My poor Dahlia of unknown cultivar (above) died. My mom gave it to me, she said it would be easy to grow. I put it in a pot and it grew, then I thought it might like more consistent watering, so I planted it in the ground thinking 'hey, all plants prefer the ground to pots!'. Wrong-o. I have to admit, this is one plant that even I won't argue is "low maintenance".Rot. I learned how I killed my Dahlia when I went to Flora Grubb Gardens over the weekend to hear a talk given by the gregarious Mike Schelp of The Dahlia Farm (cut flower grower) in Half Moon Bay. What follows are my notes, posted here to help keep more Dahlias safe from harm:Climate and lifting: In colder parts of the country, Dahlias need to be lifted because they are frost tender. Where frost isn't a problem, they should still be lifted and divided because their tubers are both incredibly prolific and prone to rot. They don't like too much heat, either, so mild coastal climates are really great for them.Sun Exposure: Since they're not keen on very high temperatures, if you live in a warmer area, consider protecting them from full sun (or at least afternoon hot sun). The color of the flowers can be "bleached out" by strong sun exposure, so if a normally deeply colored cultivar is not living up to your expectations, this might be the culprit (or it could be any number of other things as they can be pretty variable).Soil: Dahlias like a light, slightly acidic soil that is well drained (so raised beds, containers, or in a well drained location). Containers should be at least a 5 gal. size.Water: Dahlias like moderate water when they are actively growing, but will rot out easily. In the container, mine had pretty good drainage, but one wet spring in the ground was enough to kill it. Mr. Schelp grows his in semi-raised beds for this reason, and he usually does his dividing in January (so they get lifted and divided EVERY year!). Be aware that if you grow yours in a container, that moisture can collect at the bottom, causing (you guessed it)....rot.Pests: They're susceptible to all the bad bugs and also to mildew. There was a lively discussion of mildew which I won't bore you with, but let's just say it can be a serious problem for some cultivars and any affected leaves should be removed immediately. The tubers are gopher candy, so he recommends that if you have gophers, plant the tubers in a wire mesh "cage" about 15" diameter with an un-attached bottom for easy lifting.Air Circulation: oh my! Mildew can be such a problem that he recommends a few things to keep the air flowing. Pinch off leaves in the bottom 6" of the plant to allow air to flow at the base. Take away stems or leaves that make the plant too bushy for air to circulate. Plant tubers 30 inches apart to keep the air flowing between individual plants.Feeding: This is one place where I did not entirely agree with the presenter. He is a cut flower grower, so his needs are different from mine. He uses chemical fertilizers (which kill good microbes in the soil). I wrote down that he recommends a high Nitrogen fertilizer beginning when the plants start coming up. That application should be applied, diluted, throughout the season, not at once, and taper off towards the end of the season or the Nitrogen will rot your tubers. He also switches to a higher Phosphorous fertilizer when the plants are starting to bloom. I will be experimenting with not doing this, opting instead for an organic approach (coffee grounds, anyone?). Dahlias are surface feeders, so apply nutrients accordingly, but be careful not to use too much to avoid scorching them chemically.Propagation: Dahlias can be propagated by several methods, too many to go into detail here. So I found someone else who covered this information HERE. A happy Dahlia tuber can multiply ten fold in one growing season, provided you don't rot it. Plant tubers 2-6" deep, but DO NOT let the "neck" break. A tuber with a broken neck is toast.Availability: Most garden centers sell Dahlias as tubers between winter and spring or as green plants during the summer. You can find them by mail order between (give or take) December and March, tubers should be back in the ground around April.Cut flowers: If you are still brave enough to grow them, you can keep cut flowers for about a week. I was impressed that his cut flowers are delivered to a local florist no more than two hours after being cut on the farm. I only wish he had said what florist! Here's how you can do it: cut the stem and dip immediately in hot water for about an hour (hot so you could wash your hands in it, but not boil an egg). Re-cut the stem at least every other day and place in tepid water (doesn't have to be hot anymore). Remove browning petals as flowers fade, keep flowers away from produce (ethylene gas from ripening produce speeds the aging of the flowers!). Keep your flowers in a cool room, away from direct sun. If you are cutting flowers for general enjoyment in a vase, cut them when the bud has begun to open but the center is still tight - an unopened bud will not open in the vase. If you are cutting for a specific event, wait until the flowers are at their peak before cutting. They won't last as long, but they will be gorgeous.Still not dissuaded from wanting to grow Dahlias? Me neither. This fall I plan to order a Dahlia tuber or two and try again, this time in a bigger pot with better drainage and more understanding. To find my new green friend, I will attend the 2011 American Dahlia Society show at the Santa Clara Convention Center this August. Show admission is free to the public on the 20th and 21st. I will write down the names of the cultivars I like and use the Colorado Dahlia Society's "Big List" to find a supplier for my favorites.At the end of the discussion, Mr. Schelp added what seemed to be a very personal note. He asked the audience to give away their extra plants and flowers. If grown well, you are bound to have extra and sharing is the best way to pass around some good vibes. He asked that we give our flowers to hospice centers and old folks homes, friends and neighbors. His voice quavered just enough that I could hear it in the front row, and I believe that this was a very personally meaningful message he was trying to send, so I repeat it here. I plan to do the same with my new Dahlias and I urge you to do the same.
