Bulbs FAQs

What is a bulb, and how does it multiply?

A bulb is a modified bud consisting of a flat base ‘plate’, from which rise layers of fleshy or scaly food-storing leaves that enclose a bud; roots form on the underside of the plate. Bulbs such as daffodils grow larger, split, form offsets (young plants), and also produce seed. Some, such as tulips, grow for a season and then die, having produced in their place more large bulbs and sometimes several bulblets (miniature bulbs). Care has to be taken when lifting tulips such as Tulipa kaufmanniana because, apart from forming bulbs and bulbils, they also produce ‘droppers’—bulbs that are pushed much deeper in the soil and are easily broken off. Bulbils are small bulbs that form away from the main bulb. In certain lilies, for instance, bulbils form in the leaf axils; while some alliums develop bulbils in their flowerheads. Bulbils can be grown on quickly to form flowering bulbs.

What is a corm? How does it increase?

A storage organ like a bulb, a corm is a swollen stem that grows at or just below the soil surface. Usually it lasts one season, new ones forming above it (as in the crocus) or at the side (as in the colchicum). Increase is by these new corms. A crocus may form two or three; a large gladiolus corm may develop only a couple of fresh corms, but it will produce large numbers of cormlets (small corms), which may grow to full size in two seasons.

Corms are normally planted at a depth three or four times their own length; thus, small corms such as those of crocuses will have 25-38 mm (1-1 ½ in) of soil over their tops, while larger corms such as those of gladioli will have 75-100 mm (3-4 in) of soil over them.

Are the biggest bulbs of a particular variety the best?

In principle, yes: large crocus corms, for instance, will give more blooms than small ones; the larger a lily bulb, the more flowers one may expect on the stem. But the size does not always indicate superiority: daffodil bulbs grown in Cornwall or the Isles of Scilly are usually much smaller than those grown in Holland, but will acquit themselves just as well; the difference in size is basically due to different amounts of water in the bulbs. Large corms of anemones, on the other hand, are often old ones that are past their best.

Can bulbs be increased by seed?

Wild bulbs depend mainly on seed to maintain their populations. All species fertilised by their own pollen will provide new generations either identical to the parents or showing variation within close limits. Depending on family and species, new bulbs reach flowering size in 15 months to 5 or 6 years. Narcissus bulbocodium can be in bloom in 18 months, while the large narcissus hybrids may take 5 years. Tulips and lilies can produce well over 100 viable seeds per pod. Some small bulbs (for instance, bluebells and grape hyacinth) with many flowers to a head will drop several hundred seeds from one flower stem.

Some of my daffodils and tulips are developing seed pods. What will happen if I sow this seed?

Seed from wild species will give seedlings more or less similar to the parent provided the flowers were fertilised by their own pollen. Your seedpods are more likely to be hybrid—a cross between two species or varieties. Each seed in a pod will be a unique individual; some will be good, others less so. If you sow daffodil seeds when ripe (usually late summer) in pots or boxes with 25 mm (1 in) of soil over them, they will produce seedlings early the following year. After four or five years the seedlings reach blooming size. Tulip seed is best sown under glass covered with 10 mm (3/8 in) of seed compost. Depending on type, these seedlings will bloom in three or four years.

Can you suggest some autumn-flowering bulbs?

Many varieties of crocus bloom in autumn, as of course do the colchicums, commonly known as autumn crocuses. There is the very attractive pink Nerine bowdenii (good in sheltered spot) and the small yellow Stembergia lutea with dark, thick, strap-like leaves and flowers like those of the crocus.

If you can put up with the masses of large leaves they develop in spring, the colchicums are excellent, although some species are of greater botanical interest than garden merit. Colchicum autumnale is an easy to grow, with mauve flowers. The hybrids are very good value. ‘Lilac Wonder’ is a very-free-flowering, quick-increasing pinky mauve kind.

Of the many true crocuses, try Crocus pulchellus, which is quite early and has lilac flowers, and C. speciosus, which has many good garden hybrids.

My garden looks bleak in winter. Are there any bulbs that will enliven it?

