and the plants begin to grow, it is important to take inventory of the number of seeds that have successfully germinated. It is recommended that you keep the strongest seedling and remove the rest from each pot. This way the pot does not become overcrowded as the plant grows. Overcrowding will cause plants to compete within the pot for soil, nutrients, and water. The strongest seedling is not necessarily the tallest one, but is typically the stockiest seedling closest to the center of the pot.

It is best to thin when the seedlings are very small so that the root system of the plant you have chosen to keep is not disrupted. It is also best to make sure the soil is moist prior to thinning. It is good to thin after bottom watering, or to moisten the top of the soil with a spray bottle to be sure there is enough moisture. Moist soil allows the plants to slide out easier. Once the seedlings have been carefully thinned they can either be discarded or carefully transplanted into new pots if space allows.

Please click NEXT at the bottom of this page to advance through the module. To return to the list of modules, PC users click “Modules” in the top left corner, App users click the back arrow in the top left header.

Thinning in a Raised Bed

When you plant your outdoor raised bed you want to keep in mind that your seeds will eventually become much larger plants and will require a certain amount of space. Follow the spacing instructions that are on the back of each seed packet. There will also be instructions on how many seeds to plant in each hole to promote the best germination outcome. We strongly encourage you to plant the recommended amount of seeds and follow spacing instructions so your bed is not over planted. Overplanting can result in overcrowding of plants. This will create more work for you when thinning.

Watering a day before thinning helps the roots come out of the soil more easily and makes it less likely that other plants will be bothered during the process. To thin your raised beds it is best to firmly grasp each plant and gently pull out the roots. If the seedlings are growing too close together or the plants have gotten so large the roots have intertwined then you will need to use scissors to removed the unwanted seedlings by cutting the stem of the unwanted seedling flush to the soil. This is called scissor thinning.

Please click NEXT at the bottom of this page to advance through the module. To return to the list of modules, PC users click “Modules” in the top left corner, App users click the back arrow in the top left header.

GTS Seed Guide

Use this Seed guide when planting each month. 

Downloadable PDF: GTS Seed Guide

Please click NEXT at the bottom of this page to advance through the module. To return to the list of modules, PC users click “Modules” in the top left corner, App users click the back arrow in the top left header.