When spring hits Detroit's many abandoned neighborhoods, weeds, wildflowers and even trees begin to crop up in bulldozed lots and around forgotten homes like Grey Gardens - and the growth is disastrous for residents' allergies and asthma.

Ragweed, a pesky allergen, is plaguing Detroit, Michigan, and the surrounding areas.

Detroit is among the top 10 worst cities in the US for asthma-related deaths, and the top 25 for asthma sufferers on the whole.

And an expert told DailyMail.com that as the pollen surge is rising to the level of a public health problem in Motor City.

Some 20% of Detroit, Michigan's land is abandoned. The city bulldozes lots, making the soil ripe for ragweed that drives up allergies and life-threatening asthma attacks, an expert warns

There's a Manhattan-sized hole in the city of Detroit.

About 14 percent - or 20 square miles - of the city, spread out across multiple neighborhoods, has been vacated.

And where people aren't nature will be.

Fields and forests are taking back desolate homes and buildings, making for eerily beautiful, Instagram-worthy landscapes.

But all of those pretty flowers are casting pollen into the air.

As vacated homes have fallen into disrepair, the city has destroyed those structures and bulldozed the lots in an effort to discourage homeless squatters and drug users from hiding in them.

Bulldozing turns the soil, inadvertently making it fertile ground for plants, particularly one: ragweed.

Between 10 and 20 percent of Americans are allergic to ragweed

'Ragweed thrives in these recently disturbed soils,' Dr Daniel Katz, a University of Michigan ecologist who studies how allergenic plants grow, told DailyMail.com.

'It will come in and proliferate after a building has been demolished.'

And the city has largely allowed nature to take over.

Dr Katz's 2014 study found that more than a third of the vacant lots only get mowed once a year, and nearly as many don't get mowed at all.

Only about 16 percent were mowed monthly and another 16 percent were mowed twice a year.

Ragweed was growing in 25 of the 62 lots that Dr Katz and his team analyzed.

Although the difference was a small one, ragweed actually proliferated most aggressively in lots that were mowed once or twice a year.

'The reason that lots that are never mowed don't have ragweed is that other plants come in and out-compete it,' explained Dr Katz.

'If it's mowed very intermittently, then it creates conditions where ragweed thrives.'

Ragweed and allergies to it are on the rise across the US and indeed worldwide as global warming causes longer grow seasons.

And its torturous for allergy sufferers.

It's difficult to quantify just how many ER visits are directly attributable to allergies.

But some 1.8 million visits a year are for asthma and wheezing, and research has shown that these visits increase on high pollen days, which irritate the already sensitive lungs of these patients.

'Allergenic pollen is sometimes dismissed as just a nuisance, but it has profound effects on the quality of fife for someone who is allergic,' Dr Katz says.

'Hay fever can result in all sorts of unpleasant symptoms - everything from ittchy eyes to trouble sleeping and concentrating.'

He also estimates that the average allergy sufferer loses three-and-a-half work or school days to their sinus condition.

Detroit, a city which has struggled but sown resilience and maintained its 'vibrancy,' as Dr Katz puts it needs investment and care - not sick residents.

What should be done about the vacant lots and the ragweed making its irritating home there is still up for debate.

One group has suggested planting bulldozed lands with a mixture of native plant seeds.

'[They're looking at] what types of plants can be put there that will be good for the native insects and animals we want to have there but will also be aesthetically appealing,' said Dr Katz.

'There are a lot of legitimate concerns about vacant lots, and allergenic pollen is just one of them.'