uk.rec.gardening - Bulbs in Pots FAQ

Bulbs in Pots FAQ

This advice is intended for bulbs such as dwarf Narcissi, Iris, and Crocus. Thank you to Martin Froggat, and Rodger Whitlock for this advice.
Many small bulbs can be grown successfully in pots. It is important to use a pot with adequate depth of soil so that they can be planted at the recommended depth (twice the height of the bulb ) and still have enough room for root development. Deeper pots also give some protection against over watering. Long Tom or Rose pots are especially suitable.
Martin and Rodger have a slight disagreement over Crocuses which Martin thinks are okay in a shallower pot but Rodger prefers to give similar depth to all bulbs.
Rodger does not recommend over planting bulbs with other plants. Neither in pots nor in the garden. The over planting competes with the bulbs for nutrients and growing room, and may keep the soil from warming adequately to give the bulbs their necessary summer ripening.
For soil use a mixture of 50% John Innes No 2 and 50% Grit with a little bonemeal added. Don't use peat based multipurpose compost as it doesn't drain well enough.

Pests :- Rodger says weevils have not proved a problem among his potted bulbs, but slugs require vigilance. Finding the culprit as soon as damage is noticed, going out at night with a flashlight (Urglish "torch") if necessary. The worst insect pest of bulbs is the bulb fly, which comes in two delightful variants, the greater and the lesser. These horrors primarily attack members of the Amaryllidacea (snowdrops, snowflakes, narcissuses, nerines), but will switch to other families in a pinch.

Martin Froggats "Bulb Year"
August

Pots are knocked out, the contents examined, dusted with green sulphur powder and small bulbs bagged for sale or potted up to increase stocks. Pots are filled with the recommended mixture to where the bulbs are to sit and an inch of sharp sand added. The bulbs are sat on the sand and covered with another layer of sharp sand. This is to provide the bulb with very sharp drainage and prevents rotting. Fill the pot with more soil mixture and top with gravel and label.
Rodger adds that crushed rock can give a more aesthetically satisfying result. He says that it is not a good idea to re-use spent soil as small bulblets can be left in by mistake causing identification problems later when they mature among other bulbs. Such spent soil is an excellent top dressing for the rock garden where such offsets can eventually mature and add to the general planting picture.
Do one pot at a time. Nothing is worse than to decant, say, a dozen different narcissus forms and then have the cat upset the table and mix them all up on the floor!
September

All the pots of bulbs in the frame get a thorough soaking, this simulates the autumn rains that would happen in the wild.
October and November

Water thouroughly. You must remember to water the pots as the free draining mix is not very moisture retentive.
Some of the early flowering species will be showing signs of growth and at this stage feeding can be done. Initially use a high nitrogen feed, this is replaced with a high potash feed to help flower buds develop and increase the size of the bulb when some leaf growth has been made.
Rodger says he sticks to low nitrogen fertilisers at all times, using a "soluble tomato fertiliser" with an analysis of 7-28-28, at quarter-strength dilution, and applying it every two weeks to those bulbs showing any signs of life.
December

Continue watering, early species of Narcissus such as N.romieuxii should be in flower along with N.cantabricus.
January, February and March

will see the peak of the flowering. Continue to water and feed only the pots that are flowering or in active growth. Plants that have finished flowering can still be watered and fed, but much less than before. Aim to keep the compost moist. If you require seeds then let them ripen. It is not necessary to remove spent flower heads, seed production does not hinder the increase of bulbs. Remember that some Crocus have subterranean seed development if you require their seeds.
April and May

Depending on what you chose to grow you will still have pots in flower, to care for and enjoy. Water as previously explained.
June and July

The watering is eased off to the extent of only keeping the compost moist. Some bulbs like a baking, others do not.
We are now back to August when its repotting and planting time.
Martin recommends Potterton and Martin as a bulb dealer as they have a superb selection of dwarf bulbs suitable for pot culture.

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