I bought an indoor plant which was unidentified and I thought was a Garvinea. As they are meant to be super hardy and developed in Netherlands for outdoors, I planted it straight outside into some peat reduced mixture. Within 4 days all the leaves have fallen off. It's warm here in summer. It doesn't seem to have adapted too well. Could I have bought something else?
It appears that this pot is to large for your plant.
Generally a blooming potted plant is quite happy in it's original pot while it is blooming. After blooming if it appears root bound you could repot but only go up 1 size in pots.
Also watering in pots during the warm summer temperatures is very important. You may need to water twice a day if the temperatures are over 85 degrees.
What is their bloom time? (Start and finish)
Potted gerbera daisies will bloom at any time of the year, blooming for up to 6 weeks when kept indoors, and 2-3 week intervals (give or take) outdoors. With ideal conditions (and deadheading), they can bloom twice in a season, once in spring and again in summer. Grown from seed, they usually take at least 6 months to reach maturity for blooming.
Do you replant them every year?
You may be able to continue to grow your Gerbera in your growing zone.
Here is a link with more information.
What causes this? My 18 year old plant has produced two green blooms instead of pinky orange.
When gerbera flowers turn green it means they have a viral disease and must be dug up and destroyed as it can spread to other plants. There is no cure.
Gerbera Daisy don't change color but often a different colored plant was potted together and will suddenly make a blooming appearance and through off a gardener.
It is unusual for it to take this 18 years to show itself, but not unheard of.
Congratulations on this long lived plant.
I want to plant some gerbera daisy seeds to grow plants on a window sill in my bedroom. How big of a pot should I plant the seeds in? Will they need to be transplanted to bigger pots in the future - if so, how long?
Use small starter pots about 2" in size.
Starting Gerbera from seed can be a challenge and germination rate is very low.
If you are successful you should seed seedlings emerge in about 14 days.
They can generally go to a larger pot after another 2 to 3 weeks after germination.
If you have nothing in 30 days, you can toss them out.
I am told to keep the crown above the soil. What part of the plant is the crown?
The plant crown is where the plant stem meets the roots.
Here are some articles that will help you with more information.
How to fertilize a new gerbera plant?
Use a balanced liquid fertilizer once a month during active growth.