Landscape gardener and Life columnist Justin answers your questions.

I have had some cabbage trees self seed around my garden, including one seedling that is now about 600mm high. I'd like to replace an old cabbage tree that rotted and died - do you think there would be any damage or contamination in the soil if I just put the new one into the old hole? What special care do they need for transplanting? Also, my brother wants loads of cabbage tree seedlings for his land in Martinborough (on a windy hill). Would Auckland - North Shore, to be precise - varieties survive down there?

- Dave

Most problems with cabbage trees are viral and are delivered to the tree not through the soil but through sucking insects. It would however be prudent to avoid planting a new plant atop the old one. Make sure the remnants of the old tree are removed, or at least buried. Plant your new tree in good soil, making sure to mix your potting mix or compost with some soil taken from the hole the tree was transplanted from. Planting cabbage trees in Wairarapa is not a problem. Smaller plants, around 20 to 40cm high will have a better success rate and being from Auckland (the North Shore, no less) I'm sure the trees will give a good account of themselves.

Three readers have written with avocado questions. Brigitte wants to know why the Hass avocado she bought five years ago has never had flowers or fruit. Adrienne and Heather both want to know the best place to buy miniature avocado trees as they cannot find them in their local garden centre or over the internet.

Firstly Heather and Brigitte, you can buy your mini avocado trees from The trees are bred to be kept small but produce very high yields in spaces as small as two square metres. They are not strictly dwarf varieties so you will need to prune them once a year or so. Avogrow sell the trees in groups of four or eight trees which include both A and B varieties. It's all very scientific but all you need to know is that the mix of A and B will greatly enhance the yield. Which leads me on to Adrienne's question. Your Hass avocado is an A variety, so to grow true to type it will need to be on a grafted rootstock. If it has been propagated from seed, your avocado may take a long time to fruit and when it does, it may not fruit very well. Either plant a grafted tree or get a bunch of four from Avogrow. I've just been looking at their website, and your new trees may even come with a few avos already on the tree.

Establish new garden beds or dig over existing beds that have been wintering over. Add a good dose of gypsum and sheep pellets as well as some blood and bone, then cover with pea straw until the beds are ready for planting. Make sure the beds are dug over thoroughly so the tilth (crumbliness) in the soil is as fine as possible.


Add plenty of organic matter (sheep pellets, compost) to all garden beds. Grow a speedy green crop such as mustard or lupins in beds which have been previously used for low-nitrogen crops such as parsnip, onions or carrots. If you don't refresh the nitrogen content now, your next crop of plants will bolt or go to seed early. For areas where you will be planting root crops, add sulphate of potash.

When your seedlings are ready, pull back the straw and plant into the prepared bed then replace the straw around the seedlings.

If you have a greenhouse or a cold frame, start sowing seeds for everything now, including lettuce, cabbage, celery, aubergine, peppers, tomatoes, sunflowers, leeks, cucumbers, melons and spinach and herbs like coriander, basil and Florence fennel.

It's still a bit early for planting out the likes of tomatoes, aubergine and peppers, so once these are doing well in the seedling tray, pot them on to a larger container. This will make it easier to harden them off and will massively improve the health of your plants when they go into the garden.

Florence fennel and basil can be seeded into deeper trays and thinned out. The deeper potting mix allows the young plants to remain in the trays for longer, while thinning makes transplanting much easier.

Make sure your new seedlings don't dry out and keep an eye out for slugs and snails. Snail and slug traps are a must, but if it's getting really bad use bird and pet-friendly slug pellets.

Get tomato beds ready. Set out an airy sunny spot, if possible next to a fence or shed. The reflected heat from a hard surface can make a big difference to the size and vigour of your vines and fruit. If you get really behind or you can't be bothered sowing your own seed, wait a month and buy punnets in October when there is little chance of frost.

Be ambitious and put in big stakes for your tomatoes. It can be frustrating trying to keep large vines under control because the little bamboo pole you've staked it with has been swamped after a few months. If you are space-deprived go for a shrubby varieties (which are usually referred to as determinate varieties).

Direct-sow peas, beets, carrots, parsnip, turnip and radish.

Place kumara in a box or bucket of pumice sand and keep in a warm sunny place out of the rain. The shoots will emerge and once they are about 40mm long they're ready to plant

Plant gypsophila, poppies, corn flowers, carnations and sweet peas.

Dahlias can be planted now. If you are replanting last year's plants use the younger, fresher tubers instead of the old woody ones. It's also time to plant gladioli and begonias.

Sow marigolds, lobelia, eschscholzia and all your summer favourites. If you've sown these last year, many of their seedlings will come up in the garden, so keep an eye out. You can reposition these young plants around the place.

In general
Feed and mulch your citrus trees. Use a citrus fertiliser or if the foliage is yellow, a good dose of magnesium sulphate or Epsom salts. Avoid having lawn growing right up to the trunk of the tree. Establish a mulched area at least out to the edge of the drip line to help support the shallow roots of the tree; grass plants compete with the roots for nutrient.

Mulch fruit trees with seaweed covered with pea straw to help them hold their fruit. Place a layer of cardboard around your ornamental garden beds and cover with a thick layer of tree mulch - this will really knock the weeds back, but avoid doing it around annuals or vege beds as the tree mulch is very coarse and tends to suck up a lot of nitrogen from the soil, depriving the plants.

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