Dahlia Planting & General Care

 

WHEN TO PLANT:  It's important to wait for the right conditions to plant.  Tubers will not grow (and will likely rot) in wet, cold soil. Wait to plant if heavy or extended rains are forecast.  Plant after the last frost date for your location, usually between May 1 - June 15th.  Your ground temperature should be between 55 and 60 degrees.  Monitor your area's ground temperature at www.greencastonline.com/tools/soil-temperature

WHERE TO PLANT: Dahlias grow best in rich, well-drained soil. Full sun (6-8 hours/day) is ideal, but they will tolerate some shade.  In warmer climates, plant in an area that receives morning sun/afternoon shade.

HOW DEEP: 4-6 inches deep.  Plant with the eye or sprout pointing towards the surface. If the tuber has sprouted, cut the sprout back to 1-2” tall.

SPACING: 12-18” apart

WATER:  Don't water your tubers until sprouts appear above ground.  This will usually take about 2-4 weeks.  During the growing season, dahlias appreciate being deeply watered.  We utilize soaker/drip hoses and water several times a week for an hour at a time.  Rain alone will not provide enough water for successful plants.

SUPPORT: Dahlias will grow quite large and require additional support.  For individual dahlias, insert a 4-5' stake at planting time to avoid damaging the tuber later, and tie the stalks to the stake as they grow. For larger dahlia plantings, consider corralling or using horticultural netting. 

FERTILIZER:  Dahlias are heavy feeders! Amply amend your soil with aged manure or compost prior to planting. Use an equal ratio fertilizer such as 10 -10-10 as the plant grows and then switch to a bloom booster fertilizer once you see buds forming.  Stop fertilizing about a month before your first frost.

PREDATORS: Watch for SLUGS and RABBITS!  They love to munch on your newly sprouted dahlias.   Use slug and snail bait at planting, don't wait until the sprout appears. Another method (that we prefer) is to cover new sprouts with clear plastic cups or tops of water/soda bottles. The young sprouts are in the most danger of these predators before they reach about 3-4” tall.

DEALING WITH WEEDS:  Manage weeds carefully by hand.  Herbicides will stunt your dahlia's growth.  Use of garden tools may damage newly forming tubers.  

TIPS FOR MAXIMUM BLOOMS: Cut off the growing tip of your plants once they reach 12” or have 5 sets of leaves. This will force your dahlia to develop lateral shoots, which will lead to many more blooms during the season. Deadheading spent blooms will keep plants producing all season long. Cutting back to the main stems when you harvest flowers will signal the production of long new stems.