Growing Tender Bulbs in Cold Climates--TOW

Mark Wilcox
Fri, 11 Apr 2003 18:55:07 PDT
Dear all,

I've also given this topic a try, expanding into various things over the years.

I live in Washington, DC, zone 7b, where we have both hot, humid summers and
relatively cold winters.  Summers and winters can be either wet or dry, while
we usually have good rainfall in spring & fall.  While recent winters have been
extremely mild, the one from which we're just emerging was more typical.   I
believe our lowest temperature was 15ºF/-9.5ºC.  Most of the very cold weather
was unaccompanied by snowfall.

I have neither a greenhouse, a garage nor an ideal house situation for
overwintering tender bulbs.  I'm in a rowhouse that faces east/west, and is
blocked to the north/south by adjoining houses.  Therefore, I concentrate on
what's hardy under the local conditions.

Having said that, I have found that I'm able to grow various plants not
considered hardy.

I believe Jim Waddick mentioned Hippeastrum X johnsonii.  This past winter has
proven that it can shrug off a real zone 7 winter in the ground.  While new
growth hasn't yet begun, a quick check of the bulb showed it to be firm and
healthy, not the mush I've found in other cases.  Other Hippeastrums are grown
in pots that are plunged into the garden from about mid-April through the first
frost warning, usually sometime in November.  They overwinter and bloom in the
east-facing windows on the second floor.  While they may not get as much light
as they'd like there, they survive - and have flowered every winter, sometimes
producing a second set of flowers in the garden in May.

Various Achimenes hybrids have done well in the total shade of a bit of soil
between the back sidewalk and the south neighbor's brick garage, where they get
no direct sunlight but bloom like mad from midsummer until very cool weather
arrives.  Just before or after the first frost hits I collect the scaly
rhizomes and put them in the fridge for the winter in perforated plastic bags.
Some kind of mold always seems to grow on them, but it doesn't affect their
vitality when they're replanted the following spring.  Perhaps allowing them to
dry for a few days would solve the mold problem?

I tried a potted Griffinia aracensis outside in the same shade for the first
time last year.  It suffered from a couple of squirrel attacks, but it also
seemed like something was attacking the leaves, which never seemed to stay
around for a long time, though the plant produced more regularly.  When temps
threatened to go below 50ºF/10ºC I took it indoors.  Having just suffered a
final squirrel nip, it had no leaves at all.  After about 6 weeks indoors
foliage production resumed, and the leaves produced in December are still on
the plant.  It likes its situation in the east-facing window behind double
panes of glass so much that I'm going to try leaving it there, as whatever had
attacked the foliage outside is absent under inside conditions.

A few years ago I got some Scilla peruviana from a Dutch supplier.  Following
directions, I planted it 5 or 6 inches (12 to 15 cm) under the ground.  It
emerges every fall, though by that time its area receives no direct sunlight.
The foliage suffers some damage in the cold winter temps, but so far both bulbs
have bloomed every year in May.  If it's found partially above ground in the
wild, I must say that being buried seems to agree with it as well.

The pot of Clivia miniata comes inside when temps threaten to go below
freezing, but the plant seems to enjoy sometimes very cool weather in spring
and fall.  After taking a year off to adjust, it has bloomed every year in late
spring or early summer.

I know that I've gotten much different results than others with the
Hieronymiella aurea that was distributed last year around this time, another
tender bulb.  I believe I got the same large, flat black seeds as everyone
else.  What I did with them may have been different - and this does concern
overwintering lest readers think I'm straying from the topic.  I only had 2
plants that really took off.  One I planted out in the garden.  The other I
kept under lights in the basement.  The garden plant had trouble keeping
foliage up, just as with the Griffinia.  The plant indoors under lights in a
relatively cool basement grew much better, faster, and kept its leaves.  When
fall came I potted up the tiny bulb outside and brought it under the lights
inside for the winter.  Neither bulb has gone dormant during the winter, having
continued to actively grow instead.  The bulb previously outside has made
several times the progress it made outdoors last spring and summer inside over
the winter.  Both have long leaves about an inch wide, unlike the "thread-like"
foliage appearance others have noted.  They don't mind being dry at all, and
staying moist doesn't seem to hurt them either.

I also started various Rhodophialas from BX seed last spring, and have grown
them inside under lights over the winter.  R. granatiflora germinated best,
likely 100%, and has grown especially well inside.  Some R. advena went
dormant, others didn't.

Flowering sized bulbs of Rhodophiala bifida survive well in the open garden,
where they've dug themselves down to a depth of 8 inches/20 cm, which is well
below the frost line.  The foliage is damaged by winter conditions, but the
plant doesn't seem to mind, simply growing more as the weather improves toward

Amaryllis belladonna survives outside the same way, although the depth at which
it's planted seems more critical.  While the surviving plant does better every
year, it has yet to bloom for me.

With a bit of experimentation and luck, even under less than ideal conditions
tender bulbs can be grown, and even flourish, here in zone 7b.


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