Fall Planting the Colorado Gardener’s Guide

Fall Planting – what to plant

There are two significant types of fall planting: plants that bloom and thrive during the fall and plants that will be the first to emerge in the spring.

Fall gardening can be as vibrant and rewarding as spring and summer gardening, though it may require more patience.  It’s hard to say goodbye to the zinnias, roses, and sunflowers of the summer season or the tomatoes and zucchini of the vegetable garden. But just because the weather is cooling down doesn’t mean your green thumb needs to go into hibernation—more on Colorado Gardening.

Planting for Fall

When it comes to flowers and annuals that look beautiful in the fall and can survive dropping temperatures, chrysanthemums are possibly the most popular. With their fiery colors and cold-hardy temperaments, mums look lovely and festive and last a long time. Other gorgeous fall annuals, great for garden beds and containers, include coneflowers, pansies, flowering kale, black-eyed Susans, sweet alyssum, and ornamental peppers. The bright colors will liven up your balcony, porch, or garden beds all season.

Fall is also a great time to squeeze more life out of your vegetable garden. Cold-hardy vegetables include lettuce, peas, cabbage, spinach, kale, cilantro, beets, radishes, cauliflower, and broccoli. All these vegetables make a lovely fall garden, but it’s best to start in late summer. However, if you’re getting to it now, you’ll do best by purchasing seedlings from a greenhouse or planting them in containers you can bring inside when the weather dips below freezing.

Planting for Spring

If you’ve ever looked at a neighbor’s garden in March and thought, ‘How the heck did they get so many beautiful flowers in the ground this early?’ then you’ve probably seen the work of a fall gardener. Fall is the perfect time to plant bulbs that will come up in the spring, like tulips, irises, daffodils, crocuses, grape hyacinths, allium, scilla, snowdrops, and other early spring blooms. Consider a fall planting of perennials like salvia, dianthus, and hostas or shrub plants like hydrangeas or peonies. When you plant these in the fall, you’re giving the root systems time to develop and grow strong enough to survive the winter and provide you with a more robust period of growth (and flowering!) than if you planted them in the spring.

Visit Colorado’s Botanical Gardens for a real flowering treat in the spring/summer.

You can also plant some root veggies in the fall, such as garlic, carrots, asparagus, leafy greens, or onions. Putting them in the ground early means you’ll be able to take advantage of spring as soon as it hits and have a fantastic early harvest that is just as delicious as it is satisfying.

When to Plant in the Fall

There’s no perfect date for fall planting in Colorado because the climate at lower elevations differs drastically from that at higher elevations, and the season can vary dramatically from place to place.

Plant spring perennials at least six weeks before the ground freezes. This will give the plants enough time to establish a robust root system before they go into dormancy for the winter.  When it comes to bulbs, six weeks before the ground freezes is also a good rule of thumb, though some bulbs can handle being planted a bit later. In general, plan on putting bulbs in the ground when nighttime temperatures start dropping to between 40 and 50 degrees—depending on where you live, this could be August or it could be mid-October. You want to give the bulbs enough time before the ground freezes to develop some roots but not so much growth opportunity that they think it’s time to pop up out of the ground before winter hits.

How to Plant Bulbs 

We plant spring bulbs in the fall because these guys need a cold period to bloom in the spring. Nothing can spark the biochemical process that makes bulbs flower without this cold period. (These aren’t to be confused with tender summer bulbs like dahlias, lilies, gladiolus, and elephant ears, which can be planted in the spring for summer bloom and aren’t tolerant of colder temperatures.)

Try to purchase your bulbs as close to growing time as possible, but if you buy them early, you can store them in a dark, dry place or even in your refrigerator until it’s time to plant them.

When planting bulbs, an easy rule to remember is that they need to be planted about 2-3 times as deep as the length of the bulb itself. Make sure to put them where they will receive lots of sun and good drainage, and plant them pointy-side up, which will help the roots grow downward. If you’re unsure which side is the pointy end, plant the bulb on its side—the roots will probably figure themselves out—bulbs like well-drained soil that is loamy or slightly sandy. Cover the bulbs with soil and mulch, and water regularly until it gets cold.

Pro tips: Many bulbs don’t flower for long, so you can plant them in clusters if you plan. Put some early-flowering varieties in the same areas as late-flowering varieties or some taller tulips that flower later in front of shorter daffodils that flower earlier. This way, you’ll get the most visual bang for your buck without doing as much work.

Helping Plants Survive the Winter

Most flowers you plant in the fall don’t need much help from you, and if you over-coddle them or over-fertilize them, you could risk hurting the plant rather than helping it. If you live in a place where the winters are cold and long—up at higher elevations, for example—you can do a few things to help give your garden the best chances of thriving through the winter. Insulating the ground with mulch or compost will provide a bit of extra warmth and shelter for your plants and their delicate roots during the cold months, and if you live somewhere with lots of critters like deer, you might also want to consider something a little more protective, like mesh, chicken wire, or bulb cages. Also, watering your garden regularly before the ground freezes can help those roots grow strong and deep, but once the cold really starts, it’s best to let nature do its thing without any interference from you.

The Benefits of Fall Planting

Fall planting is the ultimate form of gardening for planners. It takes patience because the results won’t be seen right away, but as soon as spring hits, you’ll have a garden that will make all your neighbors jealous. If you plan it right, the time you spend planning your garden in the fall can lead to perennial blooms year after year for a truly gorgeous garden that will make you smile every spring.

By Emily Krempholtz