Our gardens often have evergreen and deciduous plants at this time of the year. This distinction results from evolution, driven by environmental factors and survival strategies.

Evergreen plants retain their leaves year-round, replacing them gradually rather than shedding them all at once. The leaves are often rigid, thick and waxy, enabling them to withstand harsh conditions like drought, cold or nutrient-poor soils. Evergreen plants maintain their photosynthesis year-round, allowing them to take advantage of any favorable conditions, such as mild winters or sporadic rainfall.

In Mediterranean climates, such as the Monterey Bay area, evergreen plants like pines or cacti conserve water and energy, avoiding the energy-intensive process of regrowing leaves annually. Examples of Mediterranean evergreens include rosemary shrubs and olive trees.

Deciduous plants shed their leaves seasonally, typically in response to cold winters or dry seasons. This strategy minimizes energy expenditure and protects the plant from environmental stresses. Shedding leaves during unfavorable seasons reduces water loss and damage from frost, drought or nutrient scarcity.

Before shedding their leaves, deciduous plants reabsorb nutrients like nitrogen and phosphorus from their leaves, storing them in their stems and roots for future use. During this process, many leaves shrivel into brown color, while others turn vibrant shades of red, orange, yellow and purple.

Colorful deciduous leaves result from biological and chemical processes. Leaves are green because of chlorophyll, used in photosynthesis. During the deciduous period, chlorophyll production reduces, making other pigments visible. Carotenoid pigments produce yellow, orange and brown hues, while Anthocyanin pigments are responsible for red, purple and blue colors.

Some tree species produce vibrant colors in the fall due to genetic predisposition. For instance, sugar maples are known for their bright reds and oranges, while aspens display brilliant yellows.

Foliage colors all year

Evergreen succulent plants exhibit a range of foliage colors due to physiological, environmental and genetic factors. Stable colors reflect the plant’s evolution, while others change during current conditions.

These color variations have various purposes, from enhancing photosynthesis to protecting against environmental stresses.

An important factor is light intensity. High levels of sunlight can trigger increased production of protective pigments like anthocyanins, resulting in red, purple or bronze hues. Conversely, shaded conditions may reduce pigment intensity, leading to greener foliage.

Foliage colors can change in response to seasonal temperature variations and water availability. For example, lighter colors or waxy coatings may help reflect excess sunlight and reduce heat absorption. Color changes also can signal shifts in metabolism: some plants conserve water by opening stomata only at night.

Today’s image gallery includes examples from my garden of succulent plants and one monocot that displays attractive colors at this time of the year. One plant with green leaves is in bloom, while the others present colorful foliage.A creative gardener could group succulent plants to combine foliage colors to produce striking displays. In the traditional RYB color model, the complementary color pairs are red-green, yellow-purple and blue-orange. The red-green combination is readily available in the garden, while other color combinations would be more challenging. Visit Canva’s overview of the color wheel (canva.com/colors/color-wheel).

This week in the garden

We are just past the winter solstice (Dec. 21) that marks the change of seasons.

As you view your garden on this occasion, you might prefer more botanical color during this time of the year. If that’s your vision, the present is a good time to pursue that goal.

This involves planning the landscape for the future. We need not consider a distant future, but this season next year. As we recommended recently, “review your garden to identify areas you wish to improve and consider designs to develop and plants to install to achieve the improvement.” When your desired improvement focuses on seasonal color, the design project begins with identifying plants that produce appealingly colorful blossoms or foliage.

A good first step involves walking through your neighborhood to spot plants providing seasonal color. Make a list. If you can’t identify the plant, ask your neighbor who grows the plant or walk with a knowledgeable plant person. Another approach begins with using your cellphone to snap a clear image of the plant’s blossom, foliage or both for an online search. The internet is already effective with plant identification and is improving.

The popular Google search engine provides a quick and free plant ID tool. When opening a new window, click the “search by image” icon and upload your snapshot of the moment’s mystery plant. This is the world of artificial intelligence. As always with AI, verify the result of this search by entering the plant’s botanical name in a new search window.

If you wish to focus on California native plants, browse the California Native Plant Society’s Calscape website (calscape.org), click on “Find native plants,” and filter by “flowering season.”

This can be a productive garden project during a cold and rainy day.

Enjoy your garden!

Tom Karwin is a past president of Friends of the UC Santa Cruz Arboretum and the Monterey Bay Iris Society, a past president and Lifetime Member of the Monterey Bay Area Cactus & Succulent Society, and a Lifetime UC Master Gardener (Certified 1999-2009). He is now a board member of the Santa Cruz Hostel Society, and active with the Pacific Horticultural Society. To view photos from his garden, facebook.com/ongardeningcom-56651 1763375123. For garden coaching info and an archive of On Gardening columns, visit ongardening.com for earlier columns or visit santacruzsentinel.com and search for “Karwin” for more recent columns. Email comments or questions to gardening@karwin.com.