Tulips provide spectacular spring colour, but sometimes fail to do well in subsequent years.
Tulips like a fertile, moist but well drained soil. Adding organic matter opens up both clay and sandy soils making them much more suitable for tulips. Adding a potassium-rich organic-based fertiliser, such as Vitax Q4 pelleted chicken maure, before planting is also helpful for poor soils.
Use only healthy bulbs, discarding any that show signs of damage or mould. Plant in autumn at least twice the bulbs' width apart and at a depth of two or three times their height. Shallow planting is often the reason for failure, especially where bulbs are intended to persist for more than one year. Planted too near the surface, the original bulb is likely to split after flowering to produce numerous bulblets which are just too small to flower the following year.
Most bedding type tulips are best replaced each year. However, some cultivars growing in warm soils where they get ‘baked’ in summer can persist from year to year and even multiply. Unfortunately this is unusual.
Encouraging reblooming
Acceptable results the following year can sometimes be achieved by lifting and drying tulip bulbs. Deadhead to prevent seed production that diverts resources from flower production and wait until the foliage yellows before lifting the bulbs (about four to six weeks after flowering). If you must lift earlier, place in seed trays until their leaves go yellow and straw-like.
Clean soil off the bulbs and discard any diseased or damaged ones. Allow the bulbs to dry thoroughly before dusting with sulphur to control moulds and rots. Store in trays or net bags in a warm (18-20°C/65-68°F), dark, airy place before replanting in autumn.
Although few of the tall bedding cultivars will flower year-after-year without lifting and drying, dwarf species tulips often thrive. They are often sold as ‘rockery’, ‘botanical’ or ‘alpine’ tulips and include Tulipa kaufmanniana, T. fosteriana, T. greigii and their hybrids. Tulipa sprengeri and T. sylvestris can be naturalised in grass. Only lift when the clumps get overcrowded.
Tulip diseases
Grey bulb rot is a fungal disease that attacks bulbs in the soil and often leads to failure of bulbs to emerge. Where bulbs fail to emerge look for rotten bulbs and check for the rounded 7mm diameter resting bodies (sclerotia), at first soft and white, later becoming brown before turning hard and black. Sclerotia can persist for years in the soil: prompt removal of infected bulbs is very important and the only means of control. A five year break from growing tulips is advisable where soil becomes infected.
Tulips are also prone to Tulip Fire and Tulip viruses.