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Bulbs & bulbous plants
Help solve your gardening problem. Here are the answers to some commonly asked gardening questions about bulbs, bulbous plants, tubers, corms and rhizomes with hints, tips and advice.
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Easy! Get hold of a copy of my book on the subject; Collins Practical Gardener: Bulbs. ISBN 0 00 719281 9.
I've just bought some begonia tubers? What's the best thing to do with them?
You've got two options; the first is the better one.
Start the tubers into growth by planting them into small (or however big they need to be to just take the tuber) pots of compost, settling the tubers concave side uppermost on the surface of the compost. Then, when growing well and filling the pot with roots you can plant them outside, where you want them to grow, after the worst of the frosts are over - usually late May/early June.
Alternatively, plant them directly into hanging baskets and containers, but obviously these would have to stay indoors until the end of May/early June.
Whichever way you chose, make sure you give the developing shoots plenty of light - but not direct burning midday sun - and keep the compost moist. Start feeding with a liquid tomato fertiliser or any high in potash six weeks after planting.
I've grown autumn crocuses, but have always been disappointed with the results. Have you any tips for a better display?
Most people buy their autumn crocus - both the true crocus and colchicums - too late. Usually they are bought and planted with the other autumn-planted bulbs.
August is the best month to get these bulbs in the ground, so you will have to start looking for them earlier than your daffs and tulips. Some garden centres stock bulbs early, but you may have to try one of the mail order bulb specialists for a good range of varieties.
I bought the roots of a plant called the Japanese wonderflower. I can't find any reference to this name, so can you tell me how to look after it?
The plant in question has the correct common name of the marvel of Peru or the four o'clock plant; the botanical name is Mirabilis jalapa. The name Japanese wonderflower is a made-up name used to try and sell it!
Although mirabilis produces dark roots that are often sold in the autumn, you'll usually get far better results from plants grown from seed sown in the spring. If you want to try and grow the plant from the roots you've bought, save them in a cool but frost-free place and plant them in spring.
Although they are often sold as being frost tolerant they are not completely hardy and should be treated like dahlia tubers.
A keen begonia grower tells me I should remove some of the flowers from my large-flowered tuberous begonias if I want a great display of quality flowers. Is he having me on?
No, your friend is absolutely right. Begonias produce separate male and female flowers. The large central flower is male and is flanked by two smaller female flowers. Removing the two females when they are large enough to pinch off will ensure all the plant's energy goes into the males enabling them to grow larger and last longer.
Removing the females is usually only done if you intend to exhibit the plants at a show, but will still be beneficial for garden displays.
Why haven't my daffodils flowered?
There are a number of possible reasons why your daffodils haven't flowered. Find the answer, read my page on blind daffodils.
Why haven't my gladioli plants flowered?
There are a few reasons why your gladioli may not have flowered.
1) Wrong planting depth - either planting too shallow or too deep can cause this problem.
2) Poorly-drained soil. If the roots are sitting in water they will rot and reduce the amount of water available to push the blooms open.
3) Thrip damage. Normally these tiny insects (often called thunder flies) attack the foliage. But sometimes they just attack the flowers or flower buds. Open one up and look for lots of tiny black insects.
Of course, it could be a combination of two or more of these.
Now that my anenome and gladioli have finished flowering, what do I do with them to make sure that they survive until next year?
What you do depends exactly on what the plants are and where you live.
Anemones are hardy and can be left in the soil all year.
Gladioli are not so hardy - but in mild districts (the south-west for example) they can be left in the ground, although they should be lifted from pots or the pots stored in a greenhouse or shed.
Carefully lift the gladioli corms, cut down the shoots and remove soil from the corms. You will see an old corm (which produced this year's flowers) which should be thrown away; large corms which will provide next year's flowers; and tiny cormlets which will take a few years to reach flowering size.
The large corms should be cleaned up and stored in dry peat or similar in a cool but frost free dry place. I know people who hang them in tights to keep them over winter.
The small cormlets are more difficult to overwinter - try using shallow trays filled with dry peat. Next year plant them out in rows to grow on for a few years to reach flowering size.
I planted a lot of oriental lilies in pots. They all flowered beautifully and I allowed them all to die down naturally. What is the best thing to do with them now?
If the lilies have only been in their pots for one year, I suggest you leave them alone - in spring simply replace the top inch or so of compost with fresh and gently work in a little controlled-release fertiliser (Osmocote or similar).
In future years as the bulbs age they will start to produce young bulbils, which take a few years to develop into flowering size - this is when it makes sense to re-pot, simply to grade out all the small non-flowering bulbs, which can be grown on elsewhere until they reach flowering size.
I have a canna, two agapanthus and three calla lilies in patio pots and although each have had leaves none have flowered. What could be the problem?
There are a few reasons why the plants haven't flowered - not fed enough, poor compost, wrong position etc, etc, and without more info to go on it is impossible to say why.
However, I'd be willing to bet (only a small amount you understand) that you potted these plants from small pots into much larger patio pots. When this happens the plants put all their energy into producing masses of roots to fill the compost, and produce lots of leaves at the expense of flowers. Once the roots have filled the pots, the plant will come into flower. Don't repot until you absolutely have to - that is until the pot starts to burst! Once potbound make sure the plants are well fed (with a high potash fertiliser) and watered.
I've had miniature tulip bulbs growing for several years in a rockery. Some flowered in the first and second year, but after that they carried on coming up blind. What's wrong?
The usual problem with species (and other) tulips is not having a hot, dry period during the summer. In their natural habitat they are almost baked during the summer, so make sure they are in a sunny position.
Also, make sure they are not being grown around plants that need regular watering in summer as this will have an adverse effect on them - negating their hot, dry pertiod.
Feeding them while in growth with a high-potash fertiliser, such as a tomato food, will certainly help. And keep the foliage growing for as long as possible. This will help build up the bulb and ensure flower buds are formed.
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