Tree · Pinaceae
Eastern Hemlock
Tsuga canadensis
Settle it into cool, moist shade and the eastern hemlock will reward you with a soft, feathery evergreen that lasts for generations.
Partial shade
Every 3–7 days
USDA 3–7
40–70 ft · 12.2–21.3 m
Overview
Eastern hemlock is a slow-growing evergreen conifer from the cool forests of eastern North America, where old trees stand for centuries, so you are planting something built to last. Its short, flat needles and small brown cones come together in a soft, feathery, pyramidal shape that feels gentler than any stiff pine or spruce. Given room it grows to forest height, yet it also takes shearing kindly, which is why so many gardeners enjoy it as a hedge.
More than anything, this tree just wants cool, moist shade, and that makes it surprisingly forgiving for a beginner. It is one of the most shade-tolerant conifers around, content beneath taller trees where many evergreens would thin out and sulk. The trade-off is that it does not love stress, so heat, drought, drying wind, road salt, and city air wear it down, and a sheltered north-facing or woodland corner will treat it far better than an open, sunny lawn.
There is one thing worth keeping an eye on, and knowing about it ahead of time is half the battle. The hemlock woolly adelgid, a tiny invasive insect, has harmed great stretches of wild hemlock across the eastern states, and a garden tree can catch it too. Still, planted in the right spot and checked now and then, a hemlock asks little of you and gives back a dense, year-round wall of green.
Care
The short version: give it cool partial shade, steady moisture, and rich acidic soil that never dries out, and take a yearly look over the needles for woolly adelgid. You have got this.
Light
Hemlock is content in partial to full shade and is one of the few conifers that truly thrives beneath taller trees, so a shady corner is a gift rather than a problem. It will put up with a little sun, but an open, hot site bleaches and thins the foliage, so when in doubt, lean toward a cool, sheltered spot.
Water
Keep the soil consistently moist and never let it bake dry, and your hemlock will thank you. This tree has no patience for drought, and a long dry spell can be the end of it, so water deeply in dry weather and lay down mulch to hold that moisture in for you.
Soil
Plant it in cool, moist, acidic, well-drained ground, and loam, sand, or clay all work fine. A pH of 5.0 to 6.0 suits it best of all. The one thing it really cannot forgive is soil that dries out or stays soggy and warm, so aim for that easy middle ground.
Temperature
Eastern hemlock is wonderfully cold-hardy, down to -40°F (-40°C), and copes with summer heat up to about 95°F (35°C). It is the dry, exposed heat far more than the temperature alone that troubles it, so cool air and shade matter more than whatever the thermometer reads.
Humidity
Ordinary outdoor humidity is plenty, so there is no number for you to fuss over. The tree simply favors a cool, moist setting over a hot, drying one, and a sheltered woodland edge keeps the air around it soft and easy.
Feeding
Feed it lightly in early spring with a balanced or acidifying tree fertilizer, and that is all it needs. Hemlock is a slow grower with modest appetites, so one seasonal feeding is plenty, and heavy feeding does more harm than good, so there is no need to overdo it.
Pruning
Hemlock takes shearing more kindly than most conifers, which is exactly what makes it such a friendly hedge or screen. Trim formal hedges in late spring to early summer. Left as a specimen it asks for almost no pruning and looks its loveliest in its own natural feathery form.
Repotting
This is a landscape tree more than a container plant, so repotting is rare and nothing to worry about. If you do keep a dwarf form in a pot, just move it up when roots circle the inside, growth stalls, or water runs straight through the soil, and your plant will let you know when the time comes.
Size & spacing
A mature forest tree reaches 40 to 70 feet (12 to 21 m) tall and spreads 25 to 35 feet (7.5 to 10.5 m) wide, so give a specimen plenty of breathing room. Dwarf cultivars stay much smaller and slot happily into beds and rockeries.
When to plant
Hemlock is happy through zones 3 to 7, and it is planted rather than rushed along from quick-sown seed, which takes the pressure off. Set young trees out in spring or early fall while the soil is still cool and damp, and if you would like to start from seed, just give it a long winter chill first, since germination comes slowly and rewards a little patience.
Northern hemisphere
Southern hemisphere
Typical months for a temperate climate: start earlier in warm zones, later where spring frosts linger.
- Sow: Sow stratified seed in late winter; seed needs about 100 days of moist chilling before sowing
- Plant: spring or early fall
- Harvest: Non-flowering conifer; tiny brown cones about 2 cm long mature in autumn
Hardiness
USDA hardiness zones: 3–7
Temperature: down to -40°C
Troubleshooting
Most hemlock troubles turn up in the needles, either as pests on the undersides or as browning from a spot that runs too hot and dry, and the good news is that most are fixable once you spot them. Catch the woolly adelgid early and you really can save the tree. Find what you are seeing below, then step in before the canopy thins, and you will be glad you did.
Soft white tufts on the twigs and a tree that is slowly thinning
If you find little cottony white blobs tucked at the base of the needles, take a breath, because this is something you can handle. That is the hemlock woolly adelgid, an invasive sap-feeder that has hurt wild hemlock across the eastern states and will weaken an untreated tree over a few years. A registered systemic insecticide, put down as a soil drench or injection from late September into October, stops it, and for a big, treasured tree a certified arborist can take that worry off your hands.
