How to Grow Arborvitae From Seed
If you’re looking for privacy, but don’t want obstructed views of a wooden fence, consider planting arborvitae (Thuja spp.) – with their naturally upright, conical shape that requires little care or pruning – around your property. You can purchase seedlings or well-grown specimens from nurseries, if you have the budget for it, but it's also possible to grow your own from arborvitae seed pods (they aren't quite a traditional cone). It will take longer to get the effect you want, but it's decidedly budget-friendlier.
Securing Your Arborvitae Seed Pods
Suppose for example that you've decided you like the look of 'Green Giant,' a popular arborvitae cultivar. You do a quick search, perhaps "green giant arborvitae for sale," and don't like the prices you see. Now you have a choice. You can do a second search for "green giant arborvitae seeds," and hope to find some locally. Working from the opposite direction, you could contact local nurseries, arborists and extension services to see which arborvitae species are available as seed in your area.
A third option, the lowest-cost of all, is the DIY approach. You'd simply identify healthy arborvitae trees that are already flourishing in your area, and harvest seeds from those. This is chancier – a 2020 study by Illinois' Prairie Research Institute found 1 percent germination from some of its wild-harvested seeds, while commercially available seeds germinated at a rate of 37 percent – but if you succeed you'll grow trees that are well adapted to your area.
Selecting and Germinating Arborvitae Seed
To have the highest likelihood of success, the American Conifer Society suggests harvesting conifers' seed-bearing structures as they're just reaching maturity. In the case of arborvitae, that's when yellow-green hue of the small "conelets" begins darkening to brown, but before they open up and scatter their seeds to the wind.
1. Locate Suitable Trees
Scour the woods (or neighbors' yards, if they're agreeable) in your area for healthy, vigorous arborvitae that have the look you want. Collect the cones as they begin to mature. Cones typically contain about 8 seeds, according to the University of Connecticut, and your best-case scenario for germination is about 1 in 3 seeds, so you'll need to allow at least one cone for every two arborvitae you eventually want in your landscape.
2. Dry the Cones
Collect cones from your chosen tree or trees into a brown paper bag. Set the bag in a sunny area for two to three days, which allows the arborvitae cones to dry and makes harvesting the actual seeds less of a chore. Once the allotted time has passed, remove the cones from the bag and shake them over a paper towel.
3. Transfer the Seeds to Peat
Cover the bottom of a small plastic container with a 1-inch layer of damp peat moss. Spread at least 50 to 100 seeds over the peat moss, as many of the seeds could be empty and won’t germinate. Press the seeds gently into the moss and cover the plastic container with a tight-fitting lid.
4. Stratify the Seeds
Refrigerate the seeds for at least two to three months. Refrigerating is essential to germinating arborvitae: They're "hard-coded" genetically to remain dormant until spring, and refrigerating them – a process called stratification – primes the seeds to germinate when they're planted.
5. Germinate the Seeds
Germinate one to two arborvitae seeds per single peat pot filled with well-drained potting soil, ideally at a neutral to slightly alkaline pH of 6 to 8. Place the pots in an area that receives full sun, or under a grow light.
6. Plant Out the Seedlings
Plant the arborvitae in an area that receives full sun after the seedlings have grown to 2 to 3 inches in height, which generally occurs two to three weeks after planting. Dig a hole for each seedling that is large enough to accommodate the root ball. Fill the hole one-third of the way with a well-draining potting soil. Backfill the hole with the original soil and tamp it tightly around the seedlings to provide support.
7. Water the Seedlings
Provide a healthy drink of water to the seedlings, or enough to saturate the ground, but not create a muddy mess. "Watering in" your seedlings will help them cope with transplant shock, but don't overdo it. The young seedlings are vulnerable to root rot if you keep the soil too wet.
Things You Will Need
Brown paper bag
Small plastic container
Plant each arborvitae seedling at least 2 feet apart, to allow enough space for the growing trees.
Water your arborvitae at least every three days, especially if the summer is unusually hot, during the first year. Don’t wait until the tree begins to brown between waterings, as you may already be too late.
It's prudent to harvest extra cones, and plant extra seeds, to allow for poorer-than-expected germination, seedlings that don't survive to transplant, and transplants lost to random critters' grazing while they're still young and vulnerable.