Dahlia bulbs are planted in the spring once risk of frost has passed. They will grow quickly and the plants will be blooming by mid to late summer.

In your region, dahlias also need to be lifted out of the ground for winter storage if you want them to bloom next year. Many gardeners treat dahlias as annuals. 

So, given where you live, you could try storing the tubers over the winter. If properly stored (usually in a vermiculite or peat moss), they should be fine. 

When dahlias bloom has a lot to do with the soil warmth and how deeply they are planted (ensure an eye is present on each tuber clump). We would suggest early blooming variety if possible. We have had late varieties that never bloomed before the first frost in the fall! Also: Once the leaves begin forming and the plants are 3 to 4 inches tall, pinch the terminal bud just above the second pair of leaves.  This will produce two main stems.  Remove the buds when the flower buds are visible.  This will increase the bloom size of the leader bud and improve the flower stem formation.  Flower buds come in sets of three. The central leader bud will produce the largest bloom.  There will be a smaller flower bud on each side of the leader bud.  Remove these side buds by pinching.  Further down the same stem, two more buds will be found in the leaf axils and these, too, should be removed.

Monitor the plants for any beetles, caterpillars, or slugs that could be munching on the foliage. If you don’t see any culprits, try using a pesticide like neem oil or an insecticidal soap.

You can also cut the flowers in the morning and place the stems in a bucket of water outdoors in the shade. The insects should leave without your doing anything else. Before you bring the flowers into the house, inspect them and, if necessary, shake them gently. Remove any bugs by hand or with a small soft paintbrush.

If you haven’t planted the tubers yet, then yes, you should trim the shoots down to 1 inch before planting. It’s recommended to pinch back stems only slightly once they have developed 3 to 4 sets of leaves. This will encourage the plant to branch out from the stems, giving you a fuller plant. 

Growing in a pot/container is essentially the same as in the ground. Make sure that the pot is large enough to give the tubers room to spread out, and if staking/support is needed, arrange it in the pot when you plant the tuber (as if you were planting in the ground). Staking later risks injury to the tuber and potentially loss of it or the bloom.

It’s not entirely clear: If you now have 30 plants in the ground, you can lift the tubers and divide them. This is best done in spring or fall. Use a sharp knife to cut the tubers apart. Note that only those with an eye (a dormant bud) will grow stems, so you can cut large clumps of tubers instead of discarding single ones without eyes. Let the roots dry for a day or so before storing (see above) or planting elsewhere.

Thank you for pointing out the error in the text. We have corrected it. Here’s what we learned: you want to dig a hole that’s 6 to 8 inches deep. Set the tubers into it and cover them with 2 to 3 inches of soil (some say 1 inch of soil is ok, too). As the plant grows/sprouts up, fill in with soil around it until the ground is level. BTW, if you plan to stake the dahlia, place the stake in the hole first, then the tuber and cover as described. If you wait to push a stake into the ground, you might strike and damage the tuber. Thanks again!