We Asked Experts About the Gardening Mistakes to Avoid This Spring—These Are Their 12 Top Tips

Autumn may be winding down across much of Australia, but late March is prime time to get serious about your garden before winter sets in. The decisions you make in the next few weeks—what you plant, what you cut back, what you leave alone—will determine how well your beds, lawns and veggie patches come through the cooler months. The trouble is, many gardeners repeat the same avoidable mistakes each year, and the damage often doesn't show up until spring, when it's already too late to fix.

We consulted with a group of horticulturalists, landscape designers and seasoned home gardeners around Australia, and they offered twelve remarkably consistent warnings. These aren't vague platitudes about "listening to your soil." They're specific, practical corrections that will save you time, money and the frustration of watching plants you've invested in fail for entirely preventable reasons. Pull on your gloves—there's work to be done.

Mistake 1: Overwatering as the weather cools

As temperatures drop through late March and into April, many Australian gardeners keep watering on their summer schedule out of habit. This is one of the most damaging things you can do. Cooler soil evaporates moisture far more slowly, and roots sitting in waterlogged ground become vulnerable to root rot—a fungal condition caused by pathogens like Phytophthora that thrive in anaerobic, wet conditions. The experts we spoke to unanimously flagged this as the single most common autumn gardening error. Reduce your irrigation frequency by at least half once daytime temperatures consistently fall below 20°C, and always check soil moisture 5–8 cm down before reaching for the hose.

Mistake 2: Pruning at the wrong time

Autumn is not a universal pruning season. While it's tempting to tidy everything up at once, cutting back plants that flower on old wood—like gardenias, azaleas and many grevilleas—in March or April removes next season's flower buds before they've had a chance to set. Prune spring-flowering shrubs immediately after they bloom, not before winter. Save your hard pruning of roses, deciduous fruit trees and ornamental grasses for late winter, when dormancy is deepest and the risk of stimulating tender new growth that gets frost-burned is lowest.

Mistake 3: Neglecting the soil before planting winter crops

Autumn is genuinely excellent timing for cool-season vegetables—broccoli, cauliflower, silverbeet, kale, broad beans and peas all thrive when planted now across most of southern Australia. But dumping seedlings into tired, depleted summer soil is a setup for disappointment. Before planting, work in a generous layer of compost—at least 5 cm—along with a balanced slow-release fertiliser. pH adjustment matters too: most brassicas prefer a soil pH between 6.5 and 7.0, and a cheap soil test kit from any hardware store will tell you where you stand. Lime raises pH; sulfur brings it down.

Mistake 4: Leaving lawn thatch unmanaged

A layer of thatch—dead grass stems and organic matter that accumulates between the soil surface and the green blades—exceeding about 1.5 cm acts as a barrier to water, fertiliser and air. Lawn care specialists recommend scarifying or dethatching in early autumn before the lawn goes into its slower winter growth phase, giving it time to recover before cold sets in. In warmer states like Queensland and the Northern Territory, this timing is slightly less critical, but in Victoria, South Australia and the southern parts of Western Australia, doing it now beats waiting until spring when the lawn is already under stress.

Mistake 5: Ignoring pH when planting autumn bulbs

Tulips, daffodils, jonquils and freesias—all suited to cooler parts of Australia and best planted from late March through June—perform poorly in acidic soils. Most prefer a pH of 6.0 to 7.0. Many gardeners in coastal areas, where soils trend acidic, skip this check entirely and then wonder why their bulbs produce weak, short-stemmed flowers or fail to reappear in subsequent years. Test before you plant, and if needed, apply dolomitic lime, which adds calcium and magnesium alongside correcting pH.

Mistake 6: Planting too deep or too shallow

Planting depth is one of those details that feels fussy until you watch an expensive plant fail because of it. The general rule for bulbs is to plant at a depth of roughly two to three times the bulb's diameter. For seedlings, the root collar—where the stem meets the roots—should sit at or just below the soil surface, never buried. Planting too deep causes stem rot; too shallow exposes roots to frost and drying winds. Landscape designers consistently flag this as a mistake they see in DIY gardens of every experience level.

