Nitrogen (N) deficiency begins as a uniform light green discoloration of the oldest leaves. The golden-yellow color of the crownshaft, petiole and rachis in Dypsis lutescens is caused by nitrogen deficiency (Fig. 1). As the deficiency progresses, younger leaves will also become discolored. When the entire crown except for the spear leaf is affected, leaves will become progressively lighter in color and may be nearly white (Fig. 2). Growth virtually stops, but the palms may linger in this state for a considerable length of time. In older palms in the landscape or field, canopy size becomes greatly reduced, very light green in color, and the trunk will taper (pencil-pointing).
In most mineral soils, N deficiency is typically caused by insufficient N in the soil. However, substrates used in container production of palms often contain a high percentage of organic components such as bark or peat. Since these components have a high carbon to nitrogen ratio, the microbes that break them down require an external source of N to do so. These microbes very effectively compete with palm roots for any available N in the soil and are the primary reason why N deficiency is such a persistent problem in container production. Water soluble N sources are also highly leachable in most container substrates, thus greatly compounding the problem.
Nitrogen deficiency is by far the most important deficiency encountered in container production of palms, and all palm species are susceptible when grown in containers. However, in the field or landscape, N deficiency is relatively uncommon, and for most species of palms, N deficiency is not the primary limiting element. In Adonidia merrillii, Ptychosperma spp., and Veitchia spp. growing in the field or landscape, N deficiency is the most common nutrient deficiency, yet even in these species, it is seldom a serious problem. Nitrogen deficiency is common on Dypsis lutescens growing in containers or on sandy or limestone field soils.
Figure 1. N deficient Dypsis lutescens. Note the golden yellow petioles and rachides and light green colored leaflets. Photo by T.K. Broschat
Figure 2. Severe nitrogen deficiency in Veitchia sp. The palm on the right has died from chronic N deficiency. Photo by T.K. Broschat