FAQ - Landscape Plants

1. Every fall the leaves on my gardenia and hibiscus shrubs turn yellow and drop.  What could cause this?
In fall and spring, when night temperatures are cool and days are warm, it is not uncommon for some leaves to turn yellow and drop. There is no treatment or prevention for this. If yellow leaves and leaf drop occur at other times of the year, it is a sign of stress resulting from water stress, improper fertilization, root disorders, nematodes, or misuse of chemicals. See: http://www.geocities.com/hibiscusred/bug/disorders.htm#Yellow_Leaves

2. The flower buds on my hibiscus and gardenia plant drop before they open.  What could the problem be?
Bud drop is often a problem with both of these plants and can indicate an insect problem, cultural/environmental problem, or a characteristic of that variety.  Insects called thrips can damage the unopened bud. These may go undetected until considerable damage has occurred and the buds drop. See Insect Management Suggestions. Too much or too little fertilizer and/or water can stress the plant resulting in bud drop. Nematodes can attack  the root system reducing the plant's ability to take up water and nutrients. Some varieties of hibiscus, especially doubles, are characterized by premature bud drop. Some varieties bloom well during one period of the year and consistently drop their buds at all other times.

Hibiscus flower bud drop is a common problem usually caused by a midge.  Peel back the petals of a flower that has, or is about to fall off.  Look for a very small yellow worm-like insect.  It is smaller than an inch worm and will hop when disturbed.  This is the gall midge larva (Contarina maculipennis).  The adults lay larvae on the plant.  The larvae develop in the bud, then drop to the ground to pupate.

There are no official recommendations for control.

3. Should I mulch my plants?
Mulching is considered a beneficial practice for all ornamental plants. Mulching conserves soil moisture, insulates the soil (keeps it cooler in summer and warmer in winter) and suppresses weeds. Organic mulches such as shredded wood, pine needles, or oak leaves are preferred to inorganic mulches such as pebbles and stone. The desired depth of the mulch is 2 to 3 inches after settling.  The area immediately around the stem of the plant should be left free of mulch.