Tulip bulbs are best planted in uneven numbers, in groups of at least five to ten. The distance between bulbs should be around 12 cm. Planting distance in a pot is about 3 cm, i.e. closer than in the bed. Five bulbs are sufficient for a pot of 20-25 cm in diameter. Ten bulbs are suitable for a pot of 40-45 cm in diameter. Some tulips are perennials. To help them form a new side bulb that will flower next year, it is a good idea to apply Zetas bulb fertiliser at the time of planting and again when the tulip is coming up in spring. There are several factors that influence the tulip's willingness to flower again. Favourable weather such as a hot summer and not too much rain. Nutrient-rich permeable soil, fertiliser and variety selection. The botanical tulips and Darwin hybrids tend to come back every year if the weather is favourable.