The National Begonia Society




The Cultivation of Cut-Blooms
Alan Harris

   There are classes at begonia shows where only the bloom is entered, and this has obvious advantages when it comes to transporting.  The blooms are taken to the Show in boxes and staged on special boards containing paper cups.

    Once cut some varieties deteriorate much quicker than others and it is quite common on the second day of a Show to find blooms that are well past their best.  This sometimes causes great discussion amongst the uninitiated ..."how ever did that one win a prize?"

      A "cut bloom" plant is just one bloom  grown on a single stem, all side shoots are taken off and can be used to increase stock.    Once the bud has been selected  the growing tip above it is pinched out but leaving one leaf to help draw the sap up, thus all the resources of the plant are channeled into the one bloom.. 

These notes are intended as a guide for those who are already aware of the basic cultivation for tuberous begonias, which are covered elsewhere on the website.
The main points to bear in mind for the successful cultivation of plants intended for exhibition as cut blooms are: -

1.  Obtain the right varieties – not all varieties are suitable for cut bloom work, some are better as pot plants whilst a few are ideal for both. The best way to find the varieties you need is by looking to see the ones that win the prizes at the shows or asking other growers.
2.  Grow only one main stem with no side shoots and allow only one bloom to flower on each plant.
3.  Provide the right growing conditions – shade at all times, high humidity up until bud selection (discussed later) and cool airy conditions.
4.  Avoid the 3 overs – Over-watering, Over-feeding and Over-potting.
5.  Time the potting of plants and buds to the intended show.
6.  Always do the right thing at the right time. If it needs doing today, tomorrow may be too late.

In view of the increased incidence of tarsonamid mite it is worth treating the tubers by immersing them in a 10% solution of Domestos and water for 15 minutes, followed by a rinse for 15 minutes in clean water. Domestos is important, ordinary bleach will not do!

If the tubers are not pipped when removed from  storage place them upside down on soil warming cables heated to 75F. for two weeks, this should pip them nicely.

The starting time for pipped tubers should be about 20 weeks before the show date. The reason for this is that we need to allow for the following growing procedure: -

Start tubers in a seed compost or 50/50 mix of multi-purpose and peat.

About 4 weeks after starting first potting into a pot that will just take the root-ball using a multi-purpose compost.



About 6 weeks later pot on 2 pot sizes (e.g. 4" to 6") using a good potting strength compost.

After a furthur 6 weeks pot into final pots (another 2 pot sizes) using the same potting compost.

4 weeks before the show start feeding at Ό strength high potash feed at 3 out of 4 feeds with plain water at the 4th.

The weeks are approximate and you should be guided by the root activity which should be about 2/3 of the way down the outside of the root-ball at each new potting on. Take great care not to over-water at any stage. The best way to avoid this is to use very moist compost and not water for several days afterwards.

Tubers should be started on heated beds at about 65 – 70F. and once potted into the first pots kept as cool as possible.  A temperature of 45 – 50F. is quite ok as long as you avoid over-watering.

It is equally important not to let the compost dry out particularly whilst on the heated beds as major root damage will occur.

In view of the need to grow only one shoot, remove all extra shoots when about 3" - 4" long and use as cuttings.  Also remove all side shoots as small as possible. If they are rubbed out as they form no treatment of the wound will be necessary.

The plants should be grown on as steadily as possible, re-potting at the appropriate time.
This is the time to prevent attacks by pest and disease.  Spray with fungicide at two weekly intervals from the first potting until 6 - 7 weeks before the show date.  If possible use a different spray each time, but don’t bother with Nimrod, as this is not effective.  Provado appears to be effective against vine-weevil and a treatment straight after final potting is recommended.

All buds should be removed until 6 weeks before the show when they should be left until selection time which is 4 weeks before the show date. The bud to look for at this time is as near to, but not over 2" in size. This size, with average growing conditions, should be right for the show day.  From now on you are at the mercy of the weather at it as well to time some buds early and some late if you have enough plants.

The plant should now be stopped (i.e. the growing point removed) leaving one leaf above the selected bud. The side buds should also be removed as soon as they can be handled without touching the main bud.

Feeding now starts as mentioned earlier. Up to this point no supplementary feed whatsoever has been given. Many growers top-dress the pots with compost at the stage, but I do not believe it is necessary and find it encourages stem-rot.

A week or so after taking the bud, the forming bloom should be starting to open and be at what is called the "oyster" stage.  It is now time to place the collar on the back of the bloom.  This collar is made either from polystyrene or cardboard and is a 9" disc with a slot cut to enable it to be fitted behind the bloom.
The collar should be fitted behind the bloom but in front of the leaves.  An extending bloom support should be fitted behind the collar to hold it against the back of the bud. This support will need adjusting as the bloom stem lengthens.

It will not now be necessary to touch the bloom again until it is actually staged.
The night before the show the blooms will be cut and this should be done by holding the back of the collar and cutting the stem as long as possible. Once the bloom is removed from the plant cut 1 inch from the stem before placing in a bloom tube containing either flower food or lemonade. The extra cut removes the air lock which forms when the first cut is made and reduces the risk of collapse on the board.

The important thing now is to avoid damage to the blooms and check the show schedule to ensure compliance.  It is a great pity to fall at the last hurdle after 6 months of work.

The criteria for a good cut blooms are: -
Good size for the variety.
Refined bloom with no coarse petals.
Fresh bloom with no sign of ageing. 
The bloom should be circular in shape with a well-formed single centre.
Pure in colour with no blotching.
Good depth in relation to diameter.
Even spacing of petals with No handling damage.
In multi bloom classes uniformity of size.
After that, and only after all that, biggest is best.

One of Alan's greenhouses

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