Friday, September 28, 2012

Propagation of Areca Palms

The Areca palm can be propagated from seeds which take 2-6 months to germinate. Fresh seed should be planted in a well drained medium with the top of the seed barely visible. Cleaning the seeds is not essential if they are planted immediately. Areca palms can also be propagated by simple divisions; the offshoots cut from the base of the palm can be used to start new plants. 

The Areca palm (Dypsis lutescens; often labeled as Chrysalidocarpus lutescens), also known as the butterfly palm, is found in sub-tropical and tropical climates. It is also used as a house plant, where it grows well under average home conditions, but after purchasing the plant, it must be acclimatized.  In the nursery, these palms are usually grown in full sun and need to adjust to the low light conditions found in most homes. Start by placing plants outdoors on a shady deck or beneath a tree in mild climates.  After a few weeks, move them to the brightest indoor location and then to their final place. They like medium to high lighting, usually doing well in the east, west, or south windows. Simple directions are as follows: plant in a large container and water frequently but do not allow the plant to sit in water. 

Because of its dense, clustering growth habit, outdoors this palm is primarily used as a hedge to create privacy or to hide unsightly areas. Unfortunately, coqui frogs, an invasive species in Hawaii, find areca palms a good habitat and hiding place.

Tuesday, September 18, 2012

Planting Bulb Onions

Bulb onions are divided into groups depending on how they response to day length. There are short-day, medium-day and long-day types.  Long-day varieties do not do well in Hawai`i.  It is best to plant only short and medium-day varieties. The time of planting is also very important.  Short-day varieties should be seeded from September to March; medium-day from March to May.  Summertime planting is not a good idea.  The short-day, mild-flavored varieties include Yellow Granex, Tropic Ace, Early Texas Grano 502, Excel and Yellow Bermuda.  The pungent varieties are Awahia and Red Creole.  Medium-day varieties include Early Harvest, Amber Express, Pronto-S and San Joaquin.

Onions are shallow rooted and require consistent moisture. Under watering is more harmful than over watering.  However, excess moisture can cause a soft rot to the bulb, irrigating should stop when the bulbs are large enough to pick and the top growth begins to fall over. 

Outside of Hawaii, check with your local University Extension Services to find the best time to plant bulb onions in your area.

Friday, September 14, 2012

Diseases of Lettuce

Lettuce Drop
There are several diseases of lettuce in which the leaves turn brown and mushy at the base. One disease is called lettuce drop, caused by the fungus Sclerotinia sclerotiorum.   It commonly occurs during cool, moist weather.  Symptoms are seen on the lower leaves as the plant approaches maturity.  The lower leaves that are in contact with the soil will wilt. Then they will develop a slimy rot, and the plant collapses.  An interesting feature is the appearance of a white, cottony fungal growth.  Tiny, hard, black ‘seeds’ called sclerotia may also be seen among the white threads.

Control is difficult: 1) keep the leaves as dry as possible,  and 2) use low levels of fertilizers since succulent growth is more favorable to the disease. 3) The fungus can remain in the soil for two or three years, so crop rotation is important. Rotating with corn and onions are two options. Other crops that are affected by this fungus include beans, carrots and celery, as well as cucurbit and solanaceous crops.

Bottom Rot
In addition to lettuce drop, a fungal disease called bottom rot (Rhizoctonia solani) also produces symptoms of a slimy rotting of the lower leaves. Rust colored spots on the leaf petioles and midribs can also be seen. The entire plant will eventually decay and die. The disease is more severe under moist, warm weather conditions. Again, control is difficult. Keep leaves as dry as possible and fertilize sparingly. Planting on raised beds can help to keep the plants free of disease.

Gray Mold
Another fungal disease called gray mold (Botrytis cineria) occurs during cool, moist weather. Symptoms include a brown, slimy decay on the undersides of leaves. A fuzzy gray growth can often be seen.

In general, various bacteria also infect lettuce plants. They enter the plant tissue through stomata or wounds. Cool and moist conditions favor the disease. Symptoms include brown spots, a slimy rot and wilting.  These diseases can result in the decay of the entire head.  Applications of copper based bactericides are recommended. 

