It was one of those March days when the sun shines hot and the wind blows cold: when it is summer in the light, and winter in the shade. ~Charles Dickens, Great Expectations, 1861
What seeds to sow in March
As the weather starts to warm up and the soil dries out, we can begin sowing seed outdoors: - broad beans, carrots, parsnips, beetroot, onions, lettuces, radish, peas, spinach, summer cabbage, salad leaves, leeks, Swiss chard, kohl rabi, turnip and summer cauliflower. Early potatoes can be planted mid March onwards though main crop are more typically planted later in April.
However my soil is still too cold and wet (the weeds haven't emerged yet - indicative that Spring is on its way), so I have started some more broad beans indoors in pots as well as peas to give them a head start before planting out next month.
I shall have to be patient before I sow outdoors and plan what next to sow in my windowsill propagator. I shall leave tomatoes and cucumber until next month. As I do not have a greenhouse for them, I will plant varieties suitable for growing on outdoors Meanwhile I have several varieties of basil so I'll put those top of the list for sowing next. Other herb seeds such as coriander, parsley, oregano, sage, rosemary, thyme and lemon balm could be sown now too.
I was thinking about what flowers I might sow; marigolds, tagetes come to mind as companion planting for my tomatoes, calendula, clarkia and cosmos. Sunflowers in the borders, stocks, poppies and cornflowers are all hardy annuals and will germinate as the soil warms up.