How to Grow Spring Blooming Bulbs, Corms and Tubers
How to Grow Bulbs Corms and Tubers
Winter and spring
Dwarf varieties and low-growing species are the most successful: scilla, crocuses, dwarf narcissi, tulips, and irises, for example. Taller narcissi will usually need supporting with wire frames or canes and string, which can spoil their appearance although they are still useful for cutting. Tall tulips tend to become very soft and floppy.
Bulbs described as ‘prepared’ have been subject to artificial temperature changes to bring them through the growing cycle, and they will flower much earlier than natural bulbs. Many hyacinths and some tulips and narcissi are treated in this way. Tazetta narcissi such as ‘Paper White’ and ‘Soleil d’Or’ flower naturally in early winter, without the bulbs being prepared or forced in the dark, and they will fill the greenhouse with scent and colour at an otherwise dull time.
Once thehave faded, you can put the pots under the greenhouse bench, but keep the compost moist until the leaves start to die. Gradually dry off the bulbs and plant them out in the garden — they will not flower well if grown inside a second time. Tazetta narcissi are not hardy except in very mild areas, but you could plant a few in the greenhouse border if you have room for them to stay undisturbed.
Summer flowering bulbs
Tender bulbs and tubers which flower in summer or autumn such as begonias, gloxinia (Sinningia speciosa), nerines, and tigridia are good candidates for growing in an. They are dormant in winter when the greenhouse is coldest, and are easy to store in a frost-free place indoors. Some hardy , especially the shorter ones, also do well in pots in a greenhouse.
Tuberous begonias flower from early summer to early autumn and are suitable for pots on the staging or in hanging baskets. There are varieties with red, pink, white, or yellow single or double flowers. Start the tubers into growth in early or mid-spring in a heated propagator or on a warm window-sill, laying them hollow-side up on damp potting compost. When shoots appear, pot them up with the top of thejust visible Keep them moist and frost-free. In autumn, when the leaves start to yellow, reduce watering gradually until the tuber is dry. Remove it from the pot and store in a frost-free place.
Nerines produce their flowers in late summer and autumn, before the leaves appear. The common species is pink, but there are other varieties. Pot up bought bulbs in mid-spring in the same way as spring bulbs and put them on the greenhouse bench. Water as necessary as soon as they begin to grow. When the leaves begin to the down in winter, letthe compost dry out and keep the pot in a frost-free place. Repot after about three years.
Planting spring blooming bulbs for spring colour
- Early autumn: cover holes in pots with crocks (pieces of broken clay pot) or coarse gravel to ensure good . Press a layer of moist potting compost lightly into the pot. Use a well-drained compost that is not too nutrient-rich; for example, a home-made mixture based on leaf mould.
- Stand the bulbs closely together on the compost; you only need 2.5-5cm between bulbs. Fill the pots with moist compost, leaving the tips of large bulbs just showing; cover small bulbs with a thin layer of compost. Water and allow to drain thoroughly.
- Keep the bulbs cool, dark, and moist, so that they make good roots and the flower bud develops in the bulb just before the shoot grows. For example, stand the pots in a black polythene bag in a cold garage, or put them in a cool shady pan of the garden and cover them with leaf mould or sand. Beware of waterlogging and damage by mice.
- Early spring: bring the pots into the greenhouse only when the shoots have made some growth: about 8cm for tall narcissi, 4cm for hyacinths, and 2cm for smaller bulbs. Keep the compost moist but do not get water on the flower buds.