Bulbils

I once saw a program where a "professional," who should have known better, described how to grow ferns from cuttings. This was especially interesting (and disconcerting) since ferns do not grow from cuttings. (And folks wonder why they have little luck with fern propagating.) Growing from bulbils, or bulblets (little nodules along the fern's rachis, the stemlike section of the leafy portion of the frond), comes close, but is not the same.

Cystopteris bulbifera has bulbils the color and size of peas loosely distributed on the undersides of the fronds. These will drop, roll about, and reproduce without human assistance. Others, most commonly on assorted polystichums and especially Poly-stichum setiferum cultivars, remain fixed on the frond and benefit from some judicious midwifery. When there are just one or two bulbils at the tip of the frond such as with P. andersonii and P.lentum, I peg the tip down on surrounding soil in the fall and let nature take its course. I do, however, pamper the rare bulbiferous sterile hybrids, such as P. xdycei. On these I remove the bulbils from the frond and pin them individually on the moist surface of light compost in a 4-in. (10-cm) pot, invert a clear plastic cup on top, creating a personalized greenhouse, and bring the whole into the plant room. Generally I do this in the fall, but one spring I happened upon an unexpected cache of similar bulbils. I picked them and put them in a bowl of water, promising that I would be back. Well, I did get back, actually several months later, and there they were sprouting away. So much for coddling.

I use a different procedure with Polystichum setiferum cultivars. Here we have masses of would-be plantlets lining the rachis. I pin the entire frond down on friable soil, sometimes leaving it attached to the parent plant and sometimes, for greater speed, in a flat of light compost, under the banks of fluorescent lights in the humid i<7 T

Bulbils along the rachis on a Polystichum setiferum cultivar.

Bulbils along the rachis on a Polystichum setiferum cultivar.

warmth of my plant room. Thus incubated, the babies will root and be ready for separation in a few months. I snip them apart and move them up to 4-in. (10-cm) pots. It will be a year, however, before they are ready to truly leave the nest. With more than 365 cultivars of Polystichum setiferum, it should be noted that not all of them produce bulbils, and not all of the bulbil producers will have them annually. The reason for this is not known but it is certainly a research project waiting for attention.

A rarely used variation of bulbil propagation was discovered by a Mr. Jackson in 1856 for growing leaf base bulbils. This specialized system is usually applied to the sterile cultivars of Phyllitis scolopendrium. In this method the desired fern is dug and thoroughly washed of soil. From the bottom of the clump, where the stipe bases are attached to the rhizome (underground stem), old frond stubs are peeled away. Although looking rather dead, they should show green tissue and possibly a few roots at the point of detachment. These are placed in a flat of the familiar light compost or sand. Dyce (1991) recommends sticking the top rather than the lower ends into the rooting medium but both ends work. The entire tray should be packaged in a clear plastic bag or placed in a mini greenhouse structure and stored under indirect or artificial light. In time and with luck, bulbils will form at the base and, once this is achieved, sporo-phytes will follow. From that point on they should be treated like any young plantlet. Unfortunately the parent plant can be sacrificed in this process. Therefore, I recommend reserving this strategy for the special sterile few, stripping only a minimum number of fronds and replanting a significant portion of the parent plant in a well-tended pot until it recovers from the surgery. Or, as a safer option, do not dig the plant but rather take a few of the outermost, dead-looking fronds and "plant" them.

Finally, for yet another vegetative propagation situation, there are the mother fern types where the babelets actually grow on the fronds. Asplenium bulbiferum, Woodwardia orientalis, and Dryopteris erythrosora 'Prolifica' all have such buds looking like miniature winged darts on their foliage. Prick them off and line them up closely in good soil in flats (or as described above in pots capped with inverted plastic cups), and nurture them in greenhouse or pseudo-greenhouse conditions. Rooting and new growth follow very quickly.

With any successful propagating procedure carried out in an enclosed system, it is very important to gradually harden off the progeny by slowly exposing them to increasing amounts of nonincubating fresh air with reduced humidity. Do not rush the procedure. Instead, gradually lift the lid and/or open the container in increments, keeping a watchful eye out for wilting.

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