What to find out about a tree

Instructional example: in mid-December, you are given a small juniper bought at a supermarket. It is green and looks healthy, in a glazed blue ceramic pot with no drainage hole, its surface covered with pebbles glued into a hard crust. Its tag reads “INDOOR BONSAI · Juniper · Water twice a week · Bright indirect light · Keep away from drafts · Easy care,” so it goes onto a warm windowsill above a radiator, out of the frosty nights that have begun outside in the course's example climate.

Followed line by line, that tag would keep a temperate conifer in a warm room all winter, short of light, watered by the calendar in a pot that cannot drain. None of it would show at first: a juniper can stay green for weeks or months while it weakens (Course 01, Lesson 14). Only knowing what the tree is tells you the tag is wrong.

Call it the gift juniper. The most useful word on its tag, “Juniper,” names a group of dozens of species, not one tree. This lesson covers what to find out about a tree before you can look after it, why some familiar labels settle less than they seem to, and how to get an answer you can trust when the label is missing or unreliable.

A name you can look up

Most plants have several names. A common name is the everyday name, such as juniper, trident maple, or Fukien tea. No one controls common names: they vary between regions and sellers, one name can cover several plants, and one plant can have several names. A trade name is a name used to sell a plant rather than to identify it: a trademarked selling name for one cultivar, or a shop name such as “ficus ginseng” for a plant grown in a particular form. Sales labels such as “indoor bonsai” go further and point to no one kind of plant at all.

A scientific name, also called the botanical or Latin name, is given under international rules and used worldwide, and each kind of plant has one accepted scientific name. Reference books, botanic gardens, and extension services file their information under it, so it is the key to everything else you need to look up.

How a scientific name is built

Course 01, Lesson 1 introduced species and cultivars. A full name has one more part, the genus. Take the nursery juniper, Juniperus procumbens ‘Nana’:

• Juniperus is the genus, a group of closely related species. It is always capitalized.
• procumbens names the species within that genus. Genus and species together, in italics, make the species name: Juniperus procumbens, the Japanese garden juniper.
• ‘Nana’ is the cultivar, a selection kept consistent through propagation, written in single quotes without italics. It is a compact form of the species.

Many names describe the plant: procumbens means lying along the ground, nana means dwarf, and the ficus's microcarpa means small-fruited.

Each level tells you more. The genus gives a tree's close relatives and some shared features: every juniper is a conifer with needle-like or scale-like leaves and berrylike cones. But a genus does not settle care. The ficus, Ficus microcarpa, is a tropical evergreen that frost damages or kills, while the common fig, Ficus carica, is deciduous and survives moderate frost, so in many temperate gardens it winters outdoors. Light needs, hardiness, and seasonal needs are usually settled at the species level; the cultivar adds size, shape, foliage color, and sometimes a difference in hardiness.

When names mislead

Common and trade names go wrong in a few predictable ways:

• One common name, two species. Chinese elm is Ulmus parvifolia. Siberian elm, Ulmus pumila, is a different species that is sometimes sold as Chinese elm. The two differ in their leaves, their bark, and even the season they flower, and advice written for one may not fit the other.
• A trade name instead of a plant name. “Ficus ginseng” is Ficus microcarpa grown with a thick, swollen base of roots raised above the soil; it has nothing to do with ginseng. “Indoor bonsai” names no plant at all.
• Misleading relatives. The Norfolk Island pine, Araucaria heterophylla, is a conifer but not a true pine, and Fukien tea is not closely related to the tea plant.
• A group name. “Juniper bonsai” could be any of several junipers, such as the Japanese garden juniper or the Chinese juniper, Juniperus chinensis.
• A changed name. Botanists sometimes move a species to another genus as they learn how plants are related. Fukien tea is now usually Ehretia microphylla but is still often sold as Carmona. Good references list old names as synonyms, so a search for either finds the same plant.

