September Gardening Tips NZ

September Gardening Tips NZ

September Gardening Tips NZ
Spring! Hooray! We’ve got through the worst weather. The days are getting warmer and longer. Your spring bulbs are flowering or well on the way. The deciduous trees are starting to flower as well.
September is arguably the most important month for gardeners in our part of the world, because it’s the start of the main growing season. So it’s particularly important to get most of your main season outdoor crops planted, to maximise the growing period. You do have to be careful in most districts with frost sensitive plants, because we can get damaging late frosts.

Tasks For This Months Gardening Tips

General September Gardening Tips

You should be finished with your planning of what you intend to do this season in your garden. Any plans you have need consider the long term 10 to 20 years, so you don’t do something now that needs to be undone in the future such as planting trees that will grow too large and/or be in the wrong location and require removal in the future. It is good idea to consult with a professional landscape designer to get advice and a plan and/or have the parts of the job that require specialised skills and knowledge done for you. We’ve probably all seen “do it yourself “jobs that are really a waste of time and money. If you want to engage a professional this month is a good time to do it before they become overloaded with the “finish before Christmas” rush that happens every year.

Snail and slug control – Their populations tend to build up over winter, when wet conditions suit them and control is more difficult. So start implementing control measures. Bear in mind that some baits are toxic to birds, hedgehogs, and dogs, that may ingest then directly or by eating dying snail or slugs. ( There are baits available that are non toxic to birds and dogs. ) So if using snail & slug baits toxic to animals it’s advisable to put them under suitable protective cover.

Ants – If you had an ant problem in the past, start putting out ant baits in places sheltered from the rain, to stop a build up, that can occur around and within your buildings.

Pruning –

All deciduous tree pruning should have been finished by now.

Planting –

Perennials – Finish planting your trees, shrubs an other perennials as soon as possible, so they make the most of the growing season to spread their roots out, before the dry weather starts to stress them.

Food Gardening


Clear out anything that is going to seed unless you’re want to keep the seed. You can get issues with cross pollination of compatible varieties, with harvesting your own seeds. I had both curly leaf and Italian flat leaf parsley, that I let self seed, and now I have a variety of parsley that has narrow flat leaves that I consider inferior, and I’m having to weed out.

If you want to test your soil Ph, it’s a good time to do it now. Then if any lime is needed it can be applied before the main planting time. Prepare your vege beds by spreading compost and fertiliser over the surface. I prefer organic fertilisers such as animal manures. Some people prefer using no dig vege gardening methods. I prefer to dig, so the compost and fertiliser is worked into the main root zone. I’ve also found if you have trees in the vicinity their roots will often take over your vege garden, so chopping through them with your spade, while their small is best.

Now you’ve got the soil sorted plant your main season vegetable crops. If you are in a frost prone area, you may want to consider using a plant covering such as a cloche. Or even just using a clear plastic container with a ventilation opening over your frost sensitive plants, that can be removed when danger of frost has gone.

I often start my vege planting season with punnets of small seedlings, because it starts you two to three weeks ahead of sowing seeds. Then later make successive sowings of seeds to replace harvested crops, there by giving you a continuous harvest over the growing season. You may want to make sucesive sowing at between two to four week intervals depending on your requirements. Generally I find direct sown seeds give you the strongest plants because there’s no transplanting damage done. The main mistake I’ve noticed with seed sowing is to sow seeds too close together, resulting in more labour required to thin out later. So when sowing bear in mind the size of the mature plant and allow sufficient space, while allowing for some seeds not germinating.

Veges to plant or sow –

Beans (both climbing and dwarf), beetroot, cabbage, cape gooseberry, capsicum, carrots, celery, chicory, Chinese cabbage, choko, cress, eggplant, endive, kohl rabi, leeks, lettuce, peas, marrows, melon, mustard, spring onions, parsnip, potato tubers, radish, rhubarb (both seed or crowns), salsify, silver beet, squash, spinach, tomato, swede, turnip.


Frost resistant herbs can be in warm districts. Chives, chervil, parsley, rocket, dill.

Fruit Trees

Pip and Stone Fruit –

Pruning should be finished.

Apply a fungicide spray of copper oxychloride or Bordeaux stone and pip fruit trees.

Grafting – If you want to graft your pip or stone fruit trees, take scion wood, generally small twigs up to pencil thickness. Wrap them in plastic and store them in the fridge until late September- early October when they can be grafted onto the rootstock, or larger trees.

Citrus –

Most citrus are reaching maturity and ready for harvesting when little or no green is visible on the skin. Although Tangelos increase sweetness if left a bit longer.

It’s best not to leave the fruit on the tree too long, as the tree will take the moisture back out of the fruit leaving it tasting dry. Leaving the citrus fruit on too long also reduces flowering and results in a lighter crop next season.

Fejoa trees can be pruned to open them up.

Berry fruits –

Time to fertilise your berry fruits. Start thinking how you will protect the fruit from the birds.

Raspberries, blackberries, boysenberries, and loganberries. – Pruning should be finished by now.

Goose berries and Blackcurrants– Pruning should be finished by now.

Strawberries – Plant them now and keep in mind the berries will need protection from birds and snails and slugs. The bird protection usually consists of netting held in place by a frame.


Green Houses/Glass house Gardening Tips –

Remove any dead matter, weed and apply compost, and dig in if needed. Plant tomatoes for an early season crop. Sow seeds in containers for transplanting outdoors later if you want a head start on the growing season.

Pot and Container Grown Plant Gardening Tips

Remove dead leaves and dust with a damp cloth or spray. Re-pot in to a larger pot with fresh potting mix if they appear to be root bound. Give them some slow release fertiliser and kill any insects on them.

Ornamental Gardening Tips

Rose Gardening Tips

Spray with a combination of copper oxychloride and spraying oil. Mulch with compost, around root zone, but keep it off the crown.


Remove weeds and apply snail and slug control measures to reduce any winter population build up.

Sow seeds of: alyssum, amaranthus, aster, balsam, bedding begonia, Californian poppy, carnation, celosia, chrysanthemum, Cleome, cosmos, dahlia (seed), delphinium, dianthus, everlasting daisy, galardia, gazania, geranium, gerbera, gloxinia, gypsophila, honesty, impatiens, marigold, mignonette nastutium, nemesia, marigold, petunia, phlox, rudbeckia, salvia, snapdragon, spider flower, statice, straw flower, sunflower, Swan River daisy, verbena, viscaria, and zinnia.

Plant seedlings of: alyssum, aquilegia, canterbury bells, carnations, cornflower, cosmos, cineraria, delphinium, pansies, polyanthus, poppy, gypsophila, forget-me not, hollyhock, stock, and viola .

Lift and divide and replant clumps of perennials.

Plant dahlia and begonia tubers.

Trees and Shrub Gardening Tips NZ

Plant any new trees and shrubs now before the growing season really gets going. Fertilise existing trees and shrubs now.

Lawn Gardening Tips NZ

Mow regularly preferably fortnightly, to keep a dense swath of grass. Don’t cut too low. The grass should be cut to between 20 to 25 mm. If you’ve got a lot of weeds, now is a good time to eradicate them, and if needed sow new grass seed to fill any empty patches.


Heaps that consist of predominantly unrecognisable matter are ready to be spread around planted areas as a mulch, or for digging in when soil conditions are dry enough. Make new compost heaps by incorporating grass clippings, dead leaves, vegetable scraps with a sprinkling of lime and animal manure etc. Turn and mix existing compost heaps that haven’t decomposed sufficiently.


Magnificent spring cherry blossom

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