Poted lemon tree blossoms but flowers and some unfolded buds crumble so I don't have desirable lemon fruits

I got this tree last September, it had some defoliation and rest of leaves were with holes, I fed it and did watering every other 5 days, then was good improvement and in March a lot of germs arrived, part of them became beautiful flowers, part crumbled unfolded. I tried pollination by soft brush bun flowers also crumbled. What can I do to have lemons?

Poted lemon tree blossoms but flowers and some unfolded buds crumble so I don't have desirable lemon fruits
From:


http://www.plantea.com/lemon-tree-indoor...





SOIL: Like most houseplants, citrus prefer a slightly acid, all-purpose mix, which you can get by using a peat-moss based growing mix. (Remember, you get what you pay for, so don't go for the cheap products.)








TEMPERATURE: Lemon trees thrive in a normal temperature range of 70 degrees during day to 55 degrees at night. TIP: Though the plants are evergreen they will go into dormancy and stop growing below 54 degrees F.)








LIGHT: Set your lemon tree in full sun from a southern exposure. Trees need lots of light. If that's not possible, supplement the light by installing 40-watt fluorescent shop lights above the plants -- especially important in the winter, when they need 12 hours of light.








MOISTURE: You'll need to keep the soil evenly moist and since most interiors are quite dry, mist your plant often -- daily if you can. Give your lemon tree a shower occasionally. (They loved to be wiped down gently with a sponge, like the one at right.)








POLLINATION: When you grow plants indoors, bees and insects can’t pollinate them. So you need to use a paintbrush or cotton swab to rub pollen within the flower. Sometimes they will produce fruit without doing this, but it's a good idea to increase your chances!
Reply:You need a male and female tree.





Had them for years. Ponderosa Lemons.


Huge. 1 will make a pie.