Are you looking to start your own forest or beautify your backyard with lush greenery? Well, look no further than germinating tree seeds. Not only is it a fun project, but it also allows you to witness the miracle of life firsthand. While some tree species require specific techniques, I’ll share some valuable tips that can be applied to various trees, including those found in Texas.
Understanding Tree Seed Dormancy
Before we dive into the germination process, it’s essential to understand tree seed dormancy. Most tree species have seeds that won’t germinate immediately upon planting due to their dormant state. Dormancy is often caused by a thick and hard seed coat. Breaking this protective layer is crucial for successful germination. This process, known as scarification, can be done through various methods.
Methods of Scarification
Mechanical scarification involves using a metal file or coarse sandpaper to break the seed coat. Another effective method is treating the seeds with boiling water. Nature has its way of scarifying seeds as well. Seed coats can be broken by microbial action, passing through the digestive tract of animals, exposure to alternating freezing and thawing, or even fire.
The Importance of Stratification
Many tree species require exposure to cool temperatures and moist conditions for several weeks or months before they will germinate. In regions like Iowa, where winters provide the perfect conditions to break dormancy, gardeners can achieve the same results through a process called stratification. Stratification involves placing the tree seeds in a moist mixture of sand and peat moss. Suitable containers include coffee cans, plastic jars, and even cottage cheese containers. Don’t forget to create air holes in the container lids. Alternatively, you can use plastic bags for stratification. Keep the seeds in the refrigerator during this process.
Tree-Specific Germination Techniques
Now let’s explore some techniques for specific tree species:
Maples
When the fruit of maples, known as samaras, turn yellow or brown and fall to the ground, they are mature and ready for collection. No need to remove the seed from the fruit. Red maples and silver maples mature in late spring or early summer and can be planted immediately. Other maple species can be sown directly outdoors in the fall or planted in the spring after stratification. Sugar maples require stratification for 40 to 90 days at 33 to 41°F, while Norway maples need 90 to 120 days at 41°F. Plant the seeds 1/4 to 1 inch deep.
Horsechestnuts and Buckeyes
Gather the fallen fruit (capsules) of horsechestnuts and buckeyes and let them dry at room temperature until the capsules split open. Collect the shiny, dark brown seeds and plant them in the fall or after stratification. Ohio buckeyes and common horsechestnuts should be stratified for 120 days at 41°F. Plant the seeds 1 to 2 inches deep.
Hickories
Collect the fallen hickory fruits and remove the husks. Sow the seeds in the fall or after stratification. Before stratifying, soak the nuts in room temperature water for 2 to 4 days, changing the water daily. Stratify shagbark and bitternut hickories at 33 to 40°F for 90 to 120 days. Pecans require only 30 to 90 days of cold stratification. Plant the seeds 3/4 to 1 1/2 inches deep.
Redbud
Collect the ripe redbud pods in the fall when they turn brown. Air dry the pods and remove the seeds. Redbud seeds have hard, impermeable seed coats and dormant embryos, requiring both scarification and cold stratification. Scarify the seeds by soaking them in concentrated sulfuric acid for 30 minutes or boiling water for one minute. After scarification, stratify the seeds at 35 to 41°F for 5 to 8 weeks. Plant the seeds promptly at a depth of 1/4 inch.
Kentucky Coffeetree
Collect the fallen coffeetree pods in the fall. Remove the seeds and break the hard, thick seed coats by filing through them with a hand file. Plant the seeds 1 inch deep in the spring.
Black Walnuts
Collect the fallen walnuts and remove the husks. Place the nuts in water, and those that sink to the bottom are viable. Discard the floating nuts. Sow walnuts in the fall or stratify them at 34 to 41°F for 90 to 120 days before planting in the spring. Plant the nuts 1 to 2 inches deep.
Apples and Crabapples
While apples and crabapples are usually propagated through grafting and budding, their seeds can also be germinated. Collect the ripe fruit and remove the seeds. Sow the seeds in the fall or stratify them at 37 to 41°F for 60 to 120 days before planting in the spring. Plant the seeds 1/2 to 1 inch deep.
Cherry, Peach, and Plum
Harvest fully mature cherry, peach, and plum fruit and remove the seeds. Sow the seeds in the fall or stratify them at 33 to 41°F. Sour cherries require 90 to 150 days of stratification, peaches need 98 to 105 days, and European plums require 90 days. Plant plum and peach seeds 2 inches deep and sour cherry seeds at a depth of 1/2 inch. Please note that most cultivated cherries, plums, and peaches will not reproduce true from seed.
Oaks
Collect ripe acorns as soon as they fall to the ground. Separate sound, viable acorns from damaged or unfilled ones by placing them in water. Sound acorns will sink, while the floating ones should be discarded. White oak and swamp white oak acorns should be planted in the fall, as they germinate immediately. Bur oak, pin oak, and red oak acorns can be planted in the fall or sown after stratification in the spring. Stratify the acorns at 32 to 41°F. Bur oak requires 30 to 60 days of stratification, while red and pin oaks need 30 to 45 days.
References for In-Depth Information
If you’re craving more knowledge and want to delve deeper into the art of propagating trees and shrubs, I recommend checking out these excellent references: “The Reference Manual of Woody Plant Propagation” by Michael Dirr and Charles Heuser Jr., “Plant Propagation: Principles and Practices” by Hudson Hartmann, Dale Kester, Fred Davies Jr., and Robert Geneve, and “Seeds of Woody Plants in North America” by James Young and Cheryl Young.
Now that you’ve gained insights into the germination process, it’s time to grab your seeds and embark on your journey of growing your very own trees. Enjoy this rewarding experience, and may your seedlings flourish into magnificent trees that provide beauty and shade for years to come.
Note: This article was originally published in the August 11, 2000 issue of “Horticulture & Home Pest News” by Richard Jauron, Department of Horticulture, Iowa State University. Some species mentioned may be more typical of the eastern United States, but the principles and techniques discussed apply to various trees.
