Tom Karwin, on gardening | Locate garden plants – Santa Cruz Sentinel


Take care of your garden

We now continue the seasonal focus on garden development, given the timely installation of new plants as we enter the rainy season (after a long wait).

The basics of garden development are the selection and placement of plants. Let’s focus on the placement.


An overview is about spacing. Some gardeners prefer to keep spaces between plants, allowing each plant to display its unique qualities. This approach can be effective especially with a collection of cultivars within the same genus, for example, a bed of roses, designed to exhibit differences between individual plants. Spaces between plants can be filled with mulch or a low ground cover, to limit weed growth.

Alternatively, providing just enough space for each plant to reach its full grown width can provide an aesthetically pleasing design and effective weed control. Narrow spacing requires more plants per square foot than open spacing. It also requires learning the possible size of each plant and patiently waiting for its growth to reach the intended conception.

An open spacing error can occur when the gardener tries to limit expenses by “filling” an area with a limited number of plants that will not grow large enough for a good effect. A better approach to planting seeds or annual flowering plant starts to complement small perennials or shrubs while they are growing.

Natural grouping

Another important aspect of plant placement concerns the relationships between plants.

The natural grouping of plants includes colonies and companions. Plants form colonies by propagating by dropping seeds; spread out the runners; create offsets; and the increase of bulbs, rhizomes, tubers, etc. Plant colonies are usually tightly clustered near the parent, but when the seeds are dispersed by wind, birds, or animals, the results can be either widespread or isolated plants.

Companion plants in nature are simply those that grow next to each other in a given habitat, which can be a forest, forest, meadow, or desert. The larger concept, a biotic community, is a group of plants and other organisms that live together and interact with each other within an environment or habitat. For the record, the even broader concept, which includes the physical environment, is an ecosystem.

The ecological design of your garden (too broad a subject for this column) includes taking into account the fauna as well as your plants.

The gardener could tightly group the plants using natural guidelines by grouping multiple specimens of a selected plant. The usual practice is to form groups of odd numbers of plants: three, five, seven, etc.

To simulate wide natural plant spacing, the gardener could install drifts or repeats of a selected plant. Repeating locations should be close enough to each other to suggest the dispersal of plants by nature.

Following Nature’s companion planting pattern might force the gardener to study the chosen habitat, as plant hunters do, as can be seen in some webinars. (Last week’s webinar, with “Oaxaca Meanderings in Search of Succulents” by Kelly Griffin was one example.)

A simpler approach is to delve into the literature of the chosen habitat. One strategy available for native California plants is to visit the California Native Plant Society website:, which provides the Calscape Garden Planner to help you find “plants unique to your zip code and design ideas.” for a range of landscaping styles ”. Remember that habitats include microclimates, so not all plants growing in a given zip code are necessarily natural companions.

Aesthetic grouping

Instead of following nature’s guidelines, the gardener could place the plants in such a way as to provide aesthetic pleasure, or at least interest. The main variables include the size of the plant, the shape and color of the leaves and the color of the flowers.

Plant size groups usually follow the rule of thumb of “taller plants in the back”, but exceptions may use plants with an open structure, for example, in the foreground. To learn more about this grouping, visit

When grouping plants by leaf shape, the usual practice is to include contrasting shapes or colors. While grouping plants with similar leaf shapes or colors together can be nice, it’s hard to imagine three trees with red leaves in a group. However, it can be interesting to combine dwarf evergreen shrubs that have similar needles but different shades of green.

Plant groupings based on the color of flowers could emphasize a single color, for example the famous white garden at Sissinghurst Castle, or use the color wheel to form analogous, complementary, triadic or tetradic color combinations.

Many plants can be aesthetically grouped together for a good effect. The success of the design will depend on the viewer, so pursue your vision. Yet even though we never say never, and a bold design might be a worthwhile experiment, the clustering of plants from disparate habitats might disappoint. Pairing a rose and a cactus, for example, might not win a design competition.

Enrich your gardening days

A good project in your garden would be to assess current plant locations or plan new groups in a developing garden. If you determine that some existing plants could be grouped differently for better effect, the current season is a good time to rearrange the plants or add plants to create a pleasant display.

Enjoy your garden!

Tom Karwin is the past president of the Friends of the UC Santa Cruz Arboretum, the Monterey Bay Area Cactus & Succulent Society, and the Monterey Bay Iris Society, and UC Lifetime Master Gardener (certified 1999- 2009). He is now a board member and garden coach for the Santa Cruz Hostel Society. To view daily photos of his garden, To find an archive of previous gardening columns, visit Contact him with comments or questions at

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