island oak
(Quercus tometella)

On a gloomy December day, I found my way to the Conejo Valley Botanic Garden in Thousand Oaks, without expectations or reservations. The garden is large, nearly always open, and admission is always free.
Could a garden this available really be that special?
Well, I am glad to report that it is not only special but, without fanfare, is the sort of place that, having gotten a glimpse of it, you will want to come back to visit soon enough. After all, it is 33 acres and a single visit could not possibly do it justice.
Visiting the garden for the first time, little did I know that I would encounter a never-seen sage (salvia) with large reddish pink flowers; an aloe with a candelabra of giant red-orange tapers; a mauve, mini-fan flower (Scaevola pallida) that is a masterfully condensed version of the common fan flower (Scaevola aemula); and several unforgettable trees, including what appear to be weeping olive trees.
There is no better place to enjoy a quiet Sunday afternoon than the Conejo Valley Botanic Garden. It is situated on a hilltop with wonderful views. Yet it is the plants themselves that provide the most impressive spectacle, even in winter. I say “even in winter,” yet this may be the best season to appreciate certain plants, especially those whose form and foliage are more memorable than their flowers.
And let’s be honest: After years of observing plants, what is it that truly fixes your gaze? Is it color or shape, temporary flowers or permanent form?
Flowers certainly have their purpose. They brighten an entry and put a smile on your face. But, especially in fall and winter, when flowers slowly disappear, it is the growth habit or form of plants that makes a deep impression. It is appropriate that fall and winter are contemplative seasons since they give us time to look back and reflect upon garden successes and failures of the previous year and to re-evaluate what a successful garden is really all about.
Over the years, I have come to value symmetrical trees that require minimal, if any, pruning. Such a tree appears to be growing here. It is labeled island oak (Quercus tomentella) and I could not help but marvel at its deep green foliage and neat, pyramidal shape. Although it grows into a 60-foot tree under optimal cultivated conditions, it seldom exceeds 40 feet in height in its Channel Island habitat.
I do not know how tall it will grow in the botanic garden, but if it did not exceed its present size (around 30 feet) in urban settings (in ornamental or parkway plantings, where a tree’s mature height is usually reduced), it would be perfect.
I was reminded of classic California native trees such as Catalina ironwood (Lyonothamnus floribundus) and single-leaf pinyon (Pinus monophylla), also appropriate for parkway planting. The former requires occasional trimming of stray branches to maintain its columnar form while the latter, symmetrical and exceedingly slow growing, should never need to be pruned.
In any case, I could not stop looking at the island oak. I photographed it from every angle but no picture can do it justice.
It does not look like any other oak. From a distance, its form may remind you of certain compact and pyramidal magnolia cultivars. It also has the familiar glowing dark green foliage for which these small-leaf magnolias are known. Island oak, which has the same drought tolerance of other Southern California oaks, deserves wider use as an ornamental tree, if only to test its limits and possibilities in our gardens and landscapes.
There is a sage (Salvia) collection in the Conejo Valley garden that merits a visit, even if most of the species on display are barely flowering.
I was pleasantly surprised by Wagner’s sage (Salvia wagneriana). Although the specimens here are sparse for now and no more than a few feet tall, they have the potential to become stout shrubs of 6 feet tall with a similar girth. Flowers seem to have every sort of red and pink in them, as well as a dash of white.
Red velvet sage (Salvia confertiflora) has furry reddish-brown flower stalks accompanied by small, velvety flowers. Rough-textured leaves on mature red velvet plants expand to 7 inches long on shrubs that nearly reach the size of Wagner’s sage. These sages in the Conejo garden are still young and spindly. It will be a pleasure to observe them as they grow to maturity.
Aside from the island oak, several uncommon trees are on display at the Conejo Valley Botanic Garden.
Two ornamental acacias are noteworthy. Shoestring acacia (Acacia stenophylla) has long and thin blue-gray foliage and small yellow pompon flowers. Knife acacia (Acacia cultriformis) has triangular leaves and similar flowers.
Marina’s strawberry tree (Arbutus marina) is a hybrid, one of whose parents is the old standby strawberry tree (Arbutus unedo). Marina’s popularity stems from its pink flowers, large and lush foliage, as well as a relatively rapid growth rate to a mature height of 40 feet. The so-called pinkball or tropical hydrangea (Dombeya wallichii) has no botanical relationship to the common garden hydrangea although their flowers strongly resemble each other.
I had never seen a weeping olive tree before, but the olive specimens in this botanic garden appear to be of that type. Weeping olive trees are only partially self-fruitful, which means that another variety is needed for maximum fruit production. By the same token, a weeping olive tree known as ‘Pendolino’ is promoted as a heavy pollen producer for other olive varieties.
A robust white sapote (Casimiroa edulis) is ripe with abundant fruit. White sapote grows wherever oranges do and you can only wonder why more of these South American trees are not found in Valley gardens. Looking something like a small green apple, white sapote has inedible skins and toxic seeds, so steer clear of these. Its flesh is custardlike and tastes something like a cross between vanilla pudding and pumpkin pie. When overripe, a sapote tastes more like a sweet banana.
I would be remiss not to mention two notable buckwheats on display: ground-hugging seaside buckwheat (Eriogonum latifolium) and shrubby St. Catherine’s lace (Eriogonum giganteum).
Buckwheats are recognizable by their pinkish flower sprays over pale blue to grayish foliage.
Although imported from South Africa, Protea laurifolia ‘Rose Mink’ is probably the easiest protea to grow in our area. It handles clay and alkaline soil conditions quite well and requires little water, eventually reaching a height of 10 feet.
St. John’s wort (Hypericum calycinum) is another drought-tolerant ground cover. It is not the most reliable plant for summer gardens but will flourish where protected from hot afternoon sun. Its neon yellow flowers do an excellent job of brightening a winter landscape.
Tip of the week
Chinese tallow tree may be the most gloriously colored deciduous tree for Valley gardens. It grows to around 20 feet tall and is strictly ornamental. During spring and summer, its foliage is a pleasant luminescent lime to kelly green. In fall and winter, leaves turn to a brilliant magenta red before dropping to the ground.