As the soil temperatures are getting warmer, it’s time to think about planting. Let’s talk about planting in your garden and how deep you should plant seeds, transplants, or bulbs.
Getting planting depth correct is really important. If seeds are planted to deeply they will struggle to germinate and grow through the soil to reach the sunlight. When seeds start all the energy that they have is contained in the seed. So, if they are too deep, they won’t have the energy necessary stored to grow above the soil surface and put out leaves to start making more energy. It is possible to plant seeds to shallow too. This is not as big of an issue as planting too deep, but seeds might dry out and have a tough time germinating if they are too shallow. Seeds do tend to have some tolerance, so if you don’t get it exactly right, the seeds will still be able to grow and germinate. A general rule of thumb is that seeds should be planted 2-3 times their diameter. For small seeds like carrots that means they will be planted very shallow. Larger seeds like corn or beans will be planted an inch or deeper in the soil. There are some exceptions to the rule of thumb so checking the seed packet to see if there are more detailed instructions is always a good idea.
With transplants you want to set the plants at the same depth as they are in the container. Burying them deeper can lead to rots, and lack of oxygen at the roots. Burying them too shallow will lead to the roots of the plant drying out more quickly. Tomatoes are an exception to this rule. When planting tomatoes you can remove the lowest branch and then place the plant at that depth in the soil. Tomato plants will easily put out more roots, resulting in a plant that has more roots to draw up water and nutrients. Whenever you buy transplants make sure that the crown of the plant (where the above ground and below ground portions meet) is healthy and strong. If it is weak and flimsy, this plant will struggle when it’s put out into the elements.
When planting bulbs a rule of thumb is to plant the bulb 2-3 times the height of the bulb. Generally speaking spring flowering bulbs (e.g. Daffodil and tulip) should be planted in the fall and fall flowering bulbs (e.g. Crocus and cyclamen) should be planted in the spring.
Soil temperature is also really important for seeds to be able to germinate. For warm season plants, generally we want soil temperatures to reach 65 to allow for the best germination rates. Our soil temperatures have hit that, and looking at the long-term forecast, it looks like most likely soil temperatures will stay at or close to 65. Most years it takes longer for our soils to warm up, but this has been a very mild winter this year.
If you have questions about planting depth contact your County Extension Office or email me at Jacob.Williams@uga.edu.