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Botanical Information

Family: Daisy Height: 1 to 7 feet A/B/P, Hardiness: tender annual Spacing: Small, 5 per square; medium, 3 per square; large, 1 per square.

Growing Season Spring: no Summer: yes Fall: yes Winter: no

Seed to Harvest/Flower: 10 to

12 weeks Seeds Storage: 2 to 3 years Weeks to Maturity: 5 to 6 weeks Indoor Seed Starting: 6 to 8 weeks before last frost date Indoor Tuber Starting: 4 weeks before last frost date Outdoor Seed Starting: after last frost date (seedlings may not bloom until late summer) Earliest Outdoor Planting: after last frost date Additional Plantings: not needed Last Planting: not needed


Native to Mexico, dahlias literally come in all shapes and sizes. They are grouped into nine sizes based on the diameter of the flower, and 18 classifications of form, from the daisy-like decorative form, to pompom, cactus, and the fully double stellar form. Flowers come in every color except blue and green, and multicolors abound. Even the leaves come in colors, from light green to deepest green to burgundy. Plus, they guard neighboring plants against nematodes. There is indeed a dahlia for everyone.

Border or dwarf dahlias grow 12 to 24 inches high and rarely need staking. Garden dahlias are in the 2 to 4 foot range. The giant forms have been known to grow to 10 feet, and make a wonderful annual hedge. Be careful of the word "miniature" when purchasing dahlias— it usually refers to the flower size, not the plant size. Since most of the showy dahlias available are hybrids, a seed-grown dahlia will be a pleasant surprise when it flowers. If you love a particular dahlia, purchase a tuber and store it over the winter


Location: Plant dahlias in full sun to partial shade for best results. Seeds Indoors: Seedlings emerge in 5 to 21 days Transplanting: After last frost date

Basil and Beyond


Watering: Water dahlia tubers when first setting them out, then wait until you see shoots before watering again unless the soil is unusually dry. This will prevent the tubers from rotting. Once the root system is established and shoots begin to show, give smaller dahlia plants 1 cup of water per day, 2 cups during the hottest summer months. Give larger dahlia plants 2 cups of water per day, 3 cups during the heat of summer.

Maintenance: When the plant reaches about 3 inches tall, pinch off the growing tip to encourage bushy growth. Mulch dahlias to keep the soil moist. Stake tall varieties. Deadhead to encourage reblooming.

Since dahlias are easily grown from seed, you may not want to bother digging up the tiny tubers of seed-grown plants. Simply start them from seed again next year. If you want to dig up the tubers, after the first frost has killed the foliage, carefully dig dahlia tubers and let them dry for a few hours. Cut off the stems, leaving a 2-inch stump, remove excess soil, and store in a box filled with peat moss, vermiculite, or perlite in a cool, frost-free location. Check the dahlias each month over the winter and discard any rotten tubers. Spray any tubers that start to shrivel with warm water.


How: Dahlias have hollow stems, and a sticky white substance will ooze from the cut. This is a nutrient that the cut flower needs to stay alive. To preserve the flower, sear the cut end with a match or candle. After searing, prick a hole in the stem just under the head of the flower. Remove any leaves that will fall below the waterline. Dahlias will last 5 to 7 days in a vase.

When: Cut dahlias when the flowers are fully open.


Earwigs, slugs, powdery mildew.

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  • azzeza goytiom
    How many seeds needed for dahlia in square foot?
    3 years ago
  • Sandy Christie
    How many dahlias in square foot garden?
    3 years ago
  • marley reid
    How many dahlia tubers per square foot?
    1 year ago

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