The Small-Tree Fix

By William Scheick, Contributing Editor

Our search started with a swath of open space abutting an alleyway.

The weed-and-grit alleyway was hardly an ideal focal point every time we looked through the glass patio doors or stepped outside. It was time to consider screening-plant options, less for privacy than for beautification.

Most of my neighbors seemed to have relied on boxwoods, photinias and ligustrums. Unfortunately, recent years of more days with higher temperatures and less rainfall have stressed boxwoods, with some nearby ones having succumbed to a fatal viral blight.

While my neighbors’ red-tipped photinias grew quickly and obviously endured heat, several have now proved vulnerable to their humid settings. Entomosporium leaf spot destroyed their tips and eventually infected much more, just as this disease has savaged Indian hawthorn (Rhaphiolepis indica).

Ligustrums have by far remained the toughest of my neighbors’ non-native shrubs, an outcome that amounts to both good and bad news. Despite their high susceptibility to foliage-ruining powdery mildew, ligustrums produce abundant fruit that relentlessly invades surrounding terrain. This behavior results in their monocultural dominance, a pattern that displaces native floral species. In many Texas locales, ligustrums (like nandinas) conquer territory at an amazing pace.

Even if they were not environmentally problematic, all of these common hedging options offer rather tame and predictable vertical forms. The lackluster horizontal line of our chain-link fence and alleyway seemed to beg for plants providing a more extravagant counterpoint — options that would be environmentally suitable yet also “jazzy.”

The little-tree theme takes root

We settled on a little-tree theme defined (as it were) by “improvised variations” — twisty single or multi-trunks bearing slender limbs thrust outwardly here and there in hard-to-predict but appealing patterns. There is good reason for the nursery trade to refer to these plants as ornamentals or, in Skip Richter’s apt phrasing, “delightful little bloomin’ trees for Texas.”

One of Skip’s 12 recommendations made our winnowed list of four.

Drought resilience figured significantly in our decision-making. Multi-season droughts have emerged as a daunting challenge to our gardening efforts. In 2011, for instance, Texas endured the driest 12 months ever recorded in our state.

That year, our home in Gillespie County received a meager annual total of 11 inches of rain, with one of the wells servicing Fredericksburg dipping to 93.44 feet below ground level. By the end of June 2018 — only halfway into that year! — this same well (which should average 68.72 feet) read 91.09 feet below the surface. During those seven years, Fredericksburg has continued to strictly enforce stage-3 water-use restrictions.

During those same years, we have reluctantly removed four drought-damaged large trees from our property, including a sizeable chinkapin oak (Quercus muehlenbergii) that had graced half of our front yard. Although new plantings have slowly begun to replace them, the loss of these mature trees has diminished the curb-appeal of our property.

This tree-sustainability problem is hardly ours alone. Our home is located in a neighborhood where other once-beautiful and long-lived trees have now been hell-stricken by years of insufficient or ill-distributed precipitation.

So at this sorry ecological point, we considered (for that blah fence line) several small yet environmentally tough, drought-hardy specimen trees ranging in height from about 15 to 20 feet.

Vitex

Chaste tree (Vitex agnus-castus) receives rave reviews during June, when its hard-to-ignore lavender (uncommonly white) floral spikes abound and attract butterflies by the dozens.

For the rest of the year (unless grown as a tabletop bonsai) vitex tends to be a less dramatic plant. Few people would choose it over, say, Texas mountain laurel (Dermatophyllum secundiflorum [formerly Sophora secundiflora]).

For sheer beauty, there is no contest between the two. Texas mountain laurel offers an attractive evergreen pattern and wisteria-like flowers, whereas vitex defoliates after a single frost and grows in a spartanly meandering manner. So, unlike our popular mountain laurel, vitex definitely tests a gardener’s pruning ingenuity.

That’s a venial demerit, however. Other than attentive pruning for shape (including the possibility of basal management to promote a single trunk) or optional cutting back immediately after flowering to foster more blooms, vitex asks for nothing else.

