Spring planting mistakes: Garden expert reveals biggest errors when planting in spring – and how to avoid them 

However, according to Neil Thomas, garden specialist and owner of FirePit.co.uk, this burst of activity is exactly when costly mistakes are made. 

“People see a few sunny days and assume it’s safe to get everything in the ground,” he says. “But spring weather is unpredictable. Plant too quickly or prepare poorly, and you can set your garden back by months.”

According to guidance from the Royal Horticultural Society (RHS), late frosts, cold soils and overwatering are among the most common causes of early plant failure.  With spring just around the corner, Thomas has shared five of the biggest spring planting mistakes and how to avoid them. 

Planting too early because of a warm spell

A few bright days in April and May often tempt gardeners into action, but Thomas warns this is one of the biggest pitfalls. “One warm weekend doesn’t mean cold weather is finished,” he says. “Late frosts can wipe out tender plants overnight.” 

The UK Met Office confirms that frost can still occur across much of the UK into late April and even May. Tender plants such as tomatoes, dahlias and bedding plants are especially vulnerable. Thomas recommends waiting until the last frost date in your region or hardening plants off gradually before planting out. 

Ignoring soil temperature and quality 

Spring sunshine doesn’t mean the soil is ready for planting. “Seeds sitting in cold, wet soil will either rot or fail to germinate,” Thomas explains. Many crops need soil temperatures of at least 8-10°C for reliable germination. 

After colder months, soil is often compacted and waterlogged, restricting oxygen to roots and increasing disease risk. “People dig a hole, drop the plant in and hope for the best,” says Thomas. “However, spring is when the soil needs attention.” 

The Agriculture and Horticulture Development Board recommends adding organic matter to improve structure, drainage and root development. Thomas suggests a simple test: “If it sticks together in a heavy clump, it’s too wet. You should wait until it crumbles in your hand. Healthy soil is half the battle.” 

Overwatering new plants

Spring showers often create the illusion that more watering is needed. It is the extra moisture which becomes a common issue. “Roots need oxygen as much as they need water,” Thomas says. “If soil is constantly saturated, plants struggle to establish.” 

According to the RHS, waterlogged soils can lead to root problems and fungal diseases. Thomas recommends watering thoroughly at planting time, then checking soil moisture before watering again. 

Forgetting to harden off indoor-grown plants 

With more gardeners starting seeds indoors, another frequent mistake is moving plants straight outside without adjustment. “Plants raised indoors aren’t used to wind, UV light or fluctuating temperatures,” Thomas explains. 

Hardening off plants gradually over 7-14 days to prevent shock; sudden exposure can cause leaf scorch, slowed growth, and long-term stress. “A short transition period makes plants far more resilient,” Thomas says. 

Overcrowding is a big no 

Garden centres make it tempting to plant densely for immediate colour, but Thomas warns this can backfire. “When you cram plants together, you reduce airflow and increase disease risk.” 

The RHS states that poor spacing contributes to fungal diseases such as powdery mildew and blackspot. Proper spacing also reduces competition for water and nutrients. “It may look sparse at first,” Thomas concludes, “but by summer, properly spaced plants fill out naturally.”