We attack the winter by a pincer movement, with late-autumn and early-spring flowers to support the genuine winter ones. Colchicums bloom in September and October, while there are crocus species that bloom from September through October and November into December. Several iris species bloom in winter: the popular J. reticulata, with violet flowers, is just 150 mm (6 in) tall; more spectacular is the brilliant blue /. histrioides ‘Major’, only 100 mm (4 in) high but with larger, blue flowers; there are also some good hybrids. Winter aconites (Eranthis), with yellow buttercup flowers, are bright on dark days; snowdrops (Galanthus) are obvious candidates for the turn of the year. Then, in February, the earliest daffodils arrive, notably the hybrids of the dwarf Narcissus cyclamineus.

Can you suggest a selection of labour-saving bulbs that will give year-round colour in my garden?

Many small bulbs—crocuses, winter aconites, scillas, and anemones—will provide colour in January and February. Daffodils and narcissi planted in natural clumps in the grass will give you flowers from March into May.

There are some tulips that can be left down for several years, providing colour in April and May. For summertime colour there are some lilies that can be left down for ever, while for the autumn there are cylamen species and Nerine bowdenii, which can also be left permanently in the ground.

When tidying my borders I often dig up bulbs that I had forgotten. How can I avoid doing this?

Discreetly placed labels are the commonest solution. They must be permanent and not too easily removed, so plastic ones are better than wood or metal types. The trouble is that, with low-growing plants, even the most unobtrusive labels tend to draw attention to themselves. It is easier to manage bulbs planted in clearly defined clumps, and this is florally more effective than lines or bulbs dotted here and there. These clumps can be located when dormant if you more or less surround them with some herbaceous plants such as polyantha primroses.

Do I need to give my bulbs fertilizers?

Normal soils contain all the nutrients bulbs need, but they do benefit from a light dressing of a general fertilizer, such as

Growmore, at planting time or when they are about to start strong root activity. Tests have shown that the most important bulb food is potassium, which is available commercially as sulphate of potash; wood ash and fresh bonfire ash are alternative sources. Several light dressings are better than one big helping: a handful to each square metre of soil is ample. Remember too, that bulbs need plenty of water while growing.

Are bulbs prone to attack from pests and diseases?

Bulbs, like most plants, are prey to pests and diseases. Pests range from dogs to organisms visible only under the microscope. Crocuses and tulips make fodder for rodents, while narcissi and some related plants contain a poison that deters them; slugs attack many bulbs, lilies and some smaller bulbs being their favourites; Tulips, alliums (the onion family), and narcissi are vulnerable to attack from different species of eelworms. These microscopic pests eat the cell material, multiply to vast numbers, and reduce the bulb to a pulp.

Eelworms and, more importantly, greenfly are responsible for spreading virus diseases among bulbous plants. The symptoms include mottling, yellowing, spotting, and curling of leaves, and blotches or other marks on flowers. Diseased plants must be taken up and burnt.

I have a small garden and need to move my bedding tulips and daffodils out to make room for summer plants. When is the best time to do this?

Some of the stronger-growing tulips can be dug up a few days after flowering and dried off in a cool airy place. Normally, however, the procedure with both daffodils and tulips that need moving is to give them a thorough soaking, dig them up with as much root as possible, and replant them temporarily in an out-of-the-way trench until they die down. To minimise the shock, the bulbs should also be heavily watered after being moved.

What is meant by ‘naturalising’ bulbs?

This is the term used for the practice of planting bulbs so that they look as if they are growing naturally—in lawns, for instance, or in ‘woodland’ settings; they are labour-saving because they are left down indefinitely. The early-blooming daffodils are the type of bulb most commonly used. Some of the wilder kinds obviously look most at home, notably the Tenby daffodil (Narcissus pseudonarcissus obuallaris). Be cautious about buying so-called ‘naturalising mixtures’ that are advertised at the end of the season; they may simply consist of various kinds of bulbs the dealer has failed to sell. Much better to go to a recognised bulb-grower and ask if he has any lower-priced selections that are suitable for naturalising.

Part of my garden is more or less wild, and here I would like to have snowdrops and bluebells emulating on a small scale what nature does more grandly. Can this be done, and are there other bulbs that might fit in with the scheme?

