Olive Trees — Sebastian, Florida

An olive tree will grow in Sebastian and keep its gray-green leaves all year, but fruit this far south is unreliable, because olive flowering is driven by winter chilling and Sebastian winters are short.

The UF/IFAS olive landscape guide (EDIS ENH1254) states that initiation of flowering time is driven by winter chilling for removing dormancy (UF/IFAS EDIS). The same guide calls olive a relatively new commercial crop to Florida whose cultural requirements are not completely known, with research ongoing on the varieties best suited to the Southeast. For a Sebastian yard, that means no published UF/IFAS cultivar list promises a crop on the Indian River Lagoon.

Gardening Solutions, the UF/IFAS home gardening site, is blunt about geography: researchers have been testing olive trees as far south as Orlando, and growers further south will have to decide whether it is worth the chance or wait for more research (UF/IFAS Gardening Solutions). Sebastian sits south of Orlando on the Treasure Coast, so an olive planted in the Sebastian Highlands or along Indian River Drive is, by that description, a trial rather than a sure thing.

What the tree does reliably in Sebastian is look like an olive. Its silvery foliage and tolerance of sandy ground make it a landscape plant first, and any olives that set in a cool year are a bonus rather than the reason to plant it.

The Vero Beach weather record kept by the National Weather Service in Melbourne, in the same county as Sebastian, shows a median of 221 days a year with no temperature below 50 degrees F (NWS Melbourne).

The NWS table tracks the last spring reading and the first fall reading below 50 degrees F at Vero Beach each year from 1950, updated through 2017. At the median, the cool season in Indian River County opens on November 13 and closes on April 5. Some years barely have one: the longest stretch with no sub-50 reading was 287 days in 2015-16, when the first fall reading did not arrive until January 11 (NWS Melbourne).

Olive bloom lands at the end of that window. Gardening Solutions says white flowers appear in April or May in Florida and precede the fruit set (UF/IFAS Gardening Solutions), which in Sebastian is the same stretch when the Vero Beach record shows the last cool nights tapering off.

UF/IFAS research has targeted that chill gap. The Indian River Research and Education Center in Fort Pierce reported on February 2, 2023 that a UF/IFAS project aims to identify an olive tree that will produce fruit in Southwest Florida with fewer chill hours required to flower (UF/IFAS IRREC). Until a cultivar like that is named, Sebastian growers are working with trees bred for longer winters.

Arbequina, from Spain, has been the most popular olive in Florida, and UF/IFAS says Koroneiki and Arbosona are often planted to support its pollination, the same pairing a Sebastian yard with room for two trees can copy (UF/IFAS Gardening Solutions).

Pollination is where olives get complicated in Sebastian and everywhere else in Florida. The EDIS guide explains that one olive tree can carry male, female and perfect flowers, that the cultivars Leccino, Pendolino, Moraiolo and Maurino are self-sterile and require pollen from another cultivar, and that multiple trees of the same clone cannot pollinate each other (UF/IFAS EDIS). Cross-pollination between two distinctly different cultivars can produce fruit, though some pairs do not work as pollinizers for each other.

Florida olive acreage is still small. The IRREC article reports that 800 Florida acres were under olive cultivation in 2020, with 60 to 80 farms in 20 counties, according to the president of the Florida Olive Council, and that over ten years researchers planted 25 commercial olive cultivars at 30 research and private orchard sites (UF/IFAS IRREC). The newer UF/IFAS trials were set at Jay and Wauchula, which the article says bookend the northern and southern extremes of Florida olive production, so no trial site sits on the Indian River Lagoon near Sebastian.

In Sebastian, an olive belongs on the sunniest, best-drained sand on the lot and away from low spots that hold rain, since UF/IFAS warns that olives are susceptible to root rot in moist or wet soils (UF/IFAS EDIS).

The EDIS guide says olives grow well on almost any well-drained soil up to a pH of 8.5, are tolerant of mild saline conditions, and do best on sand-dominated soils. A dry, sandy rise in a Sebastian Highlands yard fits that description; a swale that floods after a summer storm does not. Salt tolerance is described only as mild, which counts on lagoon-front lots along Indian River Drive.

Size is easy to underestimate. EDIS reports canopies up to 30 ft on highly fertile soils and says olives can be kept as hedges with 8 to 10 ft between plants in a row (UF/IFAS EDIS). The guide adds that tree size should be considered during variety selection so as not to interfere with permanent structures, a real limit on a Sebastian house lot.

Feeding is light. UF/IFAS says nutrient requirements are low, that trees do not produce well on highly fertile soils, and that excessive nitrogen favors shoot growth over fruiting. The UF/IFAS olive nutrition guide names nitrogen, boron and potassium as the primary concerns and notes that boron and potassium may be leached rapidly in sandy Florida soils, with a goal of 8 to 20 inches of new shoot growth per year (UF/IFAS EDIS AG405). That is a useful yardstick in Sebastian sand.

Local fertilizer rules apply as well. The City of Sebastian lists its own City Fertilizer Ordinance and a list of ordinance compliant fertilizers on its Florida Landscaping page (City of Sebastian). Indian River County Ordinance No. 2013-012, which the county says applies in the unincorporated areas, bars fertilizer between June 1 and September 30 but exempts trees grown for their edible fruit (Indian River County).

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UF/IFAS gives three to four years before an olive reaches bearing age and describes alternating heavy and light crops, though in Sebastian whether a tree bears at all depends on winter chill (UF/IFAS Gardening Solutions).

Gardening Solutions says fruit should begin to appear after three years, while the EDIS guide says trees grown from cuttings or grafts reach bearing age in about four years (UF/IFAS EDIS). Both describe olives as alternate-year bearers. In a heavy year, Gardening Solutions suggests thinning to two to three fruits per foot of twig soon after fruit set to increase fruit size. Olives are usually too bitter to eat straight off a Sebastian tree and are cured or pressed instead.

Pruning affects any future crop on a Sebastian tree. The olive never bears fruit twice in the same place on a stem, so new growth each year is essential to flower and fruit production the following year, and EDIS calls pruning tricky for that reason.

In Indian River County, cold matters more for the fruit than for the tree. EDIS says olives may be grown where winter temperatures do not drop below 12°F, but green fruits may be damaged at about 28°F (UF/IFAS EDIS), and Gardening Solutions advises protection if winter temperatures drop below 20 degrees. Pests are few: scale insects with sooty mold, plus caterpillar and grasshopper feeding on leaves.

Help is close by. UF/IFAS Extension Indian River County Master Gardeners hold a plant clinic at the North IRC Library, 1001 Sebastian Blvd. (CR512), on Wednesdays from 10:00am to 12:00pm, and at the Vero Beach office at 7961 58th Avenue on weekdays, phone (772) 226-4324; volunteers also perform soil pH tests in the lab (UF/IFAS Extension Indian River County).