Ageratum Seed Germination – Growing Ageratum From Seed


By: Susan Albert, Freelance Garden Writer

Ageratum (Ageratum houstonianum), a popular annual and one of the few true blue flowers, is easy to grow from seed.

Growing Ageratum from Seed

Commonly called floss flower, ageratum has fuzzy, button-like blooms that attract pollinators to the yard. The quarter inch fringed flowers grow in dense, one-inch (2.5 cm.) clusters from midsummer to fall. Green leaves are oval to heart shaped. Besides blue, ageratum cultivars include shades of white, pink, and bicolor in dwarf plants as well as tall plants ideal for cutting.

Choose a sunny site to grow ageratum or if summers are really hot, part shade is preferred. Plant ageratum in borders (front or back depending on cultivar height), containers, xeriscape gardens, cutting gardens, and use for dried flowers. Pair with yellow marigolds for a bold look or go soft with pink begonias.

While these plants are commonly purchased as transplants in most places, growing ageratum from seed is just as easy and fun to do.

How to Plant Ageratum Seeds

Sow seeds in moist potting mix six to eight weeks before the last frost date. Do not cover seeds, as light aids ageratum seed germination.

Water from the bottom or use a mister to prevent splashing soil that would cover seeds. Keep soil moist but not wet. Seedlings should emerge in seven to ten days at 75 to 80 degrees F. (24-27 C.). Keep plants warm with a warming mat or place in a bright location out of direct sun.

Transfer to cell packs or pots when tall enough to handle. Slowly acclimate (harden off) plants by moving them outside to a shady area then back inside. Leave them outside for increasing lengths of time. Then, after all danger of frost has passed, plant outside in fertile, well-drained soil in a sunny or part-shaded area. Water regularly but ageratum will tolerate dry spells.

Tips for Starting Ageratum Seeds

Buy seeds from a reputable source. The popular ‘Hawaii’ series blooms in blue, white, or pink. ‘Red Top’ grows 2 feet tall (0.6 m.) with magenta flower heads. ‘Blue Danube’ is a reliable, compact purple blue hybrid. Bicolors include ‘Southern Cross,’ and ‘Pinky Improved.’

Keep seeds in a cool place such as the refrigerator till ready to plant. Prior to planting outside, mix organic fertilizer into garden bed or container. Direct seeding outside is not recommended. Ageratum will not tolerate frost so cover on cold nights to extend season.

Keep ageratum tidy and increase flowering by pinching off spent blooms. Ageratum freely self-seeds so it is not normally necessary to replant each year.
Ageratum typically is not bothered by pests and diseases but watch for spider mites, aphids, and whiteflies. Diseases such as powdery mildew, root rot, parasitic nematodes, and oedema have been reported.

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How to Grow Ageratum houstonianum Plants in your Garden

Ageratum houstonianum, also called Blueweed, Bluemink, Floss flower or Pussyfoot, is a member of the Asteraceae family and is native to Mexico, where it is also known as the Mexican paintbrush.

Gardeners adore it because of the beauty of its blue flowers and how long they last. They appear in June and last until frost.

Ageratum houstonianum - flossflower photograph by Carl Lewis.

Ageratum is also prized because of is great range. It thrives in hardiness zone 2 all the way down to hardiness zone 11.

It is a marvelous plant to grow in beds, in rock gardens, or at the edges of herbaceous borders and walkways. It is also a good container plant.


How to grow seedlings

Shoots may appear in two weeks, then remove the film and, if necessary, very carefully watered. As soon as the plants have 2 rounded leaves, they are planted in boxes or cassettes for seedlings. Further care is reduced to careful watering, as ageratum does not like dampness.

Before planting in the soil, it is desirable to harden seedlings – to make them air. I have all my seedlings in April, put on the glazed loggia, with lots of light and temperature favorable – days are warm and nights are cool.


Everest Blue Cutting Ageratum

Everest Blue has large clusters of little bright lavender-blue flowers that hold their color from summer’s first fuzzy bloom through fall’s first frost. It can be pinched for wider plant spread and more uniform stem length.

One packet of about 100 seeds

  • Cutting Ageratum Sowing Instructions
    Planting Depth
    :0”
    Seed Spacing:8”-10”
    Plant Spacing:12”-18”
    Days to Germination: 7-14 days
    Germination Temperature:65°-75°F

Ageratum houstonianum, the Floss Flower. Cutting Ageratum should be started indoors 6 to 8 weeks before transplanting out after all danger of frost has passed. Sow seeds on top of soil mix, leaving the seeds uncovered but pressed firmly onto the soil surface, as light aids germination. Provide even moisture, strong light and luke warm water. Prepare a garden bed in full to partial sunlight with rich, well-draining soil. Harden off the seedlings by gradually acclimating them outside over 1 to 2 weeks. Carefully transplant them 8" to 12" apart. To encourage branching, pinch back the young plants at 8" tall. Keep them well-watered. Water at soil level only. For the best vase life, cut them once the fuzzy central flower cluster has opened and the side buds are showing pink color. Summer flowering.

