During this season of the year, most mainland gardeners become bulb conscious. Even in Hawaii, garden magazines and garden supply stores now are featuring bulb advertisements and displays. Gladiolus, cannas, gloxinias, tuberous begonias, callas, amaryllis and caladiums are just a few of the many types available.
Although they vary in their requirements, there are several basic cultural factors to keep in mind.
In general, most bulbs grow best in a well-drained soil and sunny location. The pH of the soil should run between 5.8 and 6.5. Most bulbs should be fertilized with a low nitrate analysis fertilizer according to manufacturer’s directions on the label. If you keep these factors in mind, you should be able to produce excellent bulbous plants.
Energetic gardeners can have some bulbous crop in flower every month of the year. However, let’s concentrate on some spring flowering bulbs we can plant now.
Calla lilies can be started now and will flower during spring months. Incidentally, calla lilies are an exception to the cultural suggestions already mentioned. Callas will perform best in a soil that has considerable organic matter and is retentive of moisture, but not soggy.
To obtain the best results, the clumps should be dug every three to four years and the rhizomes separated and replanted at a depth of 4 inches. Callas are at their best in cooler sections of the island such as Volcano and Waimea, but will grow in warmer sections.
One of the most popular bulbs to try is the amaryllis. Amaryllis bulbs can be planted any time during the winter months. Depending on the variety or hybrid grown, they will flower February through May.
The amaryllis is like most folks after the holidays. It must watch its diet. Too much food and the plant will not bloom, so it flourishes in poor soils like we tend to have in West Hawaii.
Here are a few tips to get your amaryllis to do their best.
First, don’t tempt them with rich foods. Nitrogen-packed fertilizer makes the plant fat and green with few blooms. Like many other bulb plants, amaryllis bloom best when fed a miserly amount of a low-nitrogen fertilizer. The idea is to starve the plant into worrying about next year’s blossom so it will store food into a nice big bulb for the future blossoms, plus giving you a proud display of blooms this year.
If the plants grow rampant on little or no food, try planting them in less fertile soil next time. Rationing water during the late growing stages will tend to produce better bulbs.
Bulbs planted now will put on a flower show in six to eight weeks. Select a fairly sunny spot for an amaryllis bed because too much shade will cause small flowers. Deep shade might cause the bulb to die.
Colors to choose from are red, pink, white and a combination of these colors.
If you can afford them, buy hybrid bulbs. With reasonable care, they will give you bigger and better blooms.
With fancy varieties, when the tops of the amaryllis die back in the fall, it is time to dig and store the bulbs. Upon digging, remove the smaller offset bulbs from the “mother” bulb. It will take about three years for the juvenile bulbils to bloom, but in the meantime, the mother bulb will show her colors plus produce additional infants for future generations of flowers.
Propagating bulbs by division is an interesting hobby. To try your luck, use a razor sharp knife and a cut a large bulb into a number of pieces. You can separate it into 60 pieces if you have the knack of thin slicing.
Be sure each wedge of the bulb has a portion of the stem tissue attached to the scale portion. Next, dust the wedges with a garden fungicide to prevent diseases and plant them in a flat or bed containing a mixture of peat and sand or other porous medium.
Keep the planting moist and humid, and in about four weeks small bulbs will appear between the scales. The tiny bulbs are ready for potting. Three years later, you will have a bulb that will bloom.
To propagate amaryllis by seed, harvest the seedpods soon after they turn yellow and begin to break open. Dry the seed pods a few days before sprinkling them onto a flat. Start the plants off in full shade, but gradually move them into full sunlight and then transplant them to a sunny spot in the garden.
There are many other bulbs that can be planted at this time in Hawaii, including narcissus. You can also grow tulips here. Just store the bulbs at 40 degrees for 60 days prior to planting and be sure to plant them immediately after removal from cold storage.
Since tulips require cold weather, they have to be replaced every year or grown at elevations of 6,000 feet or higher.
For more information about the culture of bulbs, ask at your local garden shop or nursery. Several gardening books also are available about the subject.