The Anatomy of a Prescribed Burn: 41 Days of Growth

If you’ve been following our social media over the past few weeks you may have read our blog post which featured the prescribed burn that was performed on March 20th in our natural areas adjacent to the gardens. Or perhaps you joined our Director of Horticulture, Brendan Huggins, on a virtual tour through the burned area highlighting the ecological history and importance of fire in Florida.

We want to take a moment to fully admire and appreciate the resilience and beauty of the plants in this fire-adapted landscape. The quick regeneration after the fire is awe-provoking, and seeing the boom of life after the total consumption of fire is a delight to witness. Fortunately, our members and visitors will be able to enjoy the beauty for themselves when we reopen the gardens later this month!

The plants in this ecosystem have adapted strategies to thrive with frequent fire, which was historically sparked by lightning in the spring and summer months. We now employ prescribed fire for safety reasons. In the post-fire environment there is less above-ground vegetation, an increasing amount of light to the soil surface, warming of the soil, and releasing nutrients into the soil that was previously bound to organic matter. All these things help plants resurge after the fire. Scientists have even found that the chemicals in smoke from the combustion of plant material induce the germination of seeds. Plants quickly respond to these newly available resources and are able to reallocate below-ground stored nutrients for above-ground regeneration. It’s not too long after a fire that the landscape goes from black to green and then dotted with color from wildflowers.

Here are a few of the extraordinary plants you will see and some interesting facts. Perhaps you’ll recognize these beautiful botanicals when you come to the Gardens and explore the Pine Ridge Preserve!

I think it’s only fitting, to begin with, the species that characterize this habitat, longleaf pine, Wiregrass, and saw palmetto.

Longleaf pine (Pinus palustris) is the dominant tree species in this habitat and can live for hundreds of years. Longleaf pines have an intimate relationship with fire and have adapted to thrive with fire. One important adaptation is that the meristem (the growing point) of the tree, that if damaged could kill the tree, is extremely resinous and is protected by a thick sheath of pine needles. Even a small young pine can escape mortality from the ferocious flames. In the photo you can see the protective layer of needles were scorched by the flames but the meristem is unscathed and producing new needles to replace those lost. (photo is 17 days post-fire)

Wiregrass (Aristida stricta) is the dominant grass species in sandhill that provides important groundcover habitat for wildlife. Wiregrass can flush out new growth just days after fire and scientists have discovered that only after a fire will wiregrass set viable seed. Seed viability declines between fire events. (17 days post-fire) Arguably the toughest plant in Florida is the saw palmetto (Serenoa repens). Notable for its prostrate rhizomes that trail along the ground in every which way and toothed petioles attached to the fronds. The waxy fronds are HIGHLY flammable. When the flames approach a patch of saw palmetto, every fire professional knows to take a step back and watch the show…cause things are about to get wild! First is the roar of the intensifying fire as the flames meet the fronds and then the raging flames ensue. The radiant heat is enough to send you back on your heels. The trunks, however, are extremely resistant to damage by fire and not only push out new growth after a fire but flower synchronously with fire. In the photo, the exposed tips of the fronds on the day of the fire were scorched, however, the rest of the frond was protected while encased in the trunk. (17 days post-fire)

Flowering saw palmetto.  (17 days post fire)

A fusion of the frond tips by the scorching fire caused this frond to emerge in an ornate geometric design.

Now we’ll branch out and highlight some charismatic herbaceous wildflowers.

Florida green eyes (Berlandaria subaculis) was the first wildflower to speckle the preserve with color. The yellow-ray flowers popped exquisitely against the charred surface of the soil. Just 25 days post fire! Mind you that at this point in time we had not received any substantial amount of rainfall. This wildflower has a subterranean tuber of stored reserves used for the rapid response after the fire.

A few days later more wildflowers began to add more color to the landscape.

