Alder trees are found growing in many parts of the world, and they are a popular ornamental tree. It is possible to start your own saplings from seeds or cuttings. In this article, we’ll look specifically at how to grow alder trees from seed and answer some related questions you may have.
What You'll Learn Today
Are Alder Trees Easy to Grow?
Alders are quick-growing trees that are fairly easy to grow from seed as long as certain conditions are met.
Stratifying the seeds before planting helps mimic their natural environment and can improve the germination rate of your seeds. But more on that below.
When growing alder trees from seed, it’s important to keep your soil moist at all times; don’t allow it to dry out. Alder trees typically grow in damp soil near riverbanks, so your seedlings and saplings will need plenty of water.
Where Do Alder Trees Grow Best?
Alder trees grow in many parts of the Northern Hemisphere but may be found as far south as South America. They can grow in many different environments.
That said, alders grow best in relatively cool, damp climates. For example, they are found throughout the Pacific Northwest in woodlands and on riverbanks.
Depending on the variety, many alders also grow well at higher elevations. They have been found growing at up to 8,200 feet, though other varieties can also grow at sea level.
If you’re planning to grow your own alder tree from seed, it’s a good idea to choose a variety that grows natively in your area. Collect your seeds from a local alder tree for the best chance of success.
How to Grow an Alder Tree from Seed
To start your own alder saplings from seeds, follow the steps below:
Step 1: Gather the Seeds
Alder trees produce small cone-like structures that hold the seeds. These cones are green throughout the summer but, during the fall, begin to turn brown and open up to release the seeds.
The cones are ready to harvest once they have begun browning and opening, usually in mid-autumn. Don’t wait too long; cones that are fully brown and opened all the way may not have any seeds left in them.
Using a pair of scissors or pruning shears, snip a cluster of cones and place it immediately in a cotton or paper bag, as discussed in this video:
You can then leave the cones in the bag to collect the seeds as they drop from the cones, or you can transfer the cones to another container, like a bread basket or cookie tin.
Place the container in a warm place. Over time, the cones will dry out and open up more, releasing their seeds in the process.
Once the seeds have all been released and allowed to dry for at least several days, transfer the seeds to a plastic bag or other airtight container. Place them in a cool, dry place for storage.
Step 2: Stratify the Seeds
In early spring, place your seeds in a cloth bag and soak them in cool, clean water for a day or two. You can leave them in the water for up to 48 hours.
Place the bag in a spin dryer or some old mesh pantyhose. Dry the seeds by running the spin dryer or swirling them around in the pantyhose for about a minute.
Place the seeds in plastic bags with damp sand and tie each bag loosely. Place the bags in the coolest part of your fridge and leave them for four weeks.
Check your seeds periodically to make sure none of them are going bad. If you notice any signs of mold or rot, remove the bad seeds immediately to keep them from spoiling the other seeds.
As noted above, stratifying seeds this way improves their germination rate, giving you a better chance of sprouting strong, healthy seedlings.
Step 3: Plant the Seeds in Pots
Once your seeds have been stratified, it’s time to plant them in moist potting soil. Place about five seeds in each planter.
Allow each seed to rest on top of the soil, then sprinkle it with a thin layer of soil or sand. Be careful not to bury the seeds too deeply, as this could prevent them from sprouting.
Press the surface of the soil or sand gently to firm the seeds in place. Place the pots under a grow light or in a sunny window, and keep them well watered so the soil doesn’t dry out.
Your seeds should germinate within a couple of weeks. If multiple seeds sprout in each pot, thin them to keep only the strongest and most healthy-looking seedling.
Step 4: Repot if Necessary
Once they have sprouted, alder seedlings will grow quickly if they are kept well watered and in full sunshine.
As they grow into saplings, you can plant them outside or transplant them into larger pots. Transplanting into pots allows them to grow larger and become stronger before you move them to their permanent spots in the ground.
To transplant saplings, prepare your planters with moist potting soil, creating a hole in the soil large enough for your sapling’s root ball. Remove the sapling from its current planter and plant it to the same depth it was already growing.
During the warm summer months, place your potted saplings in a sunny spot outside so they can become acclimated to an outdoor environment.
Step 5: Plant Outside
When you’re ready to plant your young alder tree outside, clear away any weeds or grass growing in the spot of choice.
Dig a square-shaped hole large and deep enough for the root ball to sit comfortably. Carefully remove the tree from its pot and place it in the hole.
Fill in the hole with dirt, packing it firmly but gently around the root ball. Make sure the tree is planted to the same depth it was in the pot; do not bury it too deeply.
Water the tree well.
How to Maintain a Healthy Alder Tree
Let’s take a look at some tips to help you keep your tree healthy and growing well.
Fertilize Potted Saplings
If you opt to keep your saplings in pots for several months to a year after they sprout, you’ll want to fertilize them regularly.
Alders do well in poor soil conditions because they can create their own nitrogen, but once they have used up all the food in their potting soil, they may need a boost.
A nitrogen-rich fertilizer applied on a regular basis according to package instructions should be sufficient.
Water Often
Alders need plenty of water. This is true at every stage of development, from the time you plant seeds until the tree is near the end of its life.
Alders do best when growing in damp soil, so you should never let the soil dry out when sprouting seeds and keeping young saplings in pots.
Once you have transplanted your trees into the ground, continue watering them regularly, especially during periods of dry weather. Watering may not be necessary during wet seasons or if you live in an area that receives a lot of rain.
Make Sure They Get Plenty of Sunlight
In addition to plenty of water, alders also need plenty of sunlight. They should receive at least six to eight hours of full sunshine every day.
When your seedlings are young, keep them in a sunny, south-facing window, or place them outside on a sunny porch or deck.
When you are ready to plant them in the ground, make sure to choose a spot that receives uninhibited sunlight for most of the day.
Conclusion
Growing alder trees from seed can be a fun and rewarding adventure. Follow the steps outlined above to get your own alder saplings growing.
