Q. I have several orchids – gifts during my recent illness. The blooms are gone. The plants are thriving. What must I do to get them to bloom again?
Mary Jane Marshbanks, Buies Creek
A. I grew orchids for many years and found the most common types – phalaenopsis orchids – are relatively easy with the right conditions. Those conditions include warm temperatures, plenty of moisture and bright, indirect light. They are usually grown in fir bark or something similar, which will provide excellent drainage. They can be watered regularly, perhaps two times weekly during the winter, or can be kept moist by misting them daily. Use an orchid or African violet fertilizer at one-fourth strength with every watering. Your plant will flower at irregular intervals about one to three times per year.
Q. Three years ago, I saw the awesome displays of Taishan marigolds developed for the Beijing Olympics. I did research on them and found that they are an African marigold developed to be short like the French marigolds but with giant heads (4 to 5 inches) not tall like the African ones. The displays were incredible. I had about 20,000 grown for me by a local grower and planted them the next year in my backyard in Raleigh. The displays were awesome, and then suddenly first week of August they were hit with Southern blight and blackened and dead within 10 days or so. N.C. State identified it as the disease. No one had a solution for what to do this summer except replace all soil in every planter and try that. So this year, we did that: replaced soil in more than 20 tree beds and plant beds, lined them with plastic, and planted again about 20,000 plants grown for us by a local grower. Incredible displays all of May, June and July, and then first week of August same disease and all were dead within a couple of weeks.
Is it true there is no preventative or solution that will deal with the Southern blight? I really want to plant them again next year because the impact of these giant marigolds in large masses is powerful, but it seems I can only get 2 to 3 1/2 months before disease destroys them.
Douglas J. Lewis, Raleigh
A. Southern blight is a difficult fungal disease to deal with in the garden. It usually shows up in the crown of perennials or the lower stems, and plants will quickly wilt and die. The fungal resting bodies can survive for several years in the soil and it will grow whenever plants are active, but will grow quickest when temperatures are above 80 degrees and there is plenty of soil moisture.
Controlling Southern blight is difficult but certainly not impossible. Replacing the soil is a very good start, but you also need to make sure you don’t re-infect the new soil using dirty tools or the like. I would advise strongly against a layer of plastic under the soil as that will impede drainage. Mound your beds up and incorporate quite a bit of organic compost as organic material has been shown to impede Southern blight growth. I would also recommend incorporating PermaTill in the soil to aid with drainage. We have found it to be among the best soil amendments. Water plants as needed but not in excess and avoid watering late in the day.
Preventative measures include solarizing your soil by covering it in clear plastic for one to two months. If done during winter, two months would be necessary to kill much of the fungal resting bodies. There are fungicides labeled for use against Southern blight. Talk to a knowledgeable salesperson at your local nursery for recommendations and follow the label directions. One way Southern blight can be transferred is via nursery soil. Make sure you are not bringing Southern blight in with infected soil from your grower.
Mark Weathington is the director of the JC Raulston Arboretum at N.C. State University in Raleigh. Info: jcra.ncsu.edu. Please send your gardening questions, and the city where you garden, to: firstname.lastname@example.org.
Ask a question, win a book
We’re trying to encourage readers to send in their gardening questions. So if you send a gardening question for the monthly Ask the Gardener column by Dec. 31, you’ll be entered for a chance to win a gardening book.
These titles are up for grabs: “Saving Vegetable Seeds,” by Fern Marshall Bradley; “Fairy Gardening,” by Julie Bawden-Davis and Beverly Turner; “Year-Round Indoor Salad Gardening,” by Peter Burke; and “Veranda: The Romance of Flowers,” by Clinton Smith.
The deadline to submit your question and be entered to win a book is noon Dec. 31. Please send your gardening question, including the city where you garden, to: email@example.com.