How to grow zucchini, and when to sow it here

Zucchini is the crop that makes a first-time gardener look like they know exactly what they're doing, and it isn't really an accident, because it grows fast and it crops heavily and it keeps going for months. You get the payoff while you're still working the rest of it out. There are only a few ways to get it wrong and every one of them is easy to head off before the seed goes in.

When to sow zucchini here

Zucchini is a warm season crop and it won't tolerate frost, so it goes in once the frost risk has passed. Around Strathalbyn that means October through to December, and a sowing in early January will still give you a crop before the weather turns. Sow it too early and the seed just sits in cold soil and rots, which is easily the commonest reason a packet of seed does nothing at all.

You can sow direct or plant a seedling. Direct sowing is usually the easier of the two because zucchini doesn't much like being shifted, so pop the seed about 2cm deep and firm the soil over it.

Picking the spot

Zucchini wants at least 6 hours of direct sun, which means north is the aspect to aim for here. The afternoon sun off the west is the harsh one in this part of the world, and an established plant with a good mulch under it copes with it fine, but a young seedling will struggle, so keep the water up until it gets going. Give it airflow as well, because zucchini is prone to powdery mildew and still, crowded air is what lets that take hold.

Soil, and how much room it actually needs

Zucchini is a hungry plant. Dig compost or aged manure through the bed before you plant and add some blood and bone, and that's honestly most of the work done. It likes a soil pH somewhere around 6.0 to 7.0, though if your beds are already growing decent vegetables you don't need to go measuring anything.

Space is the bit people underestimate. One plant will take up close to a square metre by the time it's finished, so give it 60cm to 1m from its neighbours. Crowding costs you twice, because the plants compete for food and the still air between them brings on mildew.

Watering

A deep soak a couple of times a week beats a light sprinkle every day, because a light sprinkle only ever wets the top and the roots stay shallow. Water at the base rather than over the leaves, and do it in the morning so anything that does get splashed has all day to dry off. Watering at night leaves wet foliage sitting in the dark, which is how fungal problems start.

Mulch around the plants once they're up. It holds the moisture in, it keeps the soil temperature steadier, and it saves you a lot of weeding.

Why you get little zucchinis that shrivel and drop

This is the one that catches everybody out, and it isn't a disease. Zucchini carries male and female flowers separately, and the female ones are the ones with a tiny fruit already formed behind the flower. If nothing moves pollen from a male flower to a female one, that little fruit yellows off and drops.

The fix is bees, mostly. Plant something flowering nearby and they'll find it. If you're getting no fruit set at all, you can do the job yourself with a small soft brush, or by picking a male flower, stripping the petals off and dabbing it straight into the centre of the female one. Do it in the morning while the flowers are open.

The mistakes worth knowing about

• Planting too close. Poor airflow, more mildew, smaller plants.
• Keeping the soil soggy. Let the top few centimetres dry out between waterings or you'll get root rot.
• Letting them get away from you. Check the plants daily once they start, because a zucchini goes from perfect to the size of a cricket bat in about two days and the big ones are watery and dull.
• Ignoring aphids. A blast off with the hose sorts out most of them early, and it's a lot less work than dealing with a whole colony later.

Harvesting

Pick them at about 15cm to 20cm, when the skin still marks with a fingernail. Cut them off with a knife or secateurs and leave a short bit of stem on, because tearing them off damages the plant. The more you pick the more it produces, so picking often is not just about flavour.

They keep in the fridge for a week or so, and don't wash them until you're ready to use them.

Nobody starts out knowing any of this. I certainly didn't, and most of what I know about growing anything came from getting it wrong first and then asking somebody who'd already made that particular mistake. That's what we're here for, so if something in your patch is doing the opposite of what you expected, come and ask us.

Shop related products

• D.T Brown Zucchini Lebanese Seed Pack. A reliable, heavy-cropping variety for a home bed.
• Brunnings Garden Compost with Seaweed 25L. Dig it through the bed before planting.
• Brunnings Blood and Bone Based Fertiliser 5kg. The feed that keeps a hungry plant cropping.
• Martins Organic Sugar Cane Bale 11kg. Mulch to hold the moisture in around the base.

Did you know we also carry zucchini seed in All Green Bush, Greenskin and Romanesco, plus snail and slug pellets and a slug barrier, none of which are on the website. Give us a ring on (08) 8536 4333 or come in and we'll show you what's on the shelf.

Have a look through the rest of the garden range, or come and see us in the garden centre and we'll talk it through.

More from the garden

• Keeping pests off a zucchini crop
• The native bees that pollinate a vegetable patch
• Growing carrots, and when to sow them

Still learning, still pulling the odd cricket bat out of the zucchini patch. Candeece.

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