Below is a collection of seeds that can be sown in September in Ireland. As it is later in the year, some of these varieties should be grown in a different way than the usual time of planting in Spring/Summer.
These vegetables/Herbs can be grown under cover (in a greenhouse, polytunnel, cold frame or homemade alternative) to become fully mature - Spring Onion, Beetroot, Coriander, Carrot, Onion, Turnip, Lemon Balm, Chervil.
These vegetables/Herbs can be grown outside to become fully mature - Onion (matures the following year), Radish, Turnip.
These vegetable seeds can be grown outside, or under cover just for their leaves for use in salads etc. - Beetroot, Spinach, Rocket, Lettuce, Rainbow Chard, Pak Choi, Chicory, Mustard, Cress, Peas, Dandelion.
These flower/herb seeds can be started and raised under cover in a greenhouse, polytunnel, cold frame, or an area sheltered from heavy frost. The young plants will be hardy and ready to plant out next Spring - Echinacea, Calendula, Lavender, Thyme, Pansy, Snapdragon, Sweetpea, Verbena, Foxglove, Sage, Mullein, Anise Hyssop, Comfrey, Bellflower, Delphinium, Dahlia, Lupin, Caraway, Cowslip Primrose, Indian Tobacco, Rudbeckia: Black eyed Susan, Pincushion Flower (Scabiosa), Clematis, Herb Robert Geranium, Iris.
These flower seeds can be planted directly into the flower bed outside for early flowering plants the following year. Results from this method can be varied - Echinacea, Calendula, Pansy, Sweet Pea, Poppy, Mallow, Lovage, Love in a Mist, Cornflower, Herb Robert Geranium, Doubtful Knights Spur, Corncockle.
Crimson Clover - Very good to grow as ground cover at this time if year as it will draw nutrients into your soil for the following year.
As you can see, there is some crossover here, and some varieties can be used in two ways. All of the varieties mentioned above are in the below listings.