Expert: Kenneth Joergensen - 2/3/2006

Question
USDA zone 9? Melbourne Australia
Hello. 6 years ago, I planted 4 tuberose in a pot. In the second year, they all flowered. I have divided & re-potted them twice since as the bulbs have increased. The problem is, that each year, there are less flowers, this year only 1. They are planted in a good potting mix with slow release fertilizer & dynamic lifter. What am I doing wrong to be deprived of my favourite flower? Jo

Answer
Tuberose should be planted in acidic soil. Test soil to make sure that pH is below 6.5. If above, use gardeners sulphur and never lime the soil.

Plant in full sun for best result and water regularily. The soil should be moisture retentive, preferably deeply aerated and mixed well with compost (cow manure for example). A good deep, rich soil is preferred.

You can use slow release fertilizer, but I also recommend watering every month with a liquid fertilizer. Use fertilizers with high 2nd and 3rd numbers (such as 5-10-10) rather than those very high in nitrogen (such as 33-3-3 for example). Do not use lawn fertilizers.

If you plant in pots, you usually have better ways of moving them into sun, but make sure you use a deep pot and with a good quality potting soil. You will get good result if you mix 35% compost or composted cow manure with 65% potting soil.

Watering:
The soil should be moist when planting but otherwise keep relatively dry until the green tips emerge. From that time onwards, the soil should be kept slightly moist whilst the plants are actively growing. In pots, sometimes the soil can get too dry and that can halt flowering. Make sure the soil is kept consistently moist after growth starts. Do this by using a large pot, and keeping an eye on the pot especially in summer.

My experience is that these bulbs do better if not re-potted and divided consistently. Try to leave them in the same pot for 2 or more years (undisturbed).

Offsets (new smaller bulbs) typically takes 1-2 years of active grow to flower again (due to size). They also need a good quality loam/composted soil and regular fertilizer.