Next time you go for a walk in Upper Park, look closely at the different plants you see. Notice the enormous diversity of shapes, colors, and forms. There are trees, shrubs, perennials and annuals, all different shapes and sizes of leaves, and tremendous variation in flower color and structure from one species of plant to another. This diversity is the result of evolution over the ages. Plants have adapted to the specific conditions of their native habitat. These conditions include climate, availability of water, soil type, and interactions with other organisms. Adaptations can be structural or physiological.

Some plants have co-evolved along with their pollinators, resulting in flowers that have adaptations making them very suited to particular pollinators. There are more than 250 species of monkshood (genus Aconitum) worldwide. They are mostly found in moist meadows of mountainous area of North America, Europe and Asia. The flowers have structural adaptations to accommodate pollination by long-tongued bumblebees. Unlike most flowers, the sepals are not green but are the same color as the petals (usually blue). The 2 upper petals are large and tuck under a cylindrical “hood” formed by one of the sepals. This hood resembles a monk's hood of the Middle Ages. The petals have a hollow spur at their apex, which contains the nectar. Bumblebees are large and strong enough to open the flowers, crawl inside, and find the nectaries. The volume of the hood is large enough to accommodate the bumblebee as it crawls over the anthers and stigmas, picking up or depositing pollen along the way.

Plants that live in the desert have many adaptations to help them survive living in such a harsh environment. Some plants, like the barrel cactus, store water within the stems or trunk, and have spines or hairs that help shade the surface to cool the plant. Other plants, like the ocotillo, have small leaves that sprout quickly after a rainfall and fall off when the soil dries out. The ocotillo remains alive with partially green stems until the next rainfall. Blue palo verde (Parkinsonia florida) is a small multi-trunked tree with small compound leaves, bright yellow flowers, and green bark. Similarly to the ocotillo, the blue palo verde tree sheds its leaves when the weather is hot and dry. The tree doesn't go dormant at this time because photosynthesis also occurs in the bark. During the year, about two-thirds of the photosynthesis takes place in the bark and only one-third in the leaves.

The beavertail cactus (Opuntia basilaris) is a kind of prickly pear cactus. It lacks long spines but its flat, fleshy pads are covered with small bristles that have barbed tips. The bristles help shade the pads and also protect the cactus from being eaten. The pads themselves are modified stems. They have a waxy cuticle to reduce water loss and store water within. During periods of drought the pads shrivel and then plump back up when rain returns.

All plants have very small holes called stomata on the underside of their leaves.  The hole can open for exchange of carbon dioxide and oxygen gases or close to maintain the proper balance of water.  Most plants open their stomata during the day to take in carbon dioxide for photosynthesis. They close the stomata at night to retain water. Plants in the cactus family, plus some succulents and certain orchids, open their stomata at night and close them during the day. They have a modified photosynthetic cycle, called Crassulacean Acid Metabolism (CAM), which helps to reduce water loss during gas exchange. Carbon dioxide enters the open stomata at night when less water will be lost to the outside air. The carbon dioxide is then fixed and combined with another chemical to form an organic acid. The acid is then stored until the daytime when sunlight is available to finish the process of transforming it to sugar.  CAM is an example of a physiological adaptation.

The forests of the Coastal Redwood (Sequoia sempervirens) are lush, green, and typically receive a generous amount of rainfall during the winter but little rain during the summer. How do the redwoods survive the dry season? While the North Coast doesn't get much rain in the summer, it does have regular fog. Scientists have long suspected that redwood leaves, especially those near the top of the tree, are able to absorb water from fog without adversely affecting photosynthesis. When stomata are covered by even a thin film of water, the water can block the flow of carbon dioxide into the leaf, limiting photosynthesis.

How can redwood trees absorb enough water through their stomata without impairing photosynthesis?  In 2022 Alana Chin, a graduate student at UC Davis, and her colleagues examined numerous leaf shoots from redwoods in various geographic zones and noticed that each tree had two distinct types of redwood shoots. The two shoots had structural adaptations that made them either better suited for absorbing water or better suited for photosynthesizing.  Axial shoots have leaves that are pressed close to the twig, resembling an asparagus stalk. Peripheral shoots have needle-shaped leaves that extend outward from the twig on both sides and are thus exposed to more sunlight.  Leaves on axial shoots can easily trap moisture next to the twig and absorb it at about four times that rate of peripheral shoots. A tall redwood can absorb about 13 gallons of water in the first hour after getting wet. Peripheral shoots are superior at photosynthesis, having densely packed stomata and waxy, water-repellent coatings. Redwoods in drier southern areas have a greater concentration of axial shoots higher in the tree than trees in northern areas. If you have redwood trees planted as landscape trees in your neighborhood, take a look at their axial and peripheral shoots. Learn more about them in this Scientific American article, Redwoods Grow Weird Leaves to Suck Water from Air.

Snow plant (Sarcodes sanguinea) is quite unusual looking. The parts of the plant above ground (its flower stalk and flowers) are completely red; the underground root is white. It has neither leaves nor chlorophyll and cannot photosynthesize. How does it live? Its roots obtain nutrition from underground mycorrhizae, specialized underground fungi composed of strands of cells growing in the soil. Mycorrhizae, in turn, obtain nutrition from roots of the conifer trees growing nearby. For that reason snow plant is always found growing close to conifers.  The conifer trees rely on mycorrhizae to bring them water and minerals. The conifers and the mycorrhizae have a symbiotic relationship, while the snow plant is a parasite on the mycorrhizae. The flower stalk and flowers begin to grow in late spring, when the snow melts. The flower of the snow plant has five petals, which are mostly fused along their edges, resembling a bell. The snow plant's adaptations to its habitat are so specific that it would not be able to exist without mycorrhizae and conifers.

Think about plant adaptations when choosing plants for your garden. Generally speaking, the better a match between a plant's adaptations and the conditions in your garden, the better the plant will perform.  If you choose a plant native to an area that is much different from your garden, you will probably need to make some changes in your garden so it can provide for more of the plant's needs. 

Want to learn more about this topic? Attend our workshop on Adaptations of California Native Plants (Wednesday, May 22), part of the Master Gardeners' 2024 Spring Workshop Series. For information about all the workshops, and to register, visit our website.  All workshops are free, but registration is required.

PLANT SALE!  Mark your calendar for our plant sale on Saturday, May 18, 2024 from 9 am–noon.  The sale will be held at the Master Gardeners Demonstration Garden at Patrick Ranch.  The plants, which are selected to thrive in our climate, have been propagated by UC Master Gardeners of Butte County. For more information and a partial list of the plants that will available, visit our website.

UC Master Gardeners of Butte County are part of the University of California Cooperative Extension (UCCE) system.  To learn more about us and our upcoming events, and for help with gardening in our area visit our website.  If you have a gardening question or problem, email the Hotline at mgbutte@ucanr.edu or leave a phone message on our Hotline at 530-552-5812. To speak to a Master Gardener about a gardening issue, or to drop by the MG office during Hotline hours, see the most current information on our Ask Us section of our website.