Added Frida's suggestions.

Code is more readable.
Use an enum instead of storing plants as strings.
Use a List rather than an Array.
More minor stuff.

exercises/kindergarten-garden/src/example/java/KindergartenGarden.java

 import java.util.Arrays;
+import java.util.List;
+import java.util.ArrayList;
+
 
 public class KindergartenGarden {
     private String[] students;
     private String garden;
-    final int PARTITION_SIZE_WIDTH = 2;
-    final static String[] DEFAULT_STUDENTS = {
+    private final int PLANTS_PER_STUDENT_PER_ROW = 2;
+    private int NEW_ROW_LOCATION;
+
+    private final static String[] DEFAULT_STUDENTS = {
             "Alice", "Bob", "Charlie", "David",
             "Eve", "Fred", "Ginny", "Harriet",
             "Ileana", "Joseph", "Kincaid", "Larry"
         this.garden = garden;
         Arrays.sort(students);
         this.students = students;
+        NEW_ROW_LOCATION = garden.indexOf('\n') + 1;
     }
 
     public KindergartenGarden(String garden) {
         this(garden, DEFAULT_STUDENTS);
     }
 
-    public String[] getPlantsOfStudent(String student) {
-        String[] plants = new String[PARTITION_SIZE_WIDTH * 2];
-        int studentPlantsIndex = Arrays.binarySearch(students, student) * PARTITION_SIZE_WIDTH;
+    public Plant[] getPlantsOfStudent(String student) {
+        List<Plant> plants = new ArrayList<Plant>();
+        int studentPlantsIndex = Arrays.binarySearch(students, student) * PLANTS_PER_STUDENT_PER_ROW;
 
-        for (int i = 0; i < PARTITION_SIZE_WIDTH; i++) {
-            plants[i] = getPlantName(garden.charAt(studentPlantsIndex + i));
+        for (int i = studentPlantsIndex; i < studentPlantsIndex + PLANTS_PER_STUDENT_PER_ROW; i++) {
+            plants.add(Plant.getPlant(garden.charAt(i)));
         }
 
-        int newRowLocation = garden.indexOf('\n');
-
-        for (int i = PARTITION_SIZE_WIDTH; i < PARTITION_SIZE_WIDTH * 2; i++) {
-            plants[i] = getPlantName(garden.charAt(newRowLocation - 1 + studentPlantsIndex + i));
-        }
-
-        return plants;
-    }
-
-    public String getPlantName(char plantCode) {
-        switch (plantCode) {
-            case 'G':
-                return "grass";
-            case 'C':
-                return "clover";
-            case 'R':
-                return "radishes";
-            case 'V':
-                return "violets";
+        for (int i = NEW_ROW_LOCATION + studentPlantsIndex;
+             i < NEW_ROW_LOCATION + studentPlantsIndex + PLANTS_PER_STUDENT_PER_ROW; i++) {
+            plants.add(Plant.getPlant(garden.charAt(i)));
         }
 
-        return null;
+        return plants.toArray(new Plant[0]);
     }
 }

exercises/kindergarten-garden/src/example/java/Plant.java

+public enum Plant {
+    VIOLETS,
+    RADISHES,
+    CLOVER,
+    GRASS;
+
+    public static Plant getPlant(char plantCode) {
+        switch (plantCode) {
+            case 'G':
+                return GRASS;
+            case 'C':
+                return CLOVER;
+            case 'R':
+                return RADISHES;
+            case 'V':
+                return VIOLETS;
+        }
+
+        return null;
+    }
+}

exercises/kindergarten-garden/src/main/java/KindergartenGarden.java

 public class KindergartenGarden {
-    public KindergartenGarden(String garden) {
-        throw new UnsupportedOperationException("Method has not been implemented yet.");
+    public KindergartenGarden(String garden, String[] students) {
+        throw new UnsupportedOperationException("Delete this statement and write your own implementation.");
     }
 
-    public KindergartenGarden(String garden, String[] students) {
-        throw new UnsupportedOperationException("Method has not been implemented yet.");
+    public KindergartenGarden(String garden) {
+        throw new UnsupportedOperationException("Delete this statement and write your own implementation.");
     }
 
