April showers bring May flowers

April showers bring May flowers as long as they have sufficient fertilizer. In wet areas of the island, heavy rains may have leached much of the nutrient supply away. If you live in dryer areas, the lack of moisture makes it difficult for plants to absorb nutrients. Whatever the situation, it is time to see whether your plants are perky or pooped.

The last few months have been a continuation of a long dry spell on the islands. However, spring showers, warming temperatures and more sunlight are causing active growth of coffee, ornamentals, macadamia and most other plants. Active growth requires a good supply of nutrients to assure abundant crops and healthy plants. If you have not applied fertilizer recently, now is an important time. As a general rule, established plantings should receive fertilizer every three to four months.

Some examples of nutrient deficiencies may be observed in new landscapes at some shopping centers. Initial fertilizer applications start to fade, creating a pale yellow-green appearance rather than a lush, green healthy look. If this condition continues for an extended time, shrubs, trees and grass will be stunted and sickly. Weeds will then invade, creating further problems. Where drought has been a problem, even established trees and palms have suffered and died.

It is helpful to have a soil analysis done to give a more accurate picture of what your plants need. For a soil analysis, take about 1 pound of soil, without rocks, to the nearest University of Hawaii Cooperative Extension Service office and they will send it to Honolulu for testing. Call the experiment station at 322-4896 and make an appointment to submit samples. It takes about three to four weeks to get the results and recommendations. Presently there is a nominal charge. There are also private labs that can analyze soil in a shorter time. The basic soil analysis will test for calcium, magnesium, potassium, phosphorus and pH.

The tests may show your soil is too acidic and needs lime. When soil is too acidic, plants do not respond to fertilizers as well. There may even be some dieback if conditions are severe. Some soils require as much as 2 tons of liming material per acre.

For backyard farmers, these are some additional fertilizer tips: Be sure not to overfertilize or wait too long between applications. Of course, the correct amount to use depends on the formula. The higher the numbers in the formula, the less should be used. A formula that contains the three major fertilizer elements — nitrogen, phosphorus and potash — in a 1-1-1 ratio is common and sufficient for many uses. You might use a 16-16-16, 14-14-14 or 8-8-8 for shrubs and other ornamentals.

For the lawn, turf specialists usually suggest enough fertilizer to give 1 pound of actual nitrogen to every 1,000 square feet. The formulation used for grass is usually high in nitrogen such as 21-7-14, 16-6-8 and 28-3-5. The first number in the formula represents nitrogen. The number of applications per year depends on type, grass and soil. Centipede grass does well with two or three applications, but hybrid Bermuda may need six to 12 applications for a golf course quality lawn.

Weekend farmers are sometimes confused by the vast array of fertilizer brands and formulas available. However, most plants are not so specific in their nutritional needs that they can’t use and thrive on the same or similar fertilizer mixtures. The numbers represent the percent of nutrients in a bag. A mixture with a 1-1-1 ratio is satisfactory for the majority of plants, including potted house plants. Some folks are upset when their garden supply dealers suggest a 10-30-10, 18-5-12, 20-10-10 or some other formula than a 1-1-1 ratio fertilizer. Plants will respond about the same for 18-6-12 as they will for 16-16-16. However, the middle number, phosphorus, is sometimes locked up in certain types of soils and is not available to plants. Phosphorus is the element that encourages strong roots and cell development. It is low in most Hawaiian soils. However, gardeners who use lots of fertilizer containing phosphorus may over a long period of time build up too much in the soil. They would do better to use a low-phosphorus fertilizer, if it has been supplied year after year in high amounts.

A formulation high in phosphorus and potassium like 2-8-10 has less nitrogen than most other formulations and has a tendency to stimulate flowering and fruiting of many plants. This type is commonly referred to as “bloom aid” or “fruit trees special.” A 21-7-14 or 28-3-5 is quite high in nitrogen and has a tendency to stimulate leaf development. This type is often used on ornamental shrubs, trees and grasses. The minor elements — magnesium, zinc and iron — are also important and should be included in some fertilization programs. Organic and other slow-release sources of nutrients seem to have added benefits, since they last longer and do not overstimulate growth that is susceptible to insect and disease.

The soil should be moist when fertilizer is applied, and the fertilizer should be watered in immediately after application. Also, care should be taken to ensure the fertilizer material is applied over the entire root zone of the plant. Allowing clumps of fertilizer to stand in spots under the plants or against the stems may cause excessive burning.

During times of heavy rainfall, an extra application of fertilizer may be necessary, especially in rocky or cinder soils. Organic and slow-release fertilizers generally do not leach out as readily. On the other hand, unless you’re equipped for irrigation, fertilization should be withheld during periods of drought.

Many ornamentals need extra applications of the minor elements, especially ixora, gardenia, citrus and palms. Royal, queen, areca and pygmy date palms in particular need applications of magnesium, zinc and other minor elements each year. Without it, bleached pale green leaves may occur. This is an unnatural condition of the leaves.