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Everything’s coming up crocuses

by Timber Press on January 14, 2011

in Gardening

Soon, in some parts of the world, we can expect to see crocuses poking through the snow and mud. Crocuses — harbingers of spring, bright splashes of pigment on an otherwise gray/brown/white world. I thought I’d offer some content from our newly published book on crocuses in anticipation of their imminent arrival.

Crocuses is by Jānis Rukšāns (who also wrote Buried Treasures), and has a forward by Brian Mathew, who wrote the previous genus monograph on crocuses in 1982. Here is the chapter on growing crocuses from seeds.

Growing from Seeds

It is very important to grow crocus from seed. Interestingly, in difficult seasons, when mature corms perish, it is the seedlings that survive. Many times I have not lost rare species thanks to the seedlings I grew. Other times only the seeds that had been sown the previous autumn and had not yet started to germinate survived a difficult winter. For this reason, I recommend that you always collect seeds, even if you will not actually sow them. You can put them to use in a seed exchange.

Propagating crocuses from seed has several advantages. Seed-raised progeny usually are free from viruses. Raising seedlings also helps to increase the stock faster than waiting for the stock to build up vegetatively, particularly in the case of species that are slow to increase vegetatively or do not do so at all.

Even in an ideal situation, where a grower starts with a good number of seeds which germinate well, the number of seedlings can decrease. During the years before the seedlings start to bloom, plants may be lost because of pests, diseases, your own mistakes, or simple misfortunes and other circumstances that work against you. Eventually, however, you will end up with a few flowering plants, which, thanks to natural selection, are adapted to your growing conditions. These plants retain the genes that ensure survival for coming generations.

An additional advantage (or sometimes disadvantage) of growing crocuses from seeds is the appearance of hybrids among seedlings. Most Crocus chrysanthus varieties raised in my nursery originated as unintentional hybrids. I have never crossed them intentionally. Instead, that job has been performed by bees. I only collected seeds and sowed them in favorable conditions. What a myriad of beautiful colors came up, when they started to flower! But if you want to be certain that your seedlings are true to name, you have to isolate the flowers and pollinate them by hand.

When you decide to raise your stocks from seeds you collect, you have to pollinate them yourself. Crocuses generally bloom at the time of year when weather conditions are very changeable, and in some years there are very few sunny days when the flowers are open for pollination. If your crocuses grow in pots, you can bring them inside where the dry and warm room air will quickly open the flowers. In these conditions you will need to pick the right moment to pollinate your plants before the stigma dries out. In recent years I have regularly hand-pollinated the very early blooming Central Asian species — Crocus michelsonii, C. alatavicus, and C. korolkowii — and gotten good seed crops. After pollinating the plants, the pots can be returned to the greenhouse. In hot, sunny weather the anthers open very early and pollen falls out, so it is best to use such plants on the day the flowers open. Sometimes I have succeeded in collecting pollen on a brush from a flower that was only half open.

The stigma retains its ability to fertilize for a very long time; there are reports about successful pollination even of wilted flowers at the very end of blooming. Later in the season, when bees start to come around, another problem arises — how to prevent an undesirable cross-pollination. You will need to cover the pots of pollinated flowers with muslin bags or tight wire mesh to keep insects away from the flowers. I don’t use any covering on my plants because, in most cases, I’m happy when unexpected hybrids appear among my seedlings now and then.

To transfer pollen from one plant to another, I use a very thin brush made from squirrel or camel hair (Plate 9). Another way to do this is to remove the anther from the flower using forceps, then brush it against the stigma. This method may damage the flower tepals.

