19 Tree Identification & Selection Practice Questions & Answers

1. 1. Before recommending a treatment for a declining tree, why should the arborist first determine the species?

   • A.The species reveals the tree's exact age and its remaining life expectancy.
   • B.Symptoms alone reveal the cause, so the species matters only for the written report.
   • C.Many pests and pathogens are host specific, so species narrows the likely causes.✓ Answer
   • D.All species react alike, so species affects only the price of the treatment.

   A great many insects and pathogens can only complete their life cycle on a narrow range of hosts, so knowing the species immediately rules many agents in or out and prevents a misdiagnosis. Species also governs expected growth, wood strength, tolerance of site stresses and pruning timing, all of which shape the recommendation.

   Source: ISA Arborists' Certification Study Guide, chapter on tree identification and its role in diagnosisReport a problem with this question

2. 2. A dichotomous key leads to two species that both have alternate, serrate leaves. What is the sound next step?

   • A.Pick whichever of the two species is more widely sold by local nurseries.
   • B.Record the first of the two species, because keys list the likelier one first.
   • C.Compare further characters such as buds, bark, fruit and overall form.✓ Answer
   • D.Decide by leaf size alone, since leaf size separates most look-alike species.

   A single character varies with age, light, vigour and position in the crown, so it is rarely diagnostic by itself. A reliable identification rests on several independent characters agreeing, which is why a key is worked through with buds, bark, fruit and form in hand rather than one leaf.

   Source: ISA Arborists' Certification Study Guide, use of dichotomous keys and multiple identifying charactersReport a problem with this question

3. 3. Within a full plant name, how is a cultivar name correctly presented in a written report?

   • A.Capitalized, enclosed in single quotation marks, and not italicized.✓ Answer
   • B.Capitalized, italicized, and introduced by the abbreviation var.
   • C.Lowercase, in double quotation marks, and placed after the family.
   • D.Lowercase, italicized, and written immediately ahead of the genus name.

   The genus and specific epithet are italicized because they are Latin botanical names, but a cultivar is a human selection rather than a botanical rank, so its name is set in roman type, capitalized and in single quotes. The abbreviation var. marks a botanical variety, which is a different rank and is italicized along with its epithet.

   Source: International Code of Nomenclature for Cultivated Plants, formatting of cultivar epithetsReport a problem with this question

4. 4. Why do arborists specify trees by scientific name rather than by common name?

   • A.Common names are changed each time a nursery releases a new selection.
   • B.Scientific names state the mature height and spread of the species.
   • C.One common name can refer to different species in different regions.✓ Answer
   • D.Common names are prohibited in professional arboricultural documents.

   Each accepted binomial applies to exactly one taxon worldwide, whereas a common name may be attached to several unrelated trees in different places and one tree may carry several common names. Specifying by binomial therefore removes the ambiguity that would otherwise send the wrong species to a planting site or the wrong host to a diagnostician.

   Source: International Code of Nomenclature for algae, fungi, and plants, principle of one correct name per taxonReport a problem with this question

5. 5. Two leaves arise directly across from one another at each node on a twig. What does this observation indicate?

   • A.Alternate arrangement, which appears only on the current season's growth.
   • B.Compound leaf structure, which means the blade is divided into leaflets.
   • C.Opposite arrangement, which narrows the tree to a small group of genera.✓ Answer
   • D.Whorled arrangement, which is the commonest pattern among broadleaf trees.

   Two leaves per node is the definition of opposite arrangement; three or more per node is whorled and one per node is alternate. Opposite arrangement is uncommon among temperate broadleaf trees, so recognising it cuts the candidate list dramatically before any other character is examined.

   Source: ISA Arborists' Certification Study Guide, leaf and branch arrangementReport a problem with this question

6. 6. Which observation most reliably distinguishes a leaflet of a compound leaf from a simple leaf?

   • A.A leaflet joins woody twig tissue, while a simple leaf joins green tissue.
   • B.A leaflet has no bud at its base, while a true leaf always has one.✓ Answer
   • C.A leaflet always has an entire margin, while a simple leaf is toothed.
   • D.A leaflet is always smaller and thinner than any simple leaf nearby.

   An axillary bud forms only in the axil of a true leaf where it meets the stem, never at the attachment of a leaflet to the rachis, because the whole compound leaf is one leaf. Size, margin and texture all vary too much to serve as the test, so the bud is the decisive check.

   Source: Standard plant morphology references, simple versus compound leaves and axillary budsReport a problem with this question

7. 7. A leaf blade is edged with teeth of two alternating sizes, and its main veins all radiate from one point at the base of the blade. Which pair of terms describes it?

   • A.Crenate margin with pinnate venation.
   • B.Entire margin with parallel venation.
   • C.Undulate margin with dichotomous venation.
   • D.Doubly serrate margin with palmate venation.✓ Answer

   Teeth of two sizes, small ones set on larger ones, define a doubly serrate margin, while veins radiating from a single basal point define palmate venation as opposed to pinnate veins branching off a central midrib. Parallel venation points to a monocot and dichotomous forking venation is the hallmark of ginkgo.

