Good drainage needed for gerberas

00:07, Feb 12 2014

Our gardening expert offers up tips for gerberas and potatoes.

Q How do I look after gerberas? I received a potted one a while ago as a gift and I wanted to grow it in the garden. What position, soil, care, etc, does it require?

A. Gerberas like a slightly acid soil in a sunny, frost-free spot. A mulch of peat will provide the acidic conditions they like. While plants should be kept moist, good drainage is essential as gerberas do not like wet feet. Plant in raised beds if necessary. The crown of your plant should never be covered in soil or mulch, otherwise rot may set in. Feed once a month and you should have flowers from spring through to autumn.

Q. What is the best way to treat clay soil? We want to start a vege patch but our soil is full of clay.

A. While some plants grow well in clay soil, you will be able to grow a better range of plants if you improve your soil's structure and drainage. A generous application of compost, aged manure, leaf mould or other organic matter, dug into the soil each year, will gradually improve your soil's structure. Calcium in the form of gypsum also helps break up and loosen soil. You need to add this as well as the organic matter, not as a replacement for it. However, it's not an overnight solution. You need to apply gypsum each year for at least three years.

Traditionally, potatoes are used to help break up clay soils, as they do not need a fine tilth, and earthing up the soil helps to break it down. You could try growing potatoes this year, as well as runner and French beans, which do well in well cultivated heavy soils.


Q. Last year my tomatoes had a white, hard layer under the skin. I fed them with tomato food and they were watered every second day. Could there be something lacking or some additional nutrients that I should be feeding them with?

A. This disorder is known as internal white tissue and is believed to be caused by high temperatures during the ripening period or insufficient potassium.

As you are using a tomato fertiliser, which should have sufficient potassium levels, the culprit is likely to be heat. Good ventilation and shading during the hottest part of the day during summer may help.

Q. My potatoes have wart-like growths on them. They scrub off, and the potatoes are fine, but what are they?

A. It sounds like scab. The good news is that scab is merely disfiguring; it does not affect the eating quality of your potatoes. Scab is a soil-borne organism and will reinfect your crop if you plant it in the same location the following year. You should rotate your crops each year. Next year, plant them in a spot well away from where you planted them this year. Don't add lime to the soil as alkaline soil encourages common scab. Do not add fresh manures either for the same reason. Powdery scab (which shows raised pustules with a powdery mass) often occurs when soil conditions are cool and damp when tubers are forming. So if you have powdery scab, plant them later in the season next year. Also buy certified seed potatoes for your next planting.

The Southland Times