Leaf type, leaf habit, and climate

Course 01 gave you three ways to describe a tree. Leaf type: a broadleaf has flat leaves and bears seeds in flowers and fruits; a conifer has needle-like or scale-like leaves and bears seeds in cones (Course 01, Lesson 4). Leaf habit: an evergreen keeps living foliage all year; a deciduous tree drops all its leaves for part of each year. Climate of origin: temperate trees are adapted to warm summers and cold winters, tropical trees to warmth all year, and subtropical trees to mild winters with rare, light frost (Course 01, Lesson 13).

These descriptions help you recognize a tree and read a reference. The question is how much they tell you about where it can live.

Test that on eight trees. In Four labels that don’t settle it, read each card's Foliage and In January clues, then choose its Leaf type (Broadleaf or Conifer) and Leaf habit (Evergreen or Deciduous). Each tree drops into The leaf grid once both are answered (beside the cards on a wide screen, after them on a narrow one). When all eight are in the right boxes, switch on Show where each comes from and compare the trees that share a box.

Two boxes often surprise beginners. The Japanese larch and the bald cypress are conifers that go bare every winter, and the boxwood's small leaves are still flat blades, so it is a broadleaf. Winter color can mislead too: the juniper's purple tint and the boxwood's bronzing are color changes, not leaf drop.

The climate view then split both evergreen boxes. The boxwood rests outdoors in winter, while the ficus and the Fukien tea need frost-free warmth and strong light; the juniper needs a cold winter outdoors, while the Norfolk Island pine must not freeze. The deciduous boxes held only temperate trees, but that is true of these eight, not a rule: some tropical trees drop their leaves in a dry season instead. Even the descriptions blur. A Chinese elm keeps some of its leaves through a mild winter and drops most or all of them in a cold one, so it is called semi-evergreen; in the example climate, expect it bare or nearly bare by midwinter, which is normal. What settles placement is the tree's identity, and with it the climate it comes from.

What to find out about any tree

Once you have a name, four groups of facts decide where a tree can live and how to look after it. Look them up in a reliable reference, not on a tag.

Light needs

How much direct sun the tree needs or tolerates outdoors (full sun, part sun or part shade, or shade), and whether it can grow indoors at all, which only some tropical and subtropical trees can, and only in strong light. The nursery juniper needs full sun outdoors all year; the trident maple takes full sun to part shade, though in hot summers its leaves can scorch in strong afternoon sun and wind; the ficus wants the strongest light you can give, indoors often a bright window plus a grow light. Indoor light is far weaker than it looks (Course 01, Lesson 6); Lesson 4 shows how to measure it.

Cold and heat tolerance

Hardiness is a plant's ability to survive the conditions of a place, most often its cold hardiness: the coldest winter temperatures it can survive. References often give it as a range of hardiness zones, such as the USDA zones from Lesson 1. The nursery juniper's cultivar is hardy roughly in zones 4 to 9 and the trident maple to roughly zone 5, while frost damages or kills the ficus, and many growers keep it above about 10 °C (50 °F).

Every rating comes with two cautions. First, it describes a plant in the ground. Roots are generally less cold hardy than branches, and in a pot they are exposed on every side, so a potted tree needs more protection than its rating suggests (Lesson 5 and Course 06, Seasonal Care and Timing). Second, it assumes a tree that has built up its cold acclimation through autumn outdoors (Course 01, Lesson 13). The gift juniper is very likely hardy enough to winter outdoors in the example climate, zone 7a, but after weeks in a heated shop and home it is not ready for frost yet.

Heat matters too: trees from cool mountain or northern climates can struggle through long, hot summers like the example climate's. Fewer references rate heat tolerance than cold hardiness, so look for phrases such as “prefers cool summers” or “tolerates heat.”

