Justin Newcombe: Garlic spritz

Careful watering is vital for limes. Photo / Thinkstock

Landscape gardener and Life columnist Justin answers your questions.

Some time back you had in your column a fruit tree spray containing garlic for fruit trees and for general use. Would you please be able to tell us the quantities.

- Robyn

The spray is made up of garlic water, which you make by soaking four or five garlic cloves in a jar of water for three or four days. Use the same garlic cloves three or four times. The water will stop smelling of garlic when the cloves are spent. I use this with a tablespoon of baking soda, a tablespoon of dishwashing soap and a tablespoon of vegetable or neem oil (I mostly use olive oil) mixed in a litre of water. The soap dissolves the oil in the water. The oil provides a thin, sticky film on the leaf surface for the wings of emerging pests like white fly to stick to and the garlic is an excellent instant insecticide. The baking soda dries out any sooty mould and the water is the agent of transfer. Use this spray prophylactically every 10-14 days - and remember, it's important to spray the underside of the foliage as well as the surface. If this spray wilts emerging foliage, then dilute the garlic water.

Our lime tree is blossoming. It flowered last year also, but none of the fruit set. It's in a large pot on our deck, which gets all day sun and we're conscientious about watering it. It did have scale, but we've eradicated it. What can we do to ensure we get some limes from our tree?

- Beth

It sounds like you've got your watering in hand but this is actually a big reason why limes drop their fruit. To paraphrase some responsible host advertising, it's not so much the watering, it's how we're watering. Limes are real toys-out-of-the-cot types about watering. And if they're in a pot, temperature fluctuations can be quite extreme, so water little and often for best results. I also recommend changing the soil in the pot every second year and to do this you will either need to reduce the size of the root ball so you can add new soil or you can move up to a bigger pot. If you do this, I recommend adding rain crystals to your soil mix. In the meantime there are a few pot watering mechanisms on the market that may do the trick. A homemade version is to get a plastic milk bottle, put a pin hole or two in the bottom and fill it up with water. This will provide a slow but steady supply of water for your champion limes.

My husband bought two hop plants last year. He planted them next to each other and they seemed to thrive. However, neither of them have flowered. I understand there are male and female plants, so perhaps we have two males. We're happy to go out and buy another plant, but how do we tell if they are male or female, or whether that's even the reason they're not flowering?

- Mary

The male hop plant is easy to identify as it has a distinctive five-petalled flower. The male is unproductive, unnecessary and fundamentally useless (not the first time that observation's been made), which is why commercial hops are always female. If your hop plant has this flower, it's probably male and should be removed, as it will fertilise female plants, which you don't want. Occasionally a female plant will grow sections with male flowers. These can be removed without getting rid of the entire plant.

If you have a hydrangea that needs acid fertiliser and a rose next to it, which does not need acid fertiliser, does it matter if there is an overlap? Also, my daughter and I both have gardenias. They look great when you get them from the garden shop, but never again after that. What special treatment is required here?

- Wiebke

As a general rule, you can overlap your fertilising programme a bit but if you intend to fertilise heavily there will be some effect on the neighbouring plants. A compromise is probably in order. The hydrangea likes its soil more acidic than the roses, so you could dress the hydrangea and leave the roses. If the rose loses condition because of the acidic soil, then dress it with lime to neutralise the acid burn. Gardenias like a free-draining, slightly acidic soil and morning and afternoon light. Too much middle-of-the-day sunshine and not enough water can cause a few problems. If the leaves are yellow, then water in a dose of epsom salts (magnesium sulphate). This will return the foliage to top condition.

TO DO THIS FORTNIGHT

Vege garden

Lightly mulch your garlic with straw and feed with a fertilise. I'm using a seaweed tea which is low in nitrogen. Don't let it dry out too much either but you don't want to drown it.

Bird netting is essential for your strawberries as they come into season. Birds especially will enjoy a free feed if you give them half a chance. To enhance the flavour of the berries, dual the watering back once the fruit really start to come on.

Plant out basil, coriander, summer lettuce and rocket. Dig in plenty of nitrogen-rich organic material like chicken poo, compost and sheep pellets. Mulch with pea straw as even though this is dry, it still contains a good amount of nitrogen. To combat slugs and snails use bunched-up bird netting as a barrier. I've found this to be quite effective and easy to administer. Peppers, spuds, kumara, tomatoes, aubergine, can all be planted now. These all need full sun and a friable deep soil dressed with calcium and potash. Use only well-composted materials to feed them as they are (with the exception of kumara) susceptible to black spot which is a soil-borne fungus.

Some varieties of pepper are shallow rooting and quite brittle, so staking may be necessary, while cutting off the ripe fruit will also help reduce any risk of damage. The same thing goes for aubergine. Kumara vines can be staked and tied. This helps keep the vines under control in a small space and encourages the tubers at the base of the plant to grow bigger and better tubers.

Plant runner beans in a permanent spot. I've made the mistake of removing runner beans after they've finished for the season but they're actually perennials and will grow back next year with a bumper crop.

Keep up your succession planting, especially with potential bolters such as lettuce, basil and coriander, and green-crop any unused beds.

Flowers

Even if you're not a gardener you have to have a go at sun flowers. One of my first gardening experiences was growing hundreds of these at a student flat - impressing everybody who visited.

Plant lavender, protea, leucadendron and tea tree in a well-drained rocky, neutral to alkaline soil. Plant with golf ball-sized chunks of concrete in the soil; don't over-water and avoid feeding, mulching or fertilising. If the soil is slightly acidic dress the trees with gypsum.

For a tough but beautiful underplanting in semi-shade try gardenia radicans.

These will need a regular dressing of epsom salts to keep the leaves green but otherwise they are surprisingly hardy, keep to their small habit and have proven themselves to be tough performers under pressure, namely amongst the thick matted roots of my sago palm.

Do you have a gardening, DIY or landscaping question for Justin? Email gardening@nzherald.co.nz with your question and we will be happy to answer it in our pages.