Spring bulbs
To locate images associated with this article please visit our
image collection at Country, Farm and Garden Photo Library
Be it the traditional host of golden daffodils, an ocean of bluebells, or just a bowl of hyacinths, spring bulbs are renowned for their brilliant colour and are a welcome sign that warmer days are on the way.
Yet for most of the year we don’t see any sign of the flowers or foliage and it’s all too easy to forget about spring bulbs until, well, springtime, but by then it’s too late. If you want a brilliant spring show then you need to start planning and planting around midsummer.
There are many ways to grow spring bulbs: they can be naturalised under trees, either in grass or as part of a woodland; they can be grown in formal beds; they may be dotted among shrubs or perennials; planted in rockeries; or they can be grown in containers, both indoors and outdoors.
Most garden centres will have a good stock of spring bulbs well before autumn and the range they carry will give you a good idea of those that are likely to preform well in your area. However, garden centres seldom stock the really unusual bulbs; for those you will need to scour the mail-order catalogues or visit specialist growers.
Bear in mind that not all bulbs grow well in all areas. Many of the best-known spring bulbs come from Turkey, northern Greece and the Middle East through to Afghanistan. Plants from this area, formerly known as Asia Minor, are used to experiencing very harsh winters and indeed need the winter cold to become properly dormant. Gardeners in northern areas may have difficulties with daffodils, tulips, irises and crocuses.
One way around this is to refrigerator chilling, but that doesn’t avoid the problems of gradually diminishing vigour or the bulb splitting caused by excess heat after flowering. Buying new stock each year is best, but this, while obviously practical for formal beds or containers, makes naturalising impossible.
Where dormancy is a real problem it may be better to stick with the South African or Californian bulbs that don’t require so much winter chilling. Of course Lachenalia and Calochortus aren’t really what most of have in mind when we think of spring bulbs but they may be better than the continual frustration.
Selecting bulbs
Bulb selection doesn’t just mean choosing
the right types for your garden, it also means
choosing healthy mature bulbs. If you are buying from a garden centre it is
usually best to get in early before the stock has been picked over and select
your bulbs from loose lots rather than buying pre-packed stock. Choose firm,
plump bulbs and reject any that are obviously bruised, shrivelled or showing
signs of mould.
It’s fairly easy to pick healthy examples
of the true tunicate bulbs, such as those of daffodils, irises, and tulips, but
some of the corms like Ranunculus are
naturally rather withered-looking and it can be hard to pick the good from the
bad. Of course one takes everything on trust with mail-order, though don’t
hesitate to immediately return anything that doesn’t come up to scratch.
Cultivar selection is over to you.
However, bear in mind that the simple flowers are usually the strongest
growing. Fancy split-corolla daffodils may be attractive but they won’t
naturalise like the simple single-flowered types. Also, very fancy bulbs,
particularly tulips, are prone to sporting and colour changes.
Planting site
Most bulbs require good drainage.
Improving drainage is usually done by working plenty of compost into the soil,
but bulbs generally do not appreciate high levels of organic matter in the soil
— it improves the drainage while keeping the soil moist, whereas bulbs
generally prefer very quick, free drainage. With bulbs it is better to add
extra coarse material to the soil: stone chips or coarse bark are good, as is
pumice.
Other than drainage there’s the matter of
sun exposure. Most of the traditional early-flowering spring bulbs bloom and
develop foliage before the deciduous trees have expanded their foliage. This
means that they receive plenty of light when they need it and are shaded once
their flowering is over, leaving them to slowly mature and develop the next season’s
bulbs.
That is why bulbs are perfect for
naturalising in woodlands and grass under deciduous trees — it is a perfect
symbiotic relationship. Evergreen trees are more difficult to work with.
Bluebells, cyclamen, dog-tooth violets, trilliums and wood anemones and a few
others will grow in reasonably deep shade, though they tend to become drawn and
leggy, and flower poorly. Thinning out some of the branches may help.
Full sun, especially in hot dry
positions, can also be difficult. Although the South African and Californian
bulbs often thrive in such positions, the Asian and European bulbs can suffer.
In hot soil the bulbs tend to mature too quickly after flowering and they then
break up into small weak bulbs. They can struggle on for years like this, but
the flowering diminishes and the bulbs eventually die out.
