Our experts will help you get the best from your garden
DAHLIAS
Q My dahlia tubers have grown enormous. Can I divide them?
AIf you’ve lifted your dahlias, you need to keep them dry and free from frost over winter. Trim back the stems and lay them on a tray or a shallow crate with a thin layer of potting compost. The large size of the tuber isn’t a problem and you have several options. The new shoots grow from the base of the stems, where the tubers are attached and not from the actual tubers, which are simply stores of starch to help the plant grow in spring. Therefore, in late March, as you plant them out in the border, you can just cut off most of the large tubers.
You can also cut through the tuber, vertically, to divide it into sections and, as long as each has a piece of the old stem, each will grow. Even better, pot up the tubers and start them into growth in spring in a greenhouse and take cuttings of the new shoots, removing each when about 15cm high, with a sliver of the old tuber at the base so the cutting has a solid, not hollow, base. These will root easily and you can then plant them with a trowel and discard the old tuber.
Q & A
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TREES & SHRUBS
Q Could hard pruning stop hydrangeas from flowering?
A Traditional ‘mophead’ hydrangeas respond to severe spring pruning by producing strong growths that probably won’t flower and if this is repeated annually, you’ll never get blooms. These hydrangeas should be pruned by deadheading in spring and only removing the smallest length of the main stems.
Weed it or feed it?
Q Do I weed or feed this plant spreading over our gravel areas?
A This plant is a wild viola, probably Viola canina. It should produce purple violets in spring and sometimes later flowers, but these tend to set seeds without ope
