Most asked gardening questions in Auckland, New Zealand answered

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In this blog post, Skills Update Horticulture tutor, John Grant, answers your most burning gardening questions!

How often should I water my plants?

Most plants like the soil to be moist but not excessively wet. Have a feel of the soil – if it is on the dry side it is time to water. In a very dry summer this could be daily. Seedlings, especially, are likely to need this. That said, you are better to water more deeply and less often. A quick spray with the hose can actually be damaging as the water doesn’t penetrate very deeply. This causes the roots to grow upwards and into the zone more vulnerable to drying out.

Why won’t my plant flower or fruit?

If fruit plants flower but do not bear fruit, the most likely cause – in Auckland, anyway – is lack of pollination. In order to fruit, most plants need pollen to fertilise the flower. There are a couple of things that can go wrong with this process.

A lot of this pollen-movement work is done by bees. If there aren’t many bees around – or that the weather is very bad during flowering – pollination might not happen.

Many fruit plants need another tree of the same kind to pollinate them. Even if they are a kind in which each flower is both male and female, they still have ways to avoid pollinating themselves. And it has to be one that is flowering at the same time. Plums, nashi, and some feijoas are classic examples; you can get lists of plum varieties that will pollinate one another.

Another possibility is that frost at flowering time is damaging the flowers and stopping them forming fruit.

Thirdly it is possible that your tree is putting its effort into vegetative growth at the expense of flowering. Trees that are doing this have a lot of vertical growth. Sometimes it is the result of excessive pruning. An excess of nitrogen fertilizer also encourages this problem.

When is the right time to prune?

In pruning we talk about the “three d’s” – dead, damaged and diseased. You can undertake light correction of these anytime. For more structural work, the usual time is when the plant is dormant in winter. The exception is stonefruit, in which we often undertake summer pruning when the risk of infection with the silverleaf disease is low.

Which are the fastest growing vegetables in New Zealand?

Some of the quickest are leafy greens including the Asian cabbage types, pak choi, mizuna, tatsoi, loose-leaf lettuces, and rocket. In these types you can pick just some of the leaves as you need them, leaving the rest of the plant to continue growing. Other speedsters include radish (eat three weeks from sowing!), spring onion, and beetroot.

Which vegetables grow in shade?

The leafy greens mentioned above do okay in shade. In spring/summer shade might slow their attempts at going to seed. Also, in summer the brassicas – cabbage, cauliflower and broccoli – might do well in shade. Kale and spinach would work. Among the herbs, coriander and parsley would be good summer shade choices.

How often should fertilisers be used?

This is a very broad question. For spring vegetables it is best to work organic matter such as compost, horse manure and perhaps lime into the garden in autumn and let it improve the soil through winter. Closer to sowing you can add blood and bone. It is also possible to add synthetic fertilisers as a base dressing at planting but extreme care is needed to keep the fertilizer well away from the plant roots or you risk damage. Once the plants are growing some people side dress with synthetic fertilisers. Heavy feeding plants this can be as close as three-weekly intervals. Be careful that the fertiliser does not touch the plants or it might burn them. For fruiting crops, including tomatoes, different fertilisers are used at different stages of the crop. Young plants respond to nitrogen to give good vegetative growth, while during flowering and fruit development, potassium becomes important.

Fruit trees and ornamentals are usually given fertiliser at the end of winter.

We hope you find these answers helpful!

In this internet age one can easily obtain information, tips, and advise from innumerable sources. However, if you would like to obtain hands-on assistance and guidance from an experienced professional to achieve optimal gardening results, consider enrolling in a short gardening course.