Tree · Ulmaceae
American Elm
Ulmus americana
A quick-growing vase-shaped shade tree that came back from the brink of extinction and now returns in resistant form.
Full sun
Every 7–14 days
USDA 2–9
60–80 ft · 18.3–24.4 m
Overview
Picture the American elm as it once stood along main streets across half the continent, its tall, curving limbs arching together overhead to roof the road in cool shade. It puts on height quickly, climbing to 60 to 80 feet (18 to 24 m) with an even broader crown, and it settles happily into almost any ground you offer it, whether soggy bottomland or hard, dry city dirt.
Then Dutch elm disease arrived. This fungal wilt rolled through during the 20th century and took elms by the millions, which is why only a handful of those grand old trees are still standing. Yet the species itself never gave up, and growers have since brought out cultivars with genuine resistance, so you can plant one today with confidence and clear eyes.
Your reward for a little patience is one of the finest shade trees there is, comfortable from zone 2 to zone 9 and easygoing about soil and pH. Keep in mind it grows into a big, long-lived tree with brittle wood and shallow roots that nudge up pavement, so it thrives best where it has plenty of elbow room rather than squeezed into a tight corner by the house.
Care
The short version: set it in full sun to light shade in nearly any well-drained soil, keep young trees watered through dry spells until their roots settle in, prune in late winter for a sturdy frame, and be sure to give this big, fast grower plenty of open space to stretch.
Light
Give your American elm full sun and it rewards you with the fullest, thickest crown, though it will accept partial shade without much fuss at all. The simple rule is that more sunlight gives you a fuller, sturdier tree.
Water
Keep young trees evenly moist as their roots take hold, offering a drink about every 7 to 14 days through dry weather. Once it is established the elm becomes wonderfully easygoing, weathering both drought and wet soil, so a grown tree will hardly ever ask anything of you.
Soil
When it comes to soil this is about as forgiving a tree as you could hope to plant. It is happiest in an average, medium-moisture, well-drained loam, yet it copes with clay, sand, and wet or dry ground, and it takes a broad pH span from 5.5 to 8.0, acidic right through to alkaline.
Temperature
Cold weather is nothing to fear here. The American elm holds up across zone 2 to zone 9 and shrugs off temperatures from around -51°F to 100°F (-46°C to 38°C), which is one reason it could once spread across such a vast stretch of country.
Humidity
Plain outdoor air suits it perfectly, so you have no humidity number to fuss over. Being a hardy native, it simply rolls with whatever weather comes its way.
Feeding
Help young trees along by feeding them in spring with a balanced slow-release tree fertilizer. Older, established trees rarely want anything extra and usually fare best when you simply let them be.
Pruning
Do your pruning in late winter while the tree rests, taking out crossing or weak branches to build a strong frame, since the wood snaps easily. There is also an urgent kind of pruning to know: cut away and destroy any wilting branch the moment it appears, before Dutch elm disease has a chance to travel.
Repotting
This is not a tree to keep in a pot for years, so you can forget about a repotting routine. Just move a nursery-grown sapling into the ground before its roots start circling the container, and treat roots poking out of the drainage holes as your gentle nudge to plant it.
Size & spacing
Plan for something grand. The American elm rises to 60 to 80 feet (18 to 24 m) tall and spreads 40 to 70 feet (12 to 21 m) across, so place it well away from buildings, walkways, and paving that its shallow roots are sure to lift in time.
When to plant
The American elm keeps to the rhythm of a temperate tree, and it is forgiving about it. Plant it in spring or fall while it sleeps, enjoy its tiny reddish-green blooms in March and April, and watch the winged samaras drift down as they ripen through April and May.
Northern hemisphere
Southern hemisphere
Typical months for a temperate climate: start earlier in warm zones, later where spring frosts linger.
- Plant: Spring or fall
- Harvest: Tiny reddish-green flowers in late winter to early spring (March-April), followed by flat winged samaras maturing April-May
Hardiness
USDA hardiness zones: 2–9
Temperature: down to -46°C
Troubleshooting
Most elm worries come down to just two things, and happily the serious one tips its hand early up in the canopy. Keep an eye out for a lone limb that wilts when it shouldn't, and get to know the look of beetle-chewed leaves. Find your match below, then move quickly, because Dutch elm disease responds well to a prompt reaction.
A single limb suddenly droops and browns while everything else looks healthy
Try not to panic, but a single branch that wilts, yellows, and dies back while its neighbors stay green is the warning sign of Dutch elm disease, a deadly fungal wilt that bark beetles carry in and that travels between trees through joined roots. Slice into the bark of a dying limb and you will usually see brown streaks running through the outer wood, yet elm yellows can cause the very same decline, so a lab test will tell you for certain. The good news is that fast action helps a lot: cut infected limbs out well below the streaking the instant you spot flagging, separate root grafts shared with nearby elms, and clear away dead trees quickly so the beetles have nowhere to breed.
