A WORD OR TWO ABOUT GARDENING

The garden blues and how to enjoy them

This is the first of future articles on the topic of providing color in the landscape. Paying attention to the role of color w hen landscaping is an im portant part of creating a visually attractive yard. Foliage, flow ers and fruits can all contribute color elem ents to the landscape, though it is flow ers that are the principal focus. Various schem es have been developed as to how plants should be arranged in the landscape according to flow er color, but they are based on tw o broad concepts: using com plim entary colors to create areas of contrast, or unifying w ith closely related colors. This latter approach has been further refined to selecting plants of just a single basic color, such as the purple border and fam ous w hite garden both at Sissinghurst Castle (UK). Com pare this w ith the cottage garden w here the aim is to accom m odate in a lim ited space, a diverse range of plant types differing in form and color. Although very inform al in appearance, this approach to landscaping requires skill in know ing w hich plants to choose and w here to place them , and is a challenging style to adapt to south Florida conditions. M ore often, the use of color in landscape designs falls in betw een these latter tw o extrem es. For this article I w ill discuss plants that contribute shades of blue – not the m ost frequently encountered of flow er colors, especially in tropical plants. Blue flow ering plants can create a cool, soothing effect and add a sense of depth to the landscape, in contrast to the m ore brightly colored plants that are used in tropical gardens. The various tints and shades of blue found in a range of m ore tem perate clim ate annuals and perennials are at best short- lived inhabitants of the M iam i-Dade landscape. W hen it com es to shrubs, old tim e favorites such as lilacs and hydrangeas are not suited to our tropical clim ate. How ever, rather than discussing w hat is not suitable, let us consider those blue flow ering plants that can contribute to the local landscape. I w ill focus on plants w ith som e degree of perm anency, concentrating therefore on shrubs. There are several, som e of w hich are quite fam iliar and provide a range of color from sky blue to deep purplish blue. M ost fam iliar is the ever-popular Plumbago auriculata (blue plum bago as opposed to the m uch less com m on and m ore tropical red plum bago, P. indica), a fairly com m on site in south Florida yards. The sky blue flow ers blend in w ell next to yellow flowering shrubs such as show er of gold (Galphimia gracilis), or grouped near a desert cassia (Senna polyphylla). Use blue plum bago as a low inform al hedge, or foundation plant in a sunny part of the garden – expect a spraw ling shrub w ith a height and w idth of 4-5’. Blue plum bago w ill take som e light afternoon shade, but flow ers best in full sun, and can be planted in any free draining soil. Once established it is fairly drought tolerant and w ill reliably flower from spring through fall. Prune back any straggly growth in late w inter, after w hich spent flow ers can be rem oved as necessary throughout the year. There are a num ber of cultivars available, ‘Im perial Blue’ being the one m ost com m only seen, w hile ‘Royal Cape’ has a deep blue line dow n the center of each petal. There is a w hite variety, P.auriculata var. alba, w hich can be used to alternate w ith the blue cultivars. Do not confuse P. auriculata w ith another blue plum bago, Ceratostigma plumbaginoides, w hich m ay be offered for sale locally. This form s an attractive ground cover, but is zoned for m ore tem perate clim ates. Only slightly less fam iliar and also w ith sky blue flow ers is Duranta erecta know n com m only as golden dew drop or sky flow er. This is a large spreading shrub, occasionally grow n as a tree (see below ), w ith drooping slender branches bearing sim ple, oval to elliptic, ¼ - 3” leaves often w ith serrated m argins. The branches usually have scattered spines. The inflorescence consists of m any pendent racem es of ½ to ¼ ” light blue flow ers, produced any tim e from spring through fall. After flow ering m any conspicuous, orangey yellow fruits form that attract birds, but are poisonous to hum ans. Golden dewdrop should be planted in full sun, is not particular as to soil providing it drains freely, and once established exhibits good drought tolerance. The shrub w ill take som e shade but w ill not flow er as freely. It is fast grow ing and can be drastically pruned – cut to the ground it w ill readily re- sprout. Norm al pruning should be perform ed after flow ering, and tip pruning can be used to m ake a bushier specim