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Understanding Chill Hours

Understanding Chill Hours

Any North Florida resident who has tried their hand at growing apples, peaches, or plums may occasionally find themselves frustrated by a year (or two…or three) with a poor or nonexistent harvest. What has gone wrong? Are the trees getting a disease? Were they not fertilized properly?

It may be that the tree owner has done everything correctly, but the weather is actually to blame. The answer to “what has gone wrong?” may lie with a concept called “chill hours”. Plants that are adapted to living in colder climates need some way to figure out when the winter is over. If a plant starts blooming too early, it’s likely that a frost will come along and knock out this year’s flowers. No flowers, no fruit. For a plant, this means no little baby plants this year to keep the species going. To avoid this, some plants have figured out a way to detect and keep track of how cold it’s been in a particular year. When enough hours of cold weather have accumulated, that’s usually a safe signal that spring must be near. This means it’s time to blossom when the weather next warms up.

Usually. Different varieties of plants are adapted to blossom at different times of year, depending on the average amount of cold weather the area they live in gets each year. A plant from a colder climate might not start growing flowers until it has detected 1,000 hours of cold…or more! Given that the temperature range that counts as a chill hour is around 32-45 degrees Fahrenheit, you might correctly guess that such varieties will NOT do well in Florida. In north Florida, we receive somewhere from 500-700 chill hours each year. This winter (as of February, 2023), we have received 479 chill hours in Walton County.

Chill hour total for Walton County, as of Feb 1, 2023

That’s not a lot, and we may not get much more weather that plants recognize as cold enough to count. Apple growers with varieties that need even as few as 500 chill hours may not be making many pies this year. So what can be done?

First, temper your expectations. Understand that even though we may get the occasional hard freeze, it may not count any more toward the chill hour requirement than temperatures just above freezing. Then, when it warms up the following week, those 70 degree temperatures may actually set BACK the chill hour clock for some plants.

Second, choose varieties that require few chill hours in the first place. A ‘Honeycrisp’ apple, needing 800-1000 chill hours each year, is probably never going to produce fruit in the panhandle of Florida. Other apple varieties might, though! Try varieties such as ‘Anna’ (which needs only 300 chill hours), ‘Dorsett Golden’ (250 hours), or ‘Tropic Sweet’ (300 hours). For peaches, try varieties like ‘GulfAtlas’, ‘Gulfcrimson’, or ‘Gulfsnow’ (400 hours each).

Third, consider learning to love other types of fresh fruit. Persimmons, figs, kumquats, and loquats may not show up very often in treasured family recipes, but they can offer a tasty alternative to plants that simply might not be well adapted to our climate.

Peaches are popular, but they may not produce fruit every year!

For more information, try these links:

To calculate how many chill hours your specific area has received, check out the tool at agroclimate.org.

For information on apples, peaches, plums, blueberries, or other fruits, try our EDIS publications on each.

You can also, of course, contact your local Extension office for help as well!

Evan Anderson

Walton County Horticulture Agent

Pecan Trees in the Home Landscape

Pecan Trees in the Home Landscape

Pecans are a flavorful and nutritious nut and an essential component of a southerner’s diet. The trees also provide nice shade and intense fall color to landscapes throughout the south. However, not all pecan tree varieties are suited for the Florida panhandle. There are a number of things you should consider before planting a pecan tree.

Pecan tree grove in North Florida. UF/IFAS Photo: Thomas Wright.

Site Selection – Pecan trees are native to the river valleys of North America. They perform best in deep, fertile, well-drained soils. The key is that the soil is well-drained. Pecan trees will not do well in soils that hold a lot of water and do not drain quickly. Pecan trees also need space to grow. Trees should be planted at least sixty feet apart and at least sixty feet from other large trees and structures. This will allow adequate light for the trees produce a good crop.

Disease Resistance – Pecan scab is the most detrimental pecan disease in the southeast. Trees advertised as scab resistant in the past may have become more susceptible over time. A few varieties that seem to be available at tree farms and have maintained their scab resistance are ‘Caddo’, ‘Elliot’, ‘Lakota’, and ‘Gafford’. Newer varieties that currently have good scab resistance are ‘Avalon’, ‘Huffman’, and ‘Whiddon’. However, these newer varieties may be more difficult to find at nurseries and farm stores.

Pollination – Pecan trees produce both female and male flowers on the same tree. Trees are split into two pollination groups. Type I pollinators produce mature pollen before their female flowers are receptive and Type II trees produce receptive female flowers before their pollen is mature. Timing of flower maturity may change with tree age, but it is a good practice to plant a Type I tree along with a Type II tree to ensure a good crop in each tree. A pollination compatibility chart can be found at UGA Pecan Compatibility Chart.

