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July 29, 2006

Repotting dormant bulbs: Bulbous Oxalis


The rarer and slow growing Bulbous Oxalis species perform best when repotted in the summer while they are dormant.
The highly collectable bulbous Oxalis species that hail from the winter growing areas of South Africa and South America are a far cry from the weedy pest that plague our gardens and greenhouses. This is an enourmous genus and are truly sought after by plant collectors. Once you try a few of these winter growing and summer dormant species, you will be hooked and then the collecting begins. And that is not an easy thing to do, since the finest bulbous Oxalis species are only available suring a few weeks of the summer and only from a handful of catalogs, if that.


Carefully repotted summer dormant bulb species all lined up and waiting

My greatest mid-summer chore is repotting all of the bulbs which are now dormant in the summer. A great many of my collection does come from the southern hemisphere, and most of these transcend into a deep, summer rest, with some wanting to bake high on the sunner shelves of the greenhouse where they can remain bone dry, and others just want to get splashed occaisionally to keep their cell wall turgid, but not enough to ever signal that the fall rains have arrived. Late July is when I start repotting most of these winter bloomers, and this incudes collections of Cyclamen species, Narcissus from the Mediterranean and the bulbocodium type like N. romieuxii, N. cantabricus et al, Lachenalia, Romulea, and of course, the Bulbous Oxallis species, the jewels of the collection.














1. Carefully Remove dead foliage and topdressing.

Once Oxalis stop growth and whiter around May or June, allow the pots to go bone dry until you are ready to repot.Carefully remove old foliage and discard, being careful that no bulbs are attached to stems.















2. Dump compost carefully into sieve.
Be sure to selct a sieve with holes large enough to catch bulbs. Bulb size and shape differs greatly with species. I dump the entire pot into the sieve and then depending on the species, wither remove bulbs as I see them since many migrate to the bottom of the pot and are easier to remove before crushing the root ball, or with less robust species, carefully breaking the rootball to see if bulbs have divided at all.

Many Oxalis speces send bulblets down into the ground deep, so they line up against the bottom of the pot. One theory is that these bulbs remain dormant for years. Mother Natures back up system perhaps, in case a population burns or gets eaten by baboons I am guessing.

Removing these bulbs allows you to grow your collection, which is a good thing since on a whole, thes are not innexpensive bulbs since they sell for about $3.00 - $4.00 each and one must pot at least a dozen or more to get a nice display. You will want to propagate them this way since they do not produce viable seed.















3. Sift and clean.
Carefully pick out the bulbs, which is sometimes easy and at other times a challenge since some bulbs look exactly like rocks. This is also the fun part since you can see if you either lost a collection or grew is. Some species multiply well, while others remain about the same. It's a bit like digging for potatoes.



4. Store dry until repotting in early August.

Since I am repotting a day or two later, I am using platic zip-lock bags which I keep open, I would not suggest this, they we're just handy. Some may want to catalog or keep a spread sheet on bulb count, and I have done this for some species but not yet for Oxalis, I just don't have the time, but memory does tell me that some species that I ordered from Telos last year have multiplied well. I usually order 6 bulbs and all of last years pots have grown to about 30 bulbs, of various sizes. I save even the tiniest ones, so blooming size bulbs surely are at a minimum. I think I will repot some smaller bulbs in propagation pans so that they will have mroe room to grow and pick out the larger bulbs for show pots.



Uncommon South African bulbous Oxalis in bloom in the cold greenhouse in November

Watering for all of these dormant bulbs will commence with the first arctic cold front sometime in early September. The theory here is that not only do the fall rains trigger growing but also the temperature shift. I have watered as early as Labor Day, around Sept 1, and as late as Oct. 1.

Summer repotting will continue, starting here with Oxalis since they seem to send hair-like roots first, then Cyclamen species which have a very brief dormancy if at all. I then continue with the Narcissus, the followed by the balance of the minor South African bulbs with the ultilate goal of everything repotted dry and resting on the benches by the second week in August.

The Amaryllids like my collection of Nerine sarniensis are not repotted per say, just top dressed since thier roots do not go dormant, and the bulbs are, in fact, actually growing a bit during thier summer break of foliage. These also are getting an occaisional spritz of water.


Summer dormant Bulbs can only be shipped in August, so order now for winter bloom.
This is also the time to order bulbs that will bloom in the winter. If you have a cool greenhouse that remains frost free and cold, or anyplace that is bright, sunny and frost free, the winter growing bulbs from South Africa are some of the best performers and relatively easy once you master the cycle of winter wet and summer dry. For me, in the North East, this is easy with a glass greenhouse that is kept at 45 deg. F in the winter and allowed to get hot in the summer.

2 comments :

  1. I love your plant blog and facinated with the plants you grow. I live on the tiny island of Barbados and have got a two acre garden. Love flowering plants and colourful foliage. I have an unusual oxalis that I am trying to id, it has a woody stem and grows from cuttings and seeds. It does not have a bulb or rhizome. Come visit my garden on webshots
    http://home-and-garden.webshots.com/album/37628237KeGdyE

    H Knighton
    Barbados

    ReplyDelete
  2. I love your plant blog and facinated with the plants you grow. I live on the tiny island of Barbados and have got a two acre garden. Love flowering plants and colourful foliage. I have an unusual oxalis that I am trying to id, it has a woody stem and grows from cuttings and seeds. It does not have a bulb or rhizome. Come visit my garden on webshots
    http://home-and-garden.webshots.com/album/37628237KeGdyE

    H Knighton
    Barbados

    ReplyDelete

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