How Do I Keep My Apple Tree Healthy and Happy In Denver?

Fielding Tree - Apple Tree Denver

Are you ready to ‘give in to temptation’, as the Denver Post suggests, and add an apple tree or two to your lot? Find out why apple trees in Denver naturally thrive and how to help them keep their healthy beauty.

Apple Tree Varieties Commonly Found In Denver

You will be delighted to learn that there is a whole host of apple tree varieties that grow well in Denver’s climate. Whether you’re planting for looks or for harvest, check out this guide to help you make a decision. Already have an apple tree? See these descriptions to learn more about your trees unique history and characteristics.

Cox Orange

A classic English apple tree, the Cox Orange stands upright and has a habit of spreading. Its blushing yellow-orangish apples have a tasty hint of orange and mango. They are often desired for pies, sauces, and ciders. The medium-sized tree prefers loamy well-drained soil and grows well in Zones 4-8. The Cox Orange apple tree bears fruit in September but requires another pollinator such as the Golden Delicious for maximum success.

Red Delicious

This tree produces large red fruit with a sweet flavor, better for being allowed to ripen on the tree. Apples ripen in early October and keep well. You can expect it to yield full crops every other year unless properly thinned, it is somewhat slow to reach bearing age. Red Delicious apple trees are roughly 12 – 16’ height and spread. They grow best in Zone 4, with max. elevation of 8,500 ft.

Golden Delicious

This apple tree variety is known for being highly productive, yielding large yellow apples that are sweet and juicy with a hint of spice. One benefit of the Golden Delicious is that while it is self-pollinating, it is also one of the most effective pollinators for other apple trees. Its cold-hardy and heat-tolerant disposition make it suitable for Denver’s climate, and it generally grows in well in Zones 4-9. A mature tree grows to about 12 – 15′ tall and 12 – 15′ wide.


If your idea of an apple tree is one that drips with juicy red fruit and gives off that sweet apple aroma, you’re picturing the McIntosh. The cold-hardy tree prefers loamy soil and full sun and can grow at an impressive rate. The vibrantly red and sweet-tart tasting apples ripen in August and are excellent in sauce and ciders. This tree grows well in Zones 4-8 and will measure approximately 12 – 15′ tall x 12 – 15′ wide when fully mature.


The Jonathan apple tree is an American heirloom classic. The tree has parented several varieties throughout the years such as JonaMac, Jonafree, and Jonagold. Jonathan apples are crisp with a sweet-tart taste; a favorite for eating, baking, and cooking. The tree is typically 15 – 20’ height and spread. Grows well in Zone 4, max. elevation 8,500 ft.


Originating from Minnesota, the Wealthy apple tree is cold-hardy and pairs well for pollination with the Golden Delicious apple. Wealthy apples are medium-sized, tart and juicy yellow fruit, that ripen in September. A mature tree stands about 12 – 15′ tall x 12 – 15′ wide, and grows well in Zones 4-8.


Known as an “early bird”, the Lodi apple tree bears fruit and ripens in July! Lodi apples are shockingly bright green, with a tangy sour taste. Not only is the Lodi apple tree cold-hardy, but it is also highly resistant to powdery mildew which plagues many other fruit-bearing trees. The apple tree loves full sun and does well in Zones 4-8. At its maturity, the Lodi apple tree will measure 12 – 15′ tall X 12 – 15′ wide.


The Haralson tree bears a medium-sized, bright red winter apple that keeps well. This variety of apple tree is known to be especially hardy, making it a good choice for harsh conditions. They start to bear fruit younger than most apple trees, often in the first year! Haralson apples are tart and juicy tasting. The tree grows to approximately 12 – 16’ height and spread and grows well in Zone 3, max. elevation 8,500 ft.

Crab Apple

The fast-growing, gorgeous flowering Crab Apple is a Denver favorite. Their ability to pollinate makes them a perfect complement to other apple varieties. The fruit it produces is known as the culinary or wild apple and is small but juicy. The Crab Apple is sought-after because it is highly resistant to common tree diseases. Mature Crab Apples reach approximately 15 to 25 feet.

How To Plant Apple Trees Correctly

Colorado has a reputation for being ‘orchard country’, and the passionate growers at Montezuma Orchard Restoration Project want to keep it that way. If you’re planning on planting a fruit tree or two, follow their how-to guide for best success:

  • Trees are happiest in the ground, not in a pot, so plant immediately for best success.
  • Select a site with good soil drainage and good air flow. Avoid cold sinks.
  • Proper spacing is key for optimal development. Space standard apple trees 25-30 feet apart; dwarf 15 feet apart.
  • Dig hole 2-3 times wider than the root ball and just deep enough to allow graft union to be several inches above soil line to keep traits of rootstock.
  • Do not add hot compost, manure, or fertilizer to the planting hole. Backfill with native soil mixed with one third composted compost or quality potting soil.
  • Protect your tree from deer, rodents, and other mechanical damage with good fencing. Paint lower south trunk with plain white latex paint diluted with water to protect from sunscald.
  • Most apple trees require a pollinator to be planted in close proximity. Planting a single apple tree without a pollinator will result in lack of fruit.