From my perspective, a plant that requires nothing else deserves top-tier consideration. In well-drained soil, vitex remains vibrant through heat, drought and freezes as far north as hardiness zone 7. Its overall toughness has landed vitex on the recommendation list of Texas AgriLife Research, which particularly promotes the ‘Shoal Creek,’ ‘LeCompte’ and ‘Montrose Purple’ cultivars as Superstars.

Vitex seed, which can be used as a culinary spice known as monk’s pepper, germinates fairly easily in warm, moist soil and has apparently strayed into some Central Texas limestone outcrops and dry creeks. I have heard of only two such “escapes” in far-apart fields, where neither threatens their native companions and where both vitexes nurture local beneficial pollinators.

At our Oak Hill (Austin area) home, vitexes (contrary to our over-eager elms and pistaches) show no sign of seeding themselves nearby. Decades ago we planted three, and each one tutored us on vitex preferences.

The one located between two houses receives full daily sunlight for only two or so hours. It suckers madly and strives predominantly upward with merely modest attempts at branching out. No amount of strategic pruning has quite rescued it from a vertically scrunched, corridor look.

With a little help from pruning tools, on the other hand, another single-trunked front-yard vitex has achieved an exquisite bonsai-like form suitable for a Japanese garden. It rarely suckers. Leaving the unanswerable issue of genetic predisposition aside, half-day of full-sun exposure followed by light “broken” beneath live-oak canopies seems to have fostered this striking result. Clearly, to look its best, vitex needs plenty of time in direct sunlight.

Wafer ash

We also considered wafer ash (Ptelea trifoliata), another no-nonsense single or multi-trunked small tree with “improvisational” bushy effects. It grows easily and fairly quickly in a variety of Texas soils.

While it attains about the same height as vitex, flowers do not provide the knockout ornamental feature of this Lone Star native. Instead, its small, scented, greenish-white flowers quickly transform into attractive broad-winged fruits (samaras) that cling in clusters. Historically, these disk-like fruits have served as a hops substitute in beer brewing, which explains why this plant is also known as common hop tree.

Similar to vitex, wafer ash (which is not a true ash) endures heat and drought in draining soils. It likewise benefits pollinators, including native bees and various swallowtail butterfly species (for which it is also a host plant). Similar to vitex, too, wafer-ash foliage tastes bitter and emits a faint scent — features that can deter foraging deer.

Wafer ash shares vitex’s variability in shape, though much less starkly. And like vitex, wafer ash makes its preferences known. As a part-shade understory plant, it performs best as a little specimen tree in light-dappled settings. In fact, too much direct exposure to sunlight tends to result in a bushy contour rather than a small-tree look. Too much shade, on the other hand, impedes flowering, which means missing out on this tree’s outstanding feature — the broad-winged samaras that decorate wafer ash well into winter, even long after all of its foliage has dropped.

The equivocal reproductive behavior of wafer ash varies. Like yaupon holly (Ilex vomitoria) — an environmentally tough and evergreen “twisty” we also considered — wafer-ash trees tend to be dioecious. That means each one bears either female or male flowers.

Presumably long-term genetic benefits accrue from such outcrossing (allogamy) rather than relying on self-fertilization. However, sometimes several rule-breaking bisexual flowers emerge or sometimes several unexpected opposite-sex flowers appear on the same plant.

In any case, count on female wafer ashes, which will get pollinated one way or another, to put on a good samara show. When cultivated, these “disks” germinate easily, the new plant likely gaining height more slowly than vitex but more rapidly than Texas persimmon.

Texas persimmon

Texas persimmon (Diospyros texana), another multi-trunked shrub/small tree, made our list, too. Besides being heat and drought resistant, this low-care Texas native easily adapts to many draining soils, although it favors shallow, rocky, alkaline locales.

In my experience, it attains about the same height as vitex and wafer ash, but it retains foliage longer, usually well into winter. Being adventitiously sheltered beneath thin canopies helps this persimmon species restrict moisture loss during our desiccating summers, and so does the “fuzziness” along the underside of its foliage.

Like vitex, curvy Texas persimmon has long been cultivated as a bonsai. To mimic that look in a yard, strategic cutting is necessary, especially basal pruning to favor a single trunk (if that is preferred).

