What is Damping Off and How To Avoid It When Seed Starting

Damping off is a common problem that you might encounter when sowing seeds – especially if you are doing so indoors before spring arrives. But if you are new to gardening, you might not be familiar with this problem. In this article, we will look at what this problem is, and when you might see it. Then we will discuss some steps you can take to avoid it, or at least reduce the chances of it occurring, when seed starting.

Understanding and taking steps to avoid this problem is important in order to get your gardening year off to a good start. And to prevent waste and disappointments. So read on to learn a little more about this issue.

What is Damping Off?

Damping off is a problem that can affect most seedlings. Pre-emergence damping off will mean that seedlings fail to emerge at all. Post-emergence damping off will cause seedlings to wilt some time after germination takes place.

This problem is caused by a number of different soil-borne fungi and fungus-like organisms. These include Pythium, Phytophthora, Rhizoctonia and Fusarium. These micro-organisms are naturally present in many garden soils, and in organic matter in your garden.

But when they get into pots or seed trays, they can significantly reduce germination rates. And make a big difference to how many seeds you can successfully grow to harvest. You may see a white-grey fungal growth around affected seedlings. Which is a give away that this is the problem.

When Does Damping Off Occur?

Damping off can occur at any time of the year. But it is most common, and especially damaging in spring. Since this is a time when the light levels and temperatures are low. And seedlings are growing at a slow rate.

Damping off can affect both seedlings grown under cover or indoors, and those direct sown in your garden. However, it is more common when seeds are sown early in the year indoors, or under glass.

How To Reduce The Chances of Damping Off

Damping off is a common problem. Fortunately, there are a number of things that you can do to reduce the chances of seeing this issue. Here are some things you should do to reduce the chance that damping off will lead to poor germination rates or seedling losses this year:

Clean Containers and Tools Well Before Starting Seeds

Fungal organisms can stick around in the corners and under the rims of plant pots, or attached to garden tools. Practicing good hygiene can help in preventing damping off problems, and other fungal issues. Wash everything well with natural soap and water before you start sowing your seeds and you may well be able to prevent the problem.

Dirty containers is one common way for these fungi and fungi-like organisms to invade. But it is not the only way that you might accidentally introduce them to your seed starting area.

It is best not to reuse containers in which there has previously been a damping off problem.

Choose the Right Growing Medium

Another way that you might introduce damping off organisms is in the growing medium that you choose. If you purchase a potting soil or seed starting potting compost from commercial sources, then these should not contain them. However, with cheaper and poorer quality options, there are no guarantees.

To avoid peat, reduce plastic use and make your gardening efforts more sustainable then making your own seed starting mix is a great way to go. You can make a potting mix with a little loam or loamy soil from your garden, some homemade compost, and some leaf mould. Or you can create your own soil-free potting mix using coir, composted woody material etc..

One downside to making your own seed starting growing medium, however, is that it may contain the organisms responsible for damping off. This is especially true in the case of a soil-based mix. Your own homemade compost could also potentially contain these micro-organisms.

If you persistently experience a problem with damping off when using a home-made potting mix, you can consider sterilizing it in your oven before you use it to sow your seeds.

Otherwise, just take what steps you can to reduce the occurrence by making sure you keep plant material with fungal infections away from your growing areas and composting system.

Consider Airflow and Ventilation

Seeds need oxygen to germinate successfully, and compaction in the growing medium, or poor ventilation, make it more likely that a fungal infection will take hold either before or just after germination has taken place. If you are sowing seeds in a propagator, it might be a good idea to open it up for a while during the warmest and sunniest part the day, to ensure good airflow can reach the seeds or seedlings.

Damping off can also be more likely to occur if seeds are sown too thickly, and grow up too close together, creating a humid environment with poor air flow.

Don’t Over Water

Compaction in the soil can be caused by waterlogging, and over watering is often the root cause. Too much water can be just as much of a problem when seed starting as too little. And too much water can make it more likely that you will experience damping off.

If conditions are too wet, this is often down to your own practices. Look at how much you are watering and cut down if you have been doing it too much.

Improve Poor Drainage

Even if you are not overwatering, poor drainage can also cause water related problems. This too can cause waterlogging that will make damping off more likely. Make sure that the containers you are using have good drainage, and that holes in the base of containers are not blocked.

Look To Your Rainwater Harvesting System

Speaking of water, the organisms responsible for damping off can come from the water you use too. If you use tap water to water your seedlings, then this is very unlikely to be the source of the infestation. But if you use rainwater (which is actually the better choice) then this could be the source of the problem.

Make sure that your water butt or other rainwater containers are covered to stop leaves and other organic debris from falling inside. And clean out your guttering. Organic debris in the water could harbour the damping off pathogens.

Dispose Carefully of Damping Off Infected Materials

Even when you take the above steps, damping off can still occur. If is does, you can reduce the chances of it happening again by being very careful as you dispose of the infected soil/ medium and plant material. Make sure it goes nowhere near your other plants, growing areas, or composting system.

Use Cinnamon Against Damping Off?

Finally, one other thing to mention is that cinnamon is often used by gardeners as an anti-fungal. And anecdotally, some say that it can help in staving off the organisms responsible for damping off. But cinnamon powders vary considerably in terms of their anti-fungal properties (and even come from a number of different plants). They have not been scientifically tested, and as things currently stand, there is no proof that they can help with this problem.

That said, there may be no harm in sprinkling a cinnamon around on the surface of the soil, and it may help in reducing fungal pathogens to a degree.

If you have any other tips to help gardeners avoid damping off, let us know in the comments below.