Growing up in Milwaukee, autumn was a distinct season for me, with a predictable type of weather, namely, cool dry weather. Indian Summer was welcomed, with its brisk cool days and chilly nights, preceded by stout winds, requiring the wearing of two layers of sweatshirts. In Miami, autumn is more of a concept rather than a reality. Locals might refer to autumn as "less than monsoon" weather, or "not dripping sweat" weather, or even "almost tolerable" weather. The term "winter" is different for me than it would be for local residents. "Winter" is even more of a concept here than a reality. I prefer the term "finally, nice weather", rather than "winter". Another good term for winter would be "aha, no airconditioning bills".
For people, autumn is a welcome respite, the end of summer and the start of a new round of cooler-weather activities. In the landscape world though, the growing calendar for many plants is almost over. Humans feel the drier weather and intuitively feel the shortening of daylength. Plants use shorter days to shift into dormancy mode, with leaf and stem production slowing down, possibly cueing flower production to start. With these processes in mind, we need to be mindful of their needs in addition to our own.
Many flowering trees in our area react to daylength changes as much or more so than temperature. A good example of this can be seen in cities on the equator, where the daylength is equal all year long. Many of our iconic flowering trees like Royal Poinciana and Golden Shower Cassia don't flower very well on the equator because the trees don't know when to stop growing leaves and start growing flowers. Our daylength makes plants change their habits, so we should assist them where possible. With dormancy comes a reduced need for fertilizer and water for many plants. Some trees and plants need a combination of factors to grow and flower best.
Bougainvilleas especially need a dry and fertilizer-free rest period in addition to shorter days to cue them into flowering. One of the primary reasons for bougainvilleas not to flower is that they get too much water and fertilizer in the short-day period. Bougainvilleas thrive on our climate where they get lots of heat and rain in the long days, not so much in the short days. Turf grasses also slow down in the shorter days of autumn and winter. With these considerations in mind, pay attention ! Reduce watering and fertilizing starting now, reducing the watering frequency to once every 7-10 days, and even less in December through end of March. My own recommendation is to water turf when it wilts. The best flowering tree blooming comes after prolonged drought in the short day months.
If you have lived in the area for more than 25 years, you may remember when the winters were cool and rain-free for a month at a time or longer. Long time residents remember the prolonged droughts in the winter months, followed by exceptional flowering tree blooms. Many trees and landscape plants are well adapted to periodic droughts, but humans seem less adapted. One would think that people would take notice of the fabulous blooms which arise at the tail end of a drought. Yet so many residents insist on watering on the same schedule year round. Here is the basic set of ideas for autumn:
- reduce watering by 50% now.
- the last scheduled fertilizing for landscaping for the calendar year should be in October.
- if you choose a weed-and-feed grass fertilizer use it after the daytime temperatures stay below 82 F.
- for plants that need drought to flower such as bougainvillea or some flowering trees, you can stop watering now. Water only when the plants wilt or show signs of leaf drop.
- choosing a low-nitrogen fertilizer for the last fertilizing of the year will help slow plant growth, further assisting plants to rest for the winter.
- if you plant annual plants for the winter, use slow release fertilizer mixed into the soil to keep the plants well fertilized without overfeeding them and causing soft growth that might get winter damaged.