Tropical Gardening: Welcome spring with colorful azaleas and tropical rhododendrons

April showers bring May flowers, and for those who enjoy gardening it is a great time to connect with nature.

Rudyard Kipling put it this way when he wrote: “And some can pot begonias, and some can bud a rose, and some are hardly fit to trust with anything that grows.” However, Kipling did not take into account that folks in Hawaii can grow almost anything thanks to our wonderful climate.

Now, with longer days, most of us already are getting chronic “Hawaiian spring fever.” This means getting close to nature with plants. Hydrangeas are coming in to bloom this month with blue, pink or white flowers. They also are easy to propagate from cuttings. Hydrangeas generally grow in cool wet areas such as Volcano, Waimea and Kaloko Mauka but can be grown almost anywhere if given enough moisture and shade in sunny locations.

Throughout the northwest United States and Japan, another highlight of spring is the mass blooming of azaleas and rhododendrons. In Hawaii, these attractive garden shrubs are popular in cool, mauka areas. This spring, the plants also are available as potted houseplants at our local garden shops and nurseries.

If you are looking for some spring color to perk up your home or garden, the tropical Vireya rhododendrons are a natural. To see them in full majesty, visit the plantings at the Panaewa Zoo near Hilo. The Vireya garden is planted and maintained by the Hawaii Rhododendron Society. When you visit, you likely are to run into Armon Colman, who spends much of his time caring for the plants. If you want to learn more about vireyas, the society always welcomes folks to its meetings at the Keaau Community Center. The next meeting is a potluck at noon Sunday, April 23. The society also has a plant sale scheduled for Sunday, April 30, at the zoo, so mark your calendar now.

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If you’re not quite sure about growing azaleas and Vireya rhododendrons, here are a couple of tips to remember:

• Rhododendrons are a part of a small but widely distributed family found in many parts of the world. They usually are found in cool, moist regions such as the Pacific Northwest and the Himalayas. Some species are even found on high mountains such as Kinabalu in Borneo. Azaleas actually are rhododendrons. Many are adapted to temperate regions, but some have found Hawaii a great place to live.

• Some varieties on the market bloom in reds, whites, pinks, salmon and even mixes of white-pink and white-red.

Once you buy your living spring bouquet, care is easy if you follow a few simple rules:

• In the home, plants won’t tolerate a daily scrubdown, but they will take on a healthy look with an occasional leaf washing. Dirty foliage is unattractive. If the leaves get heavy with dust, wash them off with water. This will discourage insect and mite buildup.

• The proper watering of plants is more important than giving them a bath. In general, plants require a thorough soaking at least once a week. In warmer temperatures or home air conditioning, plants might require more water. Applying too little moisture can allow the soil in the bottom of the container to dry out, causing the plant to wilt or die. On the other hand, keeping the plant roots soggy will also cause injury. Make sure the pot has sufficient drainage.

• The plants grow well at temperatures between 60 and 75 degrees. Therefore, protect the plants from being broiled alive by direct sun and in hot or windy areas. In cool mauka areas, they can be placed in sun.

• Like people, they like their food served at regular intervals. Special acid azalea fertilizers are available. The best suggestion of feeding is to follow the directions on the plant food container. Since they are relatively slow growers, they should only need fertilizer once every two to three months.

Here are some tips for diagnosing plant troubles:

• Brown tips or burned margins might mean you applied too much fertilizer, you let the plant roots dry out or you let the plant become wind burned.

• Yellowing of leaves indicates overwatering, poor drainage or poor soil aeration.

• Small leaves suggest a tight or heavy soil mixture, lack of fertilizer or not enough moisture.

• Weak growth or light green color on otherwise healthy foliage indicates too much light, lack of fertilizer, root-rot or poor root systems.

• Yellowing, wilting or soft growth means too much heat or root injury.

Remember, they require an acid soil. If you decide to plant them in the garden or repot them, give plants a mix high in peat moss. Make sure you don’t plant them in soils high in calcium. Avoid planting in concrete containers, near sidewalks or concrete foundations since these contain calcium and will cause nutrient deficiencies. Also remember, they should not be planted near the ocean or in hot, dry or windy areas.

Our experience in mauka Kona is that once established in the garden, they are easy. On the Hilo side, they are even easier to grow and some varieties of vireyas can do well grown on rocks and as epiphytes on trees along with orchids and bromeliads. Many green thumb enthusiasts find them easy to grow from cuttings.