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Ask a Master Gardener

Dear Master Gardener,

My rose buds are being eaten by many tiny, almost-translucent, green bugs. What are they and how can I get rid of them.

It sounds like you are experiencing an infestation of aphids. They are common on almost all trees and shrubs in Minnesota but most common on ash, oak, maple, willow, fruit trees and—you guessed it—roses. They are also found on many house and garden plants. They are about 1/8 inch long, soft bodied and pear-shaped with cornicles (like tailpipes) on their abdomens.

They are not always green but come in red, black ,brown and grey and have translucent wings. They multiply rapidly and are usually found in clusters. They suck plant juice through fine, needle-like mouth parts and excrete a sweet, sticky substance called honeydew that attracts ants and often falls onto car windshields and lawn furniture.

The presence of large numbers of ants on plants usually means aphids. The damage to plants may appear as off-color foliage, twisted and curled leaves, poor growth, and branch or twig dieback. The least environmentally harmful treatment is use of natural enemies such as lady beetles, lacewings, damsel bugs and a strong spray of water.

Many long-time gardeners find that several high-pressure hose sprays are usually sufficient to greatly reduce aphid numbers. The next step would be the use of insecticidal soap or neem, “biorationals” that kill aphids but not beneficial bugs. Stronger chemical products tend to kill good insects along with harmful ones and should be used only when other methods fail.

Effective chemicals are orthene, malathion, and diazanon.

Dear Master Gardener,

Are geraniums both perennials and annuals?

Geranium, commonly known as Cranesbill or hardy geraniums, is an herbaceous perennial that grows in sun to part shade. They are hardy from zone 3-8. Flowers come in white, blue, lavender, purple and pink.

The main blooming period is in the spring with sporadic bloom throughout the summer. To encourage blooming throughout the season, cut the plant down to the ground after it flowers.

Geranium is considered to be a “deer resistant” plant.

The common garden geranium that we grow as an annual is actually a Pelargonium and originates from South Africa. These plants have a large variety of flower color, growth habit, leaf pattern, and scent. Pelargonium flowers come in white, pink, salmon, fuschia, red, lavender, and bi-colors.

Wait until the danger of frost has passed and the soil temperature has reached 60° F. before planting them outside. These plants also make great container plants. Ideally geraniums should be planted in a sunny spot with at least eight hours of sunlight.

They will not bloom well if they are over fertilized. Allow them to dry out between watering to avoid root rot.

Dear Master Gardener,

How often should I fertilize my flowers during the summer?

It depends. Ideally you should have a soil test done to know exactly what amendments are really required. People have a tendency to use more fertilizer (and pesticides) than needed. You can make the biggest difference in your gardens by adding organic material (compost and composted animal manure), rather than chemicals.

With that said, almost all plants do need nutrients especially when they are producing flower buds and in their most active period of green growth.

When nutrients are limited, plants will show symptoms of distress. On the other hand, high levels of nutrients can reduce plant growth and even kill plants. When purchasing fertilizer, three numbers will be listed on the label in the following order: nitrogen, phosphorus, and potassium. Phosphorus is the element that promotes flower growth. You can purchase fertilizer in dry or liquid form.

Some gardeners like to use Milorganite as a deer repellant, but it is also a fertilizer with a 5-3-2 nutrient composition.

If you haven’t had your soil tested, the elements most likely to be needed in rose beds are nitrogen (N), phosphorous (P), and potassium (K). Evenly spread a complete fertilizer (5-10-5, 4-8-4, or 4-8-6) at approximately ¼ cup of dry fertilizer per plant, then water.

Fertilize in May when you see new growth, then a second time when the first flower buds set, then finally in mid-July. Peonies and clematis can be fertilized lightly in spring with a 5-10-10 fertilizer scattered around the drip line. As a general rule, fertilize most other perennials in the spring as new growth emerges from the ground with an application of 10-10-10 fertilizer.

Container-grown plants need to be fertilized throughout the summer because nutrients get flushed out with watering.

Use a liquid fertilizer according to package directions about every 10-14 days.

Denton (Denny) Newman Jr.
(218) 855-5889