If a dahlia with root tubers is planted, the gardener should test the tuber for firmness and note that dahlias are heavy feeders. Plant dahlias, and mix organic matter with the soil, with tips from an experienced gardener in this free video on flower bulb gardening.
Hi, I'm Jessica Smith with Blands Nursery in West Jordan, Utah, and today we're talking about planting bulbs. Right now we're going to discuss how to plant a dahlia bulb. Now, dahlias can grow anywhere from a foot high on your dwarf varieties, way up to your huge dinner plate dahlias. Your planting process is exactly the same. What you want to do, is if you're purchasing the bare root tubers in the spring, go ahead, make sure that you test the tuber, make sure it's a little bit, it's firm. You want that tuber to be firm. Look for any mildew or anything. If you find mildew or they look like they're all shriveled up and everything, don't buy them, it's not worth your money at this point. It is fall right now, so we don't have those early blooming, we don't have those early bare root ones to show you. What you want to do when planting your dahlia is, now dahlias are a real heavy feeder. Make sure you've got some nice organic matter mixed with your soil. Again, prepare your soil a few weeks before you're going to plant. With the bare root tubers, you're going to want to plant them about three weeks before your last frost. If you're going with a transplant that's already started with the foliage on the top, make sure you wait until after the frost. They don't like the cold and so if it freezes again, unfortunately, those tops are going to be frozen down. They'll shoot back up out of the ground; all's you've done though is lost time. The length of the tuber is how deep you're going to plant it. So you'll take twice the width of it, and you're going to plant it down, so basically - whoops, wrong way - we want to go about three to four inches on your smaller ones, maybe a little deeper on a dinner plate dahlia because it's a bigger tuber. Water them in at this point, and then don't fertilize until actually they start to hit with your flower buds. Go ahead and start fertilizing with a high water soluble type of a super-phosphate. This is your middle number on your fertilizers. That's your phosphate level. That's the one you want to play close attention to with your flowers. Dahlias need to be kept moist. You don't want to keep them wet; you'll actually rot out the bulb, but you want to water each time that it dries down to about an inch or so below the soil level. That's the time to water a dahlia. Left too dry, the leaves can really curl and dry up easily. Also with a dahlia, remove all those spent flowers after they're done blooming. This is just going to help encourage more and more blooms for you.