Delphiniums in the heat/results

This contains a summary of the results of our small survey concerning
delphiniums grown in the heat. It has become a page about delphinium
culture in the USA which is now posted to our web site. Thanks to you
all for assisting and to those who agreed to allowing their notes to
be published on our site.


Growing Delphiniums in the USA

In December 1997 we asked, via a few garden lists, for methods of
growing delphiniums in the heat, employed by gardeners in the USA. You
turned out to be a resourceful lot! We also received some good
information and growing tips.

The feedback may be summarized as follows

Perennial Delphiniums are grown successfully in all except the hottest
and most humid areas of the USA. They get a bad press from Texas and
no press in Florida.

Mulch. Much emphasis was placed on mulching. This should be quite
thick, maybe three or four inches deep or greater if very loose (like
straw). The mulch helps to keep the roots moist and cool (most
desirable)

Heat. People who grew delphinium successfully where summers get very
hot (95degF+) all used some sort of shading to protect the plants from
the worst heat of the day. This shading usually took the form of trees
which cast a shadow over the plants at the appropriate time. The tree 
could be quite loose leafed. Adjacent trees help cool the ground too.

Watering. General agreement here too. Most folk water every day during
hot weather. I would add a cautionary couple of notes here. 1) Never
let delphiniums get either bogged or dried out (particularly when
growing well) or they will die. 2) Keep only barely moist immediately
after cutting down after the first summer flowering (July) or they may
rot. Increase water as the plants grow back. Be sure the soil is moist
going into a hot spell.

Cold. Delphiniums are generally very hardy. They are grown without
trouble in Alberta, temperature range -35degC to +35degC. Winter
mulching benefits here and folk often use pine branches to provide a
loose protection from severe frosts. We have reports of them going
rampant in South East Alaska, growing to two stories high and being
tended through the upper level bedroom window.

Types The most common type grown was "Pacific Giants" as this is the
most readily available. General consensus was that the English Hybrid
types (such as ours I'm glad to say) were more robust and lasted
longer

Species. D.belladonna bellamossum and other belladonna types such as
Connecticut Yankees do well in most places. Gene Bush
<genebush@munchkinnursery.com> recommends the following in the
situations he describes. "Delphinium tricorne is and easy and reliable
perennial blooming in violet to deep purple that is ephemeral. There
are also white blooming types to be found. The white usually contains
traces of violet and/or pink. D. exaltum is a tall species with light
to dark violet-blue blooms that is perennial and withstands the heat
as well as being cold hardy. D. carolinianum is from Virginia to
Florida and over to Missouri and Oklahoma so that would make another
good candidate.

Comment. The following are comments from a few of the respondents to
our questions. I would like to thank these kind folk for allowing
their notes to be published on our site, and to thank everyone who
took the time to respond

From Gayle Fields, Alberta

Delphiniums grow in Lethbridge, Alberta where the temperatures
range from -35C in the winter to +35C in the summer so you shouldn't
have any difficulty.  I cut mine back after their first bloom and then
get another bloom in the fall.  I grow Blue Mirror and am going to try
"Red Rocket" this spring.  They like a bright sunny place and grow
about 4 to 5 feet high.  Sorry for the mixture of metric and imperial
- I am of the age where I am only partly converted!


Peggy Enes Kansas

I live in a Zone 5/6 US hardiness zone (NE Kansas). We also can have
some really evil summers with temperatures going 100°+ some years.
Although a fairly new gardener, I had good luck with the little Blue
Butterflies last year with *heavy* mulching and regular watering (drip
irrigation) although they flagged a little above 90°. We did not have
100°+ last summer but had long stretches of high humidity.

The butterflies were grown in my very nasty, completely depleted,
*heavy* clay soil with 1/3 cotton burr compost and 1/4 sand amendments
(1st year). They were mulched (4-6") with coca shells and regularly
watered (we had a summer with practically no rain) so I can't speak
about drought-resistance. I fertilized with Osmocote (a 3 to 4-month
timed-release fertilizer) since my soil is still a few years short of
being adequate to support much but weeds.


From: "Carolyn Zard"  Washington State

Our summers in the Pacific NW are not hot - even if we do get into the
90's it cools off at night because of the maritime air surrounding us.
The only suggestion I have is to practice good garden culture to keep
your soil & plants healthy and be sure the soil is moist going into a
hot spell. The British cultivars I've grown the last 4-5 years have
not suffered from any weather conditions except the wet Spring in '97
that greatly reduced their bloom time and seed ripening. They're
pretty rugged. Carolyn


Terry Dowdeswell
18 Henderson Ave
Tuakau, New Zealand
~~~~~~~~~~~~~~~~~~~~
Terry@delphinium.co.nz
http://www.delphinium.co.nz
~~~~~~~~~~~~~~~~~~~~
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