ISA Identification and Selection Practice Questions and Study Guide: Tree ID, Site Fit, and Nursery Stock

What Identification and Selection covers on the exam

Identification and Selection is one of the ten domains on the 200-question ISA Certified Arborist exam. ISA's Certified Arborist exam outline names it Tree Identification and Selection and weights it at 9% of the exam. ISA can change the weights when it completes a new job task analysis.

Tree identification is not a separate domain. ISA's outline lists it here, next to site fit, mature size, species tolerance, and pest and disease tendencies, and also under Tree Biology and Diagnosis and Treatment. The domain looks like memorization, but it is a decision domain: choose the tree that fits the site, reject poor stock, and read identification clues carefully. It overlaps with Installation and Establishment, Trees and Construction, Tree Biology, and Pruning, so a selection decision can turn on planting depth, root defects, or structural pruning. The ISA Certified Arborist exam domains guide shows how all ten domains fit together.

Key Identification and Selection concepts

Tree identification clues

Tree identification rests on careful observation more than obscure trivia. Know the features used in field identification:

• Leaf arrangement: alternate, opposite, whorled.
• Leaf type: simple, pinnately compound, palmately compound.
• Leaf margin: entire, serrate, doubly serrate, lobed.
• Buds and twigs: bud arrangement, bud scales, presence of a terminal bud, leaf scars, twig color.
• Bark: pattern, especially on mature trees.
• Flowers and fruit: flowers, fruit, cones, nuts, samaras, capsules.
• Form: branching habit, growth form, mature silhouette.
• Site: wet areas, dry slopes, streetscapes, disturbed soils.

Treat identification as a decision chain: note what the question gives you, decide whether each clue is diagnostic or only suggestive, check whether the species and the individual tree fit the site and objective, and reject answer choices that jump from one clue to a complete conclusion. One correct vocabulary word is not always the best answer, and when two choices look similar, the most diagnostic clue in the stem decides it.

Site fit and mature size come before favorite species

The best tree fits the site, the objective, and the long-term maintenance reality. A species that performs well in an open park may be a poor choice under utility lines or in a narrow sidewalk cutout. Site constraints to check:

• overhead utilities and mature height
• sidewalk, curb, pavement, and building conflicts
• limited soil volume
• compacted or disturbed soil
• poor drainage or saturated soil
• drought, heat, reflected light, and urban exposure
• deicing salt or coastal salt
• shade level
• foot traffic, mowing, and mechanical injury

Mature size is the easiest of these to underweight, because candidates picture the young tree they can plant today rather than the crown spread and root conflicts that come later. Read for a narrow planting strip, overhead conductors, a building facade, limited sight lines, driveway or sidewalk clearance, a small residential yard, or heavy pedestrian traffic.

The objective matters too. A small ornamental may fit under wires but fail a site that needs large-canopy shade, while a large shade tree may meet the canopy goal but be wrong for restricted soil space. The right choice matches both the tree's biological needs and the human use of the site. Prevention is the stronger approach, so be wary of any plan that ignores mature size, root space, or site tolerance.

Tolerance: drought, salt, shade, compaction, and drainage

Many selection misses are really tolerance misses. You do not need to memorize every species table, but you do need to think in categories. Before choosing, ask:

1. Is the soil wet, dry, compacted, alkaline, acidic, or poorly drained?
2. Is the site exposed to salt, heat, wind, or reflected light?
3. Is the planting location in full sun, partial shade, or deep shade?
4. Is there enough soil volume for the expected mature tree?
5. Does the species have known pest, disease, or structural problems in that region?
6. Would planting many of the same species increase future losses from one pest or disease?

This is where the domain touches Soil Management and Urban Forestry, and where the site constraint usually outweighs a preferred tree.

Nursery stock quality

Selection does not stop at species choice. A particular tree may need to be accepted, rejected, corrected, or planted differently. Watch for:

• circling, kinked, or girdling roots
• container-bound roots
• a buried root flare
• trunk wounds or mechanical injury
• poor taper
• codominant stems with included bark
• a broken leader or poor scaffold structure
• caliper and root ball size that do not match
• signs of drought stress, pest activity, or decline

Two responses are tempting and wrong: accepting a tree because the species is right while ignoring the specimen, and planning to fix every defect after planting. Some defects can be corrected before planting; severe ones are a reason to reject the tree before it becomes a long-term maintenance problem.

Species diversity and overplanting risk

This domain also supports program-level decisions. A city that plants the same species everywhere because it grows fast and looks uniform sets itself up for a large failure wave when one pest, disease, storm pattern, or site stress arrives. The same reasoning applies to a street-tree program, replacement after pest losses, canopy resilience, avoiding monocultures, and matching trees to maintenance capacity.

Do not choose diversity as a slogan. Choose it when it reduces realistic risk while still fitting the site: a diverse list of badly matched species is not better than one well-matched species for a specific location.

