Dahlia plants are amazing, another example of horticultural magic. The dinner plate types can grow a full metre high in just a few months while producing blooms almost 30 cm across.
Underground, the same thing is happening. Should you decide to dig up your dahlia tubers at the end of the season, you'll be impressed with what's been happing under the soil surface. Expect to find clumps of potato-like tubers, which often can be divided into several pieces (and plants) for next year's garden.
Could your garden use a little magic? Add a few dahlias.
1. Find a location where the soil drains well. If there are still water puddles 5-6 hours after a hard rain, scout out another site. Or amend the soil with the addition of organic material to raise the level 5-10 cm to improve the drainage. Peat moss, compost, ground bark or decomposed manure all work well and are widely available.
2. Site your dahlias where they will they will receive full sun.
3. Dig holes and plant the dahlia tubers with 5-10cm soil above them and 30-60cm apart depending on the variety's mature size. The tubers will vary in shape, with some being quite round and others shaped like long ovals. Look for the side or end of the tuber that appears to have the most "eyes" or growing points, which appear much like the eyes on a potato. Plant the tuber with the eyes facing up. Don't worry if you get it wrong, the plant will grow anyway.
4. After planting, water your dahlias lightly. Roots and sprouts will form quickly in warm soil. (If the soil is still quite cool, wait until it warms before planting.)
5. Dahlias will develop buds early summer and bloom through the autumn, until the weather cools considerably. (Or until frost, in colder regions.) When in bloom, feel free to cut dahlia flowers for bouquets. This will not hurt the plants and having vibrant blooms to bring indoors is one of the best reasons to grow dahlias.
6. After blooming has finished for the season leave the foliage in place; don't cut it off. The leaves will gather sunlight and provide nourishment for next year's show. Water as needed. (In very cold areas, if you want to save your dahlia tubers for next year, dig them about a week after the first frost. Let the tubers air dry for several days. Then store in a cool location in paper bags or boxes filled with peat moss. Replant in spring when danger of frost has past.)
1. Fill your containers with good quality, well-drained potting mix. Almost any commercially available potting medium will work fine. Make sure there are adequate drainage holes; dahlia must never sit in waterlogged soil or they will rot. Keep in mind the mature size of the varieties you have chosen; some dahlia plants get quite large and need spacious containers.
2. Site containers where they will receive full sun.
3. Plant and care for them as above. Pots need to be kept well watered inver the summer.
For extra early summer flowers try potting up your dahlia tubers as soon as you receive them. Then in early summer when they are in full growth plant them into any holes that you may have in the garden. This method achieves two things:
1. The plants will flower earlier from the head start of growing them in pots.
2. If you are like us when planting new bulbs in the spring, any gap or hole in the garden looks like a good contender, but when you start digging you find that something else is already planted there that has not started growing yet! Whoops! By early summer all obvious gaps will be easy to find!