This is because in this particular instance exposure to light will promote germination.
Instead cover the seed with a light sprinkling of horticultural grit, perlite or vermiculite. Sow the seed on the surface but do not cover with more compost. Using a good quality compost such as John Innes 'Seed and Cutting' fill pots or seed trays and lightly firm. You can sow red hot poker seed from February to June or if you miss this window you can get another shot from September to October. However there is a practice solution which is to grow your own stock from seed. Unfortunately purchasing red hot pokers for the garden can be a little addictive, and this can end up causing rows with your partner as well as leaving a little out of pocket. However, despite their common name they are not always red but they will be brightly coloured in shades of red, orange and yellow. When mature, all red hot pokers produce multiple upright flower spikes which bloom well above the foliage.
Native to the continent of Africa, red hot pokers have broad strap-shaped foliage which can be anywhere between 1 and 5 ft long depending on the species or cultivar. Red hot pokers - Kniphofia, are an extremely exotic flowering herbaceous perennial, and a perfect choice for the cold hardy, tropical effect garden.