Apologies for writing about the weather all of the time, but after this brain-frying summer and subsequent August and September superstorms, merely being able to go outside without burning skin or lungs is taken for granted through most of the world. Here, though, not only do we have the thrill of not risking second-degree burns for walking outside barefoot, but there the sheer joy of stepping outside and realizing “You know, it’s warmer inside than outside.” After four months of looking at digital thermometers with a combination of rage and horror, the real fun comes when talking about the weekend, mentioning “it’s 50 degrees in the shade,” and not having that refer to Celsius.
Because of the influx of this strange not-hot weather, the local flora responds the same way we humans do: with a mad rush to make up for lost time. This was a summer so brutal that anything bearing fruit or nuts requiring large amounts of water is just exploding right now, asking for a do-over. Plants that normally bloom in the early spring are going into overdrive at the end of September, and plants that bloom all year long don’t know what to do with themselves. Even better, the rush is on for night-blooming flowers of all sorts because the insects that depend upon them will be dying or going dormant soon, which means one thing. Yes, it’s time to get out into the garden with ultraviolet lights to view the fluorescence.
As brought up elsewhere, most of the commonly available “black light” LED flashlights and lanterns pump out far too much visible light to be effective at viewing plant fluorescence, as the visible light washes out fluorescence in anything but the strongest displays. The best affordable options for backyard naturalists involve violet laser pointers, which tend to throw off large amounts of UV, and beam splitters to turn that laser light into more of a laser flashlight. In a pinch, for financial reasons and for initial experiments, the wonderful crew at American Science & Surplus offer a very cost-effective compromise, the violet kaleidoscopic laser pointer.
(Disclaimer: ALWAYS use eye protection when using a laser. Read the laser’s user guide and all labels before using. Never point a laser at your own face, that of anybody else, that of animals, or at passing aircraft. Do not point a violet laser at any apparatus, such as camera lenses, that could be affected by ultraviolet light. If you decide to ignore this advice, the Texas Triffid Ranch and all entities associated with it are not responsible, either legally or financially, for physical, mental, or financial damages. Let’s have a little common sense here, kids.)
The big advantage with the kaleidoscopic laser pointer is that for basic experiments in plant fluorescence, the pointer already comes with a diffraction grate to spread the beam around and offer endless entertainment for cats and Pink Floyd fans. Setting the pointer’s grate so it diffuses the beam the most may affect the ability to take images or video of the fluorescence effect, and anyone wanting to understand the limits of that fluorescence should consider working with a beam splitter. For quick and dirty observation in a garden environment, though, it can’t be beat.
The photo at the top of this article sums up the situation. The white pitcher plant, Sarracenia leucophylla, not only fluoresces blue along the pitcher lip under UV, but the whole top of the pitcher famously fluoresces under moonlight. The photo doesn’t do the fluorescence justice: laser pointer use not only fluoresces the upper third of the pitcher, but it attracts local moths and other nocturnal insects even more so than usual. The effect on other Sarracenia is muted under moonlight or general light pollution, so the best results come from viewing after moonrise or moonset in an area without streetlights.
Next, it’s time to test flowers already known for attracting nocturnal insects. In this case, the moonflower (Ipomoea alba) also stands out under moonlight, but the real surprise under UV is that its stamens are particularly brilliant. This helps explain why moonflowers are so popular with so many species of hawkmoth, and the plan is to test this theory next year with angel trumpets (Datura spp.) to see if they fluoresce the same way and intensity.
The real surprise in the garden this year? The spring attempt to get luffa squash (Luffa aegyptiaca) established ran right into our early summer, and the vines are only now starting to expand and produce female flowers. The flowers are also going the reverse of previous growing efforts, with the blooms opening in the evening and closing by sunrise.
That works out very well, to be honest, because luffa blooms fluoresce slightly, but the pollen fluoresces much more. On a still night, the pollen all over the bloom makes the bloom under UV look as if it were dusted with glow powder. Get too close with a camera, and the glow off luffa pollen will wash out everything else.
Naturally, this is only the beginning of experimentation. We still have at least a month in Dallas before the standard growing season is complete and all of the carnivores start going into dormancy, with so many carnivores with UV secrets. Even better, the moon is currently new, so the nights are dark even with the moon above the horizon. Expect all sorts of discoveries.