Gardening: Potted flowers ailing
Q: I have a flower pot than I’m having a problem with. Last year when I planted it with flowers, the flowers developed white marks on the leaves and lost their vigor. I thought that some type of fungus or disease was affecting them. So I emptied the pot and washed it out with bleach and water. I planted it again this year and the same thing is happening. I have not overwatered.
Plants used were impatiens last year, and petunias this year. Is there any other solution I could use to clean the flower pot? Or any other idea as to what is going on?
- Jack, email
A: It is highly unlikely that contamination from the pot is the cause of the problem. Over the last few years, impatiens have been affected by a virulent strain of a disease commonly called downy mildew. This disease is more prevalent in cool weather and correlates with the growing season of impatiens, a cool season annual.
The movement of the casual pathogen includes being carried by mist, rain, splashing water and wind. At its most symptomatic stage, the leaves will have a whitish downy growth on their undersides.
Preventing the disease is the best way of controlling it. This involves sanitation and landscape chemicals. Another option is to grow downy mildew resistant plants such as geranium and New Guinea impatiens. The problem with the petunia may stem from a different source.
There are numerous diseases including fusarium, phytophthora, pythium and pseudomonas that may be the causal agent. Also, soon after planting, cutworms can devastate soft-stem herbaceous plants and the effect can be mistaken for a disease occurrence.
Q: Is it necessary to fertilize established live oaks, sabal palms, crape myrtles and cassia trees?
- Mark, email
A: If the trees are being grown in association with a fertilized lawn, or ornamental bed, there is generally no need for separate fertilizer applications. Under natural conditions, plants thrive without a drop of fertilizer from humans.
Further, well-established plants can “mine” nutrients from the sand, silt and clay in soils.
However, we have introduced plants estranged from their native soils and climates. Some of these plants, including some trees, especially those of tropical origins, may show yellowing of leaves in winter. This can be natural deleafing due to cool temperatures, or the plant’s inability to take up plant nutrients, due to colder soil temperatures that reduce root metabolisms.
This is not a problem for native live oaks, sabal palms and even crape myrtles. However, the leaves of some Cassias may turn yellow but recover with warm temperatures. There might however be instances where poor soil, or other conditions, warrant fertilization of both exotic and native plants.
February is perhaps our most important month for fertilizer application.
Q: Are there any homeowner classes available through the Extension office?
- Brenda, Fort Myers
A: Yes, it’s called the homeowner garden series. We have classes given each Wednesday starting Jan. 15, from 10 a.m. to noon at the new library on Lee Street in Fort Myers.
Stephen Brown is a horticulture agent with the Lee County Extension Service. Submit questions by calling the horticulture desk at 533-7504 between 9 a.m. and 4 p.m. or by emailing email@example.com.