When should you harvest plums?
As plums approach maturity, the fruit develop their characteristic color. The fruit of blue or purple varieties (‘Stanley,’ ‘Damson’ and ‘Mount Royal’) change from green to greenish-blue, then to dark blue or purple. The ripened fruit color of other varieties varies from yellow to red. Color, however, should not be the sole basis for harvesting plums. As they ripen, plums begin to soften, especially at the tip end. They also develop their characteristic flavor.

This summer, a yellow, foam-like growth suddenly appeared in a mulched perennial bed. What is it and will it harm my plants?
The “growth” in your perennial bed is probably a slime mold. Slime molds are types of fungi. Slime molds feed on bacteria and other organisms in the mulch. They do not harm plants.

Slime molds are usually a temporary nuisance. Within a few days, slime molds typically dry up and turn into white, powdery masses. Most individuals simply let the slime molds dry up and fade away. However, the slime molds can be scooped up and discarded if you find them objectionable.

Why are my junipers turning brown?
Two fungal diseases can cause tip browning on junipers. Phomopsis tip blight and Kabatina tip blight both cause the tips of branches to turn brown and die. 

Phomopsis tip blight attacks succulent new growth from mid-April to September.  Needles turn dull red or brown to ash-gray. Often small lesions form around the twigs, causing the twigs to die.  Small, round, black fungal fruiting bodies can be found in the lesions.

Kabatina tip blight attacks the plant before Phomopsis tip blight, usually in February or March. Affected branch tips turn dull green, then red or yellow.  Gray lesions with small black fruiting bodies appear on the discolored tissue.  The dead branch tips typically fall off in late May or June.

Both diseases can be prevented by planting resistant varieties of juniper, allowing for adequate airflow between plants, watering in the morning so foliage has a chance to dry during the day and pruning out infected branch tips. Pruning should be done in summer rather than spring or fall.

When should I cut glads for indoor use?
Gladiolus for decorative indoor use should be cut as soon as the bottom flower on the spike has opened. Most of the remaining blooms will open when the spike is brought indoors and placed in water. When cutting gladiolus, leave at least 3 or 4 leaves at the base of the plant. Early morning is the best time to cut glads.

What is the huge wasp in my yard?
The large wasp flying around your yard is a cicada killer wasp.  Cicada killer wasps have black and yellow abdomens, rust colored wings and are about 2 inches long. Female cicada killer wasps capture cicadas in July and August and place them in cells located at the ends of tunnels they have dug in the ground. One or two paralyzed cicadas are placed in each cell, and a single egg deposited before the cell is closed by the female. The wasp grubs feed on the cicadas and develop into wasps that emerge the following summer.

Cicada killer wasps are intimidating because of their size, but they are not aggressive wasps and will only sting if mishandled.  Control of cicada killer wasps is only necessary if a female has placed her tunnel in an area where contact with humans is very likely.

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Two print quality photos are available for this column.

Cicada killer wasp

Slime mold on a perennial leaf