Episode 43 – Do plants repel mosquitoes? Plus: why your hydrangea isn’t blooming, and one that definitely does.

Ground Breaking Banter - Rick

Thanks to social media, there are no shortage of claims out there that plants can repel mosquitoes. However, that’s not exactly true – while some heavily scented plants like mint, lemon balm, and fennel *might* have a mitigating effect if they were crushed and rubbed on your skin, no plant is mosquito “Kryptonite.” If it were that simple to repel or manage mosquitoes, a whole lot of people in countries plagued by malaria and other mosquito-vectored diseases would be a lot better off. 

When we’re talking about plants and mosquitoes, it merits serious consideration that plant pollen and nectar serves as a major food source for mosquitoes. In fact, the females eat it too – they only need blood for their young, and they sustain themselves on pollen and nectar. If deprived of sugar, males typically die within 4 days. Lacking the energy reserves needed for flying and mating that come from a sugar meal, males are unlikely to achieve reproductive success. Although females are less susceptible to rapid mortality caused by sugar deprivation, their survival rate can be compromised by reduced energy reserves.

Mosquitoes are not only terribly annoying, they are vectors for disease. They spread diseases such as malaria, dengue fever (den-gee or den-gay) and West Nile virus. According to the CDC West Nile virus (WNV) is the leading cause of mosquito-borne disease in the continental United States.  It is most commonly spread to people by the bite of an infected mosquito. The Centers for Disease Control and Prevention warned this past week of the return of locally acquired cases of malaria, meaning the infections were not linked to foreign travel and appear to have been transmitted by mosquitoes in the U.S. carrying the parasite. So far, there have been four locally acquired cases of malaria in Florida and one in Texas within the last two months. Each year, around 2,000 cases of malaria are diagnosed in the U.S., but they’re usually connected to people who’ve traveled out of the country.

It’s important to take basic precautions to reduce mosquito populations around your home. Mosquitoes need shallow (or shallow-ish) still water to breed, so avoid leaving opportunities for water to collect, like toys, buckets, old swimming pools, bird baths, and famously, old tires. If you have a pond or other area that can’t be emptied, treat it with a mosquito “dunk” – these disks are made of a bacteria that prevent the mosquito larvae from developing beyond that stage.

The plants sold as “citronella” or “mosquito plants” are actually scented geraniums, a variety called Pelargonium citrosum.  Though their scent resembles true citronella oil, they have zero repellent effect on mosquito. Similarly, many plants that are said to deter mosquitos, like lavender, marigolds, mint, lemon balm,  bee balm, ageratum, basil, catnip, lantana, rosemary, and fennel are only effective if they are crushed and applied to the skin, and even then, the effect is limited and no substitute for safer measures preventing mosquito bites. 

Check out this interesting article that suggests it could be your soap attracting mosquitoes.

Scientists at the Hebrew University in Israel have developed a new kind of insect repellent – a “chemical camouflage” – that they say will deter 99 per cent mosquitoes from landing on skin where it is applied. “First, it’s a mechanical protection against mosquitoes biting through your skin. Second, this cellulose polymer acts as a chemical camouflage,” Dr. Jonathan Bohbot, the lead researcher from Hebrew University’s Faculty of Agriculture, Food and Environment, explained. The mosquitos in the study could remember the scent of a human that had attacked it and actively avoided them.
Mosquitos can remember the smell of a person that has swatted them and use it to avoid them in the future, new research has found.
“When encountering a defensive host, mosquitoes are exposed to mechanical perturbations (e.g. swatting, shivering) that can be perceived as negative reinforcement by the insect when paired with other host-related cues such as host odours,” the paper read.

Why: ‘Annabelle’ hydrangea is long been one of the most popular garden plants and a true emblem of summertime. However, it has a few liabilities, namely, that its stems flop under the weight of the large mophead flowers, and it only comes in white. Incrediball Blush Hydrangea arborescens changes all that! Amazingly, even though its blooms are larger than typical smooth hydrangeas, they remain supported by sturdy stems. And the flower color is a beautifully unique silver-pink that looks amazing in the garden or landscape – I am particularly fond of it with burgundy and purple. 