Clumps of snowdrops can be divided year by year after flowering. The wild bluebell (Endyrnion nonscriptus, syn. Scilla nutans) increases quickly by bulb and seed; planted fairly thinly it will colonise the area. (Endymion hispanicus (syn. Scilla campanulata), with many named varieties, is the larger kind, with upright spikes; it is a quick increaser.

Winter aconites, smaller daffodils, and the ‘Old Pheasant’s Eye’ narcissus look well in a wild setting. You might also try Star of Bethlehem (Ornithogalum umbellatum) and the green O. nutans; the Star of Bethlehem has narrow, spreading leaves and star-like flowers, about 25 mm (1 in) across, borne in sprays some 150-200 mm (6-8 in) high. Later lilies such as L. pardalinum giganteum will form attractively informal clumps.

How often should I water my bowls of bulbs?

This depends on the bulbs, the growing medium, the container, and the stage of development of the bulbs. Too much water is as bad as severe drought: moist conditions start bulbs rooting; flowering failures are often due to bowls drying out. Daffodils and hyacinths growing in the living room may need watering every day. Bulbs to be kept need plenty of water after blooming. (Alternatively you can carefully tip out the bowlful and plant the bulbs in the garden where they are to grow next season. Plant them deeper than in the bowl.) Prepared bulbs will adjust themselves within 12 months.

I am planning to plant bowls of tulips and wish to have six to eight tulips in each bowl. How big should the bowls be?

Small types you will be able to get into bowls 150 mm (6 in) wide; large types may require containers 200 mm (8 in) wide. Use bowls with drainage holes and plant in John Innes Porting compost. Bulbs at the end of their season are then much better than those from fibre. Draining holes make watering easier.

Types to try include: All 7. kaufmanniana and T. greigii hybrids; early double varieties; species such as T. praestans, T. batalinii, and T. clusiana chrysantha; large-flowered but relatively short-stemmed T. fosteriana varieties such as ‘Red Emperor’. The large Darwin hybrids are unsuitable for most domestic interiors as they need large bowls and maximum light.

I grow a few bowls of bulbs each year. Is it best to grow them in fibre or in compost?

The answer depends on whether you hope to use the bulbs again. If they are to be planted in the garden after flowering or used again, it will be better to grow them in John Innes Potting compost, which contains nutrients to help the bulbs keep or increase their strength. Fibre merely provides bulbs with a moisture-retentive environment; but if the bulbs are to be discarded at the end of the season, fibre will be cheaper than compost.

I have a lovely amaryllis in bloom in a pot in the house. What do I do to ensure it flowers next year?

This belongs to the genus Hippeastrum. The varieties and hybrids should bloom every year. They are almost evergreen, but die off for a period. Your bulb should be planted in a 125-175 mm (5-7 in) pot with the nose or even one third of the bulb exposed. Newly planted bulbs are kept barely moist, which allows them to start slowly and produce new roots before being more generously watered and fed. Once in full active growth, the bulbs take lots of water provided drainage is correct. Keep your plants growing strongly, feeding with a liquid fertiliser. After flowering allow the bulbs to dry off at the end of the summer, and then repot them in fresh compost and start them slowly into growth again in the autumn.

My rock garden could do with some miniature bulbs to grow near thymes and heathers. Can you suggest some small spring bulbs that do not have untidy foliage?

The winter aconites (Eranthis) have buttercup flowers and attractive foliage and do not exceed 100 mm (4 in) in height. The dwarf tulips are also suitable: try Tulipa tarda, T. batalinii, T. praestans, T. kaufmanniana and T. greigii hybrids, T. linifolia,and T. marjoletti; the lady tulip (T. clusiana) with narrow pink and white flowers on tall slender stems, is particularly elegant. The pale blue Hyacinthus azureus and its white form are early and look like very tidy grape hyacinths. The vivid blue stars of Scilla sibirica ‘Spring Beauty’ make a wonderful show, as does the related Spanish bluebell (Endymion hispanicus), which is a sturdier, larger, upright cousin of the English bluebell. Iriso reticulata, which rarely grows taller than 150 mm (6 in), and the even smaller/, histrioides ‘Major’, and their numerous hybrids are good value.

