Expert: Kenneth Joergensen - 3/26/2005

Question
Hi, need answer to questions about starting up our tuberous begoias. Last year we ordered the bulbs or whatever they're called and instructions said plant 6" deep. We put them in big containers on the deck (we are in zone 5). The plants grew very thick and tall and were beautiful. In the fall we dug the bulbs up, dried them out, put them in the basement in paper bags.  Now.  The bulbs are sprouting, 2-3", and we are wondering what to do about them now.  Can you give us instructions?  Are we supposed to start them growing in small pots or just plant them 6" deep in their outdoor containers?  And what kind of potting soil should we use? Fertilizer?  Thank you for any help you can provide.

Sally

Answer
Sprouting bulbs are excellent news. You did a great job. You have two options:
plant them indoors in pots covered with 2" of soil. Keep warm, but not very hot. Make sure they have some light. fluoresent lights placed 3-4" above the top of the canopies of the begnoias are best, but otherwise, a sunny window is also ok. Avoid blazing hot sun on the begonias or they get damaged. Bright light is the key (too dark and they dont perform well).

If you want to wait and plant directly outdoors, you can do that too. It is up to you. If you prestart indoors, you can get flowers 4-6 weeks earlier.

I recommend starting no sooner than mid april because they grow fast and can be difficult to handle indoors without grow light.

After the sprouts have appeared and the first leaf has unfolded, add a soluble fertilizer to the water every 2nd time you water. If you use 15-30-15 miracle grow then add 1/2 tsp of the powder to each gallon of water. You can also look for 20-20-20 Peters instead (same dosis).

Outdoors, I recommend a 3 month supply of 14-14-14 Oscomote. Begonias do best in bright light but not hot afternoon sun. avoid very deep shade. Fertilize regularily, but lightly. E.g. instead of monthly with a very concentrated solution, try a weekly or every 14 day feeding with a milder solution. If necerssary, use 1/2 the recommended strength on the lable.

Begonias do best with bright light (but not direct hot sun) and regular but light fertilizer.