Tuesday, September 11, 2012

Air Potatoes

The air potato (Dioscorea bulbifera) is also known as an air yam and Puerto Rican potato. It is a member of the yam family and native to Asia and sub-Saharan Africa. Air potatoes can be found throughout the States of Florida, Louisiana, Mississippi, Texas, Hawaii and in Puerto Rico.

It is a vigorously twining, herbaceous vine often growing to 60 or 70ft. in length.  The plant produces underground tubers as well as aerial tubers called ‘bulbils’ which form in the leaf axis.  These bulbils are smooth or warty and range in color from a light tan to a dark coffee color.

In many parts of the world the tubers and bulbils of D. bulbifera are used as food, and the plant is cultivated as an agricultural crop. In Hawaii they are eaten steamed or boiled.  They have been reported as being poisonous when raw but may be eaten after peeled and cooked.  In Florida it is reported that uncultivated forms are bitter and even poisonous.  They consider these plants to be toxic and should not be consumed. 

In Florida it is listed as a Category I invasive exotic plant. This means that it is currently altering native plant communities by displacing native species and changing community structures. 

Friday, September 7, 2012

Black Bugs All Over Gardenia Blooms

In the late spring and early summer, the gardenia shrub rewards the gardener with an abundance of fragrant blooms.  And as long as they are on the tree, there doesn’t seem to be a problem.  But once the blooms are snipped off and brought into the house, hundreds of tiny black insects called thrips appear.   (It is thrips – whether singular or plural)

These Hawaiian flower thrips are small insects about 1/20 of an inch long, dark brown to black in color. They have piercing-sucking mouthparts which can cause discoloration of the flower petals: they become flecked, spotted, or deformed.  These thrips feed on the flowers, while other thrips can also feed on leaves causing a malformation of the leaf and sometimes even defoliation. Thrips are also a serious pest of coffee, mango, citrus, passionfruit, roses and bananas.

Flower thrips are concealed very tightly within the flower petals of the gardenia. It is difficult for foliar insecticides to penetrate. Using a systemic insecticide, in this case, is more suitable; products with the active ingredient imidacloprid or acephate can be used.  Perhaps a more appropriate solution would be to dip the cut blooms into a bowl of water containing a few drops of liquid dishwashing soap and swishing around. This may not get rid of all the thrips, but it will help.

Gardenias originally came from China.  When a British naturalist received one of these plants in 1761, he named it after his friend Dr. Alexander Garden, a noted botanist and physician in the US.    

Tuesday, September 4, 2012

Popolo: An Important Medicinal Plant

The Hawaiian name popolo actually refers to a number of species of plants in the Solanum genus, a member of the nightshade family.  They are annual or perennial herbs, up to 4 feet tall. There are four species of Solanum native to the Hawaiian Islands. One species, which may have been an early Polynesian introduction, is S. americanum with reportedly edible fruits. Three endemic species are pōpolo kū mai (S. incompletum), pōpolo (S. nelsonii), and pōpolo ʻaiakeakua (S. sandwicense); all of which do not have edible fruits.  S. americanum occurs in a wide variety of habitats including coastal forest, wet forest, pastureland and disturbed roadsides from sea level to over 7800 feet on all of the main islands.

Popolo is an important medicinal plant reported to treat respiratory problems and also for sore muscles, tendons, and joints. It is often used by itself or mixed with other ingredients. In addition, the blackish purple fruit and green leaves were used for dyes.

The fully ripe black berries of the pōpolo (S. americanum) were enjoyed by early Hawaiians; however, the green berries are poisonous, containing solanine along with other nightshade toxins. The leaves were wrapped in ti leaves, cooked in an imu and eaten in times of food scarcity. 

Some other edible and favorite crops in this nightshade family include tomato, eggplant, peppers, cape gooseberry (pohā berry) and tomatillo.

The following two websites give information about Hawaiian medicine and popolo in particular:  and  I am not familiar with these websites and cannot vouch for their accuracy.