|Bulbs from Seed|
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by Ian Young
With so muchinterest in growing bulbs, both in pots and the garden, it is surprising that more are not raised from seed. There seems to be a view that it is more difficult to grow bulbs from seed than other plants. This is simply not true. In some cases it can be easier; the difficult bit is having the patience to wait the three to seven years that it may take to see a flower. The rewards are therefore all the more satisfying. This long wait does not seem so bad if you sow bulb seed every year as after the first waiting period is over you should have something new coming into flower every year. The investment of the first wait pays dividends. The following notes deal mostly with the popularly grown species of Fritillaria, Crocus and Narcissus but can be used for other genera of bulbs.
Growing bulbs from seed greatly reduces the cost per bulb and means you also have a lot more to play with. You will get a good selection of forms often showing considerable variation which I find highly desirable. Many bought bulbs are often clonal and usually represent a form that multiplies itself freely; this can sometimes be at the expense of flowering. Plants that concentrate their efforts on vegetative multiplication do not always spare the energy for flowers. It also gives you the opportunity to select your own favourite forms that you can multiply clonally if you wish; it is nice to have a pot full of bulbs that are just that bit different from everyone else's and, if you enjoy showing, it might just take the judge's eye. I also like to see a pot of bulbs showing the variation in a species, and providing this is not too extreme, I find it more interesting than a pot full of a single clone.
By having a good selection of individuals which should have differing levels of resistance to different diseases you are less likely to lose the lot, if a problem strikes, than if you had a quantity of a single clone. Also you will have raised bulbs that are more suited to your growing conditions, as any that are totally unsuited will have died off at an early stage. It is much less painful to lose a first year seedling or two than to lose a flowering bulb bought at great expense which then decides it does not like your cultural methods.
You should also collect and sow some seed of all your own bulbs on a regular basis to ensure that if they are unfortunate enough to get struck by a disease or a virus you will always have healthy young stock coming on.
Much is written about not letting your bulbs set seed as this weakens the bulb; this is nonsense. A bulb that is setting seed will grow from four to six weeks longer than the same bulb would if it was not fertilised, this extra growing time more than makes up for the energy the plant needs to produce the seed. It is very important that we all collect and circulate as much seed from our cultivated bulbs as we can. We never know when wild sources of seed will dry up, either by extinction of the plants in the wild or by legislation forbidding seed collection, so we must look to preserve as wide a range of cultivated material as possible.
WHEN TO SOW
I believe that bulbs have a built-in clock that is passed on to the seeds by their parents, and this, more than any outside element or condition, triggers them into growth. Each bulb has an annual window of time in which it will grow. When growth is initiated within this window can also be affected by outside conditions such as moisture or temperature.
I know that some people say you should always sow everything fresh as this is what happens in the wild but this does not take into account the very differing conditions found between a summer season in a garden when compared to the those of the plant's natural habitat.
Fritillaria seed should be sown at the beginning of September and watered well, just like the mature bulbs (The Rock Garden vol.xxv part 1 page 30). You can successfully sow Fritillaria seed up to late November and possibly December. If I receive Fritillaria seed after December, I do not sow it until the following September, as germination in the first season would be poor if at all, because you have missed the time window for Fritillaria and there is every chance that the ungerminated seed would rot off in the long period of unfavorable conditions of a Scottish spring and summer before the next time window comes round.
Crocus and Narcissus should, ideally, also be sown in September although the time window seems to be wider in these genera and they are less susceptible to the ungerminated seed rotting off in the spring and summer months.
Seed of summer growing lilies such as Lilium nanum, and Lilium oxypetalum, and Nomocharis species should not be sown until the end of January. I have made the mistake in the past of sowing them in the autumn and they germinated in a mild period before the onset of winter giving me great problems of how to take the tiny seedlings through a winter; needless to say I was not successful on that occasion. This is how gardeners must learn; I do not think a dead plant is wasted if I have learnt something in the process.
Erythronium seeds are best sown fresh or as soon as you can get them. If they are a bit dry and wrinkled a good soak overnight in water with a tiny smear of soap, just enough to break the surface tension, should make them nice and plump again and improve germination; the same applies to Trillium seeds.
We have discovered the following methods work well for storing seed.
- Fritillaria and lily: allow the seed to dry naturally then it can be kept for at least three years in paper packets kept in a dry environment and at a cool constant temperature well away from any sunlight.
- Narcissus: store in almost dry fine sand in a plastic container also at a constant cool temperature, although the cool temperature seems to be less critical than in Fritillaria and we are still experimenting. We have found that all bulb seed, other than the lily type, store better in sand; they seem to prefer this to being surrounded by air.
A well-drained compost is needed and we use the same formula that we use for all our container grown plants: by volume two parts loam, one part humus and two parts gravel (3-6 mm). This gives us a good open compost; if your loam is heavy you may need to increase the amount of gravel to obtain a good porosity. We use leaf-mould for the humus part but peat or equivalent can be substituted. We use bone meal as an added feed.
We use square plastic pots of various sizes for all our seed sowing; they make much more efficient use of the space available. Fill the pot to about 2 cm from the top and scatter the seed evenly on the surface then fill the pot to the top with a gravel (3-6 mm).