We have some large pedestals on the patio and by the driveway. Can I grow bulbs in these, and if so which do you suggest?

The basic need for any plants growing in these containers is good drainage; so long as surplus water can drain away, bulbs should grow well in them. Pedestals suggest height and the possibility that plants may be blown about, so you need to choose plants that can put up with wind. However, even lilies are a possibility here: sturdy-stemmed types that can be tried include ‘Enchantment’ (orange blooms), L. regale (white), and ‘Destiny’ (yellow). Daffodils in spring and tulips a little later will give colour for weeks; in particular a double layer of daffodil bulbs planted in the autumn will give you plenty of colour.

Among many suitable daffodils you could try Tete-a-Tete’, ‘February Gold’, ‘Foresight’, ‘Armada’, ‘Rembrandt’, and ‘Thalia’; tulips might include ‘Red Riding Hood’, ‘Giuseppe Verdi’, Toronto’, ‘Red Emperor’, and the early doubles ‘Electra’ and ‘Peachblossom’.

I live in the middle of town and have no garden. Can I plant bulbs in growing bags?

Bulbs are packaged plants that are so adaptable that they can be used in many ways. Your idea of bulbs in growing bags is perfectly feasible: just as one can have a double layer of bulbs in a pot to give a double floral effect, so one can do the same in bags. Among narcissi the old double-yellow ‘Van Sion’ is early, cheerful, and showy; ‘Armada’ is large and gold and scarlet; ‘Royal Orange’ is large and white and orange. Among tulips the Darwin hybrids in reds, yellows, oranges, and white are hugely impressive.

I am a keen flower arranger and would like to grow some of the more unusual daffodils and other bulbs for cutting. Can you suggest a few?

Try some of the split-corona daffodils, such as ‘Baccarat’, all yellow with split trumpet laid back onto its petals; ‘Congress’, with yellow petals almost obscured by a split crown of vivid orange; and ‘Cassata’, with cream petals and split crown of primrose lemon. Other especially striking daffodils include ‘Binkie’ in luminous shades of lemon, and the tall triandrus ‘Tresamble’, with several heads, white petals, and milky cups. The numerous members of the onion family are good fresh or dried: Allium aflatunense has tall umbels of silver-purple; A. albopilosum has huge globes of metallic pinkish-violet stars.

I would like to send some bulbs to friends overseas. Is this possible?

Almost every country requires health certificates to accompany imported plant material and has a variety of other regulations. These usually involve inspection of the plants in growth by Ministry of Agriculture officials and again prior to despatch. The easiest way to send bulbs abroad is to find a bulb grower who already exports. He will have his ground cleared for export and his bulbs inspected in growth at least twice a season as a matter of course. He will also be familiar with the forms and formalities involved in sending bulbs abroad.

Cut flowers are often expensive. Are there any bulbous flowers that can be dried and used effectively for floral arrangements?

A surprising number of flowers are suitable for this. Many onion species are most effective. Allium albopilosum (syn. A. christophii) is 300 mm (12 in) tall with 150 mm (6 in) or even larger umbels of starry pink flowers; A. aflatunense is taller. Most other Allium species are suitable. They should be cut young in order to keep the flowers and colour, and dried by hanging in an airy place. Alternatively, you can delay cutting: the dried seedheads are also attractive.

Chincherinchees (Omithogalum thyrsoides) can be cut when freshly open and the spikes of silvery white, cream, or yellow flowers dried. The seed pods of some tulips are most attractive. It is worth experimenting with different plants, even small ones like Spanish bluebell (Scilla campanulata).

We are moving house shortly and want to take some of our bulbs with us. How should we tackle this?

Moving house causes problems for gardeners. Often it is best to be very selective, concentrating only on the most important bulbs and leaving the rest of them behind. Some may be nearly dormant, and these can be lifted, dried, and dealt with normally; remember to label everything clearly.

Bulbs in full growth will reluctantly tolerate some disturbance. Water them thoroughly before lifting with as much root as possible and some soil. Place the bulbs in polythene bags or pots with their leaves protruding, and keep them moist. Replant them as quickly as possible in the new garden, and water them in very thoroughly.

Sorry, comments are closed for this post.