When the Garden Conservancy started work to bring the Gardens of Alcatraz back to life after forty years of neglect, one of the fascinating aspects of the project was the plant life still surviving on the island. In 2005, an island wide survey was done and we found just over 200 different species of plants!

As most gardeners are also ‘list makers’, and like keeping track of new plantings and when the plants bloom, we started to keep track of the flowering times.

Beginning in 2009, we made simple lists by the season of what was in bloom. Our spreadsheets have gotten a bit more elaborate since then. We still list each species of plant, but also record which garden it is blooming in, if the blooming is just starting, in full bloom, or is fading.

Comparing the same months and the same gardens over the years tells us some interesting facts.

The most obvious is that we have WAY more plants blooming on the island now that we did in 2009! We do try to be consistent when we take our observations – so we aim for the same week each month. In 2009, we reached our peak number of plants in bloom in the spring with 80 different plants blooming. This year, in May, we reached 156 different plants blooming – almost double from only four years ago!

The gardens are pretty much all over the island, creating microclimates of sun versus shade, leeward versus windward, and watered plants versus ‘on your own’ plants. The survivor plants are great for looking at how these microclimates affect the blooming times under these conditions.

Persian carpet is a historic island plant that can be found in most of the restored gardens around the island. The Persian carpet on the south facing slopes began to bloom in February this year but in December 2010, we had a scattering of blooms in all the different gardens. The Persian carpet finished

Persian carpet. Photo by Shelagh Fritz

blooming on the south facing slopes last month but is still going strong on the East facing slopes. Planting the same plant with different sun exposures not only lengthens the blooming time, but it also allows more visitors to the island see this wonderful historic plant in bloom.

Another garden survivor that has had some subtle changes to its blooming time is Centranthus ruber, Jupiter’s Beard. In 2010, it started to bloom in the spring as it normally does and then finished in late September. Comparing the bloom times of 2012, the centranthus bloomed every month of the year!

Centranthus ruber. Photo by Shelagh Fritz

We will also have to now start tracking the weather conditions and the amount of rain and fog to really get a better picture of why the plants are blooming at such different times.