Recently, while rereading My Garden in Spring (Bowles 1914) I learned another method of pollination:

When you see your crocuses wide open in flower sally forth with the stick of sealing-wax or the amber mouthpiece of an old pipe in your hand. . . . Rub whichever of the two unusual accompaniments of a garden stroll you have chosen, on your coat-sleeve if it be woolen, and hold the rubbed portion as soon as possible after ceasing rubbing near the anthers of an open Crocus, and you will find the electricity thereby generated will cause the pollen grains to fly up on the electrified object, and, what is more, to stick there, but so lightly that directly they are rubbed against the stigma of another Crocus they will leave the amber and be left where you, and Nature before you, intended them to be.

And then I remembered how that when I was a child my father demonstrated the effect of electricity. He would rub his amber penholder or plastic hairbrush against his jacket, and then small pieces of paper would fly up and stick to the penholder. I immediately tried this method on autumn crocuses in my greenhouse and to my surprise found that it worked. In fact, this technique is much better for transferring pollen than either of the other mentioned techniques. When using an amber tool or sealing wax (the latter not tried by me), pollen can be easily wiped clean between different crosses. And with a brush, some pollen grains tend to stay in the fine hairs and do not always stick to the stigma. Then, when using the same brush for the next cross, those grains can be transferred, thus muddling the crosses.

Crocus seed capsules emerge from the soil at the end of vegetation. Only seed-pods of a few species (for example, Crocus caspius, C. korolkowii) remain underground. Some (for example, C. pelistericus, C. scardicus) are pushed up on long stalks and ripen very late in the season. It is easier to collect seeds right before the capsules are split. The stage of ripening can be checked by slightly squeezing a capsule between the fingers — if it is hard, seeds are ready to be harvested. It is better to store them in small boxes in a shaded, warm, and dry place where the capsules will soon open. I prefer to wait to gather seed until the moment the capsules start to split — then you can open them and allow the seeds to dry up a little.

What is the best time for sowing seeds? One can find plenty of recommendations. In recent years I have sown the seeds as soon as possible after harvesting. This has given me the best germination rate, although in a few seasons I’ve had problems with the seeds germinating way too early. When early sown seeds start to germinate in the autumn, the seedlings they produce often die in the winter that follows. For species that overwinter with leaves, autumn germination is very common and causes no problems. Seed of such species is best sown as soon as possible after it is harvested. In most cases, losses from seeds germinating too early are smaller than losses from delayed germination when seeds are sown late.

Bowles (1952) recommended sowing seeds no later than the first week of September. Older seeds germinate within several years but that depends on the species. Maw (1886) wrote of his experiment with four species. When he sowed 40 one-year-old seeds per species, the number of seeds that germinated the first year was 25 for Crocus imperati, 2 for C. vernus, 3 for C. flavus, and none for C. versicolor. In the second year, 9, 22, 1, and 13 seeds germinated, respectively.

Usually I have had the first flowers on seedlings in the third year after sowing, but the blooming starts from the fourth year onwards. David Stephens reports that he got the first flower of Crocus gilanicus in a pot of 20 seedlings in the autumn of the second year after sowing (27 months later) and the first flower of C. gargaricus 18 months after sowing. With me, seeds from a cross between C. abantensis and C. ancyrensis sown in October 2007 gave their first flowering in March 2009 — 17 months after sowing. I replanted the small seedlings in the third year after sowing.

I also sow my crocus seeds mostly in boxes or pots. A few species which are excellent growers outside and which set plenty of seed I sow in garden beds. Among these select few are Crocus abantensis, C. chrysanthus, C. heuffelianus, C. korolkowii, C. malyi, C. veluchensis, and C. versicolor.

I would like to end this chapter with an extract from E. A. Bowles (1952) (I realize I quote him frequently, but no one can say it better than he can):

The first three barren years soon pass away, and then it is good to stand before the seed bed on a sunny morning and see the rows of open blossoms with here and there one that is unlike its brethren and perhaps anything else we have seen before. A pure white seedling of Crocus sieberi rewarded me for thirty years of patience, and I still hope for further pleasant surprises.

1 Liza January 18, 2011 at 8:15 am

Wow – that’s a ton of great information! Thank you!

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