Spring officially occurs when the sun reaches the Equator as it appears to move northward. Of course what is actually happening is that the earth is tilting toward the South Pole and will continue to do so until June 21. Then it is officially Summer. Since we are roughly at latitude 19 degrees north, the sun will appear to move northward for a short time and then move toward the south until December 21. Many plants respond to day length including plants that form bulbs.
At this season most mainland gardeners become bulb conscious. Even in Hawaii, garden magazines and garden supply stores feature bulb, corm, tuber and pseudobulb advertisements as well as displays. An example of the latter are the thickened stems at the base of each growth like we see in the Chinese Ground Orchid or Phaius tankervilliae. 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 true bulbs grow best in a well drained soil and a 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 we have already mentioned. Callas will perform best in a soil that has considerable organic matter and is retentive of moisture, but not soggy. In order 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 like Volcano and Waimea, but they will grow in warmer sections as well.
One of the most popular bulbs to try is the amaryllis. Amaryllis bulbs can be planted any time. Depending on the variety or hybrid grown, they will flower from March 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. Wild Amaryllis may even be seen growing along some of our roadways and around older homes up country.
Here are a few tips to get your amaryllis to do their best. First of all, 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 that 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 6 to 8 weeks. Select a fairly sunny spot for an amaryllis bed because too much shade will cause small flowers. Deep shade may 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 divide the bulbs. Upon digging, remove the smaller offset bulbs from the mother bulb. It will take about three years for the juvenile bulblets 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 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 that 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 the seeds onto a flat of soil. 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 Fahrenheit 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 or more feet.
Clivia from South Africa is another that will bloom intermittently throughout the year. Clivia does well in the shade or sun.
For more information about the culture of bulbs, ask at your local garden shop or nursery. Several gardening books are also available on the subject. Check with our UH master Gardeners for more tips. In Kona the number is 322-4893 and Hilo call 981-5199.