Though many think we have eternal summer here, most of us and our plants know better. Today’s summer solstice marks the longest day of the year in the Northern Hemisphere. The sun rose at 5:46 a.m. and will set at 7:06 p.m. Today, we will soak up more than 13 hours of sunlight. That’s a lot of tropical sun for us and our plants.
The word solstice derived from the Latin word solstitium, which literally translates as the stopping of the sun. On summer solstice, the Earth’s rotation causes the sun to reach the farthest north point from the equator and it appears to stop before reversing its course southward until the winter solstice in December.
Though summer solstice marks the beginning of summer in many places, it is actually mid-summer for plants. Day length has been increasing for months and will now begin decreasing. These sun-filled days before and after the solstice cause our warmer summer days. From a plant’s point of view, the longer days allow for more sunlight exposure on their leaves and more hours of photosynthesis. This process combines the energy from sunlight with the water absorbed through the roots plus carbon dioxide from the atmosphere to produce glucose for the plants and oxygen that is released into the atmosphere. Summer solstice is a feast day for plants.
If our plants are enjoying this long day, imagine the picnic plants are having in Fairbanks, Alaska, where the sun rose at 2:58 a.m. today and will not set until 47 minutes after midnight Monday. The “midnight sun” is a phenomenon that occurs from approximately the end of May through mid-July in northern areas near the Arctic Circle. Those in the far north find this season worth celebrating since they will experience only about three and a half hours of sunlight on the winter solstice in December.
Even in Hawaii, a plant’s food budget is reduced during the months with shorter days and most plants will produce less leafy new growth during our winter. Though plants do not usually go into total dormancy in the tropics, growth definitely slows when days are shorter.
Throughout the centuries, people have noticed that planetary movements as well as the sun’s position affect plant growth. The movement of the sun and moon through the signs of the zodiac has long held importance in choosing days to plant, days to harvest and days to merely tend your garden. The signs of the zodiac correspond with the elements of water, earth, fire and air. The moon moves into a new sign every few days. Plants seem to exhibit preferences for different signs. For example, the best time to start seeds of annual plants is during the fertile water signs of Cancer, Scorpio and Pisces. Root crops seem to do better if planted when the moon is in earth signs and flowers especially like the air sign of Libra.
Today, the moon enters the sign of Virgo, which is not a very productive time for planting. By Friday, the moon will have moved through Leo and into the sign of Scorpio, a water sign, which encourages plant growth. Friday, Saturday and Sunday will be excellent planting days. In addition to its favorable position in the zodiac, the moon’s light is also increasing on these days. The waxing moon, the time between the new moon and the full moon, is an excellent time for planting, transplanting and grafting above ground crops. The waning moon period from full moon to new moon is best for planting root crops. It has been scientifically proven that the phases of the moon control the amount of moisture in the soil just as they control oceanic tides. Moisture levels peak at the new and full moons, which translate to good planting times. A short video on planting by the moon is available at http://www.almanac.com/video/gardening-moon. Check it out as a possible way to improve production.
Ancient Hawaiians also realized the effect of lunar movements on plants. For instance, today’s kukolu phase of the moon relates to “standing in threes.” Plantings done today will likely produce three shoots. This hinaiaeleele season also marks a time when heavens, leaves and fruit darken, gourds ripen and taro patches should be mulched.
Based on the lunar positions today, you could choose to plant or harvest or just join your plants in enjoying the day and meet with family and friends to celebrate summer solstice as well as Father’s Day.
Tropical gardening helpline
Doug asks: I have noticed that my banana plants are less productive now than they were a year or more ago. What could be the problem?
Answer: If you have cut down your trees after they produce and let the keiki come up from the corms what began as one or two trees in the original mat might be six or eight trees by now. If that is the case, it could be the reason for less production. Smaller fruit or smaller bunches usually are a result of reduced nutrition. The more trees in a mat, the stronger the competition for a limited amount of soil and nutrients. For better production you may want to limit your mat to four or five trees at different stages of development.
Also, be cautioned that reducing the number of green leaves on a banana plant will reduce its photosynthetic ability. Be careful not to remove leaves the trees need to produce food in order to improve their appearance.
Ideal conditions for bananas are in full sun and out of strong wind with an average temperature around 80 degrees. Bananas grow best where there is at least 100 inches a year of rainfall or good irrigation when rainfall is scarce. The soil should drain well but be able to retain some moisture with a slightly acid pH between 5.5 and 6.5.
Banana trees love mulch. You can mulch them by cutting up felled trees and leaving them in place or adding any other organic matter. Bananas are heavy feeders and need lots of potassium. The cut up trees will add some but a fertilizer that has a rating around 10-5-20 applied at about 2 pounds every four months should help boost production.
Email plant questions to konamg@ctahr.hawaii.edu for answers by certified master gardeners. Some questions will be chosen for inclusion in this column.
Diana Duff is a plant adviser, educator and consultant living on an organic farm in Captain Cook.