A WORD OR TWO ABOUT GARDENING Some sunny garden color In a previous article som e m onths ago the subject of color in the landscape w as introduced. On that occasion the focus w as on blue flowering plants, and it w as evident that, although there are a few spectacular plants to choose from , the range is lim ited. With yellow flow ering plants, the subject of this colum n, the choice becom es overw helm ing. From pale lem on, through bright golden to the glow of a m ore orangey yellow , these vibrant sunny colors and m ore can be found in the plants described below. Bright colors such as yellow suggest im m ediacy, shortening distances in the landscape – they are useful in foundation plants or those used to fram e an entrance. Avoid overuse in a sm all yard, especially around the perim eter w here creating a sense of depth w ould be m ore appropriate (blue/violet flow ering plants). In a larger yard, a bright yellow border w ould be ideal for an open expanse of turfgrass. In addition to shrubs and vines, space could also perm it the placem ent of one or m ore yellow flow ering trees. There are few m ore glorious sites than a leafless yellow tabebuia in full bloom against a bright blue, early spring sky. Even if the show is rather short lived, it is spectacular. Little w onder that a yellow tabebuia (Tabebuia chrysantha, el araguaney) is the national tree of Venezuela. This particular yellow tabebuia is uncom m on in M iam i-Dade, the silver trum pet tree (T. aurea syn. T. caraiba) being by far the m ost frequently planted species. The com m on nam e refers to the silvery scales present on the leaf surface. This tree has a reputation, locally at least, for being w eak rooted and prone to w indstorm dam age. To reduce the risk of trees toppling, avoid planting specim ens that are root bound, and sites that have poorly draining soil. In addition, plant w ell aw ay from roads and buildings, and prune out storm dam aged lim bs to avoid subsequent disease problem s. A third yellow tabebuia that is som etim es seen locally is the golden trum pet tree, T. chrysotricha, w hich is a som ew hat larger (30 – 40’), m ore open tree. It can be distinguished from T. aurea by having less corky bark and the presence of reddish brow n tom entum (fuzz) on the stem s, undersides of leaves and capsules (the pod-like fruit). Yellow tabebuias lose all or m ost of their leaves before bloom ing in spring, and should be kept dry during w inter. Flow ering w ill also be im proved by avoiding high nitrogen fertilizers and w aiting until after bloom ing to feed the tree. Closely related to the tabebuias w ith sim ilar yellow , trum pet shaped flow ers is the yellow elder (Tecom a stans). This 10-12’ fast grow ing, som ew hat straggly tree/shrub requires pruning to keep it tidy, and has pinnate leaves as opposed to the digitate leaves of the tabebuias. The plant is som etim es grow n as an inform al screen, but its m ain attribute is the im pressive late sum m er/fall show of brilliant yellow , sw eetly scented flow ers. Tecom a castanifolia is very sim ilar, but has a m ore erect grow th habit and is easier to train as a sm all tree. Both plants readily self- seed, and can be w eedy – rem ove volunteers as they appear. Another m em ber of the Bignoniaceae, M arkham ia lutea (m gam bo, from central Africa) is a 30 – 40’ drought tolerant, deciduous tree developing an attractive trim , pointed crow n. It has yellow , bell-shaped flow ers w ith a reddish brow n throat (the cultivar ‘Pierrii’ has a m aroon striped throat), occurring in term inal panicles from spring into sum m er. The tree is not particular as to soil, providing it is free draining. The bean fam ily (Fabaceae) contains m any yellow flow ering trees/shrubs, of w hich the cassias are best know n. Taxonom ically they are separated into tw o separate genera: Cassia spp. are larger, often deciduous trees, and Senna spp. sm aller, usually evergreen trees and shrubs. The golden show er tree, Cassia fistula, w hich flow ers in late spring/early sum m er, can be used to continue the yellow them e of the yellow tabebuias. Golden show er trees grow to about 30 – 40’ and are considered the tropical equivalent of the laburnum , w ith fragrant, very show y, pendant racem es of pale yellow flow ers. The leaves are pinnate, com