Fix:
- Prune out and destroy infected limbs well below visible streaking as soon as flagging appears
- Remove and destroy severely affected or dead trees promptly to eliminate beetle breeding sites
- Sever root grafts between adjacent elms to stop underground spread
- Consult an arborist about fungicide injection for high-value trees
Foliage chewed down to lace with beetles crawling on it
If the leaves are turning brown and being eaten down to a lacy network of veins, the culprit is almost certainly the elm leaf beetle, whose pale larvae graze the leaf undersides while the striped grown-ups nibble the tops. Japanese beetles can leave a similar mess, so take a moment to see who is really there before you worry. Take heart, because a strong tree brushes off a little nibbling without trouble, so let it be where you can, welcome the insects that prey on the beetles, and only turn to a labeled insecticide when a serious outbreak lands on a younger, smaller tree.
Fix:
- Tolerate light feeding on otherwise healthy trees
- Apply an appropriately labeled insecticide for heavy infestations on smaller trees
- Encourage natural predators
Toxicity
Here is something to ease your mind if you share your home with animals: the American elm is not toxic to pets, livestock, or people. Nothing in the tree will poison a creature that browses or chews on it. The few cautions here are physical rather than chemical, since it is the brittle limbs and the heaving surface roots that ask for your attention.
Safe for
People · Cats · Dogs · Horses · Rabbits · Livestock · Birds
Cats None
Rest easy if your cat mouths a dropped leaf or a fallen samara, because the tree holds no poison for it. The only thing to keep half an eye on is the mild tummy upset any pet can get from snacking on greenery its body is not made to digest.
Dogs None
Your dog can mouth a loose twig or chew at the bark and come away just fine. There is nothing harmful in the wood or the leaves, so a happy afternoon spent under the canopy is no cause for concern.
Horses Safe
A horse grazing beside an elm has nothing to fear from its leaves or its bark. The tree carries no toxin, and pastured animals are welcome to browse it as they please.
Rabbits Safe
Rabbits love to strip elm bark and buds through the cold months and come to no harm doing it. You can plant one near a hutch or a backyard warren without a second thought.
Livestock Safe
Cattle, goats, and sheep are free to browse elm foliage with no ill effects, and people have fed the leaves as fodder for ages. Grazing stock face no poison from any part of this tree.
Birds Safe
Birds happily eat the spring samaras and nest in the limbs without a hint of danger. To them the elm is simply a friendly, safe place to feed and roost.
People Safe
There is no poisoning risk to people from the American elm at all. What deserves your care here is physical rather than chemical, since the brittle limbs and surface roots are the parts that can catch you out.
No special handling is required for toxicity, though the tree's large size, surface roots, and falling samaras and limbs are landscape considerations.
Varieties
Nearly every American elm worth planting these days is a named cultivar raised to withstand Dutch elm disease. Here are the ones to keep an eye out for.
'Princeton'
First chosen back in 1922, this old favorite still wears the graceful vase outline and has proven itself remarkably tough against Dutch elm disease.
'Valley Forge'
Released by the U.S. National Arboretum and treasured for its especially high resistance to Dutch elm disease, though no elm is ever completely immune.
'New Harmony'
A further disease-resistant pick from the Arboretum that grows with good vigor and stands the cold reliably down to about zone 4.
'Jefferson'
A resistant American elm selected to carry the sweeping, vase-shaped silhouette that makes the species such a beloved sight.
How to propagate
Growing an American elm from seed is easy enough to manage, but if you want a tree that shrugs off disease you will need to clone a named cultivar by graft or by cutting.
SeedModerate
Sow fresh samaras in late spring soon after they mature · A few weeks to germinate; several years to establish as a tree
Starting from seed is the easy route: scatter the winged samaras while they are still fresh in late spring, just as they ripen, and you should see sprouts within a few weeks. Those seedlings will fill out into trees over several years, though it helps to know that elms grown from seed do not inherit the disease resistance bred into the named cultivars.
GraftingDemanding
Dormant season · One or more seasons
When nurseries want to reproduce the named, disease-resistant elms exactly, they graft them during the dormant season. A graft needs a season or more to knit together and asks for a practiced hand, which makes it the propagator's job rather than something to try at home.
Stem cuttingsDemanding
Softwood in late spring to early summer · Weeks to root, then years to establish
Softwood cuttings gathered in late spring or early summer let you copy a resistant cultivar precisely. They put down roots in just a few weeks, then take years to grow into proper trees, and coaxing them to root in the first place calls for some experience.
Myths
The American elm is extinct or no longer worth planting because of Dutch elm disease.
It is true that the disease swept through and devastated the species in the last century, but the American elm pulled through and never vanished. You can buy several resistant cultivars now, among them 'Princeton', 'Valley Forge', 'New Harmony', and 'Jefferson', so planting one and watching it grow tall is a perfectly reasonable hope.