Landscape gardener and Life columnist Justin answers your questions.

I have been trying to grow hydrangeas from cuttings but have had a lot of trouble with my cuttings rotting away at the base. Also, do I let the leaves grow or do I chop these off ?
- Sam Buckwell, Papakura

The most important thing with cuttings is to use a good sterile medium to plant into. Usually this is a potting mix with extra pumice, or it could be pumice on its own. The pumice provides a warm environment free of nutrients - this is important because it is usually the nutrients that feeds the pathogens that rot your cuttings. The higher the percentage of pumice you use, the more you need to water.

Select slightly woodier cuttings from as close to the base of the stock plant as possible. Woodier cuttings are more likely to throw roots than shoots.

Try using rooting hormone. This stimulates root creation and will improve your strike rate no end. And yes, keep removing the leaves because this encourages more root growth.


We installed raised planters with new soil three years ago. The first year everything grew really well but the subsequent years have seen our results drop away. Can I do anything to help before I plant this spring ?
- Mark Anderson, Northcote

It sounds to me like your soil needs a little work, so try adding a little more compost and sheep pellets in between plantings just to build up the soil health. In smaller gardens and planter box situations you may want to try "square foot gardening". This is an intensive way to garden small spaces - one of its cornerstones is crop rotation, which will help keep your soil in top condition and reduce pests and disease.

I planted a lemon tree two years ago and it has hardly grown - the flowers and fruit drop off and the leaves are always yellow and have started falling off. I have tried fertilising and watering it but nothing's working. Help!
- Fiona Martin, Kingsland

This sounds like a classic case of wet feet, so I'll assume your tree is either planted in clay soil or it is planted too deeply, or maybe both . Lemon trees like to be raised out of the ground slightly so try to gently lift it using a garden fork, not a spade. Place compost or plant mix and sheep pellets around the tree and fork into the ground as you raise the tree.

Your tree should be raised on a little mound. Once you have done this, try feeding it with Sequestrone Plant Tonic, which will provide magnesium and help repair the yellowing leaves.

Lemon trees have shallow root systems which do better without competition, such as from grass. Concentrate on growing soil around the tree rather than just fertilising. Using a fork, dig a ring from the trunk to a foot past the drip line (outer branches), cover with mulch compost and sheep pellets and top up regularly. Be careful not to heap material around the trunk . Great soil conditions produce great trees.

My tangelos are always sour, even though they are bright orange and juicy. What should I do?
- David Mitchcombe, Remuera

Firstly you need to wait a bit longer before you harvest your tangelos. The fruit will go a fiery orange quite early in their development but are not usually ready until they take on a slightly more yellow hue. Leave them until later in September and keep the tree well mulched. Once you have finished harvesting, prune, mulch and feed your tree as it will soon be flowering again.


I have oxalis all over my garden. Is there any way I can get rid of it without killing my other plants?
- Anne Mason, Henderson

You will need the patience of a saint and the tenacity of a hungry dog to get rid of this stuff, but keep at it, bearing in mind that dealing with oxalis is more about management than total eradication. Oxalis grows from small bulbs from quite deep in the soil, so sprays are usually ineffective (and damage desirable plants). Pull it out and cover the affected areas with newspaper and mulch, repeating every time it comes through.

Before planting a new patch of garden, cover the area with thick cardboard or old carpet. When you lift the card or carpet you can see the sprouted bulbs growing along the ground. Eventually the bulb will run out of juice and become unviable.

Weekend Diary


Start planning your spring and summer garden now. Take some time to sketch a plan, and visit the experts to decide which plants you should get into the ground before the soil starts to warm up.


Get your vege garden ready for spring. Clean out the last of the winter crops and prepare the beds with compost and sheep pellets to feed your next round of plants.


Sow peas, beetroot, broccoli, cabbage, carrots, cauliflowers, onions, parsnip, radish, shallots, silverbeet, spinach and lettuce (ask at Kings for the best early varieties).


Try using a "poly tunnel" to give your spring veges a head start. Bend some bamboo poles over your vege rows and cover with polyurethane to create a warm tent for tender seedlings.


Start sprouting seed potatoes in a cold frame or propagation house


Weed around any spring bulbs that are showing their heads.


This is the last opportunity to plant deciduous trees before they bloom. It's also a good time to plant citrus and get feijoa trees into the ground.


Turn your compost heap. If it is soggy from winter, cover it and add some dry material such as straw, or flesh it out with some bagged compost.

* To ask Justin a question, click on the email link below.