Dahlias – Taking Care of Business

Saturday, December 26th, 2009 at 8:36 am

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Overwintering Dahlias

I live in Grand Rapids, Michigan. I need to know the correct method for overwintering Dahlia’s. I gave it a try but I don’t think that it worked so I would appreciate your help.

A. When the dahlias are through blooming and growing, usually right around the first frost, knock them down. Allow to dry in the garden. Then, using a pitchfork, not a solid shovel, spade up the roots from all areas around the plant, being certain not to slice into the tubers. Carefully lift the plant up and shake well. Lay it out on plastic and allow to dry, or if the weather is poor, do this inside a garage, carport or basement. When totally dried, cut off the foliage at the point where the stems touch the tubers. Discard.

Lay the tubers out, clean of soil, but not wet. Place into open trays placed apart and dry. A basement works best for me, away from anyone or pets, and allow to overwinter until the ground is loose enough to work outside.

Take the tubers, shake them, clean, and break apart any ones that can be done easily. This is to increase your supply and put on a bigger show of flowers. Plant them in your beds, 6″ deep, 2-3 feet apart depending upon the variety and how far they spread out. Water in well, add slow-release fertilizer and keep evenly moist but not wet. Sprouts will appear in a couple weeks, and then you are on your way!

Planting Dahlia Bulbs

I received a gift of dahlia bulbs and would like to know how to plant them.

A. Dahlias along with glads have been my summer faves since I was a kid. They are very easy to grow.

Take the tubers out and separate them into sections, meaning, if they are grouped together, pull them apart, but do not cut them. It is possible you received only one tuber or set, but I suspect a couple.

Dig an area in your garden that is very sunny. Turn the soil up and over often to a depth of one foot. Add compost or leaf mold to enrich. Replace 6″ of the soil, so that the bed is now 6″ deep. Lay the tubers on their side, one per hole, at a space of 2 1/2-3 feet apart. Loosely cover with the soil, so that they are 6″ below the surface.

Water in well. Leave them be, making sure that if the soil dries, you add more water. Keep any weeds from growing there.

Within 2 weeks, you will see tiny sprouts popping up, several from each planted spot. Just let them grow and when at a height of 6″ give them fertilizer at 1/2 the strength the label says. Keep water well, of course, but not soggy! As the stems and leaves grow, increase the food to full strength every two weeks. They will grow and flower on their own now…very, very easy.

If you want fewer, larger flowers, pick off the side buds allowing only one per flower stem. Pick off dead flowers to keep from seeding. You may have to stake the taller branches if they are tall-growing hybrids. But, come back to me when that time comes, and let me know how they are progressing!

Must dahlias be dug up every year?

A. That depends upon where you live. If you get any frost or temperatures lower than that, the answer is Yes. If you live in a climate that is moderate, Mediterranean, frost-free, then they can overwinter in the soil. They are native to Mexico and Central America, so that gives you an idea of their culture.

In general, if you live in a zone in lower temperature than 9, they must be dug up or you stand the chance of them freezing or getting frost-damaged. Once the flowering is finished, the fall temperatures turn the foliage brown, dig up the tubers, circling the plant from a distance so as not to split into the tubers [they look like sweet potatoes]. Lift them, rinse off the soil, dry and place in a frost-free dry dark spot, as a basement. In the spring, divide the tubers, breaking off the smaller ones, and plant spaced out. They multiply readily.

If you live in a moderate climate, it is necessary to dig them up every couple years to separate the tubers and replant in fresh soil. Add organic material to the beds and be sure to fertilize well during the spring and through flowering.