Planting – Commercially, pecan trees are most commonly planted as bare-root transplants, but container-grown trees can also be used. Bare-root trees are usually cheaper and more readily available. They should be planted while dormant, between December and March and should be planted the day they are delivered. If the root system looks dry, soak the trees in water for a few hours before planting. Container-grown trees can be planted any time of the year, but they have the best chance of survival if planted during dormancy. Trees should be planted at the depth they stood at the nursery or the depth they were planted in a container. Planting holes should be at least 18 inches wide and only native soil should be used to fill in the hole. The main causes of death in young trees are planting too deep and inadequate moisture during the first two years following planting.

Pecan trees provide focal points in the landscape and a tasty treat for the belly. For more information on growing pecans and the benefits of pecans please see these Pecan Publications from the University of Georgia.

Small Landscape Spaces and Trees to Consider!

Small Landscape Spaces and Trees to Consider!

There are many considerations to make when landscaping with small trees (under 20 feet) in the landscape that are not suitable for large trees.  Some of the trees discussed can at times be considered large shrubs depending on definitions and opinions.  For the purpose of this article, if it reaches 15 to 20 feet consider it a tree.

Choosing small trees for the right setting involves a number of reasons that could include the need for more privacy from other homes, use as a sound barrier from busy roads, hiding your utility area of the landscape or something unattractive nearby and making sure power lines are not obstructed.  Other considerations might include soil types, drainage and holding capacity of the soils, irrigation needs, rate of plant growth and maturity height at 20 feet.  Below are a few to consider for the Panhandle of Florida.

Little Gem Magnolia (Magnolia grandiflora ‘Little Gem’) and Teddy Bear Magnolia (M. grandiflora ‘Teddy Bear’) are strong hardy plants once established (within the first 6 months to a year).  Both are evergreen with dark green foliage.  The ‘Little Gem’ will grow to 20 feet tall by 15 to 18 feet wide.  As it matures it tends to become more open and less dense which adds a nice character to show parts of the lower limbs.  The ‘Teddy Bear’ will grow to 18 to 20 feet tall but at an even slower rate of maturity to 12 to 15 feet wide while maintaining its density of foliage from bottom to top.  It may take a little work to locate the ‘Teddy Bear’ Magnolia.

Photo courtesy: Stephen Greer Teddy Bear Magnolia (Small compact grower)

Several hollies to consider would include the Cassine Holly ‘Tensaw’ (Ilex cassine ‘Tensaw’) and American Holly (Ilex opaca).  Both are evergreen and produce red berries during the fall that are bird favorites.  They have similar heights of 15 to 20 feet and widths of 10 to 12 feet.  Pruning can assist in shaping and slowing these measurements, but keep in mind this will change the look of the tree and create a more formal plant presentation.

Photo courtesy: Stephen Greer Cassine Holly ‘Tensaw’

The Fringe Tree (Chionanthus virginica) has been a popular tree southeast U.S. for many years.  It brings a bright spot to the landscape with white flower panicles that cover the tree in mid to late spring depending on location.  For a full color effect, plant it with an evergreen hedge behind it.  This oval deciduous tree will grow to 12 to 20 by 10 to 15 wide.  The dark blue fruit appears in the fall and serves as good bird food source.  This fruit is usually hidden behind the foliage.  There might even be a nice yellow leaf change in the fall if temperatures and weather allow.

There are so many more trees to discuss and limited space to discuss them.  Visit your local UF IFAS Extension office for additional assistance or visit the UF IFAS online for additional articles.

 

Plenty of Summer Gardening and Landscape Activities Ahead

Plenty of Summer Gardening and Landscape Activities Ahead

A watering tin and gardening gloves at a home garden.

Spending time gardening in the summer months can be difficult, especially in the Florida Panhandle. The brutally high temperatures and sometimes intensive humidity can make gardening seem unbearable. However, for those brave outdoor enthusiasts, there are always things to do around the homestead when it comes to vegetable gardening, landscape shrubs and lawn care.

Warm season vegetable gardening at this point becomes an uphill battle for some crops, with this being peak time for both insect and disease problems to occur. However, if you planted early enough, much of your harvest is probably in the safe zone. Scouting is key to prevent any major pest damage. Be sure to scout several times a week during these hot, summer days.

Shifting gears, the warm season is a good time to take extra special care of plants such as, azaleas and camellias, while they are establishing flower buds for the next bloom. A lack of water, fertilizer and pest detection and prevention can all certainly play a role in the following season’s flower production. Summer annuals always provide quick and easy color. Remember to feed established annuals with a complete fertilizer and remove faded blooms along the way. Water annuals well during hot, dry periods and control major annual pests to insure good production.