Who: Incrediball Blush hydrangea was developed by Dr. Tom Ranney of NCSU. His work on Hydrangea arborescens has led to the development of many interesting cultivars in the Proven Winners ColorChoice line, including most of the Invincibelle series

How to grow: Smooth hydrangeas are widely beloved because they are so reliable and easy to grow. Thriving from chilly USDA zone 3 all the way through USDA zone 8 (and even some parts of USDA zone 9 that aren’t overly arid or humid), these hydrangeas bloom on new wood. Technically speaking, blooming on new wood means that the plant does not create its flower buds for the summer until after it leafs out in the spring. What that means to you as a gardener, however, is that you never have to worry about when to prune, or damage from winter cold or spring frosts. It takes pretty much all the guesswork out of being successful with hydrangeas! For pruning these, we recommend cutting the whole thing back by about one-third its total height in early spring. You can also periodically remove the oldest stems at the base, which opens up the plant and keeps its growth young and vigorous.

There’s much confusion about the best light exposure for hydrangeas in general, and especially smooth hydrangeas. In cooler climates (USDA zones 3-6), they can take full sun, provided they are mulched and get regular water – these are not drought tolerant plants. In hotter climates, shade during the hottest part of the day is imperative. However, we do not recommend full or deep shade: this leads to weaker stems as the plant stretches for light, and in the case of a variety with colorful flowers like Incrediball Blush, the pink will be less vivid, taking on muddy and green tones. The plant will also take on a more sparse and open habit.

Smooth hydrangeas do not change their flower color based on soil pH, so Incrediball Blush hydrangea will be pink so matter what your soil is like. It cannot turn blue – the same is true of all the pink-red varieties in the Invincibelle series. For fertilizer, we recommend a granular fertilizer formulated for flowering shrubs like a rose fertilizer. Once a year in spring is sufficient, but if you wish, you may fertilize monthly from early spring through late July. This may be particularly beneficial on younger plants, so they can get established more quickly and start producing those extra-large, extra colorful blooms. 

If you’d like to add Incrediball Blush hydrangea – or any of the 320+ Proven Winners ColorChoice Shrubs – to your garden or landscape, you’ll find a list of local retailers here

Gardening Mail Bag - Stacey

Today, we decided to devote the entire mail bag segment to this question which is surely on many people’s minds right about now. It is hydrangea season, after all, and we know how confusing it can get when you have high expectations for your plants and they disappoint. 

Before we get into the nuts and bolts of the issue, it’s important to keep in mind that if your hydrangea was just planted last year, it’s not necessarily surprising it’s not blooming. First of all, because when you buy a hydrangea from the garden center, it will bloom much earlier that year than after it spends a year in your garden because the grower will have brought it into warmth much earlier in spring than it will experience in your yard. Second of all, sometimes hydrangeas need a little time to get established before they will bloom well. 

The real key to understanding why your hydrangea isn’t blooming is knowing which hydrangea you have in the first place. That’s why we created Hydrangeas Demystified

Do you have a question for us? We’re happy to help! E-mail us or use the contact tab above.

Branching News - Rick

What are the top scents that people enjoy most in their homes?

Floral scents (e.g. flowers, potpourri) – 17%
Citrus scents (e.g. lemon, orange)- 13%
Clean/Sanitizing (ex. chlorine bleach) – 14%
Baked Goods (fresh bread, cookies) – 11%
Wood/natural scents (e.g. cedar, pine, fresh cut grass) – 13%

Vineyards and apple orchards across the Northeast are still gauging damage from a late-season frost in May that wiped out a third to most of the crop for some growers who say it’s the worst frost damage they have ever seen. Some states are seeking federal disaster declarations, which would make low-interest loans and other programs available to affected growers, while agriculture officials across the region are contemplating together asking the U.S. Department of Agriculture for direct aid to farmers.

Police officers utilized the YouTube app on their phones to play a series of mother duck calls to lure ducklings that had fallen through a storm grate to the opening. All four ducklings responded to the sounds and waddled their way to safety.

Why is grass the only acceptable planting material in the right of way between a homeowners sidewalk and the street curb?