by Beth Bolles | Feb 14, 2017
Arapaho blackberry has chill requirements that match those received in our area. Photo by Beth Bolles, UF IFAS Extension
Many of us are enjoying warmer temperatures this winter, but many deciduous fruit crops really need cold temperatures in order to break dormancy for the year. In areas that experience cold temperatures, plants have evolved the ability to survive by slowing growth and protecting sensitive tissues by going dormant. In order to break out of dormancy and begin growth again, plants experience an amount of chill hours (temps between 32 and 45 degrees F) that is suitable for specific areas. In our area, we normally range between 400 and 600 chills hours.
If we choose a fruit plant whose chill requirements match the amount of chill in our area, the plant will generally resume growth when it is safe for buds and tender tissues to develop. If we choose a plant with chill requirements higher than the amount our area receives, then the plant is not signaled to break dormancy and we end up with very sparse growth and no fruit.
So far in the winter of 2016-17, some areas have not received ‘normal’ amounts of chilling temperatures. Common fruit like apple, peach, some blueberries, and certain selections of blackberries may be affected by this by not breaking out of dormancy. This can impact your flower and fruit formation. For commercial growers, it can impact the amount of fruit available and even fruit prices at markets.
Since fruit trees are an investment of time and money, these are not plants that can be easily replanted to match chill hours with changing weather patterns. Perhaps planting fruit crops with a range of chill hours required might be beneficial Your future decisions to grow fruit trees may include crops that don’t rely as much on chill hours to be successful. For more information, please consult the Dooryard Fruit Varieties guide from UF / IFAS Extension.
by Matthew Orwat | Jul 8, 2014
Cedar-Apple rust or Cedar-Quince rust (Gymnosporangium) symptoms on pear fruit. Image Credit Shep Eubanks, UF IFAS.
This is the season for fruit harvesting, particularly for those fruits in the rose family such as plum, quince, peach, pear and apple. Many avid home horticulturists have been enjoying the fruits of their labor, but some have been thwarted by an unlikely and ugly disease.
This fungal disorder, commonly called cedar-apple rust and caused by various species of Gymnosporangium, has the potential to ruin Quince, Pear and Apple crops in gardens throughout Northwest Florida. Early scouting and vigilance will pay off.
This condition begins on native juniper species (known as cedars). A spore producing gall forms on the branches of the cedar tree, which begin to produce spores during wet weather. Spores, once produced, can travel up to a mile via wind. If spores land on susceptible plant tissue when a film of water is present, it will germinate and infect the fruit, twig or leaf. Although black spots develop on the plant with in 7-10 days of infection, orange tubes called aecia won’t develop until 4 or more weeks after infection. Next, spores are released from the aecia located on the fruit tree and travel to infect new juniper plants . The infected junipers will not show symptoms until the next growing season but they can manifest as galls or orange ooze present under bark. Different species of Gymnosporangium will infect trees differently. Some live only for one year while others, known as ceder-quince rusts, can last up to 20 years. Twigs infected with this disease usually die within several years of infection.
Ceder-Apple Rust on infected juniper host species. Image Credit Hank Dankers UF IFAS.
Although this may seem like an impossible situation, several control strategies exist.
- Remove Infected branches: Removal of infected plant tissue will reduce the spread of the disease in your garden.
- Removal of infected juniper host species: If the juniper or “cedar” in your landscape is something you can sacrifice, removal is warranted in cases of heavy infection.
- Avoid planting susceptible species of juniper next to susceptible fruit tree species.
- Treatment of fruit trees with fungicide: Preventative fungicidal sprays of products containing the active ingredients of sulfur, captan, chlorothalonil, or mancozeb and similar products can be effective. They will not cure existing conditions but are useful if you know that rusts are present in your area. Please read all pesticide labels before application, since there are pre-harvest limitations present on some products.
For additional information, please consult you local county extension office or review these publications by UF IFAS specialists (Florida Plant Disease Management Guide) and the Missouri Botanical Garden.
by Larry Williams | Feb 11, 2014
Dormant Peach Tree. Image Credit UF IFAS Environmental Horticulture Department
It is hard to believe with all of this recent cold weather, but now is the time to plant fruit trees in the Florida Panhandle. When planning what type of fruit tree to plant, correct cultivar selection should be the top priority.
The dooryard fruit producer oftentimes finds it difficult to choose the correct fruit cultivar for this area. An inappropriate choice results in disappointment when home gardeners find that they have paid for, planted and cared for fruit trees that are not adapted to the Northwest Florida climate.
Weather is probably the most important factor determining where certain fruits can and cannot be grown.
Most fruits which grow in the northern part of Florida are deciduous, which means that during the winter the trees lose their leaves and go into a period of dormancy, or rest.
During this rest period, the tree must be exposed to chilling temperatures. This exposure to the cold prepares the plant to resume active growth in spring. Temperatures below 45°F accumulated throughout winter determines the total hours of chilling. Species differ in the amount of chilling they need. This is known as a plant’s chilling requirement. Lack of enough chill hours result in sparse foliage and little to no flower production. And if there are no flowers, there will be no fruit.
North Florida receives between 400 to 650 hours below 45°F during the average winter. This provides enough chill hours for a few apple cultivars such as Anna, Ein Shemer, Dorsett Golden, TropicSweet and Shell. However, it does not provide the chill hours required for many of the more common varieties such as Red Delicious and Golden Delicious.
This same environmental factor holds true for most deciduous fruit trees. For example, some of the better known peach cultivars, such as Elberta and Bell of Georgia, perform poorly here following most winters. Both require roughly twice as many chill hours as the Panhandle receives during most winters. There are a few peach cultivars that perform OK in our area.
Blackberry Fruit. Photo Credit: Theresa Friday, Santa Rosa County, UF IFAS Extension
The results of selecting the wrong cultivar is only one of the disappointments experienced by those wishing to grow fruits in North Florida. Even when the correct cultivar is selected, many fruit enthusiasts (people who have dreams of homemade peach cobbler, apple pies, plum jelly, etc.) are disappointed to see insects eating their fruit, diseases causing their fruit to rot or possibly all their fruit falling to the ground before it is ready to be eaten.
In order to be successful with fruit production in North Florida, a person needs to ask a lot of questions before planting the first plant.
- Which cultivars grow well here?
- How much care is needed to grow this type of fruit?
- Do I have the time to devote to pruning, spraying, fertilizing and watering?
If you don’t know the answers to these questions, talk to a knowledgeable employee at a local, reputable nursery, consult the Dooryard Fruit Selection publication, or call your UF IFAS Extension Office before choosing to plant fruit trees this winter.