Mistake 7: Skipping mulch before winter

A 5–8 cm layer of mulch applied now does three critical jobs simultaneously: it regulates soil temperature as nights cool down, retains moisture between increasingly infrequent rain events, and suppresses the cool-season weeds that will otherwise carpet your beds by July. Use a composted organic mulch—sugar cane mulch, lucerne or wood chips—rather than fresh, uncomposted material, which can rob the soil of nitrogen as it breaks down. Keep mulch pulled back a few centimetres from plant stems to prevent collar rot.

Mistake 8: Fertilising at the wrong time

Feeding plants with a high-nitrogen fertiliser in late autumn is counterproductive. Nitrogen drives leafy, soft growth—exactly the kind that gets burned by frost or exhausted trying to push through cold, slow-growing soil. Switch to a low-nitrogen, high-potassium formula as summer ends. Potassium (listed as K on fertiliser labels) strengthens cell walls and improves cold tolerance. For lawns, most professionals recommend a final autumn feed no later than April, using a dedicated autumn lawn fertiliser with an analysis such as 12-2-12 or similar.

Mistake 9: Failing to check for pests before they overwinter

Aphids, scale insects, mites and fungal spores don't disappear in autumn—many of them settle in to overwinter in bark, soil and leaf debris, ready to explode in numbers the moment spring warmth returns. A thorough inspection of stems, the undersides of leaves and the base of plants now, combined with a horticultural oil spray on dormant or semi-dormant trees and shrubs, can dramatically reduce the pest pressure you'll face in October and November. Dispose of heavily infested material in the bin, not the compost heap.

Mistake 10: Dismissing the importance of drainage

Australian clay soils—common in Melbourne, Adelaide and parts of Perth—compact further under winter rain, creating ponding zones that kill roots within days. If you've noticed water sitting on the surface for more than 30 minutes after heavy rain, autumn is the time to address it: dig in gypite or clay breaker, raise garden beds, or install agricultural pipe (slotted drainage pipe) in the worst-affected areas. Adding organic matter consistently, year after year, is the long-term fix; gypsum provides a faster improvement in heavy clay.

Mistake 11: Not deadheading and cleaning up disease-prone plants

Spent flowers and dying foliage left on plants over winter are a reservoir for fungal diseases like black spot on roses and botrytis on a wide range of ornamentals. Remove them now, clean up fallen leaves from around susceptible plants, and apply a copper-based fungicide spray before the wettest months arrive. This is particularly important for gardeners in higher-rainfall areas of Victoria, Tasmania and coastal New South Wales, where humidity during winter and early spring creates ideal conditions for fungal spread.

Mistake 12: Underestimating the value of a garden diary

This one gets dismissed as old-fashioned until gardeners try it. Recording what was planted, when, where, at what depth, and with what result gives you data that no general gardening guide can replicate, because it's tied to your specific microclimate, soil and conditions. Horticulturalists note that the most consistently successful home gardeners they work with—regardless of the size or ambition of their garden—keep some form of seasonal record. A notebook, a phone note or a simple spreadsheet is enough. Next autumn, you'll know exactly what worked and what to change.

The professional's perspective

The most expensive mistake in the garden is also the most common: buying a plant on impulse without checking whether the site conditions match what that plant actually needs. In autumn, when nurseries are stocked with tempting cool-season colour, it's worth spending five minutes researching light requirements, drainage needs and mature size before you put anything in the ground. A plant in the right place with minimal intervention will always outperform a misplaced plant that's being constantly nursed along. That's not pessimism—it's efficiency.

Keeping the momentum through winter

The work you do in March and April sets up everything that follows. Soil improved now will drain better in July, warm faster in September and support stronger root development when growth resumes. Pest pressure managed now means less chemical intervention in spring. Planting done correctly now—right depth, right pH, right drainage—means plants that establish quietly over winter and hit the ground running when conditions improve.

Review these twelve areas against your own garden over the next few weekends. Not all of them will apply to every space, but most gardeners will find at least four or five that match a pattern they recognise. Addressing them systematically, rather than waiting for the problem to become obvious, is the difference between a garden that recovers well from winter and one that spends the first half of spring catching up.

Cost of getting it right (indicative prices, vary by region and retailer)

Frequently asked questions