Justin Newcombe: The best of blooms

Hydrangea cuttings should be taken in November. Photo / NZ Herald

Landscape gardener and Life columnist Justin answers your questions.

I liked all the advice about the hydrangeas last month, but when is the best time to take the cuttings? My neighbour has some beautiful examples and I am keen to set them up along my fence-line.

- Jennifer

You still have time. Don't start your cuttings until November and keep them potted up for 12 months. This gives them a solid amount of time to develop roots. The two key things for a successful cutting are to make sure you use a sterile plant mix like pumice sand and that the cuttings don't dry out. Generally speaking the more warmth hydrangea cuttings get, the faster they strike. Though I have seen hydrangeas stuck directly into a garden bed, there are so many variables I wouldn't recommend it for your first go.

Can you give me advice on clay soils? There is a tiny section of my pathway which is made up of clay. It collects water every time it rains and becomes soft, making it hard to drive on. I tried putting pebbles/stones on the pathway to help with drainage, but today after the rain the area still flooded, although the water didn't hang around for long as it usually does. Even with the pebbles/stones that section of the pathway is still soft. Do you have any ideas on how to get rid of or improve clay soil so that cars can drive over it? I read somewhere that putting bark on clay soil can help, is this true?

- Susan

What's important here is if you can't drain or control the water in some way, that you stabilise the ground when you drive over it. To do this you need to separate the soil from the aggregate using a geotextile, otherwise silt from the soil will contaminate the aggregate and it will in a short time become ineffective.

It's hard to prescribe the best one without having seen the spot in question but a Permathene Plastics product like Syntex Nonwoven would probably help. There are also several plastic "cell" type products which hold the aggregates together making the surface more solid. A combination of the two will keep the stones on the path clean as well as making the surface more stable.

What to do right now

* Prepare the soil with plenty of organic material. Trench in seaweed and leaf mould with a light dressing of sulphate of potash for low-nitrogen loving plants and add plenty of sheep pellets, compost and animal manures to increase nitrogen. For beds not being planted out until December, consider growing a quick green crop. Dress the beds with gypsum which contains calcium. Calcium will break up heavy soils and is essential if your soil is going to retain minerals.

* Plant dwarf or shrubby beans such as borlotti, cannelloni and lima beans. Regular watering will help ward off mealy bug attacks on the stressed roots. Dressing the hole with neem tree granules at planting time can reduce these attacks but focus on planting the beans in a soil which has an exceptional tilth (crumbliness) and is light on carbonic material. Many composts have small amounts of semi or un-composted material which attracts mealy bugs and small slugs. The bugs themselves have a waxy coating which helps them resist water. Last year my crop of borlotti beans suffered a root attack of mealy bugs so this year I'm fighting back with a mixture of garden friendly dishwashing soap (around a teaspoon per litre of water) and pyrethrum spay (follow the dilution rate on the packaging) mixed in a litre and water.

* I'll water this around the roots of the plants and I estimate each litre of this mixture will treat around three to five plants. This will need to be repeated every 10 days to be effective. Be vigorous, mealy bugs will destroy a crop of beans in a week.

* Direct sow pumpkin, climbing beans, beetroot, carrots, parsnips, peas, radish, squash, swede, sweetcorn and turnips.

* In trays sow Chinese cabbage, aubergine, capsicum and chilli peppers, celery, cucumber, leek, lettuce, silverbeet, spinach, spring onions, tomatoes, watermelons and courgettes.

* Feed roses with manure or sheep pellets, no need to dig it through the soil. If you're really keen you can mix up a manure tea and pour that around the base of the plants. Check for aphids and black spot. Spray aphids with Tui Eco-pest and spray to prevent black spot with baking soda spray.

* Feed and mulch fruit trees. A healthy dose of seaweed dumped under the dripline can work wonders. Dress the seaweed with gypsum and cover with tree mulch.

* Install a tea barrel. We use a plastic barrel to soak seaweed, garden weeds and beneficial plants like comfrey and borage. The resulting liqueur or tea can be put into a spray pack, watered down and sprayed as a foliant. This is an effective, safe way of invigorating your spring plants but make sure you give them a wash when you harvest. If you add urine to this (it's quite safe) you'll have the perfect spray for your lawn.

* Give hedges a light trim. If possible try to cut through the middle of new growth. The aim is to get the new growth to bifurcate. If it's removed altogether, the plant will need to start all over again. Aim for a thick bushy plant wall through summer.

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