prising 6 – 16 unusually large leaflets (8x 3¼ ”), the fruit a long, thin, cylindrical brow n pod. The tree can be prone to root rots, so avoid poorly draining sites and root dam age. Leaf spot diseases are som etim es a source of concern, how ever this is a tem porary problem as the tree is briefly deciduous before flow ering in early sum m er, after w hich new leaves em erge. The Kenyan show er tree, Cassia afrofistula, w hich is sm aller, tends to form m ultiple trunks, w ith flow ers in upright panicles. The tree is evergreen, drought tolerant and has an extended bloom period from sum m er into fall. The Senna spp. trees flow er late sum m er to fall, though som e such as the desert cassia (S. polyphylla) can also flower on and off throughout the year. This particular tree, native to the Virgin Islands and Puerto Rico, is sm all (8 – 10’), relatively slow grow ing, w ith delicate foliage and sm all clusters of yellow flow ers. It is an excellent choice for a sunny, dry spot in a sm all yard, and like other sennas, tends to becom e shrubby. Prune out the num erous shoots that develop from the root crow n to retain a tree-like grow th habit. The glaucous cassia (Senna surattensis), w hich form s a m ore substantial sm all tree (12 – 15’), is com m only seen in south Florida and frequently used to landscape local m alls. This tree, like several other sennas, is also a favorite w ith caterpillars (sulphurs), and on occasion feeding can dam age flow ering shoots (not a problem for butterfly aficionados!). Com pared to the desert cassia, the glaucous cassia has a denser canopy, often becom ing top heavy, rendering it liable to toppling in w ind storm s. How ever, it is otherw ise a reliable tree, and rem ains attractive year round. Other sm aller sennas are used as shrubs: for instance the candlestick cassia (Senna alata), a 4- 10’ shrub w ith erect spikes of yellow flow ers, and Baham a senna (S. m exicana var. chapm anii), a native, large shrub w ith flow ers in flat panicles. Both of these sennas flow er during the w arm er m onths of the year. Staying w ith trees in the Fabaceae, m ention should be m ade regarding the confusion surrounding the yellow poinciana. There is indeed a yellow flow ered variety of the royal poinciana (Delonix regia) available as D. regia var. flavida. As the tree often does not com e true from seed it needs to be grafted, a fact that contributes to these being expensive and of lim ited availability. There is also another species, Delonix elata, w hich has m uch paler alm ost w hite flow ers and is even rarer in local landscapes. To add to the confusion the nam e yellow poinciana is also applied to various Peltophorum spp. (35 – 45’ evergreen trees), in particular P. dubium . The flow ers are a vibrant yellow , differing from D. regia var. flavida in having crum pled petals clustered in a m ore upright spike. Peltophorum pterocarpum is better know n as the copperpod, the nam e referring to the copper red seed pods. All of these trees are fast grow ing w ith shallow surface roots, w eak w ood and develop poor structure unless correctly pruned. They are show y trees, but best planted w ell aw ay from sidew alks and buildings. Another group of show y, yellow flow ering shrubs/trees from the Fabaceae are also som etim es referred to as poincianas. These are the caesalpinias, of w hich the dw arf poinciana (Caesalpinia pulcherrim a) is probably the best know n, though locally less in evidence than 20 -30 years ago. This is an open, som ew hat prickly, shrubby plant, w hich bloom s on and off throughout the year producing flow ers w ith crim son petals edged w ith yellow . A selection w ith all yellow flowers, C. pulcherrim a var. flava, is also available. Caesalpinias are suitable for open sunny areas, able to survive poor soil and drought – a good choice for xeroscapes. The divi-divi (C. coriaria - the signature tree of Aruba) survives exposed beachfront locations w here, in response to the prevailing w ind, it develops its’ characteristic lopsided, contorted, flat topped appearance. In m ore sheltered situations the divi-divi can grow to m ore than 20’ w ith very attractive, delicate foliage and sw eet sm elling cream y yellow flow ers. Nom inally evergreen, the tree drops leaves as tem peratures approach 40ºF.