How to Prepare Your Garden for Spring in Melbourne
Melbourne soil in early August sits at roughly 8 to 10°C. Tomato, capsicum and bean seed needs 15°C or warmer to germinate reliably, so anything warm-season you put in this month will sulk rather than grow. That gap is the whole opportunity. You have four to six weeks to fix drainage, feed the soil and clear the beds, so when the ground finally warms in late September your plants take off instead of struggling.
When does spring planting actually start in Melbourne?
Later than the garden centre displays suggest. Melbourne’s average last frost falls around mid-September, and it lands harder in the outer east and north than it does on the coast. Geelong and the Peninsula rarely get caught. Ferntree Gully and the Dandenong foothills still can.
To prepare a Melbourne garden for spring, clear weeds and spent winter crops, dig 5 to 10cm of compost through the top 20cm of soil, correct drainage problems now while beds are empty, prune summer-flowering shrubs, and hold off planting warm-season seedlings until soil reaches 15°C in late September.
That is the short version. Here is how it goes in practice.
How to prepare your garden for spring in five steps
- Clear the beds while they are still empty. Pull spent brassicas and winter weeds before they seed. Every weed you remove now saves you ten in October.
- Fix drainage before you plant, not after. Watch where water pools after rain and mark those spots. Raising a bed by 20cm or laying a shallow ag line is a one-hour job in an empty bed and a nightmare in a planted one.
- Feed the soil, not the plant. Spread 5 to 10cm of compost and soil improver and fork it through the top 20cm. Humus Plus Organic Compost works hard in the heavy clay through Heatherton and the south-east, where the problem is structure rather than fertility.
- Prune what needs it now. Late winter is the window for summer-flowering shrubs, roses and deciduous fruit trees. Leave spring bloomers such as camellias and daphne until after they flower, or you will cut off the show.
- Check your irrigation before you need it. Run the system, look for blocked drippers and split poly, and replace what has perished over winter. Nobody wants to find a leak in the first 35°C week of November.
Do not dig soil while it is wet. Squeeze a handful: if it holds its shape and smears, wait. If it holds shape and crumbles when you poke it, you are good to go. Working clay wet destroys the structure you are trying to build.
Does your clay soil actually need gypsum?
Probably not, and this is where most advice goes wrong. Gypsum only improves structure in dispersive (sodic) clay. On non-dispersive clay it does nothing except lighten your wallet.
Test it in a day. Drop a pea-sized crumb of dry soil into a clear glass of rainwater or distilled water and leave it undisturbed overnight. If a milky halo spreads out from the crumb, your soil is dispersive and gypsum will help. If the water stays clear and the crumb just slumps, skip the gypsum and spend the money on compost instead. The GRDC dispersive soils factsheet walks through the same test in more detail.
Peninsula and Bellarine gardeners usually have the opposite problem. Sandy soil drains too fast and holds nothing, which is why the Mornington team steers people toward compost and a wetting agent rather than clay breakers.
What to plant now, and what to leave alone
| Go ahead in August | Wait for 15°C soil (late September onward) |
|---|---|
| Broad beans, peas, snow peas | Tomatoes, capsicum, chilli, eggplant |
| Onions, leeks, spring onions | Beans, corn, cucumber, zucchini, pumpkin |
| Silverbeet, spinach, Asian greens | Basil |
| Potatoes (chitted, late August) | Sweet potato |
| Bare-rooted fruit trees and roses | Warm-season annual colour |
You can start warm-season seed indoors now on a sunny windowsill or in a mini glasshouse, ready to transplant at the end of September. Just resist buying tomato seedlings in August. They go in cold, stall for six weeks, and get overtaken by a plant plunged in a month later. Our vegetables and herbs range shifts with the season for exactly this reason.
Late winter is also the ideal time to get evergreen structure in the ground. Buxus English Box (Buxus sempervirens), Backyard Bliss Lilly Pilly (Syzygium australe) and Liriope Evergreen Giant (Liriope muscari) all establish roots through the cool, damp weeks before they are asked to cope with heat.
Should you mulch before or after you plant?
After. Mulching a cold bed in August insulates it and keeps the soil cold for longer, which delays everything you are waiting on.
Get the compost in now, plant when the soil warms, then lay 5 to 7cm of mulch over the top. Diaco’s Blackwood Mulch holds its colour and breaks down slowly, so one application carries you through summer. Keep it clear of trunks and stems by a few centimetres to avoid collar rot.
Is it too late for bare-rooted trees?
You are at the very end of the window. Bare-rooted season in Victoria runs from June to around late August, and stock thins out fast once buds start to swell. If a bare-rooted apple, plum or cherry is on your list, this is the fortnight to sort it. After that you are into potted fruit trees, which are fine, just dearer and heavier to move.
Blueberry Blue Rose (Vaccinium corymbosum) is worth a look while you are at it. It needs acidic soil and does far better in a 40cm pot of azalea and camellia mix than in Melbourne clay.
Bring us a photo of your bed before you buy
Soil is the part that is hardest to judge from a photo on a website, and the easiest to get right with two minutes of conversation. Take a picture of the bed you are planning to plant, grab a handful of the soil in a zip-lock bag, and bring both in to Heatherton, Mornington or Geelong. Our staff will tell you what it needs and, just as usefully, what it does not. Find your closest store and come and have a chat before the September rush.
Stock varies between stores and the online shop shows only part of what we carry. If you are after a specific variety, send us a stock enquiry or give the store a call and we will check the benches for you.
Frequently asked questions
When can I plant tomatoes in Melbourne?
Late September at the earliest, and early October is safer. Tomatoes need soil at 15°C or warmer and no frost risk, and Melbourne’s average last frost is around mid-September. Planted earlier they stall rather than die, and a plant put in three weeks later usually overtakes them. Start seed indoors now if you want a head start.
Should I add gypsum or compost to my clay soil?
Compost, unless a jar test shows your clay is dispersive. Gypsum only improves structure in dispersive (sodic) soils and does nothing on the rest. Compost improves any soil by adding organic matter, feeding soil life and opening up structure. Test first with a crumb of soil in a glass of water, then decide where the money goes.
Is it too early to mulch my garden in August?
Yes, for beds you are about to plant. Mulch laid over cold soil insulates it and slows the spring warm-up you are waiting on. Mulch after planting, once the soil has warmed in late September or October. Established beds, shrubs and trees are a different matter and can be topped up any time.
What can I plant in August in Melbourne?
Peas, broad beans, onions, leeks, silverbeet, spinach and Asian greens all go straight in. Late August suits chitted potatoes. It is also the last call for bare-rooted fruit trees and roses, and a good moment for evergreen hedging and screening while the soil is still damp and cool.
