Many of the plants we grow I prefer to sow directly outside and one of the most important things to consider when sowing is that the temperature of the soil is high enough for the seed to germinate.
Other important considerations include:
- whether the seed requires any pre-treatment before it will germinate, i.e stratification and scarification (mainly relevant for perennial plants particularly trees and shrubs).
- how deep you sow the seed - too shallow is better than too deep.
- that the correct moisture levels are kept constant during the germination phase - not too wet, not too dry and with the ideal moisture levels similar to that of a wrung out cloth.
Elaeagnus commutata - Epigeal germination |
This post we'll focus on soil temperature for germinating seeds. We'll look at why this is important, how to take soil temperature, and I've included a table showing the minimum and preferred soil temperatures for germination of some common plants.
Eruca sativa - Rocket germinating |
Often you will find a monthly guide on a seed pack indicating when to sow seeds and this generally works okay, but can be misleading. If you have a long cold winter and the soil is cold, germination will be delayed and in some cases the seeds may rot in the ground. On the other hand, if the soil is unusually warm in the spring, it's possible to seed earlier. Being able to tell the soil temperature and being aware of the preferences of each plant will result in more or your seeds germinating.
Tomato seedlings |
Measuring Soil Temperature
Any thermometer that will measure temperature at a specific depth can be used to measure soil temperature. Insert the thermometer into the area where the seeds will be sown and wait a few minutes before you take a reading.
Bear in mind that each area of your garden will probably have a different temperature. The soil temperature is influenced by the following factors:
- Bare soil warms much faster than mulched soil and vegetated soil.
- Dry soil will be warmer than wet soils.
- South facing soils will be warmer than north facing, and the amount of shade cast on the soil will affect the temperature considerably.
Gingko biloba seedling |
Warming up the Soil
Here's a table providing the minimum and preferred soil temperature for a number of crop seeds and the estimated time it takes the seeds to germinate
Minimum and Preferred Temperatures for Common Crops
Basil Seedlings |
Upcoming Courses
If you would like to create a forest garden and gain some practical hands on experience come and join us in the Spring. We'll be covering site surveying, landscape design software, installing access, beds, irrigation channels, planting tree, shrub, herb and ground layers and wildlife ponds. All in 3 days! And plenty of follow up material to take away with you to digest slowly.

Design and Build - Forest Garden Course - Regenerative Landscape Design Course
Registration for our April 2020 course is now open with 15% discount on accommodation and food fees when you register as a group (2 or more).
If you appreciate the work we are doing you can show your support in several ways.
- Make a purchase of plants or seeds from our Bionursery
- Consider joining us on for one our Courses or Webinars
- Donate directly to our Polyculture Project crowdfunding campaign.
- Comment, like and share our content on social media.
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Design and Build - Forest Garden Course - Regenerative Landscape Design Course |
If you appreciate the work we are doing you can show your support in several ways.
- Make a purchase of plants or seeds from our Bionursery
- Consider joining us on for one our Courses or Webinars
- Donate directly to our Polyculture Project crowdfunding campaign.
- Comment, like and share our content on social media.
Polyculture - Forest Gardens - Permaculture - Regenerative Design Webinars
Want to join us for one of our live webinars? Forthcoming webinars include ;
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Polyculture - Forest Gardens - Permaculture - Regenerative Design Webinars |
Would you like to be involved in the project? We are currently offering 1 - 6 month positions on our polyculture study.
Permaculture and Regenerative Design Internships
We offer a diversity of plants and seeds for permaculture and forest gardens including a range of fruit and nut cultivars. We Deliver all over Europe from Nov - March.
We also offer a range of products all year round from our Online Store
Give a happy plant a happy home :)
We also offer a range of products all year round from our Online Store
Give a happy plant a happy home :)
References
http://www1.agric.gov.ab.ca/$department/deptdocs.nsf/all/agdex1203
http://www.rodalesorganiclife.com/garden/plant-seeds-right-depth
http://www.rodalesorganiclife.com/garden/plant-seeds-right-depth