By Catherine Winter
There are few things as frustrating, even devastating, to a gardener as when seeds fail to thrive. We put so much loving care into tending our plants that when something goes wrong, it can be quite a severe blow. This is especially true in late winter and early spring, when we’re champing at the bit to start gardening again.
Are you having difficulty with seed germination? Or are your seedlings sickly and weak-looking? Let’s take a look at a couple of the most common issues, and how to either treat them, or prevent them in future.
I just dealt with this issue with some of my own seedlings. It’s quite common, and can happen if gardening tools (pots, spades, etc.) aren’t cleaned properly between seasons. In my case, I used a container that I hadn’t soaked in a bleach solution, because I was over-eager to get some seeds started.
There are several pathogens that can live in soil—and cling to pots and trowels—for quite some time. These include fungi such as Rhizoctonia spp. and Fusarium spp. (vascular wilt), which are two of the most common culprits responsible for damping off syndome. Add the Pythium spp. mold to that list and you have the unholy trinity of plant killers.
Damping off in seedlings manifests in a few different ways. The most common are:
- Stems shrinking to almost thread-like, unable to support the plant
- Discoloured, grey-brown first leaves
- Seeds failing to germinate and/or emerge
- Lack of root development
In some cases, you might even see what appears to be cobwebs on the soil, or on the plants themselves.
How to Solve This Issue:
These pathogens thrive in the damp conditions that are ideal for seed growth, and can cross-contaminate in a number of ways. As such, the best course of action is prevention.
- Make sure that you sterilize all your pots and tools by soaking them in a 1:10 bleach:water solution for about an hour. Then rinse well, and allow them to dry completely.
- Only use new potting soil that has good drainage, rather than garden soil, which can harbour the pathogens. Also, make sure your pots have drainage holes so roots don’t get soggy.
- If your home is quite cool, use a heat lamp above or heating pad underneath your pots/trays. These pathogens thrive in cool, wet soil, so keep it warm!
- Ensure the seeds/seedlings get enough light: window light isn’t enough, so provide 12-14 hours from grow lights or soft fluorescents.
- Only use warm water to water your seeds/seedlings. Apparently cold water can slow plant growth, making them more susceptible to diseases.
Failure to Germinate
Are your seeds just not sprouting? Or are they only growing teensy tails and then… that’s it?
There are quite a few reasons why this could happen. Such as:
- The seeds are old and no longer viable
- Those seeds could have been damaged, or exposed to too much humidity while in storage
- If you’ve started them in paper towels, they might have had too little (or too much) moisture
- The soil they’ve been popped into has high salt content or herbicide residue
- Too much light (or too little): check to see if the species you planted is light-dependent for germination
- Temperature is too cold (or too hot): again, check your plant’s individual needs
- Seeds were planted too deeply, so they’re not getting enough water or light
- The aforementioned damping-off disease, caused by soil-borne pathogens
How to Solve This Issue:
If you suspect that your seeds are old, or may not be viable, then test them.
Choose 10 seeds of every variety you’d like to test. We chose 10 (or multiples of 10) because it’s easier to sort out percentages. For example, if 7 out of 10 seeds germinate, we have a 70% success rate.
Wet a paper towel or a clean coffee filter, and spread your seeds on it. Cover with another damp towel or fold the filter over it, and place it in an open Ziplock bag, and label it with the date the seeds were placed in it.
Keep the bag open so the seeds can get air, and place in a warm location. On top of the fridge or on a high shelf is a great option. Keep the towel moist, and check the seeds every 2-3 days.
If any of the seeds are still viable, they’ll sprout within a week or two, depending on the species. Plant the ones with strong rootlets in fresh, loose potting soil. Discard the ones that didn’t sprout.
- Always use fresh potting soil for container plants
- Research the plant’s individual soil, water, temperature, and light needs
- Test your garden soil’s pH and salt levels
For additional info, check out the following articles: