Question: What is winter aconite?Answer: Winter aconite (Eranthis species) is a tiny ephemeral that bears yellow flowers on 2- to 3-inch stems. Sometimes called wolf’s bane, it blooms in late winter about the same time as the very earliest daffodils in zone seven.

There are eight species of the Eranthis genus, their native range is scattered from Japan through much of Asia and southern Europe. E. hyemalis (from southern Europe) and E. cilicica (from southwestern Asia) have been widely used in the landscape trade and are the most likely species found in the United States.

The term "aconite" comes from the Greek "acone," which means whetstone. It likely got its name because it grew plentifully on rocky ground.

Aconite blooms are about one and a half inches across and somewhat resemble buttercups (they belong to the same family, Ranunculaceae). Although a garden favorite because they bloom early, the plants go dormant after two or three months.

Aconite does well under hardwood trees, where they can take advantage of the winter sun before the trees’ leaves come back. They make a good companion for other small bulbs that bloom at the same time, such as Siberian squill or snowdrops.

Plant aconite in full sun or where it will get sun at least a few hours each day. It prefers slightly alkaline soil that is well-mulched to help hold some moisture during our hot dry summers.

Plant the tubers in the fall. If purchased tubers are dry, put them in moist sand or peat for a few days to rehydrate before you plant them.

Under the right conditions of humus-rich and well-drained but not dry soil, aconite will spread readily into large colonies.

Winter aconite is a poisonous plant, making it a good choice for gardeners who have to contend with deer. The bulb or tuber is especially poisonous and may cause vomiting and visual impairment if eaten.

Q: Is horticultural oil made from petroleum?A: The term "horticultural oil" includes various oils used by gardeners to control certain insects and plant diseases. Most of these oils are highly refined products derived from crude petroleum.

Petroleum-based oils contain paraffin and naphthene compounds. Paraffins are valuable for insect control because they are more toxic to insects and less toxic to plants than other oil compounds.

Oils containing naphthene have less insecticide value and are more likely to injure plants. Today’s highly refined oils contain fewer naphthene compounds than the older oils that were used only on woody plants before they began to get leaves in the spring.

Over the years, a number of different and often confusing names have been applied to various oils for horticultural use.

Dormant oil is used on dormant woody plants, especially fruit trees. Since modern oils are so highly refined and less damaging to foliage, the term dormant oil now refers more to the season and rate applied than to the type of oil.

Superior oil (supreme oil) refers to highly refined oils that can be used both on green foliage and on dormant stems. Modern oils on the market are superior oils, and label directions specify the correct application rates for each specific use.

Narrow-range oil is light oil that evaporates more rapidly than heavier (less refined) oil and the term means the same as superior oil. Plants have a greater margin for safety if the oil evaporates quickly.

Neem oil comes from the seeds of the neem tree (Azadirachta indica) and is used both as an insecticide and a fungicide.