en. You m ay choose to rem ove the fruits - be aw are that golden dew drop readily produces seedling volunteers in other parts of the yard, and has naturalized in parts of M iam i-Dade. It is som etim es prom oted as a Florida native, but this is in doubt and it appears m ore likely to be an introduction from the Baham as or Caribbean. Recently som e very attractive D. erecta cultivars have becom e available: ‘Geisha Girl’ has deep blue flow ers w ith a w hite center and border, w hilst ‘Sapphire Show ers” produces larger, violet blue flow ers having ruffled picotee petals w ith a narrow w hite m argin. These are som etim es available as standards (grow n to a single stem ) w ith a w eeping habit, and can substitute for a sm all tree w here space is lim ited. There are also a num ber of cultivars having variegated leaves, w hilst ‘Alba’ has w hite flow ers. Another shrub w ith light blue flow ers is the very attractive blue clererodendrum , Clerodendrum ugandense. How ever, unlike those described above, it is best suited to partially shaded areas of the yard Blue clerodendrum is a spraw ling shrub to m ore than 10’, w ith long arching stem s and toothed, bright green leaves. Individual flow ers are com posed of five petals, four that are light blue plus one low er petal that is a m ore conspicuous violet blue. This petal arrangem ent, together w ith the four long protruding stam ens, gives the im pression of butterflies hovering just above the foliage. Flow ers are produced in term inal panicles, and appear throughout the year on new grow th. Choose an area of the yard w ith dappled shade or part afternoon shade, and m oist soil. Pruning can be done at any tim e to keep the plant w ithin bounds and prevent it from becom ing too leggy. Alternatively it can be allow ed to spraw l and supported on a trellis or grow n against a chain link fence. C. ugandense is one of the better behaved of the clerodendrum s, w ith an absence of the vigorous root suckering seen in m any other species. Eranthemum pulchellum is another blue flow ering shrub that is best suited to partial shade, and is often m isleadingly called blue sage or Indian sage. Eranthem um is a soft w ooded, m ulti- stem m ed shrub from India grow ing to about 3- 4’ w ith a spread of 5-6’. It has erect stem s w ith dark green prom inently veined shiny leaves, and from Decem ber through M arch produces handsom e spikes of deep blue flow ers. In M iam i-Dade, Eranthem um is best planted in enriched soil choosing a site w ith either dappled or som e afternoon shade. In full hot sun the shrub w ill rapidly w ilt unless w atered frequently. Rem ove spent flow ers, then once flow ering is finished drastically prune, cutting stem s back by a half and totally rem oving those that are dead or yellow ing. Apply fertilizer after pruning and again in late sum m er. This is a personal favorite that although rather unassum ing for m uch of the year (the foliage is quite attractive) definitely earns its place in the landscape for the uniquely blue, w inter flow ers. Flow ering com m ences as another blue-flow ered m em ber of the Acanthaceae (Barleria cristata) is past its peak flow er show . Like Eranthem um , B. cristata (Philippine violet) prefers som e partial shade, and m oist soil, developing into a 4 x 5’ sem i-w oody, m ulti-stem m ed, stiff, branching shrub. Barleria com m ences flow ering as days shorten, producing spikes of pale violet blue tubular flowers from m id-October through Decem ber, then on and off until spring. Pruning out dead flow er heads helps to prolong flow ering. M ore substantial pruning can be perform ed any tim e after bloom ing ceases up until Septem ber. This plant induces a love hate relationship – you w ill be captivated by the prodigious flow er display, but not so taken by its habit of producing num erous seedling volunteers in the surrounding landscape. Be prepared to pay a price for the flow er show w hen it com es tim e to pull up these unw anted visitors. Form s of B. cristata are also available w ith w hite, pink or m auve flowers. Although dissim ilar in appearance to the tw o shrubs just discussed, thunbergias are also part of the acanthus fam ily. Thunbergia grandiflora, sky vine, is a vigorous, som etim es invasive, w oody, tw ining vine, w idely grow n in the tropics w here space is available. The flow ers are light blue to violet and trum pet shaped - ‘Augusta Blue’ is a rare cultivar that is especially esteem ed for its’ deep blue flow ers. M ore suitable w here space is a consideration, king’s m antle (Thunbergia erecta) grow s into a 4-6’ shrub w ith thin tw ining stem s, dark green leaves and yellow - throated blue violet flow ers. It w ill grow in full