Gardening Q & A

Read our Q & A postings with Keith Funk answering common Colorado gardening questions here. You can also hear him on the Garden Wise Radio Show on Legends 810AM, every Saturday morning from 7-9. Special thanks to Kelly Grummons who answered these prior to 2024.

Have gardening questions? Click here to send us your question on our contact form. Use our search window below to find Colorado gardening questions & topics.

Dec 21 min read

How to Grow Paperwhites

Q: What’s the best way to grow Paperwhite Narcissus? A: One of the most popular methods is to choose a water tight, fairly shallow...

Dec 21 min read

Overwintering Potted Japanese Maples

Q: I have a Japanese Maple in a large pot. I understand it is risky trying to overwinter potted trees, shrubs and perennials in their...

Dec 21 min read

Online Seed Sources

Q: I’m looking for odd and interesting vegetables, rock garden plants, and perennials, and I feel like I’ve exhausted my local retailers....

Dec 22 min read

Voles in Lawn?

Q. Once the snow melted from that last big storm I notice mounds of soil, shallow burrows and meandering, shallow runways in the lawn...

Nov 11 min read

Autumn Blaze Maple Tree Care

Q. I planted an Autumn Blaze Maple last year. Do I need to wrap the trunk again this year? A. Young, thin barked trees like maples, ash,...

Nov 11 min read

What should I do with my Amaryllis this time of year?

A. I bring mine indoors at the very last minute before the first predicted frost. I feel like they benefit from the cool nights...

Nov 11 min read

Care of Streptocarpus Plants

Q. I’ve been trying to grow Streptocarpus, aka Cape Primrose. They keep dying on me but I’m told they are easy. What am I doing wrong?...

Nov 11 min read

Watering Bulbs in Winter

Q. I planted lots of spring flowering bulbs this fall including tulips, daffodils and crocus. I watered them in thoroughly after...

Nov 11 min read

Winter Watering in Colorado

Q: I planted quite a few perennials, some shrubs and a tree this year. Should I water them during the winter and how often? A. Our...

Sep 301 min read

Drainage Rocks for Potted Plants?

Q: When transplanting potted plants, is it a good idea to add a layer of gravel at the bottom of the pot to ensure good drainage? A:...

Sep 301 min read

Storing Dahlias, Cannas and Begonias

Q: How do I store tender bulbs like dahlias, cannas and begonias for next year? A: In a dry climate like Colorado, storing tender bulbs...

Sep 301 min read

When to prune back shrubs like butterfly bush, roses, and bluemist spirea?

Q: Can I prune back shrubs like butterfly bush, roses, and bluemist spirea in the fall or should I wait until spring? What about clematis...

Sep 301 min read

Do I cut my perennial flowers and grasses for winter?

Q: Do I cut my perennial flowers and ornamental grasses back in the fall or the spring? A: In general, it doesn’t really matter to the...

Sep 61 min read

Pine Trees Losing Needles?

Q: I’ve noticed my pine trees are losing yellow needles. Is this a symptom of a problem? A: Fall needle drop in conifers, where trees...

Sep 61 min read

Should you aerate your lawn in the fall?

Q: It’s been a few years since I aerated my lawn. Is fall a good time? A: Fall lawn aeration is an important task for maintaining a...

Sep 61 min read

Planting Trees in Fall

Q: I’ve noticed local nurseries have put their trees and shrubs and perennials on sale. Is it okay to plant this time of year? Fall...

Sep 61 min read

Bringing Plants Inside for Winter

Q: I have a hibiscus, spider plant, coleus and several other tropical plants that have spent the summer outdoors. Do I need to do...

Jul 282 min read

What to do about powdery mildew

Q: I’m seeing that white, powdery mildew developing on the leaves of my peonies, garden phlox, lilacs, roses, squash. Should they be...

Jul 272 min read

How to check sprinkler output?

Q: How do I measure how much water my sprinklers are putting down each time I water? A: Unless you know how much water in inches you...

Jul 272 min read

Q: How much should I be watering this time of year?

A: Watering effectively during the heat of summer can be tricky, especially with new plants. My first response is to water deeply and...

Jul 271 min read

Colorado Fall Vegetable Garden

Q: What vegetables are good choices for a fall harvest and when should they be planted? A: Our average first frost date in Denver is...

Jul 61 min read

Is it too late to plant now that it’s hot?

Q: Is it too late to plant now that it’s hot? A: Planting during the heat of summer is perfectly fine. It just takes some extra...

Jun 281 min read

Should I remove flower heads from garlic?

Q: My garlic is sending up what look like flower spikes. Do I leave them or cut them off? A: Those are the flowering scapes of the...

Jun 281 min read

What is eating circles in my rose leaves?

Q: Something is removing perfectly circular sections from the edges of my rose leaves. Is this a problem I need to treat for? Will it...

Jun 282 min read

Pruning Dwarf Conifer Tree

Q: I planted what was supposed to be a dwarf conifer many years ago & it's now about 10' tall & so exuberant that's taken over the...

