|Sixty six Chempaks
in a 16x8
By Paul Barlow
I guess there
aren’t too many places in the U.K. where Chempak Roses are grown and
flowered under glass, however in Aberdeen I’ve managed to do just that
for five or six years now (but then I am a bit closer to the Arctic Circle
than most other growers!) Last year I flowered 22 plants each of Chempak
Rose and purple and red sports in my 16ftx8ft greenhouse.
This article covers my growing methods in general and my 2007
season with Chempak Rose and sports.
Invariably I get Chempaks on the show bench in the second half of
September, in 2007 I decided to try to get some flowers for the first half
of the month. Cuttings were taken in two batches on 21st and 28th
of November 2006. The compost used was Levingtons multipurpose mixed with
perlite (3 parts compost to one part perlite).
mainly use two types of container when propagating my cuttings – 84 cell
plug trays (12x7) which gives me a fairly large sized cell, and standard
seed trays into which I put up to 40 cuttings depending on cultivar and
number of cuttings to be taken.
inserting cuttings the compost is thoroughly watered and then sprinkled
with a layer of perlite.
are snapped to length and lower leaves removed before being dipped in
hormone rooting powder and inserted into the compost.
When the required number of cuttings is taken the tray is watered
again and then placed on the bench
in a cold part of the greenhouse for 7-10 days. Only after this cold
period are trays transferred to the propagator at appx 55F bottom heat.
Fourteen days later all cuttings are rooted.
a cold period for the cuttings? The late Jim Innes from Fraserburgh
promoted this idea; Jim’s view was that the cutting needs to form a
callus before roots can develop and callus formation can occur equally
well without a heat source. One thing is clear, the method works and very
few cuttings fail to root.
on to first stage
When rooted cuttings are taken from the propagator they are left for about
one week to acclimatise in a cooler part of the greenhouse. For the first
stage of potting on I made a change in compost for 2007 – sticking with
Levington Multipurpose but this time adding John Innes no2 in the ratio
three parts Levington to one part JI2. This is a very convenient mix
because Levington comes in 75 litre bags and JI2 in 25 litre bags –
combining one bag of each gives the ratio I’m looking for.
used at this stage can be either standard seed trays (12 plants to a tray)
or 3˝” pots. Is there a difference in the end result? Hard to tell
really – when moving plants to the next size container plants grown in
the seed tray appear to have a more expansive root system than those in
pots. Whether this is actually the case is debateable since the root
system in the pot may actually be similar but it’s been constrained by
the size of the pot. Certainly what I see above soil level is very similar
from both methods.
is normally the time when I use a growth retardant to keep the plants
short and stocky prior to stopping. I find most cultivars will produce a
good crop of even breaks when the leaf joints are close together.
Application of the growth retardant three to four weeks before the stop
helps to achieve this.
on to second stage
After approximately five weeks in the small containers my plants
are moved into individual pots. Depending on cultivar vigour and length of
time each plant will be in the next pot I use either 5” pots or l˝
litre pots. Plants may be in these containers up to six weeks so a liquid
feed is given towards the end of the period to keep them moving.
cultivars are moved from the greenhouse into the cold frame for a few
weeks prior to planting out, but the Chempaks remain under glass since
that would be their final planting position.
Chempaks were stopped while in the second stage containers; dates for
stopping were 12th March for the first batch and 19th
March for the second batch.
did drop a bit of a clanger at this point. Towards the end of April the
plants were well advanced with laterals 15-18 inches in length. I was
concerned that ultimate flowering height might exceed the height of the
eaves of my greenhouse so I decided to spray the laterals with growth
Only much later, as blooms were developing, did I realise this
was not such a good idea. (See 2007 Conclusions).
analysis and base dressing to Machin start point
I’ve long been a fan of soil analysis. Every year in early March
I send soil samples from my greenhouses and the outdoor beds for analysis.
The results are eagerly awaited. One common problem in Aberdeen is low pH
and invariably I have to apply lime every other year. Ideally I would like
a pH slightly higher than 6.5 at the start of the season, this will allow
for a slight drop as the season progresses and still be close to 6.5 at
results for my greenhouse for March 2007 were
– 25ppm P –
30ppm K – 360ppm
Mg – 210ppm pH– 6.6
Conductivity – 310 microseimens/cm
on the analysis results I calculated the required base dressings to raise
the nutrient level where necessary to that recommended by Barrie Machin,
– 175ppm P – 50ppm
K – 200ppm Mg –
dressing takes place about ten days before planting; lime application (if
required) takes place at least 4 weeks prior to base dressing.
you can see from the analysis results only Nitrogen and Phosphate required
out distances and system used
For years I’ve planted out in rows of two down each side of
the central path in the greenhouse. In 2006 I experimented with one batch
of Red Chempak Rose and planted out using a ‘domino five’ system.
Plants were positioned such that the breaks in the back row of
plants (furthest away from the greenhouse path) ran parallel with the
path, while the breaks on plants in the front and centre rows were set at
90 degrees to the greenhouse path. This meant I could still get easy
access to the plants in the back row. The experiment was successful, both
plants and blooms had adequate spacing and so in 2007 all Chempaks
followed the ‘domino five’ system.
did I arrive at 66 plants? I originally planned for 60 plants, 20 of each
cultivar in two batches of 10. But like most of us, when I want 10 plants
I will have 12 to choose from, and being reluctant to discard good plants
I found I could put in another six plants with no noticeable compromise on
out usually takes place during the first week of May and 2007 was no
exception. Of course planting under glass does not carry the same frost
risk as planting outdoors. All Chempaks were reduced to two breaks by the
end of the second week in May.