sun, but is best w ith som e shade during the hottest part of the day. Avoid drastic pruning, w hich w ill reduce flow ering – frequent light pruning is preferred to m aintain the shrub w ithin its’ allotted space. Tw o other species are less often seen: T. battiscombei (blue boy) has sim ilar flow ers to king’s m antle, but larger leaves and a m ore scandent habit, w hilst T. crispa has sm aller deep blue flow ers and is covered in stiffer, som ew hat w avy, sm all gray green leaves. Less fam iliar in local landscapes are the iochrom es, attractive, dim inutive relatives of the brugm ansias (angel trum pets), w ith Iochroma cyaneum (M exican bluebell) being m ost readily available. It grow s to form an 8’ erect shrub w ith som ew hat lax stem s, attractive gray-green leaves and clusters of deep blue to purple, slender, tubular flow ers. Flow ering can occur on and off throughout the year but is usually best durng the cooler m onths. Grow in full sun, but sheltered from w ind (w ood is brittle), and provide w ater during periods of drought. The cultivar ‘Sky King’ has light blue flow ers and ‘Royal Blue’ deep blue flow ers, w hilst ‘Plum ’ has rosy purple flow ers. Foliage can be dam aged by leaf eating beetles. Like the iochrom es Brunfelsia grandiflora (yesterday today and tom orrow) is also in the potato fam ily. Although the flow ers are not truly blue but initially purple, bluish shades develop as they fade through lavender to w hite. B. grandiflora grow s to 8-10’ and benefits from som e afternoon shade. Flow ering occurs from w inter into spring. There are several other blue flowering shrubs for w hich m uch less inform ation is available. Cornutia grandifolia is from Central Am erica and the tall spikes of light blue flow ers have earned it the com m on nam e of tropical lilac. Each erect flow er spike can be up to 18” tall and consist of m any hundreds of buds of w hich 20-30 w ill be fully open at any one tim e. Flow ering occurs during the w arm er m onths of the year, and is follow ed by a few purple colored drupes (fruit). Although the flow ers are not fragrant, the leaves have an unusual though pleasant arom a w hen bruised. Individual leaves are large, m ore than 12 x 8”, bright apple green, soft and velvety. Tropical lilac grow s to about 12’, and requires som e shade and m oist soil. It appears to perform well in M iam i-Dade. Spring is a good tim e to prune, w hen any w inter dam age can be rem oved, and rising tem peratures w ill perm it rapid re-grow th. This is a fast grow ing plant that can send up vigorous basal suckers. There is less certainty on the long-term use of the next three blue flow ering shrubs in local landscapes, but all are w orth trying. Pycnostachys dawei (som etim es referred to as blue w itches hat) is a tropical m em ber of the m int fam ily, and produces an unusual cone shaped inflorescence, consisting of m any deep cobalt blue flow ers, from late sum m er w ell into fall. This is a rapidly growing herbaceous perennial from Uganda reaching about 5’ w hen full grow n, w hich prefers m oist enriched soil, and som e afternoon shade otherw ise it is prone to w ilt. This is not a drought tolerant plant. Otacanthus caeruleus is a tropical relative of the foxglove from Brazil that grow s as a 2-3’ shrub producing short spikes of curved, tubular, deep violet blue flow ers. The author’s experience w ith this very attractive plant w as disappointing as the foliage w as severely blighted for m ost of the sum m er. It needs full sun to partial shade w ith m oist enriched soil. Tweedia caerulea is a Brazilian relative of the m ilkw eed that grow s as a low straggly shrub w ith soft gray green leaves, and jasm ine like pale blue flow ers. Grow in full sun w ith som e afternoon shade in any free draining soil, keeping it som ew hat dry once established. Flow ering occurs sum m er into fall. Finally, although not a shrub, no discussion of blue flowering plants in the M iam i- Dade landscape is com plete w ithout m ention of the native lignum vitae, Guaiacum sanctum. I have already m entioned this sm all native tree in a previous article, but it is certainly w orth repeating here. The overall form of the tree is appealing, w ith a crooked trunk and furrow ed bark. The leaves are pinnately com pound w ith three to four pairs of deep green leathery leaflets and the flow ers, sm all w ith dark blue petals fading to white. Flow ering occurs briefly in the spring after w hich attractive yellow /orange fruit appear w hich split to reveal a deep red aril. A slow grow ing, drought and salt tolerant tree requiring full sun, and a definite m ust for enjoying the blues in a M iam i-Dade garden.

John M cLaughlin February 17 2004