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BLACK LOCUST (Robinia pseudacacia)

Distinguishing characters: The bark of the trunk is rough and deeply ridged. The buds are hardly noticeable; the twigs sometimes bear small spines on one side. The leaves are large, compound, and fern-like. The individual leaflets are small and delicate.
Black Locust Compound Leaves
Form and size: The locust is a medium-sized tree developing a slender straight trunk when grown alongside of others.
Black Locust Tree
Range: Canada and United States.
Black Locust Range
Soil and location: The locust will grow on almost any soil except a wet, heavy one. It requires plenty of light.

Enemies: The locust borer has done serious damage to this tree. The grubs of this insect burrow in the sapwood and kill the tree or make it unfit for commercial use. The locust miner is a beetle which is now annually defoliating trees of this species in large numbers.
Locust Borer
Value for planting: It has little value for ornamental planting.

Commercial value: Though short-lived, the locust grows very rapidly. It is extremely durable in contact with the soil and possesses great strength. It is therefore extensively grown for fenceposts and railroad ties. Locust posts will last from fifteen to twenty years. The wood is valuable for fuel.
Black Locust Wood
Other characters: The flowers are showy pea-shaped panicles appearing in May and June. The fruit is a small pod.
Black Locust Flowers
Other common names: Yellow locust; common locust; locust.

Comparisons: The honey locust (Gleditsia triacanthos) can be told from the black locust by the differences in their bark. In the honey locust the bark is not ridged, has a sort of dark iron-gray color and is often covered with clusters of stout, sharp-pointed thorns. The fruit is a large pod often remaining on the tree through the winter. This tree has an ornamental, but no commercial value.
Honey Locust Tree

Directions

Study the lesson for one week.

Over the week:

  • Read the lesson.
  • Review the synopsis.
  • Recite aloud the vocabulary words and their definitions.
  • Learn the concepts.
  • Complete the enrichment activities.
  • Study the review questions.

Synopsis

This lesson addresses the black locust, a flowering tree with compound leaves and a slender trunk. The flowers of the locust are pea-shaped panicles, arranged around a central axis of symmetry. The scientific (Latinized) name of the black locust is Robinia pseudacacia.

Vocabulary

Grub: The larva of an insect, especially a beetle.
Panicle: A loose branching cluster of flowers, in which the flowers are arranged along a single central axis of symmetry.
Axis: An imaginary line around which an object spins (an axis of rotation, e.g. the axis of a spinning top) or is symmetrically arranged (an axis of symmetry, e.g. the axis of the flowers of the black locust).

Concepts

PANICLES

  1. The flowers of the locust are pea-shaped panicles.
  2. A panicle is a loose branching cluster of flowers, in which the flowers are arranged along a single central axis of symmetry.

Study the examples of panicles below and identify their central axes.

  1. Buddleja forrestii Panicle
  2. Meadow Brome Panicle
  3. Panicled Oat Grass and Meadow Grass
  4. Reed Panicle

Enrichment

Activity 1: Narrate the Lesson

  • After reading or listening to the lesson, narrate the lesson aloud using your own words.

Activity 2: Study the Lesson Pictures

  • Study the lesson pictures and describe how they relate to the lesson.

Activity 3: Take a Nature Walk

  • Bring a small sketchbook and a specimen collection bag and embark on a nature walk.
  • If they grow in your area, seek out a black locust tree. Otherwise, either find a plant that grows panicles or choose another interesting tree to study.
  • Study and sketch the appearance and habitat of the tree.
  • Collect a leaf specimen from the tree.
  • Use the sketch and leaf specimen to create the field book entry.

Activity 4: Complete a Field Book Entry   

After your nature walk, complete page 47 in 'Science Field Book for Fourth Grade.'

Review

Question 1

What is a panicle?
1 / 2

Answer 1

A panicle is a cluster of flowers arranged about a central axis.
1 / 2

Question 2

Are the flowers of the black locust arranged around a central axis of rotation or symmetry?
2 / 2

Answer 2

The flowers of the black locust are arranged around a central axis of symmetry.
2 / 2

  1. What is a panicle? A panicle is a cluster of flowers arranged about a central axis.
  2. Are the flowers of the black locust arranged around a central axis of rotation or symmetry? The flowers of the black locust are arranged around a central axis of symmetry.

References

  1. 'Studies of Trees' by Jacob Joshua Levison. gutenberg.org/ebooks/16116. n.p.
  2. 'Panicle.' Wikipedia. Wikipedia.org. n.p.

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