Unfortunately, the growth rate of Texas persimmon can be very slow — sometimes less than a foot a year! Eventually, the luminous paleness of its trunks reward the wait, particularly when their bark exfoliates (similar to crepemyrtles) to reveal patches of pastel gray, tan and pink.

As with wafer ash, Texas persimmon usually distinguishes between male and female flowers. Presumably only the female trees carry the abundant sweet, prune-tasting fruits — a human and avian treat that ripens from green to purple-black during August.

Even so, male trees have been known now and then to produce a few female flowers, just as female trees sometimes carry a few male flowers. Moreover, the patient cultivation of a female graft on a male Texas-persimmon rootstock amounts to a gender reassignment yielding a fruit-bearing crown.

Mexican buckeye

Mexican buckeye (Ungnadia speciosa), another Lone Star native preferring draining soils, shares the heat and drought resilience of Texas persimmon, wafer ash and vitex.

Its multi-trunk, shrubby habit can be tamed to cultivate a single-stemmed, tree-like effect. Mexican buckeye (not a true buckeye and also the sole member of Ungnadia) handles plenty of sunlight but also performs well in part-shade, particularly as an amply lit understory plant.

Too much shade, however, means fewer spring flowers. That would be a missed opportunity because the fragrant fuchsia blooms of Mexican buckeye are oddly and dramatically structured wonders — a sight to behold.

Beyond their beauty, they also present a bit of mystery. The unpredictable number of their variously sized pink stamens does not conform to general botanic rules for these male organs. Equally odd, whitish, truncated tubular structures cluster at the stamen bases — apparently atrophied male organs. Perhaps this basil cushion provides a perch for pollinators, but who knows? Their precise purpose remains undetermined and might simply be a botanic quirk serving no functional purpose.

These asymmetrical (zygomorphic) floral bee magnets will form into three-chambered pods that turn from green to brown and then cling to the small tree year-round. While the foliage yellows and falls away by winter, these brown capsules remain, gently rattling in the wind (if still seed-filled) and (even if empty) providing ready ornamentation for Christmas.

Actually, these pod husks often hang on the tree so long that they serve as curious objets d’art behind the late-February/early-March flush of new pink flowers. These dangling “shells” once housed glossy, dark-brown, marble-sized seeds — three per pod — that look like a buck’s gleaming eyes.

Of the mainly four specimen trees we considered, these Mexican buckeye seed-spheres would geminate the easiest and grow the fastest — facts especially appealing to our thrift-minded DIY outlook. So in late September we tucked firm, healthy buckeye seeds about two inches down in draining soil — only one seed in each 10-inch-deep container. We set a row of these planted containers (large enough to accommodate a deep-going taproot) under our live oaks, where they sprouted within a few days.

They did not last long, sorry to say. One evening, fox-squirrel bandits dug up all of our sprouted buckeyes. The following morning, the bitten-apart and scattered remains of their work lay beside the tipped-over containers. Who knows whether these environmentally displaced and over-abundant rodents ever actually consumed any part of the extracted seeds? With their brains enlarging during autumn and their chewing instincts always on overdrive, these squirrels will dig up any bulb-shaped kernel while searching for an edible. So we had to start over, this time placing the newly planted containers inside old pet crates and birdcages.

New sprouts grew rapidly through autumn, defoliated (while sheltered with other plants beneath grow lights in the garage) during winter, then leafed out and resumed growth once outside again beneath live oaks.

Also during that spring, tiny larvae of some kind (maybe Henry’s elfin butterfly) kept munching bits of the fresh green foliage, but never devoured entire leaves. By July, moreover, orangey nymphs of the beneficial milkweed assassin bug (Zelus longipes) nimbly patrolled these saplings.

So the container buckeyes robustly soldiered on, putting out more leaves and growing taller, nearly two feet by the end of their first summer. That October, marking the end of their first year in containers, they became in-ground plants. They have adapted beautifully. Their unstoppable drive to live and flourish has amounted to a mighty plus in the increasingly challenging environment of our home landscape.