New Scientist - USA (2022-02-05)

5 February 2022 | New Scientist | 51

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These articles are

posted each week at

newscientist.com/maker

What you need
Sweet pea seeds
Large plastic soft-drink bottles
Bamboo canes

IN MY garden, bulbs such as

snowdrops are coming up. Every

year, I wonder if spring is arriving

earlier due to climate change.

One study from 2006 found that

many signs of spring, such as plant

species unfurling their leaves, had

been hastened by 7.5 days across

Europe in the previous 30 years

(Global Change Biology, doi.org/

b7vmgk). And research published

this week has found that UK plants

are flowering nearly a month

earlier than they did before the

mid-1980s, probably due to

warmer temperatures from

January to April (see page 7).

You might think that warmer

weather would be welcomed

by gardeners, but some plants,

particularly fruit trees and bushes,

require a period of cold before

they break their winter dormancy,

so warmer winters could lead

to worse crops. In the UK,

blackcurrant bushes may be

especially vulnerable, although

new varieties are being bred to

tolerate a warmer climate.

Early springs are good for many

crops, as they extend the growing

season, letting you sow seeds

and plant seedlings earlier. But

gardeners need to beware of late

frosts, when an unexpected

cold spell means temperatures

overnight fall below freezing,

which can blacken foliage and

kill off tender plants.

After a few disasters, including

a year when I lost my entire crop

of new potatoes, I now keep a

close eye on the weather forecast.

If plants look in danger, they can

be protected by overlaying them

Temperature swings can prove challenging to young plants,

says Clare Wilson, who offers some simple solutions

Science of gardening

A cloche of ideas

with a thin sheet of fabric called

horticultural fleece. In a pinch, old

sheets or net curtains will suffice.

Another option to protect new

seedlings is a cloche, a transparent

dome that creates a miniature

greenhouse around a young plant.

You can buy them or make your

own by cutting large soft-drink

bottles in half and pushing each

dome firmly into the soil. “You’re

bringing a plant on by changing

its microclimate to a warmer one,

so it will grow and develop faster,”

says Tim Sparks at the University

of Cambridge, who was involved

in both the 2006 study and the

new flowering research.

If using cloches, you must keep a

close eye on the weather, as a sunny

spell could mean young plants

overheat and dry out to a husk. But

if you use the top half of a bottle,

you can put the cap on and off to
ventilate or keep heat in as needed,
without disturbing the plant.
I use these cloches for seedlings
of peas, beans and ornamental
sweet peas, among other things.
Depending on where you live,
you may soon be able to start
sowing sweet peas indoors in
small modules for planting into
the ground or large pots outdoors
later, under bottle cloches. When
the weather gets warm enough,
or the plants too big, remove the
cloches and stick bamboo canes
into the soil for the plants to climb,
helped by regular tying in. Three
canes lashed together make
Science of gardening a sturdy tripod structure.  ❚
appears every four weeks

Next week
Citizen science

Clare Wilson is a reporter

at New Scientist and

writes about everything

life-science related.

Her favourite place is her

allotment @ClareWilsonMed

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