How often to repot

Uli via pbs pbs@lists.pacificbulbsociety.net
Mon, 02 Aug 2021 16:42:17 PDT
Hello Judy,

Repotting bulbs can become quite a job once your collections has a 
certain volume.... Personally I repot almost all my mature bulbs every 
year (so far, but thinking of alternatives) it is a big job which still 
lies in front of me for the winter growing ones.

You ask which genera would have priority and which can remain in their 
pots for longer.

First of all it is a matter of observation.  If a bulb performs well in 
the same pot and compost year after year there is no reason to repot 
frequently. The best examples for these are Vallota and Clivia. But most 
bulbs will flower less or even end up with masses of smaller and smaller 
leaves and few flowers after a while. This is a clear sign that they are 
overcrowded, lack room and food. And in your climate, keeping winter 
growers under glass these overcrowded pots are prone to pest and disease.

Most Amaryllidaceae do not like root disturbance and many have permanent 
roots which remain alive during dormancy. They can stay in their (deep) 
pots for quite some time, many like to be crowded and pot bound. I do 
not grow Rhodophialas in pots but in the open garden only but am not 
successful with them. I put it down to Narcissus fly but that is a 
different issue. I grow the seedlings in pots for mostly two seasons and 
find they make a massive root system, so they would need big deep pots 
if grown permanently this way.

Cyclamen can also remain for quite some time in their pots provided the 
diameter of the pot remains bigger than the one of the tuber.

Freesia and other Iridaceae like Babiana, Sparaxis, Tritonia, especially 
those which produce a lot of bulbili are best repotted every year, maybe 
every second one. If left in the same pot for too long I find they tend 
to overcrowd and make a lot of foliage from their offsets but flowering 
becomes sparse. If repotted every year I only use the biggest corms and 
make extra pots with the offsets if I want to propagate or give them 
away. This way the flowering size corms give a good show.

You do not mention Gladiolus. The smaller species have small corms and 
even smaller offsets so I always worry to miss some in the process of 
repotting. Most are dainty and do not overcrowd their pots (I wish they 
did....)  so they can also remain in the same pots for several seasons. 
The very vigorous ones should be treated like Freesia if pot grown at all.

For Lachenalia I would think they can remain two or maybe three seasons 
in the same pot. Only the ones producing many bulbili might overcrowd 
but the bulbili can be mostly removed from the surface of the pot once 
the foliage has died down at the beginning of dormancy.

A must for repotting every year is Oxalis, for two reasons. Having a 
fairly large collection of winter growing Oxalis I have discovered that 
here in Portugal there is some spontaneous self seeding. This is new to 
me and has not occurred in Germany when I grew them under glass. To keep 
a collection true to name these seedlings must be removed. I do so by 
only replanting the big bulbs, hoping that the seedling bulbs will be 
smaller in their first season. I discard the compost to avoid 
invasiveness and mix ups. The other reason is that many, not all, Oxalis 
are so very prolific that they overcrowd their pot within one growing 
season. And again, overcrowded pots do not perform as good.

I fully agree with the other comments. A stable compost is a 
prerequisite for successful growing of plants which resent bad drainage. 
Fertilizing is an issue that can not be overemphasized, bulbs do benefit 
from repeated feeding, especially in the weeks before the onset of 
dormancy. This also applies to those which are repotted annually.

Seedling bulbs always remain in their initial seed pots for their second 
season. If I find they overcrowd during their second season I repot them 
in the green and have never had any losses this way. On the contrary: 
the freshly potted seedlings burst into a new flush of leaves after 
being  potted larger.

One personal comment: To reduce the sheer number of pots I am using the 
technique of "companion planting" which means I plant up to 4 different 
bulbs into an 8  liter pot. 6 liter and 8 liter pots have turned out to 
be the optimal size under my given conditions in the open year round in 
Portugal. These companions need to have the same cultural requirements, 
of course. What has proved very sucessfull is a combination of for 
example: Lachenalia with dainty Gladiolus with not too vigorous Oxalis. 
Or dwarf Narcissus with dwarf Oxalis and dainty Moraea or dwarf Scilla. 
It is important that one plant does not outgrow its partners and also 
that the bulbs can be easily distinguished in the dormant state when 
repotting is due. It is not a good idea to plant different closely 
related bulbs into the same pot, under no circumstances different 
Oxalis. The very vigorous bulbs like Freesia Hybrids, Arum species or 
climbing plants like Tropaeolum are best planted on their own. I write 
comments on the plant labels if a combination is not good or which would 
be good partners in future, here again is another reason for me 
repotting every season....

Hope that helps, bye for now

Uli

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