So-called red lobelia is a rose/purple and not ideal.

For a predominantly yellow border, there is not much better than this trio, although somewhere I would also find room for the crimson, spiky-leafed Kafir Lily (Schizostylis coccinea 'Major'), to provide autumn contrast and perhaps the red Lobelia tupa, or even redder Lobelia 'Queen Victoria' with its copper foliage.

The seeds are Bubble mint Golden Jubilee, Columbine cottage mixture, Milky bellflower, Cerinthe Yellow Gem, Delphinium cottage mixture, Geranium hardy mixture, Heuchera Emperor's Cloak, Giant (6ft) red lobelia, Blue Poppy, Evening Primrose Sunset Boulevard, Primula candelabra and Potentilla Monarch's Velvet.