Dahlias are so versatile – they come in so many colors, sizes, and shapes! The size of the gorgeous dahlia flowers ranges from 1/2 inch to 12 inches and more. There are daisy-like single types and fully double types with intermediate forms such as collarettes and anemone types. Dahlias come in every color except blue.
These beautiful spiky flowers originate from Mexico and are tuberous-rooted perennials that bloom from mid-summer till the first frost. We love them not only for their undeniable beauty but also because they are so low maintenance and easy to grow!
If you’d like to try and grow dahlias in your garden, then you will need to know the basics of how to plant them and care for them. As always, we are here to help with 10 easy tips…
1. Where to plant
Dahlias love the full sun as well as well-drained, rich, and fertile soil. They also love lots of food while they grow, so make sure you dig in lots of compost or manure as well as a top-dress with a general-purpose fertilizer.
If there is enough food, dahlias will make big fat roots crucial for the growth of leaves and flowers. With well-prepared soil and lots of suns, you will have beautiful dahlias in no time.
2. Growing from seeds
If you decide to grow your dahlias from seed, then you should sow them somewhere between February and April. Fill a pot or seed tray with compost. Firm the surface, then gently push the seeds into the compost. Watering is needed to keep the soil moist. Expect seeds to germinate in 7-21 days. In about five weeks, when the plants have two or more sets of leaves, it is time to transplant them. Gently transplant the seedlings in 10cm pots of multipurpose compost, firm, and water well. In the middle of May, harden off the plants by standing them outdoors during the day and bringing them in at night. Once all risk of frost has passed, plant them in their final positions.
3. Growing from tubers
Dahlia tubers should be planted directly in the ground from the middle of April. This means you do not need to wait till the frosts are over, as the soil will insulate them. Make sure you make a 10-15cm hole deep and wide enough to fit the tuber comfortably. The eye of the tuber should be facing upwards. When planted, water thoroughly.
4. Growing from potted plants
Potted Dahlias should be planted in May or June. Once you have chosen your healthy potted dahlia, choose a sunny location to plant them in your garden. Make sure the soil has a pH between 6.5 and 7. Cover the planting area with slow-release fertilizer and mix it into the ground. Dig a hole, remove the plant from the pot and shake off the soil from the tuber. Place it into the hole and pack the soil around it. Water thoroughly twice a week.
5. Growing in containers
Dwarf dahlias work best for container growing. If you want to grow bigger varieties, have in mind that you will need a much bigger container. You can use a multi-purpose compost but make sure you mix in some slow-release fertilizer because, as we mentioned before, dahlias are heavy feeders. Plant the tubers 10cm deep. Keep your soil slightly damp or cool to the touch after planting, not soaking wet. Once the plants are 12 inches high, they will need more watering and more fertilizing.
6. Caring through the season
Dahlias are fast growers, and besides food, they need plenty of water. This means keeping the soil moist but never soaking wet. It is best to water them thoroughly twice a week. You should also pay attention to weeds as they compete for food, water, and light with the dahlias. Keep your plants weed-free by hand weeding. Use organic mulch to keep the soil cool, especially in summer. Black polyethylene mulches are preferable in the spring. Some dahlia varieties can become massive, so they need support. Tie plants to the stake that was driven next to them at planting time. If you use string or soft twine for tying dahlias, tie the string tightly to the stake but loosely to the stem to avoid constricting the developing plant.
7. Food and Fertilizer
As we said previously, you should prepare the soil by adding compost and fertilizer before planting the dahlias as they react dramatically to food. Once the plants are one foot tall, it is time to add a handful of 5-10-5, 5-10-10, or similar fertilizer around them in a 2-foot ring. After applying the fertilizer, add plenty of water. Repeat this at the very beginning of August. Feeding them once a month is desirable. Just make sure you use a low nitrogen fertilizer.
8. Pests Protection
If you want your blooms to be perfect, then you should use an insecticidal soap or a commercial pesticide. Slugs and snails are common enemies of dahlia plants, so it is best to remove them manually each morning. Japanese beetles like eating dahlia flowers, so remove them manually into a bucket of soapy water. For deer, control grows deer-resistant plants around your dahlias.
Who can resist the gorgeous dahlia flowers when they start showing up somewhere in July? If you want to use them as cut flowers, wait until they are fully opened. Make sure you use sharp sheers or knives to make a clean cut. Plunge the cut ends into warm water immediately. Change the water every 2 days to prolong the life of the cut flowers.
10. End of Season Care
Dahlias will bloom until the first frost comes. The frost will kill the plant. You can decide to do nothing and buy new tubers next year, but you can also dig and discover that the plant has produced half a dozen new tubers! You can store the tubers and plant them next season. There are many methods of storing the tubers, but we recommend storing them in plastic wrap. You can read the full storing process here.