  • Cutting Ageratum Sowing Instructions
    Planting Depth
    :0”
    Seed Spacing:8”-10”
    Plant Spacing:12”-18”
    Days to Germination: 7-14 days
    Germination Temperature:65°-75°F

Ageratum houstonianum, the Floss Flower. Cutting Ageratum should be started indoors 6 to 8 weeks before transplanting out after all danger of frost has passed. Sow seeds on top of soil mix, leaving the seeds uncovered but pressed firmly onto the soil surface, as light aids germination. Provide even moisture, strong light and luke warm water. Prepare a garden bed in full to partial sunlight with rich, well-draining soil. Harden off the seedlings by gradually acclimating them outside over 1 to 2 weeks. Carefully transplant them 8" to 12" apart. To encourage branching, pinch back the young plants at 8" tall. Keep them well-watered. Water at soil level only. For the best vase life, cut them once the fuzzy central flower cluster has opened and the side buds are showing pink color. Summer flowering.


Stage 2 Hypocotyls (Stem and cotyledon emergence)

Time of emergence 10-14 days.

  • First start reducing moisture levels once the radical emergence occurs. At this point allow the soil to dry out slightly before watering again, this will aids in the germination and rooting process.
  • The temperatures at this point should be 68 to 75ºF (20 to 24ºC).
  • The soil pH at 5.5 to 6.2 with soluble salts ( EC of .50-.075).
  • Keep light levels high during this time period and keep temperatures in control.

Stage 3 Cotyledon (Growth and development of true leaves)

Timing of this growth 14-21 days.

  • Maintain the soil pH at 5.5 to 6.2 with the soluble salts ( EC .75-1.00)
  • You can increase the feed at this point to 50 ppm N- using a complete balanced fertilizer. Increase the nitrogen concentration to 100ppm after a week and continue with this program until you are ready to transplant.
  • It is important to alternate your fertilizing feed schedule with every 2 -3 clear water irrigations. Do not allow plants to wilt, as this will cause drought stress and burn the leaves
  • The temperature for days should be between 65-72ºF (18-22ºC).
  • Keep light levels high during this time period and keep temperatures in control. This will help in the production of producing a well branched plant.
  • Ageratum are very sensitive to high salts so do not overfeed.

Stage 4 Getting ready for transplant/growing on period

  • Do allow the soil to dry thoroughly however do not to allow the plants to wilt.
  • Keep your temperatures maintained at for Days at 70-80ºF (21-27ºC) and for nights at 58-62ºF (14-17ºC)
  • Maintain the soil pH at 5.8 to 6.2 with the soluble salts ( EC between 1.5-2.50)
  • You can continue to fertilize at a feed level at 150 to 200ppm N with a complete balanced fertilizer as needed, however the pH and the EC must be maintained as stated.
  • Ageratum do not require a high feed level they prefer a low to moderate level. By having excessive amounts of feed your result will be lush and vegetative stretched seedlings. This is what you do NOT want.
  • A good option would be to have a low feed program without having any salt accumulation for the plant.

For the growing on to finish stage:

  • Night temperature: 58-62ºF (14-17ºC)
  • Day temperature: 70-80ºF (21-27ºC)

USDA Hardiness Zone -First Frost Date- Last Frost Date

  • Zone 1 -July 15th -June 15th
  • Zone 2 -August 15th- May 15th
  • Zone 3 -September 15th May 15th
  • Zone 4 -September 15th May 15th
  • Zone 5 -October 15th April 15th
  • Zone 6 -October 15th April 15th
  • Zone 7 -October 15th April 15th
  • Zone 8 -November 15th March 15th
  • Zone 9 -December 15th February 15th
  • Zone 10 -December 15th January 31st (sometimes earlier)
  • Zone 11 _No frost. No frost.

Terms and their meaning:

  • EC=Electrical Conductivity

Plant injury resulting from excessive soluble salts may first occur as a mild chlorosis of the foliage, later progressing to a necrosis of leaf tips and margins. This type of injury is largely attributed to the mobility of soluble salts within the plant. As these salts are rapidly translocated throughout the plant, they accumulate at the leaf tips and margins. Once the salts reach a toxic level they cause the characteristic "burn" associated with excessive salts. For an accurate reading get an EC meter. Soluble salts in irrigation water are measured in terms of electrical conductivity (EC). The higher the salt content the greater the EC. In general EC values exceeding 2.0 are considered toxic to plant growth. Monitor your water quality frequently in order to avoid potential problems from soluble salts.

Light intensity is a primary factor in the photosynthesis of all plants. Full unobstructed sunlight has an intensity of about 10,000 fc. Where as an overcast day will produce an intensity of around 1,000 fc. A window sill or light around a window or patio glass door can range from 100 to 5,000 depending of course what direction the light source is facing, or the time of year and your latitude.

  • PPM=Parts Per Million

This unit of measure is relatively unique to the greenhouse industry and often there is some confusion on how ppm is calculated. I. To calculate the ppm contained in 1 ounce of material first solve for B: A x 75 = B A = the % active ingredient (AI) in the fertilizer B = ppm contained in 1 ounce of the material in 100 gallons of water Example: Calcium nitrate contains 15% N (0.15 x 75 = 11.25). If 1 ounce of calcium nitrate is dissolved in 100 gallons of water the solution will contain a II. To calculate the number of ounces of material required to make up a desired ppm concentration solve for C: C = Desired ppm conc. / B B = ppm contained in 1 ounce of the material in 100 gallons of water (from above). C = number of ounces of material to add to 100 gallons of water to achieve the desired concentration. Example: To make up a 250 ppm solution of calcium nitrate first multiply the AI x 75 (.15 x 75 = 11.25). Next divide the desired concentration by 11.25 (250/11.25 = 22). To make up a 250 ppm solution of calcium nitrate you would add 22 ounces to 100 gallons of water. Approximately 11.25 ppm N.


Watch the video: Ageratum, lobelia, cherry tomatoes and swiss chard growing on my deck this summer


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