Dahlia Black Jack

Dahlia tubers can be started indoors in spring, then planted outside once the risk of frost has passed. In most parts of the UK this is usually from late May, while colder areas may need to wait until early June. If you are searching for dahlia tubers ready to plant, they can also be planted directly into the ground from mid to late April, although growth will be slower until the weather warms up. Dahlias are tender plants, so new shoots must be protected from frost.

Dahlia tubers can be slow to sprout, particularly in cool conditions. They need warmth, good light and only lightly moist compost while they are starting into growth. Cold, wet compost is one of the most common reasons a dahlia tuber fails, as overwatering can quickly cause rot before shoots appear. Check that the old stem or growing point is facing upwards and sits just below the compost surface. Some tubers take longer than others, so give them time before assuming they will not grow.

Dahlia tubers can look wrinkled or slightly dry while dormant, particularly after delivery. They can still grow if they remain firm and are attached to a section containing a viable growing point, often known as the crown or old stem area. A tuber that has broken away without any crown tissue is unlikely to produce shoots on its own. Do not plant tubers that are soft, wet, badly mouldy or hollow, as these are signs of rot or serious deterioration.

Dahlia tubers should produce flowers in the colour and form described on the product page. Natural flowers can look slightly different in shade depending on sunlight, weather and soil conditions, while product images can also appear brighter or darker across different screens. Dahlias flower from summer into autumn, often continuing until the first frosts. A sunny position, regular watering during dry weather and removing faded blooms will help plants produce the strongest display.

Dahlias are not fully hardy in most of the UK and will not tolerate frost. After the first frost has blackened the foliage, cut the stems back and lift the tubers to store somewhere dry and frost-free over winter. They can then be replanted the following spring. In very mild areas, some gardeners leave tubers in the ground under a thick mulch, but lifting them is the safer option, particularly in colder or wetter areas.