Pictured are two members of the Euphorbiaceae family, Queens delight (Stillingia sylvatica) and Tread-softly (Cnidoscolus stimulosus). The latter, as you may have guessed from the common name, serves as a warning, look but don’t touch! Tread-softy, as you can see in the photo, is covered in utriculate hairs that if touched will release an irritant that causes contact dermatitis. I speak from experience…it’s several days of unpleasant burning, little blisters, and sensitivity. However, butterflies love visiting the flowers of this plant.

Queens delight (Stillingia sylvatica)
My Gardener’s Latin book tells me that the species name sylvatica relates to this plant “belonging to wild places.” So I suppose you can consider Pine Ridge Preserve a part of the wilds of Florida. (33 days post-fire)

Tread-softly (Cnidoscolus stimulosus)
Remember…look, don’t touch.

Two species belonging to the Commelinaceae family now adding pink and purple to the palette of the landscape. (41 days post-fire)

Florida Scrub Roseling (Callisia ornate), a Florida endemic species. (41 days post-fire)

Whitemouth Dayflower (Commelina erecta) (41 days post-fire)

Trailing Krameria (Krameria lanceolata) (49 days post-fire)

A pretty groundcover that’s popped up all over the preserve with reddish-orange little flowers. Another common name for this species is sandspur and refers to the super spiny fruits. As does the species name, lanceolata, relating to being armed with a lance or spear point.

Rose-rush (Lygodesmia aphylla) (49 days post-fire)
This one is a beauty. A tall and delicate aster, seemingly without leaves, as the species name, aphylla, implies and not very abundant.

We have several species of rare and endangered plants on the preserve as well. You may think we would be apprehensive to allow a rip-roaring fire to move through an area with such protected plants. However, these plants have adapted to periodically having their above-ground growth consumed by fire and are able to resurge in the post-fire environment.

Florida jujube (Ziziphus celata) (33 days post fire)

A clonal shrub adorned with thorn-tipped zigzag branches. This species was believed to be extinct until it’s rediscovery in 1987 and has been the subject of extensive research ever since, particularly due to its rarity and fussy breeding system.

Emerging Lewton’s Polygala (Polygala lewtonii)

A diminutive herb which can easily go unnoticed due to its small size, even when in full bloom. The interesting little pink flowers have two small dorsal petals and a third petal adorned with a feather-like crest. Plants are typically found in small colonies or clusters, not often scattered about with individual plants far from one another. It is believed that plants exist in these colonies because ants likely disperse the seeds, and the ants are only able to carry seeds short distances from the parent plant. (33 days post-fire)

Flowering Lewton’s Polygala (49 days post-fire)

Sweet-scented Pigeonwings (Clitoria fragrans) (Fabaceae) (49 days post-fire)The common name refers to the flowers resembling a bird with the wing-like petals attached to the keel.

Sweet-scented Pigeonwings (Clitoria fragrans) (Fabaceae) (49 days post-fire)

And finally… here is a landscape view of the “before and after” photos showing the progression after the fire on the Pine Ridge Preserve. Do yourself a favor when you visit the gardens and walk the preserve trail to see these extraordinary plants and surround yourself in the beauty of nature.

March 20, 2020 – photo taken the morning before the prescribed burn.

March 21, 2020 – photo taken the day after the burn. The only green color is in the pine canopy.

April 6, 2020 – pine needles scorched by the fire now cover the charred soil, and bits of green from the new flush of wiregrass are stippled among the pine needles.

April 22, 2020 – a little more green color is added as many woody and herbaceous plants begin to flush with new growth.

April 30, 2020 – a little rain helped things along…

May 20, 2020 – Now it’s difficult to notice that a fire ever happened. The ensuing summer rains will help add new growth and more color to this landscape over time, providing a sanctuary for our wildlife and visitors alike.

The blog was written and photographed by Whitney Costner, Conservation Biologist for Bok Tower Gardens’ Rare Plant Conservation Program.