Seasonal needs

Whether the tree needs a winter rest, with enough time in the cold to meet its chilling requirement, or grows whenever it is warm and bright enough. Temperate trees such as the trident maple and, very likely, junipers need that rest. In a warm room they miss it, and the harm shows the next spring as late, weak bud break and, over several winters, decline (Course 01, Lesson 13). Tropical trees such as the ficus and the Fukien tea have no chilling requirement. Subtropical trees vary; many do best in winter in a cool, bright, frost-free place. A good reference also says when the tree usually leafs out, flowers, and rests, so you know what normal looks like.

Growth habit

A tree's growth habit is the shape it naturally grows into and the way it grows: upright, spreading, weeping, or low and creeping, fast or slow. The nursery juniper's cultivar is low, spreading, and modest in its yearly growth; a trident maple in good conditions grows fast and upright. Habit tells you what a tree tends to become. Later courses add behavior such as how a tree responds to pruning (Course 09, Pruning and Managing Growth) and whether it buds from old, bare wood, which many junipers do not (Course 01, Lesson 5).

This tree's history

One more fact belongs to the particular tree rather than its kind: where and how it was grown before it reached you. A tree from a local outdoor nursery has lived through your weather. One from a heated greenhouse or shop has not, and needs time to adjust to strong sun and cold (Lesson 3). Lesson 6 returns to this when you buy a tree.

Reading a shop tag

Tags usually get the common name roughly right, sometimes the genus, and occasionally the full scientific name. A label from a nursery that grows its plants outdoors often adds the cultivar, a hardiness zone, and the sun exposure the plant wants.

Care lines are another matter, especially on mass-market bonsai. One tag is often printed for a whole shelf of different trees, so its advice suits an average houseplant rather than the tree it is attached to. “Indoor bonsai” goes on temperate and tropical trees alike. Watering comes as a fixed schedule, although how fast a pot dries changes with the weather, the light, the pot, and the roots (Course 03, Watering and Daily Observation). And tags rarely say where or how the tree was grown.

Now read the gift juniper's tag as evidence. In Read the tag like a detective, Step 1 is Judge each line on the tag: for each of the six lines, choose Useful as given, Check it first, or Wrong for this tree, and look at the clue that lights up in the picture. In Step 2, What do you still need to find out?, tick the facts you still need (the step says how many), then press Check my list.

Only “Keep away from drafts” is fine as printed, and it is a minor point. Three lines would mislead you: “Indoor bonsai” and “Bright indirect light” describe a houseplant, not a temperate conifer that needs full sun outdoors and a cold winter rest, and “Water twice a week” sets a schedule for a pot that cannot drain. “Easy care” depends on where the tree lives, and “Juniper,” the most useful word on the tag, names a genus, not a tree. The five facts on your list are the ones this lesson has built; the price, the pot's color, the shop's guess at its age, and a watering count would change nothing about what the tree needs.

Getting a reliable identification

Its foliage and tag make “a juniper” a safe working assumption for the gift juniper, and the likeliest candidate is Juniperus procumbens ‘Nana’, but nobody has confirmed it. To turn a likely guess into a name you can rely on, for this tree or any other:

1. Ask the seller for the botanical name, and where and how the tree was grown. A supermarket may not know, but the tag or pot may name a grower or supplier who does.
2. Take good photographs in daylight: the whole tree, the leaves or needles close up from above and from below, a twig tip with its buds, the bark, and any flowers, fruit, or cones, with something of known size beside the close-ups.
3. Treat a plant identification app as a first suggestion. Apps often recognize common plants in their usual form, but a small, pruned bonsai with reduced leaves or juvenile foliage can fool them. Check the suggestion feature by feature against a reliable description: leaf shape and arrangement, foliage, bark, and any flowers or cones.
4. Ask people who know. A local bonsai club can usually name common bonsai trees from a photo, and specialist nurseries, botanic gardens, and extension services also identify plants.

Aim for two sources that agree, such as an app's suggestion confirmed by a club member, or a seller's name that matches a reliable description. Until then, treat the name as likely, not settled.

Before you know what it is

An identification can take days or weeks, and the gift juniper is on a radiator in December, so some decisions cannot wait for it.