P90629KKIncandescent light bulbs were the standard form of electric lighting for more than a century after their invention. It took a while for fluorescent and halogen lamps to become popular; and by the time they did, high intensity discharge (HID) lamps had already become available. Nowadays, light emitting diode (LED) lamps seem to be replacing all sorts of electric lighting.
For a brief time in the late 1980s, high intensity lamps that were being used for large scale applications and street lamps became a fad for exterior household lighting. They worked nicely for driveways, so many of us believed that they would work just as nicely for night lighting of home gardens and patios.
By that time, most of us had realized that the sickly yellowish glare of the sodium vapor type of high intensity lamps that were so common as street lamps was not at all appealing around the home, and was downright unflattering for foliage and flowers in the garden. Mercury vapor high intensity lamps became more popular for such applications instead, even though their slightly bluish bright glare is no more inviting.
During this time, while the renowned landscape designer Brent Green and I were still studying horticulture at Cal Poly in San Luis Obispo, his father had a rather fancy mercury vapor lamp installed in his backyard.
Of course, Brent was furious! He had put so much effort into cultivating a remarkably inviting outdoor living space, only to have it illuminated at night like an industrial warehouse. When turned on, the lamp made a constant buzzing hum. It hung from a wall like a big glowing paper wasp nest. Brent referred to it at the ‘beehive’.
The quality of light produced by modern electrical light sources has fortunately improved since then. Nonetheless, contraptions such as this street lamp suspended on an otherwise exemplary ponderosa pine are not easy to warm up to.

The Late Show

P80425Color in the garden is nice as long as we can see it. There is not so much to see after the sun goes down. That is why some gardens that get used at night are illuminated.

Sometimes it is important to illuminate walkways, driveways and stairways for safety, even if exhibiting the landscape is not important. For such applications, the quality of the light is not as important. Sodium vapor light that works so well for street lamps can make plants look rather sickly. Mercury vapor lamps can make them seem rather pale and bland. Modern LED lamps just look creepy.

So, what happens when foliage that already looks sickly get illuminated by light that enhances the sickly appearance? Well, like many styles of contemporary art, it is a matter of taste . . . or perception . . . or some other big word that a horticulturist neither knows the meaning of, nor has any business using in a sentence.

Golden honeylocusts, as they mature, are not really sufficiently golden to be as pretty as they might look in gardening magazines. Young specimens look good with contrasting purple leaf plums, particularly where warm weather enhances the yellow color. By the time they grow into nice shade trees, and growth is not quite as vigorous as it used to be, the foliage is just rather light yellowish green. They are still very pretty trees, with lacy foliage and light shade that lawn or other plants can grow under. They are just neither here nor there; not bright yellow enough to be flashy, but not green enough to look lush. By that time, their only advantages are that they cast a lighter shade and stay somewhat smaller than those with richer green foliage.

Then the sun goes down. Honeylocusts with richer green foliage are just as bland as any other tree obscured by darkness. If illuminated, they might show off handsome trunks and branch structure, outfitted with distinguished furrowed bark, but not much more.P80425+

This is where the golden honeylocust shines. The paleness of the foliage, enhanced by efficient but aesthetically insensitive light, contrasts with the darkness. It can look spooky. It can look striking. It can look ethereal. I would not know, since I do not even know what that last word means. Regardless, these golden honeylocusts illuminated by common streetlamps in a parking lot at a strip mall really look sharp. It is doubtful that whomever designed the landscape planned it like this. It is just as doubtful than any reputable designer would ever recommend planting a specific cultivar of a long term tree to exploit bad lighting that could change as soon as something more efficient becomes available, but it happens to work in this particular application.P80425++