{"id":2773,"date":"2019-05-18T00:05:01","date_gmt":"2019-05-18T07:05:01","guid":{"rendered":"https:\/\/depts.washington.edu\/hortlib\/pal\/pal-question-564\/"},"modified":"2024-01-30T16:38:55","modified_gmt":"2024-01-31T00:38:55","slug":"on-overwintering-dahlias","status":"publish","type":"pal","link":"https:\/\/depts.washington.edu\/hortlib\/pal\/on-overwintering-dahlias\/","title":{"rendered":"on overwintering dahlias"},"content":{"rendered":"

I have some beautiful red dahlias in two flower boxes on my front<\/strong>
\nporch. Two questions: I noticed some of the leaves at the bottom<\/strong>
\nof the plants are turning yellow and dropping although the plants<\/strong>
\nare still blossoming. What to do? Also, do I need to remove them<\/strong>
\nfrom the soil for the winter here?<\/strong><\/p>\n

 <\/p>\n

To answer your second question first, you don’t have to dig up your
\ndahlias unless you prefer to do so. Here is what local gardening expert
\nMarianne Binetti says on this subject in her Seattle P-I
\ncolumn<\/a>:<\/p>\n

“Laid-back gardeners should just leave their dahlia tubers in the ground.
\nCut back the top growth after the first hard frost and then cover the
\ndahlia bed with a waterproof oilcloth tablecloth or tarp. Secure with
\nrocks or bark mulch. This keeps the tubers dry and in the spring you can
\nremove the covering and see what comes up. For dahlias worked into a
\nmixed bed, you can pile sword fern leaves on top and weigh these down
\nwith a rock.<\/p>\n

“It is the wet more than the cold that kills dahlia tubers.<\/p>\n

“If you really need to dig and store dahlias, place them in open paper
\nbags, never plastic, and let them dry in a covered area for a few days
\nbefore storing.”<\/p>\n

As for the yellowed leaves, it is hard to diagnose the problem via
\ne-mail. There is a chance that you could safely just keep removing and
\ndisposing of the yellowed leaves. However, there are problems like
\nleafhoppers (an insect which feeds on the leaves and causes them to
\nbecome speckled, then turn dry and drop off), or viral diseases which can
\ncause yellow spotting or mottling of the leaves. I looked at The
\nGardener’s Guide to Growing Dahlias<\/em> by Gareth Rowlands (Timber Press,
\n1999), and found descriptions of leaves which have turned yellow due to a
\nnumber of causes, including chlorosis (the leaves are unable to produce
\nenough chlorophyll, and turn yellow if there us still carotin present, or
\nwhite in only xanthophyll remains). When a mature dahlia turns yellow, it
\nmay be due to a nutrient imbalance (such as lack of magnesium or iron).
\nWithout having the plants diagnosed, it is impossible to recommend a
\nremedy, so you may want to bring samples to a Master Gardener Clinic.<\/p>\n","protected":false},"excerpt":{"rendered":"

I have some beautiful red dahlias in two flower boxes on my front porch. Two questions: I noticed some of the leaves at the bottom of the plants are turning yellow and dropping although the plants are still blossoming. What to do? Also, do I need to remove them from the soil for the winter here?   To answer your second question first, you don’t have to dig up your dahlias unless you prefer to do so. Here is what…<\/p>\n

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