|
Plant the tubers on their sides; normally one end is more knobby or complex than the other, and that's where the tuber will sprout. Plant three times as deep as the tuber is thick. Do not water: Dahlias are very good at pulling the water they need from the soil all by themselves. After sprouts emerge, you can hill soil up farther and farther, which provides more support. Full-size dahlias can be "hilled" to six inches or even (if you've got enough of the loose and light soil they crave) a foot.
For dahlias that you know will need staking, "plant" the stake right when you plant the tuber. Plant it an inch away from that knobby or "complex" end of the tuber. If you wait until the plant clearly needs staking, you'll inevitably shove the stake through one of the new tubers that the plant has formed all Summer, which is rude even if not, really, harmful. Dahlias that are four feet and shorter can usually get away with just pea stakes, but the big-flowered and full-height cultivars need serious support. I'm partial to the one-inch square wooden "tomato" stakes that my local lumber yard (believe it or not) cuts to order. Six-foot bamboo stakes also work.
Tie the dahlia stems to the stakes gently and loosely, with wide and soft material; wire or even twine can cut into the stems. If you have the patience, cut old pillowcases into one-inch strips. Given how unattractive a lot of bright-white pillow-case ties would be, though, it would be worth it to buy a pillow-case, or even an entire sheet, that was tan or even brown.
Soon after the plants begin to flower, it's time to start dead-heading. The buds of flowers-to-come are round, whereas dahlia flowers that are done flowering and are now hoping to go to seed are pointed; it will soon be second nature what to clip and what to leave.
Dahlias are often at their best the last weeks before frost; September and October are always the peak of the dahlia season. Let the plants get thoroughly frosted (which may take several nights of sub-freezing temps), and then don't do anything! Let the dead plants contemplate their fate for two weeks or so before you even think about digging up the tubers. This interval helps the tubers themselves go dormant.
The single tuber you planted in May will have matured to a starfish-like clump when you dig in October. Start digging a foot out from each stake until you get the feel of how large your tuber clumps will be and how easy they'll be to extract from the soil. The clumps are fragile but not maddeningly so. Cut off the stems several inches above the tubers, not right down at them.
As soon as you've dug up a clump, gently tie a water-proof label around it; dahlia tubers can rarely be distinguished down to the level of cultivar and color. If you've dried the tubers enough, you can write directly onto the tuber with a waterproof marker, such as a "Sharpie." If you don't label, all you will know is that the smaller tubers are, indeed, the tubers of your dwarf dahlias. But you won't have a clue about which cultivar they actually are.
Gently remove most of the soil, but don't be dogmatic about it. Leave the clumps in the sun (or store them frost-free and under cover for a few days until there is sun) to dry for a few hours; don't leave them out overnight, though: If they don't get hit by frost, they'll get covered with dew, which defeats your effort to dry them in the sun. Then load them loosely into cardboard boxes or wood or plastic crates—upside down so any water in the stems drains out, not down into the tuber.
The tubers don't like to feel lonely during their long Winter in the crates, but neither do they want to be packed together. A gentle association, so to speak, is best. Try loading them in no more than two layers in your crate, and only as many as will fit with absolutely no nudging or twisting or packing-in.
Unless your frost-free basement or garage is unusually humid, then cover the tubers gently with loose dry leaves or vermiculite or sawdust. The goal of any of these covering materials is to slow down transpiration from the tubers but without trapping the water vapor that does leave even so, lest it condense and encourage growth of mold.
Especially your first year or three of overwintering dahlia tubers, check your tubers monthly to see if they're drying out or rotting. If the former, sprinkle with water, add more coverage, and see if you can't move the tubers to a slightly cooler location. If the latter, reduce or remove the coverage entirely, and store in a single layer on newspaper with no tuber clumps touching any of their neighbors. I have a client who stores his dahlia tubers—naked!—in their wine cellar, which, indeed, is the perfect combination of temperature and humidity.
If you have the space and energy and warm sunny windows, you can pot up your tubers again in late Winter, as much as two months before the last frost. Divide the clumps into individual tubers in that case; you'd need huge pots, indeed, to pot up whole clumps. When dividing, be sure that each tuber retains a portion of the central mass of the clump, which is where the sprout will arise. Use a steak knife for your surgery, or buy a purpose-built "soil" knife, instead.
Or you can just wait until the soil is warm and the weather's balmy, and plant your still-dormant tubers right out into your garden in Spring. The second week of May works for me. In that case, you can skip dividing the clumps into individual tubers.
|
