It’s April, the soil is warming up nicely and many more herb seeds can now been direct sown into the ground. Having said that, there is no harm in continuing to germinate your herb seeds in pots indoors and it can be particularly useful to do this if, like us, you have your fair share of birds or mice that are partial to the odd seed or ten!
We’ve already covered the basics of seed sowing in our earlier guide - Sowing Herb Seeds Under Cover – The Basics.
In this guide we look at some of the problems you may encounter along the way:
Damping Off
Damping off can affect the seedlings of all plants but there are some herb seeds which we have found more susceptible than others. Damping off is a fungal disease which causes seedlings to collapse and die; they rot off. It spreads quickly and it can be very soul destroying, having sown your herb seeds to find that they have all damped off.
Good hygiene and ventilation are key. Make sure that seed trays and modules are scrupulously clean. Sow seeds thinly, make sure that seedlings have adequate ventilation and avoid over watering. Herb seeds sown too early are more prone to this problem and the prolonged period of cold we have had this year has made early sowings troublesome.
Herb seeds which we have found more prone to damping off if started too early include salad burnet, summer savory, purslane, dill, thyme, sweet marjoram and basil. It is best to sow these herb seeds later when the germination rates will be far more successful. Those herb seeds which can be sown early and without difficulty include chamomile, sorrel, chives, garlic chives, coriander, parsley and chicory.
Non-germination
There could be any number of reasons for this, not all of which are obvious and sometimes, it has to be said, seed packets can leave a bit to be desired in terms of instructions (hopefully ours don’t fall into this category).
Some herb seeds require a period of cold in order to germinate. This is called stratification. Ideally these herb seeds should be sown in autumn and allowed to over-winter. This process breaks down the seeds’ protective coating and they should germinate when the weather warms up again the following spring. If you can’t wait it is possible to artificially stratify your herb seeds by refrigerating them. Soak your herb seeds for 24 hours and then mix with moist sand or compost. Put them in a plastic bag and put them in the fridge for 3-5 weeks.
Herb seeds which require stratification include sweet cicely, angelica and sweet violet.
If your herb seeds did not require stratification and have still failed to germinate then you should consider:
Seed viability – some herb seed is viable for a very short period of time (angelica) and needs to be sown fresh.
Is your herb seed too old? Herb seeds over two years old lose viability. This does not mean that old seed will not germinate as many people successfully use old seed. However, germination rates do reduce with age.
Has your herb seed been stored correctly – in a cool, dry place?
Have your tiny herb seeds been covered with too thick a layer of compost or vermiculite?
Damping off can occur even before your seedlings come up so don’t rule this out, particularly if you know that the particular herb seed you are sowing is prone to this infection.
Weak Spindly Growth
This is not something you want. Tough, strong, herb seedlings is the goal. Light levels will have an impact here. If seedlings have insufficient light they will grow taller to try and reach the light. If your herb seeds are grown on a windowsill seedlings will also lean towards the light and will need turning often to make sure that they stay upright.
Overcrowded herb seedlings will compete for light and so make sure that once the second set of leaves appears (the first true leaves) that you prick out your seedlings to give them more space.
Ventilation is also important. Don’t pamper your herb seedlings too much. Seedlings will not toughen up if they are never subjected to any air movement. Even just gently brushing your herb seedlings with your hand will help in this regard.