Finally, lawn maintenance is a need for many homeowners during this time of year. Almost all highly successful herbicides are no longer recommended at this point, as many will burn the turfgrass at temperatures above 80 degrees Fahrenheit. Depending on the weed pest and type of turfgrass, most likely the best way to control weeds in your lawn is to wait until cooler fall temperature to treat. Keeping good cultural practices this time of year will help in maintaining a healthy lawn and reduce pest pressure. Be sure to water lawns thoroughly when needed by applying one to three quarters of an inch of water weekly, depending on rainfall. Be sure to keep in mind mower height/frequency, as this is critical in keeping your lawn healthy. As stated in the “Mowing Your Florida Lawn” UF/IFAS EDIS publication, mow often enough so that no more than 1/3 of the blade height is removed per mowing. For example, if your St. Augustinegrass lawn is mowed at a height of 4 inches, it should be mowed before it grows to a height above 6 inches. It is important to always leave as much leaf surface as possible so that photosynthesis can occur, particularly in a grass that is subject to environmental or site stresses.

Unfortunately, it is chinch bug time again. Chinch bugs are prone to feed on St. Augustine lawns during hot, dry weather and may cause serious damage if not controlled. Damage usually occurs as a patch with a brown, dead center and yellowish margin. It seems chinch bugs get the blame, and often unjustly, for everything. Consult with your local county extension office to be sure the damage is not due to other reasons.

For more information, please contact your local county extension office.

Supporting information for this article can be found in the UF/IFAS EDIS publications/websites below:

Florida Vegetable Gardening Guide: https://edis.ifas.ufl.edu/publication/VH021

North Florida Gardening Calendar: https://edis.ifas.ufl.edu/publication/ep451#SECTION_7

Lawn Maintenance: https://edis.ifas.ufl.edu/entity/topic/lawn_care

Mowing Your Florida Lawn: https://edis.ifas.ufl.edu/publication/LH028

UF/IFAS Extension is an Equal Opportunity Institution.

Summer Lawn Weed Control

Summer Lawn Weed Control

Summer weeds are here.  What should we do?  As we are officially into summer you are probably noticing many of those summer weeds poking through your lawn by now, or perhaps they have taken over completely. Do not give up, there is still hope for a beautiful lawn with less weeds.

The first thing is to be able to identify the weed and identify the type of grass.  Now you may be thinking that is impossible and maybe you are thinking why it is important to identify those?  The answer to that question is simply that not all chemicals are the same and understanding what you have and the best time of year to spray for that will save you both time and money.  Weeds fall into three categories: Broadleaf, Grass, and Sedge.  Remember, a weed could be any plant that is out of place.  Weeds will compete with desirable plants for nutrients, water, light, and space.

Once you understand what category your weed falls into the next step is to know the life cycle.  For example, winter annuals will die out naturally as the temperatures increase and a chemical may not be needed.  There are weeds that complete their cycle in one year (winter and summer weeds) and there are weeds that complete their cycle in two years (biennials).  A biennial has vegetative growth the first year and will flower and die the second year, examples are Carolina false dandelion, Oldfield toadflax, and cudweed.

Next you will want to identify the indicator species.  What does this mean?  It means that there are some weeds that grow well in compacted soils like goosegrass and annual bluegrass.  Others like it very wet (poor drainage) such as dollar weed, sedges and torpedo grass.  While there are weeds such as sandbur and rustweed that like it very dry and sandy.  Knowing this can help you do preventative weed control.  Grow a healthy turf starting with the right selection, proper cultural practices, pest control, traffic control, and sanitation.

When you are faced with the decision to use chemicals to combat your lawn weeds there are a few things to know.  There are selective herbicides that control certain species without hurting others (your lawn) and there are nonselective herbicides that control green plants regardless of species.  Also, there are contact herbicides, which are exactly how their name implies.  They affect only the portion of the plant that the herbicide touches.  There are also systemic herbicides which are translocated through plant’s vascular system.

The best time to spray herbicides is when the weeds are actively growing, young and not drought stressed or producing seed heads.  A table below shows the active ingredients best for the three categories of weeds.

Broadleaf Weeds Grassy Weeds Sedge Weeds
Centipede 2-4D + Dicamba +MCPP   Thiencarbazone+iodosulfuron + dicamba Sethoxydim Halosulfuron-methy, Sulfentrazone, Imazaquin, Bentazon,
Bermuda 2-4D + Dicamba +MCPP   Thiencarbazone+iodosulfuron + dicamba Quinclorac Halosulfuron-methy, Sulfentrazone, Imazaquin, Bentazon,
Zoysia 2-4D + Dicamba +MCPP   Thiencarbazone+iodosulfuron + dicamba Fluazifop, Quinclorac Halosulfuron-methy, Sulfentrazone, Imazaquin, Bentazon,
St. Augustine 2-4D + Dicamba +MCPP   Thiencarbazone+iodosulfuron + dicamba None Halosulfuron-methy, Sulfentrazone, Imazaquin, Bentazon,
**temperature restrictions

The key is to identify the type of turf you have and the type of weeds you have in the lawn.  Further, look into if there are any factors that can be adjusted that might be causing the excess of weeds.  And lastly, make sure you are using the right method, chemical, and timing for control.  For more information on summer weeds and lawns, please contact your local county extension office.

Information for this article can be found Managing Weeds in Warm Season Lawns | Home & Garden Information Center (clemson.edu)