More recent landscape questions and answers

Horticulture

Plant containers in winter

Do empty plant containers require any special precautions during the winter?

Small containers made from clay, plastic or metal need to have the soil removed and the containers cleaned. Large permanent planters containing winter hardy plants will need little protection if the drainage in the container is good.

Jay Chism
Agronomy Specialist

Plant samples for analysis

I have plant samples I want analyzed for nitrogen, phosphorus and potassium contents. How should I prepare the samples? What size sample is needed? How quickly can I get the results? And what is the cost?

Oven dry clean plant samples at 65 degree C and grind the samples using a Wiley Mill or dry grinder. The Soil and Plant Testing Laboratory needs a minimum one gram of dried ground sample for nitrogen, phosphorus and potassium analysis. Results will be available within five working days of the laboratory receiving the samples. The cost is $17 per sample.

Manjula V. Nathan
Director
Soil Testing and Plant Diagnostic Services

Deep-root fertilization

A lawn service company has recommended a deep-root fertilization for all of my ornamental trees and shrubs. They contend this is more effective than applying any granular fertilizer. What are your recommendations for fall feeding of ornamental trees and shrubs?

There are various methods of fertilizer application for shrubs and trees including injecting liquids into the soil, placing dry fertilizer in holes drilled in the soil, applying fertilizer to the soil surface and spraying it on the foliage. Which method you choose should depend on the site and plant condition.

With most woody plant species, surface application is as effective in provoking a positive plant response as other methods. This method requires the least application time and is the least expensive, but it could cause excessive growth in high quality turf areas.

Liquid injection of soluble fertilizer into the soil is rapidly absorbed by the roots, and is an excellent method of correcting deficiencies quickly. Injection sites should be two to three feet apart, depending on pressure, and six to nine inches deep. Fertilizing deeper than nine inches may place the fertilizer below the feeder roots. The addition of water to dry soil is desirable in summer or during periods of drought.

A major advantage to the drill hole method is the opening of heavy (clay) or compacted soils, which allows air and fertilizer to penetrate. With this technique and liquid injection, you avoid the excess grass growth that surface applications cause in turf areas.

The drill holes should be placed in concentric circles in the soil around the plant, beginning three feet from the main stem and extending three feet beyond the drip-line. Space holes two feet apart and drill them 15 to 18 inches deep. The recommended rate of fertilizer should be uniformly distributed among the holes. Fill small holes with sand following fertilization, but only partially fill large holes.

Manjula V. Nathan
Director
Soil Testing and Plant Diagnostic Services

Bringing insect-free plants inside

I brought my ficus tree outside this summer and now need to bring it back inside. What do I need to do to it to make sure I'm not also bringing in unwelcomed pests without resorting to poisonous and toxic chemicals?

Carefully inspect your ficus before bringing it inside this fall. This should be done with a hand magnifying lens in that some insects and insect eggs are very small. If you do see insects or insect eggs then treating with insecticidal soap is a very safe way to rid your plant of unwanted pests. This material is available at most yard and garden stores; M-Pede is a popular brand name.

David H. Trinklein
Department of Horticulture

Postharvest handling of sweet potatoes

I am ready to dig my sweet potatoes. I should get about 50 pounds or more with several three pounds or bigger. How should I handle my harvest? Should I clean them or leave the dirt on? Should I refrigerate or store in a cool, dark place?

MU publication G6368, Growing Sweet Potatoes in Missouri should answer your questions.

James Quinn
Regional Horticulture Specialist