Dahlias are vibrant and lovely flowers, available in a wide range of colors. However, because they can get very tall, many gardeners are skeptical of planting them in pots. They grow vigorously as long as the container is large enough, but varieties reaching 90cm tall and beyond may need additional support.
Steps
Method 1 of 3: Preparation
Step 1. Choose a variety to grow in pots
Since it does not overgrow, the dwarf dahlia lends itself best to living in plant containers, although you can grow almost any kind of dahlia if you have a large enough pot.
Step 2. Choose a large vase
To begin with, a good container should be about 12 inches deep and equally long in diameter. However, larger varieties may need even larger containers, especially if the flowers are over 90cm in height.
Step 3. Choose a heavy vase
If it is light, it may not be strong enough to hold the weight of the dahlia.
Step 4. Drill additional drain holes
This step is probably not necessary if the container already has several large holes, from which excess water can drain quickly. If the pot has small holes or only one central hole, you may need to drill a few more to improve drainage.
Step 5. Clean the jar
If it's dirty, it risks spreading disease and hiding insect eggs at the bottom. Remove these threats by cleaning the container before planting the flower. Just a little soap and water.
Step 6. Choose a coarse soil
Standard potting soil is too porous and may expel growing shoots. A good mix includes potting soil and garden soil or potting soil and compost. Alternatively, an earth-free composition made of fine bark, peat and various minerals may work as well.
Method 2 of 3: Planting
Step 1. Plant the tubers before the roots start to overgrow
When they are long, the roots can get tangled and if you try to untangle them, you risk damaging them. If the tubers take time to form new roots, the plant will grow late and may produce small flowers for the season.
Step 2. Start on a day in April or May
- If you plant the dahlia in a pot that you will place outdoors, wait from mid-April to all of May.
- If you plan to grow it indoors at first, you can plant the tubers in early April.
Step 3. Place one or two biodegradable coffee filters over the holes in the bottom of the jar
They will eliminate moisture, preventing the roots from soaking up water. If you place gravel in the bottom of the bowl, you will have the same result, but bear in mind that the roots of the dahlia need enough space to grow, so the coffee filter method takes up much less space than gravel. By placing the filters on the holes, you will also prevent insects from entering.
Step 4. Fill almost the entire container with the soil mixture
Make sure it isn't too compact, but allow the soil to breathe.
If you are using a pot that is deeper than 12 inches, you will probably need to use more soil. That said, dahlias need to be planted about 15cm deep, and therefore, you should leave 2.5cm of empty space between the top of the soil and the edge of the pot once filled
Step 5. Moisten the soil
Keep it moist, but don't get waterlogged.
Step 6. Mix a handful of bone meal and fertilizer into the soil
Dahlias need a lot of nutrients to grow vigorously. Fertilizers from fish or algae are also capable of providing additional micro-nutrients.
- Additionally, you can purchase the polymers at a nursery or florist instead of using bone meal and fertilizer. Follow the instructions on the package.
- If by mixing polymers, fertilizer or bone meal in the soil, you move the coffee filters from the bottom of the pot, remove the soil and combine the elements like this: re-add the soil on top of the repositioned filters, once you have mixed it.
Step 7. Plant the tuber in the soil
Place it horizontally and leave at least 6mm of space between the main end of the tuber and the wall of the pot. If it has already developed an eye (growth point), place it in the center of the pot and leave it facing up. The sprout will pop out of the eye.
Step 8. Cover the tuber with previously moistened soil
Don't bury it yet, but cover it with a little soil to control its growth.
Step 9. In case the tuber has any eyes, make sure it protrudes from the ground
Lightly water the growth with warm water, just enough to moisten it.
Step 10. Add more soil as the stem grows
Do this carefully to avoid damaging the stem, which will be quite brittle at this stage. Never cover the leaves. Continue adding soil, leaving 2.5cm of empty space between the soil surface and the edge of the pot.
Step 11. Insert a rod into the vase and tie it to the stem
The giant dahlia needs more support to keep the stem from breaking. Therefore, use a 1.2m rod with most varieties. If it's metal, that's better because it's more solid. The lower part must reach the bottom of the container, while the whole rod should remain firm in its position, stuck in the ground or secured by wires tied to the holes made in the walls of the vase.
Method 3 of 3: Treating the Dahlia
Step 1. Water the tubers abundantly once the stem has grown over the edge of the pot
Get a good watering two or three times a week. Dahlias that grow in hot, dry climates may need water on a daily basis. However, be careful not to soak the soil.
Step 2. Place the pot in full sun
Dahlias grow best if they are given six to eight hours of direct sunlight.
Step 3. Provide additional lighting using fluorescent lighting if you are growing the plant indoors
Dahlias that grow indoors often don't get adequate sunlight, so you may need to add a lamp to stimulate them to grow properly. When the tubers have recently been planted, place it about 6 inches above the top edge of the pot and increase the lighting according to the growth of the plants.
Step 4. Fertilize the flowers once every two weeks, from June to September
Use a low-nitrogen fertilizer and avoid overfeeding the plant.
Step 5. Remove the leaves from the base towards the end of the season, usually around mid-July
This will improve air circulation and reduce the risk of mold forming.
Step 6. Spray the dahlia with some fungicide or insecticide as needed
These flowers are subject to attack by molds, earwigs, snails, mites, aphids and cucumber beetles.
Advice
- When cutting the flowers, run a little hot water only on the cut parts. This is a way to keep them moist and prolong their life.
- If you live in a cold climate, put the tubers indoors. Unearth them two weeks after the first frost has destroyed the top. Wash off dirt with water and air dry them for a day. Wrap them in paper and store them in a cool, dry place.
