Horticulture Principles and Practices

FIGURE 11–16 Using fertilizer
spikes and pills in fertilizing
potted plants.
Stick used
to push pill
Fertilizer spike pushed
down with a finger
Fertilizer pill
11.3.12 FERTILIZING HOUSEPLANTS
All plants need balanced nutrition to grow, develop properly, and produce well. The
nutrients in the potting soil are gradually depleted as the plant grows and develops.
Unlike field plants, whose fertilizer needs usually consist of only macronutrient elements
(nitrogen, phosphorus, and potassium), potted plants need both macro- and micronutrients
as part of a fertilizer program. Both types of nutrients are required because whereas
mineral soil has some native nutrients, greenhouse soilless mixes are often deficient in
nutrients, especially micronutrients.
Fertilizers for indoor use are available in several forms—solids, liquids, powders,
crystals, or granules. Powders and crystals, which are dissolved in water before being
applied to the soil, are called soluble fertilizers. Fertilizer sticks and spikes are examples
of solid fertilizers packaged in cylindrical shapes similar to pencils that are inserted into
the soil for gradual release of their nutrients (Figure 11–16). Such fertilizers may also be
packaged as pills. Specially coated fertilizer granules are commonly used in feeding houseplants.
These solids are called slow-release fertilizers. Finally, fertilizers may be applied in
liquid form as foliar sprays to plant leaves. While all plants grown in soil respond to fertilizers
placed in the growing medium, foliar application is especially beneficial to plants
such as epiphytes (e.g., bromeliads), which absorb little nutrition through their roots. The
concentration of foliar sprays should be carefully selected to avoid scorching the leaves.
Timing of feeding is essential in houseplant nutrition. It should be remembered that
other growth factors (e.g., light, temperature, and water) must be adequately supplied for
fertilizers to be effective. Some home growers misdiagnose plant problems, thinking a
poorly growing plant is starving when it actually is overwatered or not receiving adequate
light or warmth. As previously mentioned, fertilization should take into account
the growth phases of the plant. When a plant is growing actively, it needs more nutrition;
when dormant, nutrients should be reduced or eliminated altogether.
372 Chapter 11 Growing Houseplants
11.4 S EASONAL CARE OF HOUSEPLANTS
11.4.1 SEASONAL CHANGES
The four seasons are characterized by certain key changes in meteorological factors,
which impact how houseplants are cared for from one season to another. Seasonal care
of houseplants also depends on the plant growth cycle, among other characteristics. The
key seasonal changes are as follows:
Spring
The key changes in weather during the spring season that have a significant bearing on
how houseplants are cared for are increasing day length and gradual rise in temperature.