I don’t know any gardeners who casually grow dahlias. Their fireworks riot of color has an intoxicating effect. You may start with one dahlia, but before you know it you have torn out the roses, planted five hundred tubers and (in at least one documented case), transformed an old tennis court into a fenced garden to make room for more flowers.
But dahlia devotees pay a price. In cold climates (read: the ground freezes), dahlia tubers need to come out of the garden if they are to survive the winter. Dig them up and store them in the basement, garage, or a protected shed—and dahlias will reward you next summer with more enormous puffball blooms. It’s worth the effort.
Here are step-by-step instructions for how to store dahlia tubers in winter:
Photography by Mimi Giboin for Gardenista.
1. Wait for the first frost.
Above: Dahlias will bloom well into autumn if you deadhead them to coax more flowers. But frost will put a stop to that.
Flowers will wilt, leaves will blacken, and dahlia stems will die back after the first frost; you’ll know it’s time to store tubers in a safe spot for the winter.
2. Dig up dahlias.
Above: Be careful when you dig up dahlias because, as you can see, a single plant may have a clump of connected tubers and a far-reaching root system.
To dig up, first cut back stalks to a height of 2 to 3 inches. Then start about a foot away from the plant, loosening soil all around the roots and digging deep enough (18 to 24 inches) to get your shovel underneath the dahlia to tease it out of the ground.
Dig up one clump of tubers at a time and be gentle; the tubers are fragile and break apart easily.
3. Rinse off dirt.
Above: Use a gentle spray from a garden hose to wash off soil so you can see the tubers and root system of individual clumps of dahlias.
While spring may seem like a long way away—summer doesn’t even technically end until September 22—there are things you can do over the next month or so to prepare your garden for a successful spring.
Fall is a great time to amend the soil and put down compost (better, some argue, than spring). This is particularly helpful if your soil is heavy and compacted. Work it into the soil with a garden or broad fork, gently. This is best done while plants are still standing and you can identify where they are to avoid damaging them. For more on soil amendments in autumn, see Fall Fertilizing: How to Prepare Your Lawn, Shrubs, Trees, and Perennials for a Restorative Winter Sleep.
2. Plant, plant, plant.
Now’s the time to revamp your garden or just fill in the holes. The cooler temperatures mean less evaporation. Transplant shock happens when the fine, hair-like feeder roots are damaged during the transplant process. Less transpiration means less need for water from the roots and less stress for the plants. You will still need to water your new plants, just less than if you planted them in the heat of summer. Additionally, the cooler air temperatures and warmer soil support new root growth. See Fall Gardening 101: Autumn Can Be an Ideal Time to Plant for more on this topic.
Seed saving is all about prepping your garden for spring. By saving seeds you are helping your garden grow for next year. Literally. While seed saving can be specific to the plant, in general you should wait until the seed heads and pods are completely dry. Some will rattle like baptisia, others will fly away on the slightest of breezes, like milkweed. Some seeds—many native plants—may need cold stratification and stored in the refrigerator for a period of time. Do your research and store your seed properly. Mark your calendar now for when to sow in the spring.
6. Plan for support.
Everyone knows that a peony will flop over with its massive blooms unless you surround the plant with a peony ring before it gets too big. But they are not the only ones in need of support. Joe pye weed, Sedum ‘Autumn Joy’, any number of taller perennials that bloom profusely, need support. Find those splayed perennials now and make a list with locations for next year so you’ll be ready to prop them up before they get too large.
Take away and trash any diseased plant material. Do not compost them because home compost piles may not reach the proper temperature to kill pathogens. Leave the leaves, though. They provide food for your plants, keep moisture in the soil, and provide shelter for pollinators and insects that help with pest control. And resist the urge to “tidy” up perennials and grasses by cutting them back. Leave at least some of them intact (including the seed heads) for overwintering creatures in need of food and shelter. For more on this topic, see 6 Nature-Based Garden Tasks for Fall.
This is part of a series with Perfect Earth Project, a nonprofit dedicated to toxic-free, nature-based gardening.
“A seed contains the past and the future at the same time,” said the poet and writer Ross Gay, in a recent interview in The Nation. Hilltop Hanover Farm, a Perfect Earth Project partner in New York’s Westchester County, understands this firsthand. Through their native plant seed initiative, they are preserving the past by cultivating the plants that have been growing on this land for millennia, while sowing a resilient and biodiverse future.
Native plants have become a buzzy topic in recent years, and not just for their good looks. People are beginning to understand how vital they are to a healthy and robust environment. But to provide the greatest benefit, restore depleted lands, and give insects, birds, and other animals the food and habitat they really need, we must look beyond the plants that are native simply to North America, and be sure to include species local to our specific regions.
Above: Showy goldenrod (Solidago speciosa) is one of the keystone species Hilltop Hanover grows in production. This fall-blooming beauty can reach six-feet in height and is a favorite of birds, who love to eat their seeds.
Hilltop Hanover is doing just that, led in their work by Adam Choper, the farm’s director, and Emily Rauch, the native plant programs manager. The farm is part of a new group called Eco 59, a seed collective formed to grow and collect valuable local natives of the Northeastern coastal zone (ecoregion 59) for conservation and restoration in Westchester County, and to preserve them for the future through the Northeast Native Seed Network. “We’re working together as a collective to figure out supply chain issues, find out where the gaps are, and find a way to get the seed out into the world,” says Choper.
Above: The farm crew helps harvests seeds of coastal plain Joe-Pye weed (Eutrochium dubium) by hand.
