In a previous post, Seed Dormancy – Explained, I discussed different types of seed dormancy and briefly discussed various seed pre-treatments. In this post I’ll provide you with a series of steps that you can follow to germinate just about any seed.
What is Seed Pre-treatment?
Seed pre-treatment is anything that you do to the seed before you plant them. This includes soaking, changing temperatures to mimic winter, or even keeping them in the dark.
Each type of seed has a specific pre-sowing process that will over come dormancy, and allow germination to take place.
Determining The Right Pre-treatment
Here are some simple guidelines to determine the right pre-germination treatment for your seeds.
- Read the seed packet. If a pre-treatment is required, it will be described on the package.
- Vegetable seeds usually do not need a pre-treatment.
- Annual flower seed usually do not need a pre-treatment.
- If you collected seed from a fruit or vegetable, like an apple or tomato, wash the seed well to remove all pulp which can contain germination inhibitors.
- All seed needs to absorb water. This is a pre-treatment, but for most seeds this will happen after planting, so you can ignore this step unless instructions specifically say that you should soak the seed.
If you don’t have a packet for the seed you can probably find pre-sowing information from one of the following sources.
The best, and easiest to use source is the Ontario Rock Garden & Hardy Plant Society website which lists the pre-treatment requirements for thousands of different seed. You can access it here:
Go to the Germination Guide menu, and find your plant name by genus and species. It will then give you pre-germination instructions.
Another good source, that is a bit harder to use since it consists of 3 books, are the seed starting books by Dr. Norman Deno. You will need to look at all three books to find complete information. You can get free copies of these books by clicking on the Free Garden Books menu of this website.
And my third recommendation is Tom Clothier’s Germination databases.
If you can’t find the plant in one of these sources, try searching the internet. If all else fails, use the pre-treatment for a similar species – that usually works.
If you still have no idea how to germinate the seed, try a cold stratification for 3 months followed by a warm period. This treatment works for many seeds. You can also scarify half the seed to see if that helps.
Note added March 17, 2016: Here is another good source for info on woody seeds; Woody Plant Seed Manual
The following are some of the more common pre-treatments.
Scarification is any process that weakens or damages a hard seed coat so that it is easier for water to enter the seed. This can be done with sand paper, a nail file, a triangular file, nail clippers, hot water or even acids. For home use I would not recommend using the acids – they are dangerous and rarely required.
For larger seed I like using a triangular file. I hold the file still and moved the seed along one edge. For small seed I use 2 sheets of sand paper rubbed together on a table as shown in the video below. I also use a utility knife (similar to an Xacto knife) for mid sized seed.
Here is a video showing you how I scarify seed.
If you can’t see the above video, try this link: https://youtu.be/icB9HrqdQqU
Stratification is a common requirement which means the seed needs to go through one or more temperature changes to initiate germination.
Generally, a warm period is house temperature or 20 – 25 deg C (70 deg F) and a cold temperature is 5 – 10 deg C (40 deg F). Some seed likes to undergo freezing temperatures and then the best pre-treatment is to put them outside in winter so they experience freeze – thaw cycles.
Stratification can be done with dry seed, or moist seed, but the term almost always refers to moist seed. Unless the instructions specifically say ‘dry stratification’, assume it is to be done moist. That means storing dry seed in the fridge does NOT normally qualify as stratification.
Many sites on the internet and even gardening books will tell you to keep dry seed in the fridge to ‘stratify them’ – they are wrong. Keeping dry seed in a fridge is not stratification, unless the requirement is for dry stratification.
Soaking is fairly easy to do. Place seed in water and leave them for the specified period of time. If no time is given, use an overnight soak. Then proceed with the germination process. For longer soaks it is a good idea to replace the water every 24 hours with fresh water so that any chemicals that are extracted from the seed can be discarded.
This short video will show you how to soak small seed.
If you can’t see the above video, try this link: https://youtu.be/dhL57pqnHHQ
Seed such as pulsatilla and clematis have tails on their seed. Some people feel that the presence of a tail inhibits germination. My studies on clematis germination do not support this idea, and I suspect it also does not apply to the genus Pulsatilla. However, there is certainly no down side to removing the tails and you might find it easier to handle seeds with the tails removed.
GA3 Hormone Treatment
As seeds come out of dormancy the relative amounts of certain hormones inside the seed change. It is quite common to see the level of GA3 (gibberellic acid) increase just before germination.
In some cases adding GA3 to the seed will speed up germination. In other cases adding GA3 can speed up the development of the shoot.
When required, I treat seeds with GA3 following the method described in Dr. Deno’s main book found in the Free Garden Books section of this website.
GA3 is not normally required for germination, but may speed up the process.
Combining Multiple Pre-treatments
The above sections describe a number of pre-treatments, but the reality is that a seed may need more than one of these. In that case the order in which you do them can be important. Unless instructions are different, I would carry out the pre-treatments in this order:
- Remove tails
- Wash pulp off