A Guide to Cultivating Stunning Dahlias

Planting Dahlias at the Right Time

For the successful growth of dahlias, it’s essential to consider the timing. Dahlias should be planted when the soil temperature has reached a minimum of 15°C, and the threat of frost has subsided. A good rule of thumb is to think of planting dahlias when it’s warm enough for tomatoes to be sown. Planting in cold, damp soil can lead to tuber rot.

Choosing the Ideal Location for Your Dahlias

Dahlias thrive in full sunlight, requiring a minimum of 8 hours of direct sunlight each day. It’s crucial to select a site with efficient drainage. Avoid planting in areas prone to water pooling, as dahlias are intolerant of overly saturated soil. As they grow, especially on hot summer days, they will demand generous watering, so ensure your watering system can reach your dahlia garden.

Planting Dahlia Tubers Directly in the Garden

1. Soil Preparation Preparing the soil is a vital step to ensure your dahlias flourish. They thrive in a sunny spot with warm, well-drained, and fertile soil. In a 12″ wide circle, dig to a depth of 8 inches and mix in the following:
   • Approximately 3 inches of compost or well-rotted manure. Avoid soil treated with weed killers or fertilizers, as it can harm young dahlias.
   • A light dusting of bone meal (skip if you have pets or animals that may disturb the area).
   • Lime to increase pH or sulfur to decrease pH if you know your soil’s pH level, as dahlias prefer soil with a pH of 6.5 to 7.0.
2. Planting Plant the dahlia tuber 4 inches deep, lying completely horizontal with the eye or sprout facing upwards. Do not water until you observe shoots emerging; the moisture in the soil should suffice. Insert a support stake (wood, bamboo, rebar) at this point to avoid accidentally damaging the tuber later. Don’t forget to label your dahlias and space them 15 inches apart for ample room to thrive.

Starting Dahlia Tubers Early in Pots

To gain more control over the environment and avoid potential frost, heavy rains, or critter interference, we recommend starting your dahlias early indoors. Here’s how:

1. Pot Selection Use a 1-gallon pot (6″-7″ wide and tall) with proper drainage holes. If necessary, you can use a smaller pot for smaller tubers.
2. Potting Mix Opt for a potting mix without weed killer or fertilizer to prevent damage to the tender roots. If you have insufficient potting soil, mix it with garden soil at a 1:1 ratio.
3. Planting Fill the pot and plant the tuber horizontally, about 2 inches deep, or at an angle if it’s large. Ensure the end with growing eyes faces upward. Cover with soil. If your potting soil is fresh, it should be adequately moist, and you don’t need to water until sprouts appear. Water lightly if the potting soil is dry, ensuring proper drainage. Dahlias may take 3-5 weeks to sprout.
4. Hardening Off Before planting your potted dahlias outdoors, gradually expose them to outdoor conditions over a week or two. Begin by placing them outside for a few hours on a cloudy or shaded day, protecting them from strong winds. Move them inside each night. Increase their outdoor exposure and sun gradually. After the hardening-off process, your potted dahlias will be ready for planting in the garden.

How to Pre-Sprout Dahlia Tubers

Pre-sprouting your dahlia tubers can be advantageous to increase the chances of successful growth. It ensures they’ve already begun growing before planting, which is especially helpful in areas with heavy rainfall. Here’s how to do it:

1. Pre-Sprouting Setup Use a tray or shallow pot filled 2 inches deep with moist potting soil, vermiculite, or peat moss. Ensure the mix does not contain weed killers or fertilizers.
2. Tubers Placement Label your tuber and place it horizontally in the mix. They don’t need to be completely covered with soil, but enough to prevent drying out. Space tubers about 1 inch apart.
3. Provide Warmth Place the tray in a warm location, at least 22°C or use a heating mat. Keep the soil moderately moist to allow the tubers to grow roots.
4. Readiness for Planting Your dahlia tuber is ready to plant when you see a waxy green or red sprout. Now, you can confidently transplant it into the garden or a pot, if the outdoor soil is still too cool. Avoid letting the sprouts grow excessively, causing tangled roots.

Caring for Your Dahlia Plants

Once your dahlias are in the garden, it’s essential to monitor and maintain their well-being. Follow these care guidelines:

1. Watering When young, dahlias require less water, but as they grow and the weather gets hotter, they’ll need deeper watering. Water thoroughly 2-4 times a week, depending on weather conditions and soil type, ensuring the water reaches the bottom roots to avoid tuber rot. Avoid overwatering.
2. Pinching After your plants have four sets of leaves, pinch the top of the growing center, removing the top pair of leaves. This promotes branching, more blooms, and longer stems.
3. Staking Dahlias can grow tall and will need sturdy stakes (wood, bamboo, rebar) for support. As your plants grow, remember to tie them to the stakes to prevent wind damage.
4. Pest Control To protect your young plants from slugs and snails, apply slug/snail bait when planting and as needed throughout the season. Use insecticidal soap weekly to deter insects like aphids, mites, thrips, and whiteflies. You can create your own insecticidal soap with water and Dawn dish soap (4 tbsp of Dawn in 1 gallon of water). Make sure to spray the undersides of leaves and avoid spraying on very sunny days to prevent burning. Test the spray on a small area first.

To safeguard your blossoms from earwigs and grasshoppers, use drawstring mesh bags to cover buds before they open. Organza jewelry or gift bags work well; just ensure they are large enough to accommodate the fully bloomed flower. Place the bag over the bud and tie the drawstring snugly to prevent earwigs from entering.

When to Harvest Dahlia Flowers

1. Once your dahlia plants have flourished, it’s time to enjoy your hard-earned blossoms. Follow these tips for a successful harvest:

   1. Optimal Time for Harvest The best time to pick dahlia flowers is in the morning, when the plants are well-hydrated and the stems are full of water. Picking during the heat of the day can stress the plants and shorten the vase life.
   2. Proper Cutting Bring a clean bucket or vase filled with room temperature water to the garden. Cut the stems with sharp, clean snips or scissors, leaving at least 12 inches of stem. Cutting deeply into the plant encourages more branching, more blooms, and longer stems, similar to pinching. The more flowers you cut, the more blooms you’ll get later.
   3. Deadheading Remove spent flowers (deadhead) regularly to divert the plant’s energy towards producing more blooms rather than seed production. Cut off at least 12 inches of the stem during deadheading.
   4. Post-Harvest Care After picking your dahlia flowers, let the bucket sit in a cool, sheltered area for a few hours to recover and hydrate. Trim the ends of the stems about 1/2 inch at an angle before placing them in their final vase. Change the water daily to prolong the vase life of your flowers. Under healthy conditions, dahlia flowers can last 5-7 days in a vase, with dinnerplate-sized dahlias typically having a shorter vase life than ball varieties. Regardless, the impact of a single bloom is truly stunning!

What’s a Dahlia tuber anyway?