Apple Tree Infestations and Diseases

Don’t let insects rob you of your delicious apples! Be on the lookout for these pests that prey on apple trees:


  • Pinhead-sized insects, ranging in color depending on the species. They congregate on stems and under leaves, sucking plant juices.
  • Symptoms: Leaf curl, yellowing, and death. Aphids leave behind “honeydew”, a sticky residue that will attract other unwanted insects. Honeydew can, in turn, cause unsightly sooty mold.
  • Control: Pesticide

Apple Maggot

  • Adults maggots look like a housefly, but smaller. In infancy, larvae are yellowish-white grubs. Apple maggots attack the fruit, laying eggs inside.
  • Symptoms: pinpoint-sized sting marks can be seen on the outside of the fruit. Eggs are laid under fruit skin and when larvae hatch they tunnel, making a groove-like pattern.
  • Control: Pesticide

Japanese Beetle

  • This easy to spot metallic-green beetle devours leaves down to the skeleton. Beetle grubs feed on turf roots before they are fully mature.
  • Symptoms: Adults are often seen in groups – large infestations can cause stunted growth and stress by skeletonizing a majority of the leaves.
  • Control: Pesticide, turf pest-control may help reduce grub populations.

Codling Moth

  • Adults are moths, gray with brown patches on wings. Larvae are worms, about 1-inch long. Pests and damage are similar to Oriental Fruit Moth. Traps are an option for luring moths.
  • Symptoms: Affected fruits will have holes from outside to core.
  • Control: Pesticide

Pests are a serious problem plaguing apple trees, but they are also prone to certain diseases. Learning about each can help you take steps to prevent them from affecting your trees!


  • Caused by a highly contagious bacteria, spread to different areas of the tree by wind, splashing rain or irrigation, birds, or insects. Develops during cool to warm wet weather.
  • Symptoms: On Flowers – Blossoms appear brown, withered and scorched. On Foliage – Dark brown or blackened leaves. Tips of branches curl, leaving a “Shepherd’s Hook” appearance. Twigs and branches die back. On Bark – Cankers may form, and bacterial ooze may appear.

Powdery Mildew

  • Caused by a fungus that overwinters in buds and emerges during humid, warm weather progressively throughout the growing season.
  • Symptoms: Whitish-gray powdery mold or felt like patches on buds, young leaves, and twigs. Leaves may crinkle and curl upward. New shoots are stunted.


  • Caused by a fungus that is spread by splashing rain or irrigation. Favors cool fall, wet weather.
  • Symptoms: New cankers appear on bark, they enlarge and become sunken orange to brown areas in the bark. Eventually, bark falls off exposing wood beneath. Brown spots appear on leaves and fruit, and fungus may infect the fruit.

Apple Tree Care And Treatment Options

The success of care and treatment depends on timely diagnosis and a proven plan of action. Fielding Tree & Shrub Care operates a simple four-step process for identifying the root cause of your apple trees problems and helping them recover to the fullest possible extent.

Treatment and Care for Disease

Tree trimming: Trimming is an effective way to remove areas with heavy infection. Trees sustain less damage and have more time to heal when they are trimmed during winter. They will incur less stress and are not at risk of becoming further infected. Once trimmed, infected trees should receive one or more chemical treatments.

Cambistat soil injection: Cambistat is a chemical growth regulator applied Spring-Fall. It lasts for 3 years. For trees infected with fire blight, it is used to minimize shoot growth, which will minimize the shoot blight stage of a fire blight infection.

Treat with Bacistat trunk injection: When your body has an infection, you take an antibiotic. Bacistat is an antibiotic for your trees! We typically apply Bacistat every year in April to May. We recommend treatment every 2 years to limit trunk damage. Bacistat will reduce only the twig stage, not the blossom stage of infection. Optimal results with Bacistat occur when applied prior to the onset of visual symptoms.

Treatment and Care for Infestation

Insecticide treatment options are available to effectively treat apple trees threatened by Aphids and other pests. Here are two types of treatment and delivery that we recommend for success:

Soil-root injection: this is a two-year protection program that protects against Aphids only. The industry-standard cost is $10 per inch of DBH (diameter of the tree at waist height).

Direct tree trunk injection to protect against infestation: This is three-year protection that protects against Japanese Beetles and Aphids. The industry-standard cost is $15 per inch of DBH. As mentioned earlier, a tree’s DBH is the diameter of the tree at waist height.

For best results, the right time of year to apply treatment for pest protection is in April and May. The timing has to do with the life cycle of the insects. There is a small window of opportunity to control the adults before any new eggs or larvae arrive.

Create a custom care plan for your apple trees! Team up with our Fielding team and get a  consultation on all the best practices today.