Top 5 Tips for Growing Delightful Dahlias!
Tuberous Dahlias are in the Daisy (Asteraceae) Family and are native to Mexico and their national flower! Wild dahlias produce single or double flowers and are red, orange, yellow or pink. They are related to sunflowers, chrysanthemums and zinnias. There are 42 recognized species and approximately 60,000 registered cultivars, which makes it incredibly hard to pick just one variety/cultivar to buy in spring! Most dahlias available in garden centres are hybrids. They come in different heights and flower sizes. These gorgeous flowers bloom from mid-summer into the fall.
Dahlias are divided into groups and subdivisions according to their flower size and shape. Here are just a few! Dinnerplate, Giant Dinnerplate (the largest flowers), Cactus- (the petals are rolled inward), Semi-Cactus, Ball, Pompom, Single, Collarette, Decorative, Anemone, Mignon and Waterlily. Many beautiful dahlias from most of these groups are available at Floral Acres! (While supplies last!!)
Top Five Dahlia Growing Tips You Should Know!
When and Where to Plant Your Dahlia Tubers
Dahlias love a full sun location; in ground or in very large containers! Avoid growing dahlias in terra cotta pots.
Dahlias are very sensitive to cold and frost. Many gardeners in our zone start their dahlia tubers inside about a month before planting them out any time between the end of May and the middle of June. Be aware that a late frost will injure planted dahlia starts, turning the leaves black.
Soil Preparation and Planting
Dahlias prefer a slightly acidic soil (pH -6.5) and it is important that they have excellent drainage.
You should amend the soil in the planting area each year with compost, coir or a small amount of moistened peat moss. This area should also be kept free of old leaves, weeds and other debris that could harbour fungal diseases.
Once the soil has been amended, you can plant your tubers.
Most dahlias must be supported with a very strong stake. Stakes are best placed before planting the tubers. As the Dahlias grow, tie the stems to the stakes in numerous places. Some gardeners use tomato or peony cages.
When direct planting dahlia tubers, bury them about 10-15 cm. deep. Space the plants 45 – 60 cm apart. Plant with the ‘eye’ facing up. The ‘eye’ is similar to a potato eye. Bury pre-started dahlias at the same soil level they were in the pot.
Watering and Fertilization
DO NOT WATER right after planting. Wait until the first shoots appear – this usually takes two to four weeks. Young plants do not need a lot of water. If you do overwater, this may rot the tubers.
On the other hand, dahlias do not like to totally dry out; as they grow, keep the soil moist; never soggy. Water at ground level to avoid fungal/bacterial diseases.
Dahlias are heavy feeders and should be fertilized once a month until the end of August with a 5-10-10 water soluble flowering plant fertilizer, Miracle–Gro Bloom Booster 10-52-10 or tomato food. Yes; tomato food! Deep water after every fertilization.
Disbud dahlia stems to create bigger flowers on the end of the stems. You don’t have to do this but do take a look at a couple of YouTube videos on the topic, then make your decision. A video is worth a thousand words!
Propagation
Propagate by division. This can be done when preparing the tubers for winter or early spring.
Getting Ready for Winter
In our Zone 3b, dahlias must be lifted and stored inside over winter. Once a frost kills the leaves, cut the main stem to just a few inches above the soil and leave the buried tuber for 10 more days. This properly hardens off the tubers and gives them the signal to go into dormancy. Do not compost the old foliage if it has experienced disease or insect infestation. Attach a waterproof name tag to the remaining stem. Dig up the tubers, allowing lots of room so you don’t slice through the tubers. Brush off soil and thoroughly wash the tubers and dry on a mesh screen in a well ventilated, semi-shaded area. Do not dry in full sun. Remove any diseased or damaged tubers with sterilized tools. If the root ball is very mature and contains lots of tubers, remove the shrivelled mother tuber and prune off the ragged roots at the end of each remaining tuber. You can cut the tubers from the main stem at the point where they attach to the crown, making sure you have at least one eye per tuber. Some gardeners prefer to divide the tuber ball in spring when you can see the eyes swelling. The eyes are similar to eyes on a potato. This is helpful if you want to divide the root ball into single tubers.
Before storing for the winter, shake the tubers in a brown paper bag –outside-with some dry vermiculite and a small amount of powdered fungicide. Always wear gloves and a mask when working with fungicide powder. Some gardeners prefer to store their tubers in dry peat moss, vermiculite or dry cocoa fibre. Others like to use the new method of wrapping each tuber tightly in saran wrap. Keep them in a dark room (cold room or basement) that has a temperature of 7-10 C with the humidity between 65 and 75 %. Check on them periodically through the winter. If you encounter a few that are moldy, throw them away. If shrivelled, mist them with a bit of water.
You can pot them up in spring around the end of April– first of May and keep them inside until it is time to harden them off closer to June.
Dahlias are beautiful and striking in mixed floral arrangements but should only be harvested in the morning or evening and when the flowers are fully open. Cut each stem at an angle, above a node. Remove the lower foliage and buds to avoid bacterial growth in the water.
Dahlias can attract Slugs, Snails and Japanese Beetles. Slugs and snails especially love the smaller new shoots and Japanese Beetles devour the fully open blooms.
Shrivelled dahlia tubers can be rehydrated in water for a few hours and then plant as directed.
Dahlia tubers are also edible when cooked but the skin is fairly bitter. I think I will continue to grow them only for their flowers!