I know that the traditional advice is to sow seed thinly but with bulb seed you can get away with and in fact get better results from sowing quite thickly. We often have pots that resemble a lawn on germination because we sow so thickly; bulbs do seem to enjoy company.
Polystyrene fish boxes are very useful for sowing very large quantities of seed in and we grow Erythroniums, Trilliums and lilies in these until they reach flowering size without the need to repot.
One recent exception to this sowing method is Narcissus. We now fill the pot just over half way with compost then sow the seed, add more compost then top off with grit; we get much better results this way. I learnt this from observing the seeds that shed into the sand plunge in the bulb house, they always seem to do better than the ones that we sowed and I wondered why. If you compare the way Fritillaria seed and Narcissus seed behave at germination you will find that in Fritillaria the growth tip pushes down into the compost and the bulb forms at the end of this tip whereas in Narcissus the bulb forms beside the seed and the roots penetrate the compost. In subsequent years the Narcissus bulb then forms contractile roots that gradually pull the bulb down to its preferred depth.
Sowing the seed 2-3 cm down not only saves it from having to pull itself down but also places it in a much more stable environment less likely to dry out or be attacked by pest or disease.
We place all our bulb seed pots on a sand bed in an outside plunge bed which is left open in all weathers until germination starts to occur. Some Crocus and Narcissus species can start to germinate in the winter before the year ends and you need to look regularly at the seed frames to check for growth. Once a pot has started to germinate it needs to be covered to protect the fragile young growth from the physical effects of the weather and any prolonged periods of frost. A good flow of air should be maintained to prevent any fungal disease attacking the growth. If the seed coat is stuck to the end of the cotyledon do not worry, this is quite normal and you are only going to do harm trying to remove it.
Also watch out for slugs, they can devour a whole pot of precious seedlings in no time, we have to admit to using slug pellets in the seed frames.
As spring arrives and the seedlings are in good growth we apply regular doses of balanced liquid feed - ideally once a fortnight and at least once a month. We, being good Scots, tend to use whichever one is on offer at the cheapest price at the garden centre. It is important to keep the seedlings growing for as long as possible in their first year, constantly watering and feeding until the shoots show signs of yellowing.
Once the young bulbs start going into their dormant period, keep the frame covered to prevent excessive moisture, but do not let them dry out completely. The tiny young bulbs have not yet built up a big enough store of energy and moisture to take them through long periods of drought.
The frames are kept covered as required through autumn and winter with occasional openings during light rain to keep the compost always moist.
SECOND AND THIRD YEAR
The same procedure is followed for the next few years with plenty of watering and liquid feeding in spring while the plants are growing and holding them just moist during the dormant period. It is important to remember that the seedling bulbs will be starting to root from September on, even though you may not see any growth above the surface for six months or more, so a good soaking at this time is essential. Always be on the look out for slugs and aphids, which not only weaken and damage the plant but can also spread virus.
We use any available systemic insecticide spray to protect the plants and have never found one that causes any problems to the bulbs.
We usually do not start to repot seedlings until the end of the third growing year. Many bulb seeds will germinate sporadically, especially if they have been stored, so if you repot too soon you could lose the ones that will germinate in their second or third season. One exception may be Narcissus, if you have sown them on the surface there is a big advantage in getting them down a centimeter or two into the compost.
We repot seedling bulbs in August/September once we have finished repotting all the mature bulbs. The ones that are due to be repotted are allowed to get slightly drier which makes sorting them out that bit easier. Tip them out and carefully sift the compost until you find them all, shaking the compost in a tray as if panning for gold will bring the young bulbs up to the surface. Remember you could have one, two and three year old bulbs in the same pot. Repot them into a fresh batch of the same compost mix increasing the pot size or making two pots from one, as you think necessary.
Once the bulbs have reached this stage we either move them on to a covered bulb-frame or bulb-house as they now require more protection or plant them into the garden if they are suitable. It is a strange fact that seedling bulbs seem to be hardier when they are young than when they are at, or reaching, maturity.
Some Narcissus and Crocus will flower in three years from seed as will many lilies but it is normal to have to wait until year five to seven for Fritillaria and Erythronium.
We normally use clay pots for flowering size bulbs we intend to grow under glass. Most bulbs that we plant in the garden are grown in plastic mesh pond-baskets for ease of relocating and splitting in future years. We also have several open plunge beds where we grow Erythronium, Trillium, Fritillaria, Crocus, Corydalis, etc in square mesh pond-baskets; these beds act as a halfway house between the bulb-house or bulb-frame and the garden. It also allows us to lift and split the plants on a regular basis without having to disturb other plants growing in our densely populated garden.
By growing bulbs from seed it also gives you that extra few that you can try out in the garden and we are increasingly surprised at how many of these, that we always grew under glass before, can survive and sometimes thrive if the correct conditions can be found in the garden.
At the moment we are spoiled for choice with the great variety of bulb seed available through the SRGC Seed Exchange as well as the exchanges of our sister societies. There are also many specialised commercial seed lists, offering mouth watering gems both from cultivated stock and wild locations, advertising in our journal. There has never been a better time to start growing bulbs from seed.
For further information and our method of growing bulbs see the article 'Bulb Growing' in The Rock Garden vol. 25 part 1 page 30
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