Feeding commenced towards the end of May 2007. Initially a
nitrogen only feed based on Nitrate chalk or sulphate of ammonia, 200ppm
is my standard feed strength. Unfortunately summer 2007, as we all know,
was dreadful, endless rain, dull days, very little sunshine etc. Under
these conditions I reverted to Vitafeeds 1-0-1 and 3-0-1 to ensure
adequate potash while still providing 200ppm nitrogen.
continued every five to seven days right through until late July and calyx
at this stage, was as always, carried out on an “as needed” basis. I
know many areas had real problems with white rust in 2007, fortunately in
Aberdeen this problem did not occur and to my knowledge no grower in
Aberdeen or further north was troubled by white rust. The products I use
are ‘off the shelf’ garden centre regulars – Systhane, Bug Clear,
Fungus Clear, Rose Clear 3 etc.
in the flowering laterals takes place every time I go down my garden.
Whenever the growing tip of a lateral is more than 12 inches above the
support ring I move the ring up another four to six inches; I find that
one support ring is sufficient to keep each lateral securely attached to
it’s cane. This is especially true with Chempaks given that they are
well protected from wind and rain inside the confines of my
early June I remove the top row of glass along both sides of my
greenhouse, even in Aberdeen it can get quite hot under glass so partial
glass removal is one way to keep the temperature down.
were secured at the end of June through the first week of July. At this
stage my spraying programme is stepped up a bit to ensure buds remain free
from pests as they develop, once again, Garden Centre products are used.
buds develop and calyx split approaches I apply the first of three layers
of shading. Layer one consists of cool glass applied to the roof glass on
both sides, then the end of the greenhouse and lastly the remaining glass
on the west side of the house. The second layer is internal and is a
curtain of rokolene netting which can be raised or lowered on wire runners
attached from the apex of the greenhouse to the top of each vertical
support along the sides of the greenhouse.
final level of shading consists of a muslin or fleece tent erected above
the area where the blooms will develop.
last element in protecting the blooms is to put polythene in place of the
row of glass that was removed earlier. The polythene is not the same size
as the original glass so this allows air movement above and below the
polythene while preventing the entry of driving rain.
know this sounds like a lot of shading, and you may expect to see some
colour loss when blooms reach maturity, but if this does happen it is so
small that my blooms are not distinguishable from those of other growers
on the show bench – leastways not for colour!
Bud and Bloom protection
In general, no bags are used with Chempak Rose and sports. If there
are some early buds then I may bud bag them but once the majority of buds
reach calyx split I abandon the bud bags and rely on regular visual checks
for earwigs, slugs, snails and aphids. This often means going into the
greenhouse after dark armed with a torch, as this is the most likely time
to catch the larger of these pests. Of course this method is not foolproof
and there have been occasions when entering the greenhouse first thing in
the morning that I’ve been greeted with the presence of a few chewed
petals around the base of the odd plant.
The first blooms of Chempak Rose and Red sport were shown at Aberdeen
Royal Horticultural Society Show on 26th August. Showing
continued through to the Naturally Fife Show on 15th September.
This means my two batches of each cultivar covered three elapsed weeks of
the early part of the Show season, and over 50% of available blooms were
used in my exhibits. In 2007 only Joyce Frieda, Billy Bell and John
Wingfield provided me with more blooms on the show bench than Chempak Rose
Rose (Best Vase) and Red Chempak included in 4x5 entry at Dundee
Purple Chempak included in 6x5 entry at Scottish National
with Chempaks – yes of course there are a few – no cultivar is 100%
perfect. Shallow and one-sided blooms are quite common; even what appears
to be a level bud may eventually produce a slightly one-sided bloom. Neck
extension between top leaf and bloom is in many cases too short and some
leaves have to be removed to allow petals to fall naturally and
Conclusions from 2007
Using growth retardant on flowering laterals was a mistake. In
cultivars that already have a problem with neck extension and distance
between leaf joints, I just compounded the problem. This resulted in
having to remove more leaves than expected to allow blooms to develop
unimpeded and even shorter leaf joints on the top half of each lateral
which generally made plants more difficult to handle when tying in etc.
feed heavily – I think my 2007 plants could have withstood heavier
feeding during the summer period giving the potential of better blooms.
This is something to think out in 2008, especially after reading Ian
Rankine’s article in the 2007 Year Book.
space is at a premium the ‘domino five’ planting system works well,
plants and blooms were adequately spaced. Although I’m not sure this
would be the case for blooms that require bagging throughout their
development as reaching through to the back row to put bags in place may
prove a bit difficult.
stopping dates were a bit too early in 2007; I know I wanted earlier
blooms but not necessarily in August. I think the earlier stop, combined
with a very warm bright spring, produced much faster early growth and
ultimately lead to blooms sooner than expected.
had Chempak blooms in early September and late September in recent years
I’m tempted to conclude that in 2007 my earlier blooms were smaller and
shallower than the later blooms of previous years.
Summary of Activities
- Chempak Roses 2007 season
- 21st and 28th November 2006
Potting on 3˝” pots/trays
- 3rd and 8th January
Potting on 1˝ litre pots
- 4th and 8th March
- 12th and 19th March
Planting out -
First Buds visible
- 17th June onwards
- 28th June to 6th July
Calyx split -
21st July to 8th August
Full bloom -
26th August to 15th September
Average leaf count
- 37-40 per flowering lateral
updated: 19 December, 2008