   Source: Standard plant morphology terminology, leaf margins and venation patternsReport a problem with this question

8. 8. In winter, with no foliage on the tree, which set of features does an arborist rely on to identify a deciduous tree?

   • A.Trunk diameter, total tree height, and the tree's estimated age.
   • B.Flower color, fruit flesh color, and the shape of the leaf apex.
   • C.Fallen leaf shape, leaf litter depth, and the litter's autumn coloring.
   • D.Bud arrangement and scales, leaf scars, bark, and overall form.✓ Answer

   Buds, bud scales, leaf scars with their bundle scars, lenticels, pith, bark and silhouette all persist through the dormant season and are species characteristic, so winter identification is built on twig and bark anatomy. Leaf litter under a tree is unreliable because it blows in from elsewhere, and trunk size reflects age and site rather than species.

   Source: ISA Arborists' Certification Study Guide, winter twig and bark identificationReport a problem with this question

9. 9. How does an excurrent growth form differ from a decurrent form?

   • A.Excurrent refers to compound-leaved trees; decurrent to simple-leaved trees.
   • B.Excurrent describes any evergreen species; decurrent describes any deciduous one.
   • C.Excurrent means a rapid growth rate; decurrent means a slow growth rate.
   • D.Excurrent keeps one dominant central leader; decurrent spreads into codominant limbs.✓ Answer

   Excurrent form results from strong apical control that holds a single leader above subordinate lateral branches, giving the conical silhouette typical of many conifers. Decurrent form arises when apical control weakens and several limbs grow at similar rates into a spreading, rounded crown, as in many mature hardwoods, and this distinction is a form character rather than a statement about foliage or growth rate.

   Source: ISA Arborists' Certification Study Guide, tree form and crown architectureReport a problem with this question

10. 10. Needles are borne singly, are four-sided, roll easily between the fingers, and each sits on a small woody peg. Which genus is indicated?

    • A.Juniper
    • B.Pine
    • C.Fir
    • D.Spruce✓ Answer

    Spruce needles are four-angled in cross section, which is why they roll between the fingers, and they are attached to persistent woody pegs that leave the twig rough after the needles fall. Pine needles are bundled in fascicles, fir needles are flat and will not roll and leave a smooth round scar, and juniper foliage is scale-like or awl-like rather than needle-like on pegs.

    Source: Standard conifer identification references, needle attachment in Pinus, Picea and AbiesReport a problem with this question

11. 11. Why is it wrong to treat the words conifer and evergreen as interchangeable?

    • A.Some conifers bear true flowers and fleshy fruits instead of woody cones.
    • B.Some conifers, such as larch and baldcypress, drop all their needles each year.✓ Answer
    • C.Broadleaf species are all deciduous, so evergreen can only mean conifer.
    • D.Evergreen species shed no foliage at all once their leaves have expanded.

    Conifer is a taxonomic description meaning a cone-bearing gymnosperm, while deciduous and evergreen describe foliage habit, and the two classifications cut across each other. Larch, baldcypress and dawn redwood are conifers that shed all their foliage seasonally, and many broadleaf species in warm climates are evergreen.

    Source: Standard plant taxonomy references, gymnosperms and deciduous conifersReport a problem with this question

12. 12. Palms are monocots rather than eudicots. What does this mean for the palm trunk?

    • A.It has a vascular cambium but adds rings only in years of good rain.
    • B.It has no vascular cambium, so it forms no annual rings of secondary wood.✓ Answer
    • C.It compartmentalizes wounds in the same manner as a broadleaf tree does.
    • D.It forms true bark that keeps thickening as the trunk continues to expand.

    Monocots have scattered vascular bundles and no vascular cambium, so they cannot add successive layers of secondary xylem and phloem and produce neither annual rings nor true bark. Because there is no cambium to generate woundwood, a palm cannot compartmentalize or close injuries the way a woody eudicot does, which is why trunk damage on palms is permanent.

    Source: ISA Arborists' Certification Study Guide, monocot anatomy and palm growthReport a problem with this question

13. 13. A dry, one-seeded fruit bearing a flattened wing that makes it spin as it falls is called what?

    • A.A drupe
    • B.A capsule
    • C.A pome
    • D.A samara✓ Answer

    A samara is a dry indehiscent fruit whose pericarp is extended into a wing, and the asymmetric wing makes it autorotate so wind carries it away from the parent tree. A drupe has a fleshy layer over a stony pit, a pome has a fleshy receptacle around a papery core, and a capsule is a dry fruit that splits open to release several seeds.

    Source: Standard plant morphology references, classification of fruit typesReport a problem with this question

14. 14. What is the correct order of work when selecting a tree for a specific planting site?

    • A.First choose the species the client prefers; then amend the site to suit.
    • B.First assess the site's soil, space and exposure; then choose the species.✓ Answer
    • C.First buy the largest stock available; then find a site able to hold it.
    • D.First choose the cheapest species offered; then fix problems after planting.