19 ISA Identification and Selection practice questions

These are original questions written for study, not real ISA exam questions. Treat them as a short closed-book drill:

1. Give yourself about 25 minutes for all 19 questions.
2. Do not use species lists, nursery catalogs, or notes while answering.
3. Mark each answer as confident, uncertain, or guessed.
4. After scoring, label each miss: ID clue, site tolerance, mature size, nursery stock, diversity, wording, or overconfident conclusion.
5. Re-study the weakest category before taking another mixed practice test.

Score guide

Use the score as a repair signal, not as a prediction of your exam result:

• 16–19 correct: This domain is probably not your biggest leak. Review guessed and uncertain answers, then move to mixed questions or a timed mock.
• 11–15 correct: You understand the broad ideas, but one category is leaking. Sort misses by category and drill that category again.
• 0–10 correct: Pause mixed mocks. Review the concepts above, make a site-constraint checklist, and drill short sets before moving on.

A short quiz cannot prove readiness, but it shows whether you read the stem carefully or jump to a familiar tree name. The pattern matters more than the number: three nursery-stock misses call for different work than three leaf-arrangement misses. Three sections further down add questions on leaf and bud arrangement, site selection, and nursery stock quality.

How Identification and Selection questions are phrased and common traps

The questions on this page follow a few patterns:

• Clue stack. Several identification clues, such as leaf arrangement, compound leaves, buds, bark, fruit, or branching habit, with one more diagnostic than the rest. Read all of them before committing.
• Constraint first. A site with overhead wires, salt, limited rooting space, compacted soil, poor drainage, or shade. Read the constraint before you think about the species.
• Accept or reject. A specific nursery tree with circling roots, included bark, poor form, or damage: accept it, correct it before planting, or reject it.
• Program level. A street-tree plan or replacement program that tests diversity and pest risk.
• ID, then selection. The tree is identified correctly, and the real question is whether it belongs on the site.

Common traps:

• choosing a favorite or familiar species
• ignoring mature size, overhead wires, or limited soil volume
• treating native status as the only criterion
• trusting one leaf clue or a common name when the stem gives stronger evidence
• accepting poor stock because the species is right
• fixes that create new problems: topping to clear wires, planting deeper, fertilizing to prevent pests, or heavy crown pruning to balance roots

How to study Identification and Selection

Study traits in groups instead of memorizing isolated leaves. Pair leaf arrangement and type with buds, twigs, bark, fruit, form, and site context, then practice deciding how those traits affect species selection. A two-column method keeps this from turning into flashcard chaos: in the first column, write the clue; in the second, write the decision it should change.

Then drill by category. Do 15 to 25 tree ID questions and review the misses, then 15 to 25 site selection questions, and drill nursery stock separately if the misses involve delivered-tree defects. Mixing everything too early hides the exact weakness. Once both sides feel stable, answer 25 to 50 questions from the whole domain, sort misses by category, and retest the weakest one with new questions rather than memorizing old answer letters. Move to a timed 200-question practice exam when you are no longer missing basic ID or site-fit questions and want to test pacing and stamina.

Leaf and bud arrangement

Arrangement is read at the node, where leaves and buds attach. Opposite means two at the same node, alternate means one per node, staggered along the twig, and whorled means three or more. Buds follow the same pattern, so a winter twig still shows it. A bud sits at the base of a whole leaf, not at each leaflet, which separates simple from compound leaves.

ISA's exam outline lists buds, nodes, leaf scars, leaf arrangements and margins under Tree Identification and Selection. The trap is treating one trait, such as arrangement or a serrated margin, as a full identification.

Site selection

Site selection starts from the site's limits, not a favorite species. Read the stem for rooting space in paved sites, reflected heat and drought, crown spread near buildings, and clearance for signs and sight lines. The tree has to fit at mature size, since nursery size is temporary, and a plan that relies on topping later fails that test.

ISA's exam outline lists choosing trees for a planting site under Tree Identification and Selection, including assessing exposure, drainage and rooting space, and recommending species to other parties. Client preference does not override a known site mismatch.

Nursery stock quality

Most questions below hand you one tree, container-grown or balled-and-burlapped, and ask whether to accept it, correct a manageable defect before planting, or reject it. Look below the crown: find the root flare, check for circling roots and a cracked or loose root ball, and weigh trunk wounds. Deeper planting, fertilizer and staking do not fix bad stock, and a sound tree of a poorly suited species is still the wrong tree.

ISA's exam outline lists nursery stock types, assessing planting stock quality, inspecting the root system before purchase and removing root-ball packaging under Installation and Establishment. Choosing the species belongs to this domain.

How Arborist Practice fits

Arborist Practice is the practice-and-feedback layer after you review the concepts: domain drills, explanations for wrong and guessed-right answers, bookmarks for scenarios that keep tripping you up, glossary support, timed mock exams, and study analytics. The AI tutor is useful for asking why the best answer beats the close distractor, such as why one tree is a better match for a constraint.