Herb Gardening – Seed Sowing Tips

February 25, 2011

basil seedlings

Basil seedlings

Hopefully you are soon planning to sow some seeds for your annual herbs (indoors to start with) if you like to grow your own. I’m hoping this article isn’t too basic for you too but there are a wide range of visitors to this website and we all have to start somewhere. If you want a really detailed guide, try Jekka McVicar’s book – Seeds: The Ultimate Guide to Growing Successfully from Seed

Here are a few tips and some information for you:

Seeds need four things to germinate: moisture, air, light and the correct temperature.

1. Moisture.  The compost or soil surface should not dry out especially with tiny seeds.  To prevent this you can place a piece of glass or clear plastic or even a clear plastic bag over the pot or tray to help keep moisture in.  However, as soon as the seedlings appear you need to remove it to prevent ‘damping off’ which is when the seed/seedling goes mouldy or starts to rot due to excessive moisture.

2.  Air – A young plant needs some air near its roots so make sure that seeds are not sown in compacted or waterlogged soil.

3.  Light – Many seeds need light to germinate.  A general rule of thumb is to cover the seed with compost up to the depth of the seed.  However, very fine seed eg basil, sweet marjoram, poppy, primula, thyme and yarrow need lots of light to germinate so are best left uncovered; just press the seed into the moist compost.

4.  Correct Temperature.  Herbs from hotter climates usually require temperatures of between 15 to 21 degrees centigrade, the exception to this is lavender which germinates best at a lower temperature (4 to 10 degrees centigrade).

Seeds native to colder climates such as northern Europe and north America can germinate at temperatures between 5 to 13 degrees centigrade.  Again there is an exception to this which is parsley which needs a much higher temperature (18 to 21 degrees centigrade).  Rosemary needs an even higher temperature (27 to 32 degrees centigrade) which is why it is simpler to either buy a young plant or grow it from cuttings.

You can re-create this heat by placing containers in a warm spot eg near a heater or on a heating mat in a propagator or in a greenhouse once the weather is warmer.  Apparently, some people even put seed trays on top of their tumble dryer!

Seeds can be sown in trays or pots or direct into the ground; the seed packet will be more precise.  Seed trays are good for starting off seeds because they help to prevent overcrowding of seedlings and excessive moisture around their roots, however if the plants are ones that dislike having their roots disturbed eg basil, coriander and dill then their seeds are best either sown direct into the ground where they are to grow or into root trainers/plug trays/pots to minimise root disturbance when/if replanting.  You can of course recycle some plastic containers as long as you make some drainage holes in the base of them.

So the basic steps are:

1.  If you don’t have your own supplies, buy seed from a reputable supplier (see the list on my blog here for online suppliers) or purchase from your local garden centre.

2.  Fill the container with seed compost leaving a gap of approximately 2 to 3 cm from the rim, firm down gently, water thoroughly, sow the seeds, cover lightly with compost (sieved if necessary) and water lightly with the fine rose of a watering can or use a spray mister. If desired, place some kind of clear cover over the pot.

3.  Check moisture levels daily and remove plastic cover as soon as seedlings appear.

4.  Thin out seedlings as necessary.

5.  Gently transplant seedlings from seed trays into pots once the first set of true leaves appear (pricking out) or leave in root trainer containers until large enough to plant out or transfer into  a larger pot or into the garden once the risk of frost has passed.

If you have any tips of your own, feel free to leave a comment below.

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