Fertilizing Foliage & Flowering Plants

Meeting Plant Needs:

Plants brought into the store or home from the greenhouse are moving to an environment where light is less intense and hence where growth will be slower. Most plants already have sufficient fertilizer in their soil to sustain growth for up to three months under interior conditions. This is particularly true during fall and winter.

Even if plants continue to grow vigorously, it is wise to wait a month while it adjusts to its new environment, before adding fertilizer. Likewise, a newly potted plant needs time in which to grow new roots to absorb the fertilizer you will be applying.

It is often easier to feed a number of plants at the same time, and the schedules can be combined in this way: for a general practice, apply fertilizer to most indoor plants every 1-2 months while growth is rapid, and once or twice only during the winter months. Alternatively, apply the plant food more frequently in a dilute form; this accommodates plants which would be injured by full strength fertilizer. Approximately half the recommended strength means using only half as much fertilizer per plant or in solution.

Annual plants grow very quickly and need fertilizing every two or three weeks during their short season. Some flowering plants, like Azalea, should not be fed at all while they are in flower.

Fertilizer Types:

Any prepared mixture for the type of plants you have is fine: for most foliage and flowering plants, an N-P-K analysis ratio that is close to 1-2-1 will give balanced growth. African Violets grow best with a mix containing more nitrogen (N); and there are other formulations available for acid-loving plants like Azalea and Gardenia. For annuals and other garden plants growing in hanging baskets, an outdoor fertilizer is fine.

Soluble compounds are easy to apply and provide quicker results than solids or slow release pellets. Simply apply the fertilizer solution in place of water when you would normally be watering the plants. However, be sure the soil is slightly damp when you fertilize; never feed plants with dry soil, because roots will be damaged by the chemicals you add unless they are diluted further by soil moisture.

Use all fertilizers at or weaker than the recommended strength of dilution, never stronger. Newly rooted cuttings, seedlings, and young plants will benefit from weaker solutions to avoid damage to the soft young roots.

Table 4. Fertilizers for foliage and flowering plants.

Name & Formula N-P-K Analysis Others
Ammonium Chloride
25-0-0 0
Ammonium Nitrate
33.5-0-0 0
Ammonium Phosphate (di)
21-53-0 0
Ammonium Phosphate (mono)
11-48-0 1.4% Ca, 2.6% S
Ammonium Sulfate
20-0-0 24% S
Calcium Nitrate
15-0-0 37% S
Sodium Nitrate
16-0-0 0
45-0-0 0
Urea-Formaldehyde 38-0-0 0
0-20-0 18% Ca
Treble Phosphate
0-42-0 12% Ca
Phosphoric Acid
0-52-0 12% Ca
Potassium Chloride
0-0-62 0
Potassium Nitrate
13-0-44 0

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