-    public String[] getStudentPlants(String student) {
-        throw new UnsupportedOperationException("Method has not been implemented yet.");
+    public Plant[] getPlantsOfStudent(String student) {
+        throw new UnsupportedOperationException("Delete this statement and write your own implementation.");
     }
 }

exercises/kindergarten-garden/src/main/java/Plant.java

+public enum Plant {
+    VIOLETS,
+    RADISHES,
+    CLOVER,
+    GRASS;
+
+    public static Plant getPlant(char plantCode) {
+        switch (plantCode) {
+            case 'G':
+                return GRASS;
+            case 'C':
+                return CLOVER;
+            case 'R':
+                return RADISHES;
+            case 'V':
+                return VIOLETS;
+        }
+
+        return null;
+    }
+}

exercises/kindergarten-garden/src/test/java/KindergartenGardenTest.java

 import static org.junit.Assert.assertEquals;
 
 public class KindergartenGardenTest {
+
     @Test
     public void singleStudent() {
         String student = "Alice";
         String plants = "RC\nGG";
-        String[] expected = {"radishes", "clover", "grass", "grass"};
+        Plant[] expected = {Plant.RADISHES, Plant.CLOVER, Plant.GRASS, Plant.GRASS};
 
-        assertEquals(expected, new KindergartenGarden(plants)
-                .getPlantsOfStudent(student));
+        assertEquals(expected,
+                new KindergartenGarden(plants).getPlantsOfStudent(student));
     }
 
     @Ignore("Remove to run test")
     public void singleStudent2() {
         String student = "Alice";
         String plants = "VC\nRC";
-        String[] expected = {"violets", "clover", "radishes", "clover"};
+        Plant[] expected = {Plant.VIOLETS, Plant.CLOVER, Plant.RADISHES, Plant.CLOVER};
 
-        assertEquals(expected, new KindergartenGarden(plants)
-                .getPlantsOfStudent(student));
+        assertEquals(expected,
+                new KindergartenGarden(plants).getPlantsOfStudent(student));
     }
 
     @Ignore("Remove to run test")
     public void twoStudents() {
         String student = "Bob";
         String plants = "VVCG\nVVRC";
-        String[] expected = {"clover", "grass", "radishes", "clover"};
+        Plant[] expected = {Plant.CLOVER, Plant.GRASS, Plant.RADISHES, Plant.CLOVER};
 
-        assertEquals(expected, new KindergartenGarden(plants)
-                .getPlantsOfStudent(student));
+        assertEquals(expected,
+                new KindergartenGarden(plants).getPlantsOfStudent(student));
     }
 
     @Ignore("Remove to run test")
     public void oneGardenSecondStudent() {
         String student = "Bob";
         String plants = "VVCCGG\nVVCCGG";
-        String[] expected = {"clover", "clover", "clover", "clover"};
+        Plant[] expected = {Plant.CLOVER, Plant.CLOVER, Plant.CLOVER, Plant.CLOVER};
 
-        assertEquals(expected, new KindergartenGarden(plants)
-                .getPlantsOfStudent(student));
+        assertEquals(expected,
+                new KindergartenGarden(plants).getPlantsOfStudent(student));
     }
 
     @Ignore("Remove to run test")
     public void oneGardenThirdStudent() {
         String student = "Charlie";
         String plants = "VVCCGG\nVVCCGG";
-        String[] expected = {"grass", "grass", "grass", "grass"};
+        Plant[] expected = {Plant.GRASS, Plant.GRASS, Plant.GRASS, Plant.GRASS};
 
-        assertEquals(expected, new KindergartenGarden(plants)
-                .getPlantsOfStudent(student));
+        assertEquals(expected,
+                new KindergartenGarden(plants).getPlantsOfStudent(student));
     }
 
     @Ignore("Remove to run test")
     public void fullGardenFirstStudent() {
         String student = "Alice";
         String plants = "VRCGVVRVCGGCCGVRGCVCGCGV\nVRCCCGCRRGVCGCRVVCVGCGCV";
-        String[] expected = {"violets", "radishes", "violets", "radishes"};
+        Plant[] expected = {Plant.VIOLETS, Plant.RADISHES, Plant.VIOLETS, Plant.RADISHES};
 
-        assertEquals(expected, new KindergartenGarden(plants)
-                .getPlantsOfStudent(student));
+        assertEquals(expected,
+                new KindergartenGarden(plants).getPlantsOfStudent(student));
     }
 
     @Ignore("Remove to run test")
     public void fullGardenSecondStudent() {
         String student = "Bob";
         String plants = "VRCGVVRVCGGCCGVRGCVCGCGV\nVRCCCGCRRGVCGCRVVCVGCGCV";
-        String[] expected = {"clover", "grass", "clover", "clover"};
+        Plant[] expected = {Plant.CLOVER, Plant.GRASS, Plant.CLOVER, Plant.CLOVER};
 
