For a proud few weeks, I carefully tended to what I thought were burgeoning broad beans. That was until I realised my ‘broad beans’ were growing everywhere (including in gutters and between paving stones), not looking very vegetable-like and in fact not broad beans at all.

For many gardeners, this would be blindingly, embarrassingly obvious, but for a keen amateur desperately trying to cultivate their first ever garden, it was just a bit sad.

But as millions more British adults are flexing their green fingered skills, according to new research. And despite this gardening enthusiasm, nearly two thirds admit they often struggle to tell the difference between plants and weeds. Almost nine in 10 believe a bluebell to be a plant, although it’s most commonly described as a weed as it spreads across gardens with ease and three quarters say their general garden knowledge is average to very poor.

Mike Norton, Market Director Outdoor, from B&Q who commissioned the study and have just launched a new app to help gardeners tell the difference between a plant and a weed commented: “Gardening in Britain is back in vogue and we’re delighted to see people flexing their green fingered skills. But it’s clear that some outdoor education is still needed.”

So what other weeds are out there masquerading as plants? What other ‘flowers’ am I dutifully watering, unaware they’re a weed silently plotting their big border coup?

[Read more: 8 of the world’s smelliest plants, from corpse flowers to skunk cabbages]

Clover

Clovers are important wild flowers, good for bees and grazing animals and they also improve the soil by ‘fixing’ nitrogen from air. However in gardens as opposed to on farms they can often be weed that spreads in thick mats in beds and borders and can infiltrate lawns. In lawns they are hard to remove but that does not necessarily matter. 

Unacceptable as they may be in fine or sports turf (they make the short grass slippery) they can benefit more modest lawns by their drought resistance and absence of need for fertiliser. Lawn weedkillers often have some effect but feeding the grass with fertiliser can squeeze out the clovers.

Daisy

Daisies are unacceptable on the finest lawns, but in more utilitarian turf they add a cheerful note and are beloved by children (and insects) and most people are happy enough to refrain from persecuting them. Lawn weedkillers generally see them off when they are too numerous to excise with an old knife.

Oxalis

Being robust survivors, oxalis occupy suitable spots in gardens but often in places nothing else will grow – waste areas and cracked paving for example. They make a cheerful summer groundcover, resembling the ‘shamrock’.

Unfortunately they have to be ‘managed’ as an acceptable groundcover or they can soon be a tenacious occupier of borders and lawns. Persistent, thorough cultivation over a period of months can remove them but often only an application of glyphosate-based weedkiller (Roundup, for example) followed by reseeding of lawn and replanting of borders is the only realistic remedy.

Forget-me-nots

Widely sold as bedding plants, Forget-me-nots set abundant seed and come up all over the garden. Avoid this by disposing of all plants before they set seed. Self-sown ones sound enticing but they are usually rather ordinary and often heavily infected with powdery mildew. It’s best to buy better forms from the garden centre.

Aquilegia

‘Willing but not invasive’ sums up the aquilegia – well, not usually invasive anyway.  Self-sown aquilegia have a lot of charm for the ‘cottage garden’ type environment. If they don’t please you, pull them up and don’t let them set seed in future.

Slender speedwell

Pretty ivy-like foliage and blue flowers belie a persistent almost-impossible-to-control lawn weed. Prevention is best as weedkillers are none too effective against it. But having said that, it is usually an acceptable component of many workaday lawns, and lifting them with the lawn rake before mowing provides sufficient control.

Foxglove

Foxgloves are delightful citizens of shady glades and often seed well. Many gardeners report though that no matter how often you spread foxglove seed, they seldom come up where you want them - therefore you should change plans to accommodate any serendipitous if inconvenient foxgloves.

If there are too many, just remove some with an old knife or hand fork to give the remainder space to thrive. Be aware that foxgloves are potentially harmful and gloves should be worn when handling them and care should be taken that pets do not have access to uprooted plants.

Birds-foot trefoil

Like clovers, birds-foot trefoil is an important wild flower, good for bees and grazing animals and they also improve the soil. However in gardens as opposed to on farms they can often be a persistent lawn weed. Lawn weedkillers often have some effect but feeding the grass with fertiliser can squeeze out the trefoil.

[Read more: 11 surprising edible garden plants]

Bindweed

Children love bindweed – the flowers can be popped form their stalk in a most satisfying way, but gardeners baulk when this weed gets a grip. Its fleshy white roots have amazing powers of recovery not matter how zealous the gardener is in treating the shoots and digging out the weeds.

A ‘fallow’ period is often the only answer removing desirable garden plants to holding pots and then spending a summer digging out or spraying off any sign of the weed.

Bluebell

Iconic wildflowers can be weeds as well. In the wrong place the native bluebell is incredibly deeply embedded in the soil and can take years to eliminate by careful digging. Its glossy foliage sheds weedkiller sprays although this can be overcome to some extent by bruising the leaves by trampling or bashing with the back of the spade.

The new B&Q Gardens app can be downloaded now for free from the Apple and Google play stores.