Jun 281 min read

Will any verbascums rebloom if you cut off the dead flower stalks?

Q: Will any verbascums rebloom if you cut off the dead flower stalks? A: Yes. The smaller growing varieties of perennial verbascums...

Jun 281 min read

Brown sunken spots on the bottoms of my tomatoes

Q: What is causing the brown sunken spots on the bottoms of my tomatoes? Is it a disease? Can I still eat them? A: What you are...

May 311 min read

What to do with spring flowers after they bloom?

What should I do with my spring flowering perennials that are done blooming? They are looking a little messy. A: Remove spent flower...

May 311 min read

Should I test my soil every year?

A: I purchased an inexpensive soil test kit from my local independent garden center to test my pH, Nitrogen, Phosphorus and Potassium...

May 311 min read

How often should I feed the plants in my landscape?

A: If it’s been more than 3 or 4 weeks since you last fed your gardens, it’s time to do it again. Our Colorado soils are notoriously low...

May 311 min read

Broken Branches

The wind storms we had this year has caused some branch breakage in my Autumn Blaze Maple. When is the best time to prune it out? A:...

May 311 min read

Thinning Fruit Trees

My fruit trees are loaded with fruit this year. Is it a good idea to thin some of it out? A: Those of us with fruit trees are...

Apr 231 min read

Should I feed my lawn in May?

A: If it has been more than four weeks since the lawn was last fertilized, apply slow release, high nitrogen lawn food this month. It is...

Apr 231 min read

My tall growing flowers like peonies, dahlias, hollyhocks, gladiolus, lilies and salvia have a tendency to flop over by mid summer. How can I stop this from happening?

Trying to stake them after this happens makes them look weird and unnatural. A: Stake tall growing flowers that are prone to water and...

Apr 231 min read

When can I set out my tropical houseplants that have been indoors all winter?

A: Houseplants scheduled to spend the summer outdoors should be kept inside until late-May or early-June when night temperatures stay...

Apr 231 min read

When is it safe to plant potted roses out in the garden?

A: While there are no guarantees, mid-May is typically a safe bet but be prepared to cover newly planted, greenhouse grown roses if the...

Apr 231 min read

I have a garden pond with hardy water lilies that stay out all year round. I’d like to add some tropical night blooming water lilies this year. How warm does the water need to be?

A: When pond water temperature reaches 70F. it's safe to set out tropical water lilies, water hyacinths, water lettuce, callas, water...

Apr 231 min read

How soon can I start direct sowing flower seeds in the garden?

By Keith Funk A: Seed tender annuals like marigolds, zinnias, and cosmos directly into the garden by mid-May. Most all annual...

Apr 231 min read

When is it safe to plant out warm season veggies like squash, peppers and tomatoes?

By Keith Funk A: April and May are excellent months for controlling Japanese Beetle grubs that overwintered from last fall. My personal...

Apr 41 min read

When should grub killer be applied to control Japanese Beetles?

By Keith Funk A: April and May are excellent months for controlling Japanese Beetle grubs that overwintered from last fall. My personal...

Apr 41 min read

When and how often should I feed my perennials?

By Keith Funk A: My first application of plant food on my perennials is in early April. I prefer a granular fertilizer with an analysis...

Apr 41 min read

Are there any flowers I can plant outside in April for some extra spring color?

By Keith Funk A: Yes. There are several cold-tolerant annuals and perennials that will flower beautifully during our cool/cold spring...

Apr 41 min read

What should I do when my early spring flowering bulbs are finished blooming?

By Keith Funk A: Remove spent flowers but keep all the foliage to rebuild the bulb’s strength to rebloom again next year. Show them...

Apr 41 min read

When do I prune my flowering shrubs?

By Keith Funk A: Shrubs that flower before Memorial Day can be pruned immediately after flowering. These shrubs include lilac,...

Apr 41 min read

When is the best time to lift and divide perennials?

By Keith Funk A: That depends on the plant. Most perennials can be lifted and divided now, in early spring as you see new growth...

Apr 41 min read

When should I prune my raspberries?

A: Now. For fall-bearing raspberries like Fall Gold, cut all canes to within 6-8” of the ground. This type of raspberry produces fruits...

Mar 131 min read

When should we divide our irises

When should we divide our irises? I have several huge clumps that don’t bloom as well as they used to. A: Irises (Tall-bearded,...

Mar 21 min read

Harvesting Overwintered Root Vegetables

Q: We still have a lot of root vegetables left in the garden from last year. They are showing new growth. When can we harvest them? I...

Mar 12 min read

Do Aphids Overwinter?

Q: I grow kale in a raised bed. Last year it got covered (smothered) in aphids. After using Neem oil spray on it for a month, I decided...

Feb 121 min read

Beheaded Beans

Q: I planted a bunch of bean seeds July 1st and had very poor germination though I watered 2X a day. One of the four that did sprout was...