My Top Tips for Growing Dahlias - Zone 7b

Dahlias are stunning flowers that can brighten up any garden with their vibrant colors and intricate petal formations. If you live in zone 7b like me, with hot summers and likely heavy clay soil, growing dahlias can be a bit challenging. But fear not, with the right knowledge and care, you can successfully cultivate these beautiful blooms from early summer up until your first hard frost! Here are my top tips to help you achieve the most from your dahlias.

Choose the Right Varieties

When growing dahlias in here in zone 7b, it's essential to select varieties that are well-suited to the climate. Look for dahlia cultivars that are known for their heat tolerance and adaptability to heavy clay soil - some that thrive especially well here for me are Bloomquist Alan, Caitlin's Joy and Apricot Desire. One that does not enjoy it here? Pink Pearl - I recommend this one for colder areas.

When and Where to Plant

Once there is no danger of a freeze and soil temperatures are close to 50 degrees, it's time to plant! Before planting your tubers, it's worth the effort to prepare the soil properly. Heavy clay soil can be a challenge in my area, so amending it with organic matter like compost or peat moss helps improve drainage and encourage tuber production.

Plant your dahlia tubers about 5-6" deep in location that gets at least morning sun - in the hottest parts of the year, your dahlia plants might actually appreciate a little afternoon shade, though as long as they are well watered they can handle all day sunshine.

After planting, avoid watering your tubers until green spouts have reached the surface, as dahlia tubers are susceptible to rot especially during this time. Don't panic about a little rain, and if your soil is bone dry then a little water can help, but avoid any areas of standing water.

Support 

Many dahlias are tall plants, and most will need some sort of support. For individual plants, consider staking the ground while planting (to avoid accidentally skewering the tuber) or a large tomato cage. For a whole row, you can using baling twine and corral them, or Horotnova trellis netting for efficient support.

Watering and Mulching

After sprouts have emerged, it's safe to water! As the growing season progresses, particularly in the hot summers we experience in Virginia, dahlias will require regular watering to thrive. Water deeply and consistently a few times a week, and more often during during especially hot + dry spells, to help the plants direct moisture to their large floppy leaves. Mulching around the base of the plants can help retain moisture and regulate soil temperature as well.

Cut Flowers & Deadheading

To encourage continuous blooming and avoid pests like thrips, it's important to harvest and deadhead your dahlia blooms regularly. Cutting deeply into the plant when harvesting blooms encourages your dahlia to produce offshoots, leading to more gorgeous blooms. Removing any faded blooms promptly helps to redirect energy into new growth. Additionally, stripping the bottom 12" of leaves of mature dahlia plants can help improve air circulation and help prevent powdery mildew in humid conditions.

Fertilizing

Feed your dahlia plants with a balanced fertilizer throughout the growing season to promote healthy foliage and abundant blooms. Dahlias are not heavy feeders, so a few times a season in relatively healthy soil should be sufficient. 

With a little care and attention, your dahlias will thrive and reward you with their beauty throughout the growing season!