Dawn of the dahlias
Winter dahlia care
A reader has asked what he should be doing with his dahlias, still in the ground from last season. In all but the coldest parts of the country, dahlias can happily be left in the ground over winter, providing the soil doesn’t get too waterlogged, in which case the tubers may rot.
There’s not a lot to be done to them now, apart from weeding around them and ensuring other plants are not too close. Most dahlias need at least 30cm around them clear, and maybe 50cm for big varieties. Remember: they get bigger every year, all going well. (That said, pompom varieties tend to do best when planted close, only 40cm apart.)
Every two or three years, the plants benefit from being lifted and divided, which is best done in late autumn, after the leaves have died down. Then, cut the tubers up with a sharp knife, ensuring each piece has an eye – similar to eyes on potatoes – where growth begins.
Feed now with a nitrogen-rich fertiliser, or blood and bone, which encourages leafy growth. But once the buds form in summer, provide a more phosphate-rich feed as it promotes roots and blooms, and potash or a potassium-rich fertiliser to encourage strong stems and tubers.
On the other hand, those who prefer a more general approach could ply theirs with compost as a winter mulch (it’s not too late for that), then sprinkle some dolomite lime about now to lower the pH of the soil, and in a month or so, sprinkle the aforementioned blood and bone. Lime and blood and bone are best applied at least a month apart.
Ornamentals
Prune hydrangeas by cutting to the base of the plant’s second-year wood, which is lighter in colour and has old flower heads on it.
Cut back dogwood and salix grown for their colourful stems.
Edibles
Sow coriander and lettuce in a sunny, sheltered spot. They tend to do better now than in the heat of summer.
Brassicas and other hardy crops such as carrots, onions, peas, silverbeet and spinach may be sown direct into the garden.
If you haven’t already done so, stake broad beans before they grow too tall and floppy, and before the strong equinox winds arrive in September. A few stakes with string between usually does the trick.
Feed fruit trees with fertiliser, or a hearty mulch of pea straw topped with wellrotted horse manure, or a generous application of compost out to the drip line.