-        assertEquals(expected, new KindergartenGarden(plants)
-                .getPlantsOfStudent(student));
+        assertEquals(expected,
+                new KindergartenGarden(plants).getPlantsOfStudent(student));
     }
 
     @Ignore("Remove to run test")
     public void fullGardenSecondToLastStudent() {
         String student = "Kincaid";
         String plants = "VRCGVVRVCGGCCGVRGCVCGCGV\nVRCCCGCRRGVCGCRVVCVGCGCV";
-        String[] expected = {"grass", "clover", "clover", "grass"};
+        Plant[] expected = {Plant.GRASS, Plant.CLOVER, Plant.CLOVER, Plant.GRASS};
 
-        assertEquals(expected, new KindergartenGarden(plants)
-                .getPlantsOfStudent(student));
+        assertEquals(expected,
+                new KindergartenGarden(plants).getPlantsOfStudent(student));
     }
 
     @Ignore("Remove to run test")
     public void fullGardenLastStudent() {
         String student = "Larry";
         String plants = "VRCGVVRVCGGCCGVRGCVCGCGV\nVRCCCGCRRGVCGCRVVCVGCGCV";
-        String[] expected = {"grass", "violets", "clover", "violets"};
+        Plant[] expected = {Plant.GRASS, Plant.VIOLETS, Plant.CLOVER, Plant.VIOLETS};
 
-        assertEquals(expected, new KindergartenGarden(plants)
-                .getPlantsOfStudent(student));
+        assertEquals(expected,
+                new KindergartenGarden(plants).getPlantsOfStudent(student));
     }
 
     @Ignore("Remove to run test")
         String[] studentArray = {"Samantha", "Patricia", "Xander", "Roger"};
         String student = "Patricia";
         String plants = "VCRRGVRG\nRVGCCGCV";
-        String[] expected = {"violets", "clover", "radishes", "violets"};
+        Plant[] expected = {Plant.VIOLETS, Plant.CLOVER, Plant.RADISHES, Plant.VIOLETS};
 
-        assertEquals(expected, new KindergartenGarden(plants, studentArray)
-                .getPlantsOfStudent(student));
+        assertEquals(expected,
+                new KindergartenGarden(plants).getPlantsOfStudent(student));
     }
 
     @Ignore("Remove to run test")
         String[] studentArray = {"Samantha", "Patricia", "Xander", "Roger"};
         String student = "Roger";
         String plants = "VCRRGVRG\nRVGCCGCV";
-        String[] expected = {"radishes", "radishes", "grass", "clover"};
+        Plant[] expected = {Plant.RADISHES, Plant.RADISHES, Plant.GRASS, Plant.CLOVER};
 
-        assertEquals(expected, new KindergartenGarden(plants, studentArray)
-                .getPlantsOfStudent(student));
+        assertEquals(expected,
+                new KindergartenGarden(plants).getPlantsOfStudent(student));
     }
 
     @Ignore("Remove to run test")
         String[] studentArray = {"Samantha", "Patricia", "Xander", "Roger"};
         String student = "Samantha";
         String plants = "VCRRGVRG\nRVGCCGCV";
-        String[] expected = {"grass", "violets", "clover", "grass"};
+        Plant[] expected = {Plant.GRASS, Plant.VIOLETS, Plant.CLOVER, Plant.GRASS};
 
-        assertEquals(expected, new KindergartenGarden(plants, studentArray)
-                .getPlantsOfStudent(student));
+        assertEquals(expected,
+                new KindergartenGarden(plants).getPlantsOfStudent(student));
     }
 
     @Ignore("Remove to run test")
         String[] studentArray = {"Samantha", "Patricia", "Xander", "Roger"};
         String student = "Xander";
         String plants = "VCRRGVRG\nRVGCCGCV";
-        String[] expected = {"radishes", "grass", "clover", "violets"};
+        Plant[] expected = {Plant.RADISHES, Plant.GRASS, Plant.CLOVER, Plant.VIOLETS};
 
-        assertEquals(expected, new KindergartenGarden(plants, studentArray)
-                .getPlantsOfStudent(student));
+        assertEquals(expected,
+                new KindergartenGarden(plants).getPlantsOfStudent(student));
     }
 }