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More questions you always wanted to ask about gardening

Why do gardeners use Latin names?

Many years ago, plants were known by long, descriptive names that were different all over the country. Then the botanists got together and worked out that if a plant had a single name, they could all be sure they were talking about the same one - not just in this country, but all over the world.

Many of the Latin names are simply descriptive of the leaves, flowers, growth habit, the place where the plant was found or where it prefers to grow. Others are named after people, especially plant hunters or the people who financed them. Learning a few of these terms, far from being “snobby”, can help you get the right plant for the right place.

What does deciduous mean?

Trees and shrubs are either deciduous or evergreen. Ever-green plants keep their leaves through the winter, shedding older leaves all the time throughout the year. Deciduous plants lose their leaves in autumn, usually over a short period and especially after a frost. Nutrients within the leaf are drawn back into the body of the plant to help it survive the cold weather, then the tree or shrub literally shuts off the connection and the leaf falls away.

Why do plant leaves turn yellow?

Assuming that this is happening when it is not autumn, the main reason is a nutrient deficiency. Plants need food to survive and, if they run out, it shows as yellowing leaves. Different deficiencies show in different parts of the leaf (between the veins or round the edges, for instance) and also as different colours, including purple.

Yellowing may also be caused by insects feeding on the leaf and sucking out the sap. This is usually patterned, rather than patchy, and you may see the insects if you look underneath the leaf.

What does hardy mean?

A plant’s tolerance of cold conditions is classed on a scale of hardiness, with some able to withstand deep freezing cold and others being killed by a single frost. Even when a plant is described as “hardy”, it may not survive below a certain point and if you live in a particularly cold area, you may need to take precautions like erecting a windbreak or tent to protect your favourite plants.

The term half-hardy is used to describe plants that will tolerate being outdoors through the late spring, summer and early autumn, but even moderately low temperatures are likely to kill them.

What's the white fuzzy stuff on the compost of my indoor plants?

This is a mould that is present in the compost and grows on residual fertiliser within the compost once it is kept constantly damp. It is easy to remove and you can prevent further regrowth by watering the plant from below, using a saucer, and keeping it a little drier. It tends to be worse in spring and autumn, when the air is moist. Do insects kill plants?

Eventually, given a bad infestation they can kill plants because they suck sap from the plant and deprive it of food. Some insects can transfer deadly virus from plant to plant, as is the case with the current rapid spread of the Xylella (pronounced Zylella) virus that has wiped out thousands of olive trees in Italy and has been identified in both Spain and France.

It is vitally important to the UK that no-one brings back cuttings or plants from holiday in their suitcase for this reason.

Are garden chemicals dangerous?

Any chemical is potentially dangerous if it is used incorrectly. In the UK, we have some of the tightest controls anywhere in the world and the products are rigidly tested. As long as the instructions on the pack are followed, then “the right chemical, used in the right way and at the right time” can save a lot of damaged plants. Remember that even beer is, technically, a chemical but it is not tested or approved for use in a slug trap.

Untested chemicals can have unwanted side-effects - for instance, using washing-up liquid is not a safe way to deal with aphids. Old-fashioned insecticidal soap (on which this is based) was a very different product to the one designed to strip grease from today’s dirty plates. The outer coating of a plant leaf is based on waterproofing natural oils and the washing-up liquid strips this away, leaving the leaf vulnerable to sun scorch. Using chemicals, whether man-made or based on natural extracts, is a matter of personal preference.

Can you keep a poinsettia for another year?

Poinsettias originate in Mexico, where they grow into big, sprawling bushes, but they have become a staple of the Christmas market. The look best when they are young and healthy, and can quickly begin to shed leaves if they get chilled or dry. Keeping them for a second (or subsequent year) means trimming them back to keep them compact, repotting and feeding well.

In order to get red bracts in time for Christmas, the plant needs at least 14 hours of total darkness for 8 weeks. The easiest way to do this is to cover it with a black bag from 6pm to 8am every day for 8 weeks, starting in mid-September. During the day, provide as much light as possible.

What's the difference between annual and perennial plants?

A perennial plant lives for many years, an annual for just one year and a half-hardy annual only for the summer months as any cold temperatures will kill it. A biennial plant grows one year and flowers the next, then dies off so you need to keep seed if you wish to grow it again.

What does “organic” mean?

Literally, it means life forms based on carbon, but today it refers to a gardener who does not use any manufactured chemical products, even those based on natural extracts. This form of production is labour-intensive and can incur heavy losses due to pest and disease attack initially, but if a good balance of wildlife can be encouraged in the garden, the results will improve and with the added bonus that edible produce is free from chemical residue.

Do beware of “quack” online remedies that use dangerous and potentially carcinogenic extracts instead.

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This story was published on: 09/11/2019

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