Bulb planting should be in full swing by now, but I thought it might be a good time to understand a little more about these wonderful additions to gardens. When considering which bulbs to buy, look at your borders and photos, if you’ve taken any during the year, and figure out where you want to place them. As an aside, it is good practice for all gardeners to take photographs throughout the year so that you have a visual diary.
Bulbs and corms are great to use in both pots and borders and they are easy to plant, easy to care for but above all fill gaps in tops or become the stars of your outdoor space.
The first thing is to understand what are bulbs and corms and then you start thinking about how they can be used. Both are underground storage organs for an immature plant inside. The buds in the tubers are enclosed in overlapping fleshy leaves, layer by layer, similar to those of an onion. They have periods of growth, flowering and dormancy. Corms are also storage organs, like true bulbs.
Each bulb has a flat end called the basal plate, from which roots emerge. If you cut a bulb in half, you’ll find the fleshy scales (the storage organs) and the tunica, the papery-like covering outside, such as in narcissus, hyacinth and allium. At the top end, we have the shoot, which has flower and leaf buds.
Sometimes new bulbs form around the outside of the main bulb, these are called offsets. When multiple offsets occur, the main bulb in the flower begins to decline. This is the perfect time to lift the bulbs to divide them. Some bulbs do not have a papery tunic, such as lilies, and these need to be kept moist before planting to prevent the scales from drying out.
A corm, however, is a swollen stem base, which is a mass of storage tissue. If you cut a corm in half, you will not get a visible storage ring. This differentiates it from a true bulb. Like a bulb it has a basal plate, a thin tunic and a growing point, like gladioli and crocus.
Read more: ‘The right time to plant tulips’: clever bulb tricks to stop slugs in Mark Lane’s column
Layering in the ‘bulb lasagne’ style works best for bulb pots. This means planting the larger bulbs at the bottom and the smaller bulbs and corms at the top. This way you can have color from January to March with crocuses and narcissus; April to May with narcissus and tulips; May for allium and camassia; lilies, gladioli and begonias from June to August; Nerin for September; Cyclamen from October to December. Try several pots grouped with a combination of these bulbs. This way you can bring out those who are glaring and just want to be seen.
For ideal flowering, it is best to plant the bulbs in a sunny location; However, narcissus, scilla, anemone blanda, and martagon lily do well in partial shade. Therefore, growing bulbs in pots works well, as you can move the pot into the best position. Also, don’t pack too many bulbs into one pot, thinking more will reward you with better flowers. Plant at least twice the width of the bulb and remember that flowers are sometimes much larger than the bulb, so space your bulbs accordingly. Also remember to feed your potted bulbs with a liquid fertilizer once a week.
When planting bulbs in the ground and in pots, it is always good to do a little research online or in books to find out where the bulbs grow in the wild, as this will give a good indication as to the conditions needed. When planting large bulbs in a lawn or in a border it’s a good idea to use a long-handled bulb planter, especially one with a tread edge to make things even easier – this will protect against back strain . For smaller bulbs and corms, a hand trowel works very well, as does a hand bulb planter. Try out the tools and find the one that suits you best and works within your budget.
It’s a good idea to use a layer of grit under each bulb to help deter slugs in the ground and to prevent the bulbs from rotting. Once the bulb has flowered, remove the spent flowers to prevent the bulb from setting seed. This means the plant’s energy will go back to the bulb for the next season. Always let the leaves die back naturally. If you want your flowers to naturalize themselves and increase in number, especially in tall grass, allow the leaves to die completely before mowing.
Newly planted bulbs grow and bloom well, but there may be fewer flowers or no flowers in subsequent years. The leaves and any flowers are known as ‘blind’ and this is caused by a number of things. If you’ve planted good quality bulbs at the right depth, in moist but well-draining soil and fed them with a general fertilizer, you might think you’ve been sold a worthless batch. Ask yourself:
- Did you remember to remove or pinch the flowers when they fade?
- Did you let the leaves die off naturally, at least six weeks after flowering?
- Did you forget and leave the flowers to go to seed?
If you’ve done everything right as described here, it’s likely that the bulbs, especially narcissus, have become overcrowded. If so, dig them up, divide them into individual bulbs, and plant again. Otherwise, your bulbs may become victims of certain pests and/or diseases. For example, the daffodil bulb fly and daffodil eelworm damage bulbs below ground resulting in daffodil blindness. Viruses do not kill a plant, but can cause loss of vigor, discoloration, deformity, and blindness. Basal rot, however, is a fungal disease that destroys the basal plate, and if ingested will result in yellowing and blindness.
There is no need to plant all bulbs between September and November. Many types of bulbs will do perfectly well when planted in December. The trick is to get them inside before the risk of frost if there is no water in the ground, so they can start producing roots. Once rooted, they are quite frost tolerant. Summer-flowering bulbs such as gladioli and begonias are typically available from early February through April. If you have a cold frame or cold greenhouse, pot them up as soon as possible and keep them outside until all danger of frost has passed. However, lilies can be planted in autumn or spring, as they are relatively hardy.
By understanding the bulbs, you can create a wonderful, personalized display that will look good for years, and with the right care and attention you’ll have a handful of cut flowers and extra color when you need them.