    Right tree, right place means the site is the fixed constraint and the species is the variable, because soil texture, drainage, rooting volume, light, wind and overhead and underground conflicts cannot be changed cheaply or permanently. Assessing those first, including a soil sample where warranted, defines the envelope of species that can actually thrive there.

    Source: ISA Best Management Practices: Tree Planting, site assessment before species selectionReport a problem with this question

15. 15. Why is underestimating a tree's mature size the costliest common error in species selection?

    • A.Its roots cannot reach the depth needed to anchor a trunk of that size.
    • B.It grows into utilities, structures or sight lines, forcing pruning or removal.✓ Answer
    • C.Its nursery price rises for every year that the canopy keeps expanding.
    • D.It stops growing early and never reaches the size given on the planting plan.

    A tree is placed once but grows for decades, so a species whose mature crown or trunk exceeds the space available creates a permanent conflict with wires, walls, pavement or sight lines. The remedy is then recurring heavy pruning that damages structure and health, or premature removal and replacement, both far more expensive than choosing a smaller-maturing species at the outset.

    Source: ISA Best Management Practices: Tree Planting, mature size and site constraintsReport a problem with this question

16. 16. A street tree pit provides only a small volume of rooting soil. How should that constrain the species choice?

    • A.Select a large-maturing species, because large trees root deeper and faster.
    • B.Select any species and irrigate more often, since water can replace volume.
    • C.Select a small-maturing species, since little soil volume cannot support a big crown.✓ Answer
    • D.Select any species and fertilize yearly to make up for the limited volume.

    Crown size is supported by the water and nutrients an absorbing root system can gather, and that system is limited by the volume of usable soil, so a large-maturing species in a small pit stalls, declines early and stays chronically stressed. Fertilizer does not create pore space or water-holding capacity, and irrigation cannot substitute for rooting volume.

    Source: ISA Best Management Practices: Tree Planting, soil volume and rooting spaceReport a problem with this question

17. 17. Why does a good planting plan spread trees across many genera and families instead of repeating one species?

    • A.Mixed plantings need no maintenance once the trees are fully established.
    • B.One species always depletes a single soil nutrient and starves the planting.
    • C.Mixed plantings measurably outgrow plantings made of a single species.
    • D.A host-specific pest could otherwise remove much of the population at once.✓ Answer

    Most serious insect pests and pathogens are limited to one host species, genus or family, so a monoculture presents them with an unbroken supply of susceptible hosts and can be lost in a few seasons. Spreading a planting across unrelated taxa means any single outbreak removes only a fraction of the canopy, which is the resilience argument behind diversity targets.

    Source: ISA Best Management Practices: Tree Planting, species diversity in urban plantingsReport a problem with this question

18. 18. When inspecting container-grown nursery stock before purchase, which root condition matters most?

    • A.The root flare shows near the soil surface and no roots circle it.✓ Answer
    • B.The container is packed with dense roots that hold the shape of the pot.
    • C.The stem is buried deep in the container so the root ball stays moist.
    • D.The largest roots have been cut back so the tree lifts out more easily.

    A visible root flare shows the tree is not buried too deeply in the container, and roots that circle the trunk will keep enlarging until they compress the stem and strangle its conducting tissue years after planting. A pot-shaped mass of dense circling roots is a defect rather than a sign of quality, and good stock is also judged on trunk taper and well-spaced structural branches.

    Source: American Standard for Nursery Stock, root ball and root system qualityReport a problem with this question

19. 19. Compared with container stock, what happens to the root system when a field-grown tree is dug balled and burlapped?

    • A.The number of roots doubles, because digging stimulates a flush of growth.
    • B.The entire root system travels intact inside the soil ball on the pallet.
    • C.The roots are unchanged, because the burlap holds every root in place.
    • D.A large share of its absorbing roots is left behind in the nursery field.✓ Answer

    Field-grown roots extend well beyond the diameter of any diggable ball, so balling and burlapping severs most of the fine absorbing roots and the tree arrives with a root system far smaller than its crown. That imbalance is why balled-and-burlapped stock needs a longer establishment period than container stock, while bare-root stock loses soil contact but keeps a wider spread of roots and is limited to dormant handling.

    Source: ISA Best Management Practices: Tree Planting, nursery stock production methods and root lossReport a problem with this question

Practice questions based on the published knowledge domains of the ISA Certified Arborist examination outline and on standard arboriculture references. ISA and Certified Arborist are marks of the International Society of Arboriculture; this site is not affiliated with or endorsed by ISA. Answers here deliberately avoid pesticide products and rates, standard clause numbers and the dimensions recalled from them, regional species recommendations and local ordinances, all of which change and vary by place — always follow the pesticide label and your jurisdiction's applicator licensing, the tree-care safety standards in force, and the requirements of the authority having jurisdiction. Confirm current exam requirements with ISA before testing. About the ISA Certified Arborist credential →