This Week's Podcast: A Replay: Discoveries Under Glass with Alan Petravich
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Our guest this week is Alan Petravich. He is a research specialist at the world famous Longwood Gardens in Kennett Square, PA, where he has been for 13 years. In addition to growing plants to test from all over the world, his work deals with tissue culture – growing plants from tiny bits of meristem – cells of new growth — in nutrient gel in test tubes in sterile laboratory conditions.
He has worked with culturing Chrysanthemum and Sarracenia and done breeding of Verbascum, Kalanchoe, Clivia and Canna.
There is a virus infecting many of the canna plants in our gardens and those for sale. Alan, who has a Masters of Science in Ornamental Horticulture from Penn State, tells us that one way to defeat the virus is to grow new plants from the uninfected meristem tissue.
Alan also talks about programs at Longwood that include finding new plants to force into bloom for some of the remarkable winter displays under glass. The busiest time for visiting Longwood is between Christmas and March, and the exuberant conservatory displays are the big attraction. One plant that Alan has grown is Echium wilpretii from seeds collected in the Canary Islands (above).
Alan’s personal passion is the genus Clivia, and he mentions a couple of selections developed at Longwood 
(Clivia ‘Fireworks’, left). Not only does he breed new varieties of the winter-blooming plants, Alan has also become the president of the North American Clivia Society.
So, why don’t my Clivia plants bloom? Alan tells me how to do it!
I just printed out your information about Clivia – that beautiful houseplant. Very informative but i have a ? for you. Our clivia is at least 50 -55 years old and has been transplanted I believe only 3-4 times. It has been in a big pot and become very very root bound. I put outside in summer and usually bring in in fall. However – it has become so big and heavy my husband needed help to bring it in. Unfortunately it had to be left out all winter with a lot of freezing temperatures. I agonized over it and covered it everynite with blankets and such. By the way it has bloomed every year for probably the last 10 years. So–now– we had a olevely 68 temp day here in Seattle, WA and we got it out of the pot and surprising there are more tubors alive thn I thought there would be.. There was a lot of roor rot at the bottom and it is sitting outsice in the sun to help dry it out a bit. How can we separate the tubors as they will not pull apart?? I love this plant as I purchased it when all 4 of our children were in grade school as one little start in a little pot for 1.00 over 50 some years ago. Would really appreciate your help in helping us be able to save this plant.
sincerely.
Blossom and Arthur Morris
6700 NE 190th
Kenmore, WA 98028
email – almorris101@msn.com
You’ve got your work cut out for you.
I’ve seen thick roots on Clivia, but not tubers. Since you got the plant out of its pot, with a very clean knife, cut between the individual plants. You will lose some roots, but that will not hurt the plants. Cut away and dead or rotten roots. You can repot the individual plants in single pots, or place them together. Do not use a large pot — just one large enough to hold the roots. It will be difficult to get potting mix around the roots. Push it down with dowel or similar blunt tool. Clivia like to be potbound and on the dry side, as you know. When weather warms, place the pot(s) in a shaded place for the summer (not directly on the ground, and not in a saucer that will hold water – you can place it on an upside-down saucer to elevate it and keep worms and bugs form entering the pot). Good luck.
Ken