Earth Day typically involve activities that focus on native plants and restoring habitats, but the day was also an opportunity to demonstrate that gardeners can landscape with drought tolerant non-native plants that are not invasive. Hosting a garden table with Alcatraz Cruises’ Earth Day celebration last week was a chance to highlight plants growing on Alcatraz, that while not native, are extremely well suited to the climate they have been thriving in.
From over 200 species of plants that survived the closure of the prison five plants were chosen to be on display. Each of the five plants has different adaptions to coping with drought, wind, poor soil and sun exposure.
The first plant always receives a lot of attention – Aeonium arboreum, or hens and chicks as most people call it. This succulent is able to store water in its fleshy leaves, and will drop the lower leaves when water becomes scarce. Producing few seeds, the plant mainly propagates itself by the forming roots along its stem. The roots will grow downwards, seeking any soil to root into. The plant is able to thrive in poor soil; I have even seen a massive clump of aeonium growing out of 5 inches of debris that had accumulated on top of a tunnel entrance.
Another popular succulent is Persian carpet. This little beauty is coloring the hillsides of the island pink right now. As tiny as the leaves are, they store water and the slightly dimpled leaves reflect light. The ice plant is great for stabilizing poor soils. Although an ice plant, this little guy is not the common invasive ice plant that is often seen along freeways.
A common garden plant in the 1940s and 50s was Pelargoniums, commonly known as geraniums. Pelargoniums are from the Southern Hemisphere and are from the
Mediterranean regions of South Africa. Five different cultivars survived on the island. The rough leaves reflect light, as well as the plant will drop its lower leaves when stressed by drought. It is not known exactly how, but the scented leaves of pelargonium are thought to be a survival mechanism.
Another survivor is the common garden nasturtium. It is surprising that the fleshy green round leaves are able to cope with the strong winds and lack of water, but these annuals have been self-seeding since they were introduced in 1924. They are able to complete their life cycle by the time water is becoming scarce in the soil.
Many visitors are surprised to see Calla lilies
thriving in the gardens. The callas, growing from a rhizome, are able to grow with the rains and then store energy for next year’s growth. The arrow shaped leaves will even funnel water to the roots. As we don’t water our callas, they do go dormant, the green leaves fading to yellow.
Growing a garden with just native plants is a wonderful goal, but gardeners can also select suitable plants for their area that are not native. Taking a walk around Alcatraz this month really shows how dramatic creating garden on a bare rock with non-natives can be.