FIELD ELM BONSAI

The Country Elm Bonsai: The Rusticity of Our Countryside

The CountryElm(Ulmus minor or campestris) is the tree that perhaps most of all represents the rural Italian landscape of the past. Unlike its Chinese "cousin"(Ulmus parvifolia), the native Elm is a decidedly deciduous plant, giving us a distinct seasonal change. It is loved by bonsai growers for its bark, which, in some specimens, becomes wrinkled and corky ("suberose" variety), for the fine branching it manages to build up over the years, and for its incredible robustness. It is a "forgiving" tree, ideal for learning, but capable of becoming a masterpiece.

Origin & species

Native to Europe, North Africa and southwest Asia. It is an indigenous plant that grows wild in our forests and plains. Unfortunately, in the wild the population has been decimated by Graphiosis (a fungal disease), but grown in pots as bonsai it is easier to protect and preserve. It is a vigorous tree with strong apical dominance.

Exposure and Microclimate

It loves full sun.
Direct sun exposure is essential to reduce leaf size (which otherwise tends to become large) and to keep internodes short.
It withstands wind well. In midsummer, in warmer areas, it likes light afternoon shade only to avoid burns on the leaf tips, but it is much more heat tolerant than Chinese Elm.

Watering

The Field Elm drinks with gusto.
Water generously when the soil begins to dry on the surface. In summer, never let it lack water: if it goes into water stress, it sacrifices its leaves causing them to yellow and fall early (a defense mechanism). In winter, when the plant is bare, reduce drastically, keeping the soil barely moist.

Water quality

This is a hardy plant, accustomed to our soils.
It happily tolerates tap water, even if limey. It does not require special or acidified water.

Substrate

Adapts to many soils, but optimal bonsai cultivation requires drainage.

  • Recommended mix: 50 percent Akadama (for fine branching), 30 percent Pumice and 20 percent quality Universal Potting Soil.
  • Akadama is good for stimulating a capillary root system, essential for small leaves.

Repotting

It is done every 2-3 years (every year for fast-growing juveniles).
When: In late winter, as soon as buds swell but before leaves open (February-March).
Elm has very strong roots and tends to fill the pot quickly. Don't be afraid to prune the roots firmly when repotting, it responds very well by issuing new rootlets everywhere.

Fertilization

Fertilize from spring to fall.
Use a balanced fertilizer in spring to push vegetation. If the tree is already formed and you want to control growth, use less nitrogenous slow-release fertilizers and start fertilizing only when the leaves are already mature (May). Fall fertilization essential to prepare winter buds.

Flowering and fruiting

Blooms in late winter, often before setting leaves, with tiny flowers.
They then produce samare (greenish winged seeds) in clusters. They are pretty to look at, but they consume energy: if the bonsai is under construction, remove them so as not to slow vegetative growth.

Structure pruning

This is done in winter, with the plant bare, when it is easy to see the structure of the branches ("the nakedness of the tree").
Remove branches that grow straight upward, those that cross or arise under the axils of the main branches. Use mastic on large cuts, as the Elm heals by creating a "callus" that can become unsightly if not managed.

Maintenance pruning

During the growing season, the Elm grows quickly.
Allow new shoots to elongate to 4-6 leaves, then shorten them to 2 leaves. This continuous work is to create and maintain "stakes" of dense vegetation.

Pruning

On newly opened shoots in spring, you can intervene with your fingers (stapling) by detaching the central tip to immediately stop elongation and encourage immediate back branching. Useful on already finished plants.

Binding & folding

Field Elm branches are flexible when young, but become stiff and break sharply once lignified.
Tying should preferably be done in fall or early spring on 1-2 year old branches. Check the wire often: the bark grows fast and the wire becomes incarnate in a few weeks during the growing season.

Diseases and pests

  • Elm Galerucella: This is enemy number one. A small beetle that eats leaves, reducing them to a "skeleton" of veins. If you see holes in the leaves, take immediate action with insecticide.
  • Red spider mite: In summer, turns leaves bronzed.
  • Graphiosis: Less frequent in isolated bonsai than in woodland, but deadly (sudden drying up of entire branches). Keep the plant healthy and strong to prevent it.

Winter & protections

It is hardy and frost-resistant.
It can stay outside all year round. Only in exceptional and prolonged frosts, protect the pot to prevent the root ball from becoming a single block of ice, which could damage the finest capillaries.

Annual calendar

  • January-February: Structure pruning, cleaning.
  • March: Repotting, flowering (if present).
  • April-May: Galerucella control (important!), fertilizing, topping.
  • June-July: Constant watering, defoliation (optional).
  • August: Summer rest.
  • September-October: Fertilization, wire control.
  • November-December: Leaf fall, rest.

Useful products for this bonsai

Frequently Asked Questions about Field Elm

How is it different from Chinese Elm (Zelkova)?
The Field Elm(Ulmus minor) has duller leaves, often somewhat hairy or rough, and a bark that becomes dark and wrinkled (sometimes corky). It loses its leaves in winter. Chinese Elm(Ulmus parvifolia) has shiny, smooth leaves, bark that flakes in plaques (spotted) and tends to keep its leaves if it is hot.

I found the leaves pitted like a colander, what's going on?
It is almost certainly Galerucella. The larvae of this insect eat the green part of the leaf leaving only the veins. Treat with an insecticide as soon as you see the first holes, otherwise they can defoliate the tree in a few days.

What is the "corky variety" Elm?
Some Field Elms naturally develop corky "wings" on the branches and trunk to protect themselves from heat/cold. In bonsai, this feature is highly valued because it gives the tree an ancient and dramatic appearance even at a young age.