A Little Introduction
• Citrus has been cultivated for thousands of years, originating in modern day China and surrounding regions.
• Citrus spread across the ancient world from China to the rest of Asia, Europe, and North Africa prized for its beauty, flavor, and nutritional value.
• The Spanish brought citrus to the New World on their first journeys, planting seeds in Florida by 1600 AD.
• Seedlings of all plants are genetically unique organisms and may exhibit characteristics wildly different from their parents, very similar to the parent plants, or somewhere in between. Many citrus cultivars produce seedlings that are very similar to their parents but variation is always a possibility.
• Cloning unique plants that have desirable characteristics allows farmers and gardeners to work with plants that have predictable and reliable attributes. These clones are referred to as “cultivars” and all members of a cultivar are genetically identical. ‘Meyer Lemon’ is one example.
• All citrus in the nursery industry is composed of various cultivars and most of them are grafted.
• Grafting is a process where two different plants are fused together. The top of the resulting plant is called the “scion” and is the portion that produces all of the above ground parts of the plant including the fruit. The bottom portion of the plant is called the “rootstock” and is selected to be a strong root system.
Isn’t It Too Cold Up Here In Tallahassee?
• There is a degree of risk growing citrus in North Florida due to freezes. However, as a home gardener the financial stakes are rather small while the potential rewards can be exceptional! When compared to other fruit production in the Tallahassee area citrus is one of the easiest crops from which to obtain a large yield.
• Microclimates are an important concept to understand to grow citrus successfully where freezes are expected. The primary observation says locations even just a few feet apart can experience substantially different temperatures at the same time. Buildings, water, and earth all absorb and release heat at different rates while exposed areas also lose heat faster due to wind than protected areas. Use the microclimates in your own yard or even create new ones to give your citrus the best defense against the cold.
Quick Thoughts to Consider
- Any windblock can help, plant on the south side of hedges and structures
- Large tree canopies trap heat at night, plant along the edge of the canopy
- Plant under well spaced pine trees for trapping heat and stopping wind on cold nights.
- Buildings release heat at night, plant 10 feet from walls.
- Water releases lots of heat at night, plant near ponds or swimming pools
- Concrete releases heat at night, plant near driveways and roads.
- Cities are warmer than the countryside.
- Lower elevations get colder than higher elevations. Avoid low spots for citrus.
• Some locations just aren’t ideal for citrus. An open field located on a low plain in the country will be a continuing struggle for citrus. If you aren’t able to construct beneficial microclimates in such a situation a different crop should be considered.
• Tallahassee is listed as zone 8b for winter hardiness, that means an “average annual extreme minimum temperature of 20-15 degrees F”.
• However the average low during winter is only 39 degrees F in Tallahassee. Most nights even in the winter are no problem for citrus.
• Many citrus varieties are cold hardy to a range of 22-18 degrees F. Shop with knowledgeable nurseries who can tell you which varieties are most and least cold hardy. Some citrus varieties are killed as early as 32 degrees, while others survive down near 10 degrees. Do your research and ask questions.
• Certain rootstocks can impart extra cold hardiness to a citrus plant. However, the University of Florida notes that scion selection plays a larger role in cold hardiness. If you plan on developing a grove or commercial production you should do extensive rootstock research. For the home gardener it is more important to choose the right scion variety (the scion variety is the name you’ll see on the plant like ‘Meyer Lemon’ or ‘Hamlin Orange’) and manage microclimates.
Starting Off On The Right Foot
• Dig a hole 2-3 times the width of the rootball but only just as deep as the rootball. Breakup the existing soil well so no clumps remain.
• Heavy clay soils should be amended with fine ground pine bark or a combination of peat moss and fine ground pine bark. Very sandy soils should be amended with large amounts of peat moss. Do not mix fertilizer in the planting hole for citrus.
• After filling the hole back in around the new plant the top of the root ball should be at the same level as the surrounding soil or slightly higher than the surrounding soil.
• Site citrus in a location where it will receive bright light which can range from all day sun (sun up to sundown) to bright filtered shade (like that under the edge of very large Live Oaks or well spaced pines). The more direct sun a citrus plant receives the faster it is able to grow but it will need more water and could suffer extra stress from insects, disease, and cold. Sites with less intense sun will require less watering, can help protect from freezes, and may result in a more carefree tree that can still produce plenty of fresh fruit. If planting under large tree canopies be sure to cite citrus as far from other trees as possible to reduce root competition.
• Determining how much sun is enough can be a process of experimentation. Lawn grass is a very good indicator of sufficient sunlight for fruit production. If turf grass is growing well in a location it is likely bright enough for citrus fruit.
• Inspect your yard for microclimates that might keep your new tree warm all winter and try to combine as many helpful factors in your planting site as possible. For example, a perfect spot would be on the south side of a brick wall, with a concrete driveway to the east, a small koi pond to the south, and a large Live Oak tree to the west.
Tender Love And Care
Maintain a 2-4 inches thick layer of any form of organic mulch around your trees to suppress weeds, build soil, and reduce watering needs. Pine straw, leaves, wood chips, and pine bark are all good options. Mulch rings should be as large as your space allows but always maintain 1-2 feet of bare soil around the trunk.
Bare soil absorbs more heat during the day and releases more heat at night than mulched soil. The best results possible would then be achieved by mulching your citrus in the early spring but raking it back just before freezes begin.
Fertilizer can be applied from February through September to citrus plants. Young plants should be fertilized 2 weeks after planting and then every 6 weeks (in the Feb.-Sept. window only) for optimum growth. Continue this fertilizing schedule for 2-3 years. This level of fertilization is intended to produce lots of early growth at the expense of fruit production. Ask your favorite garden center for advice on which type of fertilizer and how much to use. Spread it evenly in a circle twice as wide as the branch canopy. As citrus matures fertilize only three times a year in February, May, and August.
Insufficient watering may be the single most common cause of death, for newly installed plants. The following is a guide to ensure the highest possible chance of strong plant vigor. Apply at least 1 gallon of water slowly and directly to the root ball every 2 days for the first Spring and Summer. Apply at least 1 gallon of water slowly and directly to the root ball every 4 days for the first Fall and Winter
• Only rain over ¼ inch counts as a watering
The second year watering needs will reduce, water when leaves first show signs of wilting. Your plant may very well survive on less water (even perhaps much less water), but the healthiest, happiest, and most fruitful plants always receive enough water.
Pruning citrus generally leads to fewer flowers and less fruit. The more a citrus tree is pruned the less fruit it will produce. Removing all or half of long errant branches can be done at any time but heavy pruning should be avoided. If more extensive pruning must be done try to trim back as far as tolerable so the process can be avoided for the next few years.
Any growth below the graft line should be pruned as soon as it emerges.
Young citrus is more susceptible to freezes than mature plants and can benefit from extra protection in the first few years. Frost cloth is a product specially designed and manufactured to protect plants from cold temperatures. Sheets and blankets may help slightly but are much less effective than frost cloth which can increase temperatures an average of 4-8 degrees F.
Frost cloth works by trapping heat released from the ground. To be effective the cloth must cover the entire plant and make contact with the ground all the way around the plant. Weigh the cloth down every few feet to ensure there are no gaps and the cloth doesn’t move in the wind.
*This article was written by Jonathan Burns (Tallahassee Nurseries Outdoor Manager, FNGLA Florida Certified Horticulture Professional) using information published by the University of Florida combined with years of personal observations growing in the Tallahassee area.