Fix:
- Apply a registered systemic insecticide (soil drench/injection or basal bark) per label, most effectively late September through October
- Treat high-value landscape trees preventively and re-treat on the label interval
- Consult a certified arborist for large trees needing soil injection
Yellowing needles with slim scales hiding underneath
When a branch starts to yellow, gently flip it over and look for the narrow waxy covers of elongate hemlock scale pressed against the needle undersides. You can manage it with horticultural oil or a systemic insecticide timed for when the young crawlers are out, and simply prune away any branch that is heavily crusted. Keep your tree well watered and it will brush off a light case far more easily than a stressed one would.
Fix:
- Apply horticultural oil or a registered systemic insecticide timed to crawler emergence
- Prune out and destroy heavily infested branches
Stippled, bronzing needles with faint webbing in the heat
If the needles look dull and stippled with a bronze cast and you notice a little fine webbing, the likely culprits are spider mites, and they tend to show up in hot, dry stretches. Hold a sheet of white paper under a branch and tap it to watch the tiny mites move, then rinse the foliage with a strong spray of water and reach for horticultural oil or a miticide if things have really gotten away from you. A bit more water and some afternoon shade go a long way toward keeping them gone for good.
Fix:
- Spray foliage with water to dislodge mites
- Apply horticultural oil or miticide if severe
- Improve watering and provide afternoon shade
Browned, scorched needles on a hot, open spot
Browning needles and a canopy that is thinning out on a sunny, windy, or salt-splashed site usually point to drought and scorch, not a pest, so there is no bug to chase here. Hemlock just was not built for hot, dry, exposed places. Water it deeply through dry weather, mulch to keep the roots cool, and give it some shelter from afternoon sun, drying wind, and road salt, and it will steady itself. The kindest long-term fix is to settle it into a cool, moist, shaded spot from the very start.
Fix:
- Water deeply and regularly during dry periods
- Apply mulch to keep roots cool and moist
- Provide shelter from wind, afternoon sun, and road salt
Toxicity
Here is some welcome reassurance for homes with pets and little ones: the eastern hemlock conifer is not poisonous. The ASPCA lists it as non-toxic to cats, dogs, and horses, and no part of the tree is harmful to chew or handle. Just be sure not to mix it up with poison hemlock, an unrelated weed covered in the myths below.
Safe for
People · Cats · Dogs · Horses · Rabbits · Livestock · Birds
Cats None
You can relax with a cat in the house, because the ASPCA lists this conifer as non-toxic, and a curious nibble at the needles will not hurt.
Dogs None
Your dog is fine chewing the foliage or mouthing a fallen cone, though, just like with any plant, a big greedy mouthful might bring on a passing tummy ache.
Horses Safe
Horses are perfectly safe around an eastern hemlock and can browse nearby with no worry of poisoning at all.
Rabbits Safe
Rabbits have nothing to fear here, since the needles hold no poison, so a wild or pet bunny nibbling the lower branches is just fine.
Livestock Safe
Cattle, goats, and sheep can graze right around the tree in safety, as no part of it carries a toxin.
Birds Safe
Birds are in good hands, and many species happily shelter and feed in hemlocks while the seeds give them a natural meal.
People Safe
Nothing on this tree is poisonous to people. It is the gentle, harmless conifer, not the deadly poison hemlock herb it happens to share a name with.
No special handling precautions for toxicity; foliage is harmless.
Varieties
Beyond the towering forest tree, growers have selected gentle dwarf and weeping forms that fit a small garden or rockery beautifully. These are the ones you are most likely to come across at a nursery, and any of them makes a friendly starting point.
'Pendula' (Sargent's weeping hemlock)
This is a low, mounding weeper whose branches spill all the way to the ground and end up much wider than they ever grow tall.
'Jeddeloh'
A gentle dwarf that grows slowly into a shrub with a soft, dished, nest-like center, perfect when your space is small or you are filling a foundation bed.
'Cole's Prostrate'
A ground-hugging dwarf that creeps flat over rocks and slopes instead of climbing upward, so it is easy to tuck into tight corners.
How to propagate
You can raise eastern hemlock from seed or from cuttings, and while neither is fast, both are doable with a little patience. The named garden forms are almost always grown from cuttings so they stay true to the parent.
SeedModerate
Collect seed from cones just beginning to open; sow after stratification in late winter to spring · Slow; several months to germinate and years to establish
Raising hemlock from seed is a quiet exercise in patience, and it is well within your reach. Tuck the seed away for about 100 days of moist chilling through winter before sowing it in late winter to spring, because it simply will not wake up without that cold rest. Germination takes months and the seedlings need years to settle in, but they handle deep shade better than nearly any other young conifer, so you have a forgiving little plant on your hands.
Stem cuttingsDemanding
Late fall to winter using semi-hardwood cuttings · Several months to root; rooting can be slow and erratic
Cuttings are how the named dwarf and weeping forms stay true to type, since seed will not copy them faithfully. Take semi-hardwood cuttings from late fall into winter and dip them in rooting hormone to give yourself the best shot. Even so, rooting comes along slowly and unevenly, often over several months, so go gently and let the plant set its own pace.
Myths
The hemlock tree is the deadly poison hemlock that killed Socrates, so it is dangerous to grow.
You can put this fear to rest, because the eastern hemlock tree is a gentle, harmless evergreen conifer in the pine family, and no part of it is poisonous. The poison that took Socrates came from poison hemlock, an unrelated weed in the carrot and parsley family, and water hemlock is yet a third toxic plant from that same family. The tree and those poisonous herbs share nothing but a name, by pure coincidence.