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How to Start Ash Trees From Seed

Updated November 21, 2016

Plant common ash (Fraxinus excelsior) for its height, grace and spread. In ideal conditions, ash trees can grow to heights of more than 100 feet, with spreads of 60 feet, but more often they'll be 70 to 80 feet tall, according to the University of Florida Extension. Though the emerald ash borer has decimated the ash population in the United States, it's worth trying to grow this beautiful shade tree. You can propagate it from seed, though you'll wait a long time before it grows tall.

Watch for fruits to develop on ash trees in summer. They are 1 to 3 inches long, flat and green. In fall, they turn brown and brittle, and tend to stay on the branch until well after leaves have fallen. Collect the fruits in early winter.

Rub the fruits between your hands to break them open and free the ash seeds. Separate the seeds from the chaff. Place the seeds in a paper envelope and put them in the freezer.

Leave the envelope in the freezer for the winter. This process, called dry cold stratification, mimics weather conditions outdoors and is necessary for ash seed germination.

Remove the seeds from the refrigerator in mid-April. Fill a seed tray or flat with soilless potting mix and sow the ash seeds on top. Cover with an additional 1/2 inch of potting mix and moisten thoroughly.

Set the flat in a sunny, warm room, keeping it moist for the next two weeks. Seeds will germinate and sprout if they are viable. Thin the seedlings to 6 inches apart. Transplant them into individual pots full of moist potting soil when they reach heights of 2 inches.

Tip

Transplant ash seedlings to their permanent location one year after sprouting. They will grow faster if you plant them in full sun and keep weeds and grass away from the root zone.

Warning

Ash trees are vulnerable to the emerald ash borer, carpenterworm and lilac borer. Prune away affected branches and destroy the prunings. If borers infest the trunk of an ash tree, it will be very difficult to preserve it.

Things You'll Need

  • Paper envelope
  • Seed tray
  • Soilless potting mix
  • Small flowerpots
  • Potting soil
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