Soil preparation
Other than the already mentioned drainage improvements, soil preparation comes down to achieving the right pH and fertility levels.
Some bulbs, usually the true woodlanders,
prefer acidic conditions and grow well with rhododendrons and other acid soil
plants. Others, particularly tulips and irises with I. tingitana in their background, prefer slightly alkaline soils and do best
with added bonemeal or dolomite lime. Most bulbs however, will grow well with a
soil pH of around 6.5, and require no special fertilisers. A general garden
fertiliser will provide all the nutrients they need. Apply any fertilisers at
about half the recommended rate or you may find that you get very good foliage
growth but few flowers. For the same reason it is better to avoid fertilisers
that are high in nitrogen.
Planting
Don’t just throw the bulbs in the ground,
planting at the correct depth can make a vast difference to bulb health and
flowering performance. While it is necessary to use some common sense and vary
the depth according to the soil type (shallower in heavy soil and deeper in
light soils), the old rule of thumb — the depth of soil above the bulb should
be roughly equal to twice the height of the bulb — holds true for most
spring-flowering bulbs.
Also, though it may seem obvious, make sure you plant the bulbs the right way up. It can be hard to work out which way is up with some bulbs; if in doubt ask at a nursery or garden centre.
Bulb boxes and other containers
Growing bulbs in containers eliminates
the risk of poor drainage and also makes it easy to lift the bulbs without
having to disturb other plants. Pots and boxes look great when the bulbs are
flowering, but as they die off something has to be done to hide their untidy
post-bloom appearance. Plant fast growing annuals, such as
petunias, to hide the browning bulb foliage.
Use containers at least 30 cm deep
and build the soil up in layers. Use coarse gravel chips for the bottom layer
to ensure good drainage. Next, add a layer of free-draining potting mix to
about 1/3 of the depth of the box. The bulbs should be
planted in this layer; the base of the bulb nestled in the compost. Fill the
remainder of the box with a gritty soil mix to the appropriate depth for the
bulbs being grown. Add a little general fertiliser so that the bulbs get a good
start. A topping of fine gravel or bark chip much will keep the crowns dry and
rot-free.
Bulbs in grass
The sight of brilliant flowering bulbs on
what was, a few weeks previously, plain lawn is one of the wonders of
gardening. Although not all bulbs grow well in grass, daffodils, crocuses and
snowdrops and bluebells generally thrive and can be left undisturbed for years.
The main problem is knowing when it’s safe to mow the grass. You can forget close mowing, the idea is that the area is treated more like a meadow. Don’t attempt to mow the grass while the bulb foliage is still green. It should be left to die off naturally because, like any other plants, bulbs depend on their foliage for photosynthesis. The foliage doesn’t need to be completely dried before mowing, but there should be no more than a couple of centimetres of green stem remaining.
When you will be able to mow depend on
the selection of bulbs. Early flowering bulbs, such as snowdrops and daffodils,
generally dry off quickly after flowering, which will allow mowing by early to
mid December in most areas. If possible choose a fairly short grass, such as a
variety of fescue, that won’t overwhelm the bulbs or require too much mowing.
Pests and diseases
Provided the drainage is good, bulbs are
not greatly troubled by diseases other than viruses, which are usually
incurable and often show up as yellow flecked foliage or distorted flowers.
Some viruses are relatively benign and can be tolerated, but most gradually
diminish a plant’s vigour to the point where it’s better to replace the plant.
The number one pest is the narcissus bulb
fly. The larvae of this small fly eat away the flesh of daffodils and related
bulbs. Before long the bulbs are severely damaged. They will often continue to
grow and flower despite fly damage, but are usually stunted and distorted.
Careful inspection and soaking in an insecticide solution before planting are
the best ways to avoid this problem. Other burrowing pests, such as wireworms
and millipedes, also feed on bulbs, while slugs, snails and cutworms attack the
foliage.
Aphids are also common pests and frequently occur in large numbers on tulips. The damage caused by the chewing and rasping pests can often be tolerated, but sucking insects, such as aphids, may spread virus diseases and should be kept under control.
Copyright Geoff Bryant
|
