It's time to get the dahlias growing
We all long for warmer temperatures and long, sunny days at this time of year. But we'd like more than a day or two of hot weather, followed by more cold! The calendar tells us it's spring, and we gardeners are itchy to get started.
In the southern part of the U. S., dahlia planting is well underway, but for us in the northern part, soil temperature has been too cold so far. Soil temperatures need to reach at least 60 degrees, as measured with a soil thermometer. Remember that soil warms slowly, and cannot be judged by air temperature. Dahlias hate cold, wet feet, and rushing them into the ground too soon often results in rotted tubers.
If you have not purchased your dahlias yet, you will be pleased and surprised at the many colors, sizes, shapes, and styles available. They range from pompoms to dinner plate size, short to tall, and many available that are suitable for raising in containers.
This is the time of year dahlias in storage begin to sprout, and if you find long sprouts, just trim them back to an inch or two in length. Don't worry — they'll grow back. And if you have had tubers shipped to you, just open the container for a little air circulation, and leave them in their packing material, where they can remain for at least a month.
A dahlia bed needs a sunny location, and, if your soil is like most in the Rogue Valley, will need to be amended with plenty or organic matter. Dahlias will not grow well in clay soil, as they need good drainage.
While you are amending the soil, you might want to work in some fertilizer for these heavy feeders. Use a fertilizer that is low in nitrogen, such as 5-20-20. Do not put the fertilizer directly in the planting hole when you plant the tubers, as the dahllias don't need it until they are growing well. Besides, direct contact with the fertiliizer could damage the new roots that will be developing.
When the soil has reached 60 degrees — usually late in May — and you can see the sprouts on the tubers, it's time to plant. Lay the tuber on its side, about 6 inches below the soil surface. Put a stake in at this time, near the sprouted end of the tuber. Most dahlias need staking, and putting the stake in now eliminates the danger of hitting the tuber if done later. Remember to make note of the name of each dahlia, either on the stake or directly on the tuber itself, with a felt tip pen.
Do not water the tubers at the time you plant them, as this promotes tuber rot. Water them after they come up, and during the summer, water them deeply, as the risk of tuber rot will have passed when the dahlias are well established. Hand watering is not recommended, as the water does not reach the roots, where it is needed.
Enjoy these summer bloomers until hard frost, usually well into October, or, if we're lucky, even November. Dahlias are also long-lasting as cut flowers, so enjoy them in bouquets in the house, too. The larger blooms are striking when floated in a bowl of water on your dining or coffee table.
Coming up: Don't forget to vote by May 20 on some issues that are critical to the future of horticulture in the Rogue Valley!
From 7 to 9 p.m. on Thursday, May 29, Bonnie Bayard, landscape architect and Master Gardener, will teach a class about small space garden design. Bonnie will tell us about not only design, but plant selections for small garden spaces. The class will be held at the Southern Oregon Research and Extension Center, 569 Hanley Road in Central Point. The cost is $10; call 541-776-7371 to register.
Carol Oneal is a past president of the OSU Jackson County Master Gardeners Association. Email her at email@example.com.