How to grow Dahlias in the Bay Area
by Ted Marr, Rose Marr and Deborah Dietz
There are many approaches to growing healthy and happy Dahlias. These “Simple Five Steps” are intended to be one of the approaches. These suggestions are generally consider more reliable and safer methods. They have been time tested by many experienced Dahlia growers.
Step 1: GERMINATION (March to May)
Purchase dahlia cuttings (preferred) or tubers at the DSC Annual Sale (first Saturday of every April) at the Hall of Flowers, Golden Gate Park. Transfer the cuttings to a larger temporary container (4 inch pots or a milk carton cut open sideway with drainage). Let them grow indoors in a well lighted room until they are about 12 to 18 inches tall. Be sure to keep the soil moist, but do not water at all. For tubers, place each tuber in the same kind of temporary containers with the crown (buds) of the tuber sticking slightly above the soil. When the shoots appear, allow only one to grow per tuber, cut off the excess ones. Spritz the young shoots at least once every other day to keep them moist.
Step 2: PLANTING (April to June)
When your plants are 8 inches tall, put them outside during the day. After a few days, you can leave them outside overnight. When the plants are about 18 inches tall, plant them in the ground. Dahlias like well drained soil. While your plants are germinating, start to augment your soil with organic material, such as chicken manure and compost. Or, add two or three pounds of 5-10-5 or 10-10-10 fertilizer to 100 square feet (1/4 pound per 10 square feet). You should start your fertilization process about 6 weeks prior to planting if using chicken manure which takes time to break down. Avoid getting the fertilizer on the plants so rake the fertilizer into the soil and then water. The location should have sunshine for at least 6 hours each day. Place the plants 30 or more inches apart. In hot weather areas, choose a spot with morning sun only. As soon as the plants are in the ground, on the same day, protect your young plants from snails and slugs. Sprinkle snail bait liberally. Label and stake plants other than the dwarf cultivar. Insert a four to six foot stake into the ground at the edge of the hole before the tuberous roots are planted. Dahlias are large plants and require support. The tall cultivars cannot support themselves and plant breakage will occur without support.
Step 3: MATURING A BUSHY PLANT (May to July)
Your plants will grow tall rapidly. To encourage the plants to grow more branches to bear more flowers, take these six actions:
1. Cut off the tip of the center stem after the plant has three sets of leaves.
2. Fertilize the plants with a well balanced fertilizer (10-10-10) about once every three weeks.
3. Diligently monitor and eradicate undesirable pests.
4. Water at the soil level (do not use overhead spray) once every three to four days. Water deeply each time. Do not leave any stagnant water,
5. As the plant matures, remove the bottom two rows of leaves.
6. As the plant gets bushy, tie the main stem to the stake
Step 4: BLOOMS, MORE BLOOMS (June to November)
To encourage your Dahlias to produce bigger and more blooms take the following five actions:
1. Use a fertilizer that has a higher phosphorous content such as, 10-30-20.
2. For each flower bud that appears, make sure you disbud any neighboring buds.
3. After a Dahlia bloom opens, cut it for your indoor display. This will encourage more blooms. Even if you don’t cut it, you should dead-head it by removing before pollen appears so new blooms would be encouraged.
4. Always cut the bloom at a point that is one node below the bloom. This will encourage more laterals to produce more blooms.
5. Clean out the under growth of leaves, allowing for at least 12 inches of space above the ground for good air circulation.Three flower buds becomes one central bud after removal of the two side ones.
Step 5: PROPAGATE A NEW GENERATION (November to January)
Your Dahlia plants will bloom from June to the end of October, or even November. After October, let the plant wither naturally with no more watering. Keep them in the ground until December when the heads turn brown. In December or January lop the stems to about six inches above the base stem, leaving at least three nods, so water will not drain down to the tubers and rot them. Make sure to retie the label at this lowest point. In January, dig out the tuber carefully and keep them in a cool dry place for next year’s planting. You may divide the root tubers for more plants next year.
Photos courtesy of various DSC members including: Deborah, Ted, Franck, DJ and many others.
We like to thank many DSC Dahlia Experts for sharing their years of experience at our regular meetings. Without them, this essay could not have been written.
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