From: DK Books - Herbs
What Do You Need?
The bare essentials for raising seedlings include containers, growing media, labels, and the living plant material you are going to grow from. You will also need a watering can with a range of sprinkler heads and a waterproof pen or pencil for labeling.
Buying the full range of pots and plugs can be expensive in one go, but do buy the more robust as they can be reused again and again. Small, frost-resistant terracotta pots are not expensive and are an attractive way of presenting herbs. Organic pots are available, but they are only suitable for one, short-term usage.
A fine sandy texture is good for seeds and cuttings while a coarse grade is better for transplanting older plants. Old compost can harbor pests and diseases.
Using and Buying Vermiculite
This is a mineral that can be added to compost to help alter its air and moisture-holding capacity. It makes the art of growing seeds and seedlings more predictable (Image 1).
Buy a suitable grade of vermiculite, depending on the size of your seed. The coarsest grade can be broken down by rubbing between your fingers (Image 2).
Seeds That Germinate Rapidly
Seeds that seem to spring up from nowhere need extra care to ensure they have enough space, water, and light. A moment's inattention can result in them becoming cramped and straggly.
Chive seedlings, seen here, emerge quickly and the first leaves are the most fragile — remember that the sun can burn them very easily.
Seeds That Germinate Slowly
Some take longer, occasionally much longer, so be patient and resist the urge to dig around looking for signs of growth as this disturbance is sure to damage any new sprouts.
Fennel seedlings, seen here, emerge after a month or so, but more may pop up a little later — they will soon catch up if there is space.
Sowing Too Much Seed
Dense sowing results in weak seedlings that are more susceptible to disease and failure (Image 1). Do not sow thickly unless recommended on the packet.
Mixing Up Seed
To avoid mixed pots of seedlings use fresh compost and only sow one type of seed at a time (Image 2). Save unfinished packets by folding and sealing with a clip.
Plants Quick to Bolt
Coriander is prone to bolting, missing the leafy stage, if stressed in pots or by too high a temperature. Avoid by sowing directly into the ground in spring (Image 3).