Littleleaf linden

Identification and origin

Tilia cordata belongs to the Malvaceae, the mallow and hibiscus family. Its native range covers almost all of Europe, from Spain, France and Great Britain to Scandinavia, the Baltic States, central Europe and the Balkans, and reaches east into Russia, the Caucasus, Iran, Kazakhstan and western Siberia. It has naturalized in several US states and in Uzbekistan. The epithet cordata means “heart-shaped,” a reference to the leaves.

It is a medium to large tree, pyramidal at first and then oval, casting dense shade. In cultivation it usually reaches 49–59 ft tall and 34.5–49 ft wide, and sometimes exceeds 65.5 ft. Growth is medium, much slower on a stressed tree; it takes twenty to fifty years to reach full size. It sometimes sends up suckers from the base.

• Leaves: alternate, simple, heart-shaped with a pointed tip, 1–3 in long, with toothed margins. Glossy dark green above and paler below, they are hairless except for small tufts of reddish-brown hairs where the veins meet, on the underside. They turn yellow in fall.
• Flowers: small, creamy yellow to greenish yellow, with five petals and a strong, sweet scent. They hang in clusters of four to ten from a long, strap-like bract and open in midsummer.
• Fruit: small, rounded nutlets about 0 in across, pale green turning light tan, ripening in late summer in hanging clusters.
• Bark: gray-brown and smooth on young trees, breaking into flaky plates with age.
• Twigs and buds: reddish-brown twigs, red on top and olive green underneath in winter; smooth, shiny red buds under 0 in, with two or three scales.

To tell it from its relatives: common linden has white hairs where the veins meet, and large-leaved linden is hairy over the whole leaf underside.

Once a dominant forest tree, it has become rare in woodland; in some parts of England its presence marks an ancient woodland. Its soft, light, fine-grained wood is used for turning, carving and piano keys, and the bark was once made into rope. The most common cultivar, ‘Greenspire’, copes better with urban conditions.

Light

Littleleaf linden grows in full sun or partial shade, with two to six hours of direct sun a day. It likes a south-, west- or east-facing spot, sheltered from cold winds. As a bonsai, it does well outdoors in a sunny or lightly shaded, airy spot; it should not be kept indoors for long.

Watering

It prefers moist but well-drained soil. It tolerates neither wet ground nor severe drought. Water during dry spells, especially young trees: check soil moisture deep down at the base of the tree and water deeply when it runs short, rather than following a schedule.

In a container, water generously as soon as the surface of the mix is dry, without leaving standing water. In winter, during dormancy, water less, but never let the root ball dry out completely.

Potting mix

It adapts to many soils: chalk, clay, sand or loam, acid, neutral or alkaline, and it tolerates lime well. It does best in a fertile, moist, well-drained loam. It handles pollution and salt spray poorly: wrongly planted as a street tree, it stays stunted, its leaves scorch at the edges and it is prone to windthrow. In a container or as a bonsai, use a free-draining mix.

Temperature

The tree is hardy in USDA zones 3b to 7b and easily handles winters across northern Europe. In the ground it needs no protection. In a container the root ball is far more exposed: as a bonsai it tolerates about 10 °F, and young trees should be protected from hard frost in a cold frame or with mulch. It needs a cold winter rest.

Repotting

In the ground, this is a tree for parks and very large gardens: allow more than 59 ft of open space. It is used as a specimen shade tree on a lawn, as a hedge or as a screen.

In containers and as a bonsai, repot young trees every two years in early spring, before bud break, and older trees every three or four years. Keep root pruning moderate to maintain a balanced root system.

Pruning

Grown as a tree, it needs very little pruning, but it takes hard pruning very well. That is why it can be pollarded, coppiced or pleached, and clipped as a hedge or a screen.

As a bonsai, frequent pruning in spring and summer keeps growth compact and refines ramification: let shoots develop three or four nodes, then cut them back to one or two leaves. Its small leaves reduce well in cultivation, which makes it a good species for this purpose.

Propagation

• Seed: seeds need cold stratification. Set them out in containers outdoors in spring so they receive it.
• Cuttings: softwood cuttings taken in early summer root easily, especially with a little rooting hormone.
• Grafting: grafting or chip budding onto a carefully chosen rootstock; this is how cultivars are propagated.

Common problems

The same symptom can have several causes: leaves scorched at the edges can come from drought, salt or an overly exposed site. Look at the tree before treating.

• Pests: usually no serious problems. Japanese beetles can skeletonize the foliage where they occur. Aphids, scale insects, caterpillars, sawflies, leaf miners, lace bugs, borers and gall mites, including the nail gall mite, can also appear. Spider mites show up in hot, dry weather.
• Diseases: powdery mildew, leaf spots, sooty mold, cankers, sometimes bleeding, Phytophthora root rot and honey fungus. Verticillium wilt is uncommon but can kill the tree.

The tree is valuable for wildlife: its flowers feed bees, which make a prized honey from them, and its leaves feed the caterpillars of several moths, including the lime hawk-moth.

Toxicity

No toxicity has been reported: littleleaf linden does not appear among the plants listed as toxic to dogs and cats in veterinary references, and American linden, a close relative, is classed as non-toxic to these animals. Even so, keep children and pets from chewing the leaves or twigs.