Growing Citrus in Containers
Dwarf citrus trees are especially suited for container growing as they can be kept at manageable sizes. Container growing allows gardeners to overcome poor soil conditions or limited space in a landscape. People enjoy their trees in decorative pots on a patio or apartment balcony. Many customers have cold winters and bring their citrus indoors during freezing weather. For some pictures of successful container plantings take a moment to view this slide show.
These tips can help you on the way to successful citrus growing in containers:
- Select the right size pot with adequate drainage holes. A 2-3 year old citrus tree typically wants to grow in about a 12” diameter nursery pot (commonly referred to as a “five gallon”.)
- Use a soil mix that is lightweight and drains well. If the mix contains a large proportion of dense, absorbent material, such as peat moss or worm castings, amend with 1/4-1/3 volume of 1" cedar or redwood shavings. Water in thoroughly, using Vitamin B-1 rooting tonic in the first few applications, if desired. Once the roots have settled, we prefer using slow release fertilizers applied to the soil surface, rather than mixing fertilizer into the soil or using plant stakes. This avoids any risk of burning the roots.
- When shopping for the perfect citrus soil mix, please avoid those that contain chemical wetting agents or fertilizers. Soil mixes formulated for outdoor use are preferable to potting mixes for indoor plants, since the later often contain chemical wetting agents, causing tree roots to remain too wet after watering. You can start with a good rich organic soil and amend with about 1/3-1/2 volume shavings, perlite or coco fiber. Mixes for Cactus/Citrus have a lot of sand but can work. Use your judgment to amend as needed.
- Develop a watering schedule so the roots maintain even moisture, but are not waterlogged. Water before leaves show wilting, and when roots have reached about 50% dryness. Elevate pots above standing drainage water.
- Provide 8 or more hours of direct sunlight per day. If less than 6 hours of natural full sun is provided, supplement with grow lights. Usually an unobstructed South or Southwest facing window is ideal. See grow light tips here: littlegreenhouse.com
- Plant the tree so the root collar (crown roots) show above the soil line and the top of the fibrous root mass is just below the soil surface. Make sure that soil or mulch is not pushed up against the trunk of the tree.
- A moisture tester can be an excellent tool to help determine when roots are in need of a drink. Because most commercial moisture testers rely on an electrical conductivity method, however it is possible to get miss-readings due to high salinity or other conditions. An alternative method recently shared by a New England citrus enthusiast simply employs a plain wooden dowel about the diameter of a pencil. Sharpen it with a whittling method (sharp knife) or pencil sharpener. Then insert this into the pot at varying depths, shallow to deeper, determining moisture using your direct senses (feel, smell, etc.).
- As the previous example of an alternative moisture tester shows, indoor citrus trees inspire innovation! There is no one “right” soil mix, except all the ones that now contain happy citrus trees. People over the years and in every state have experimented, using locally available materials and resources to develop methods that work for them.
- If the adventure feels daunting you can start slowly with one of these three “easiest to grow” trees: Meyer lemon, Bearss lime, Trovita orange. Order Here
Selecting Planting Containers
We recommend a 6-9" container for our one year trees and a 10-14" container for our 2-3 year trees. A variety of decorative plastic containers are available at reasonable prices. Clay pots and wooden containers are attractive but less mobile choices. When selecting a container, be sure there are sufficient drainage holes. Drilling extra holes is an easy way to improve drainage with wood or plastic. As the tree grows, increase the container size to a 16-20" diameter pot (the next pot size up). Do not start with a pot that is too large as it makes soil moisture levels harder to control with small trees.
How to Plant in Containers
We recommend using commercially available potting mixes. Some experts make their own mixes using wood shavings, sand, and compost. Using dirt (native soil from your yard) in a container is not advisable. We also advise against putting gravel or any other material on the bottom of the pot, as this negatively impacts drainage over time.
The perfect high porosity soil mix can be hard to find, but we have found rose garden soil mixes (formulated for outside use) work well. Soils that are too heavy can be amended with about 1/3 – ½ volume of 1" redwood shavings or cedar hamster bedding. Pine and spruce shavings tend to break down more quickly, so are not ideal. Try to select hardwood chips that will last longer. If necessary, moisten the mix to reduce dust and make it easier to handle.
Once your soil mix is prepared, the container is selected and the tree's eventual location is known, you are ready to begin potting.
Place prepared soil mix in the bottom of your new container. Gently slide tree roots out of the old container, trimming off any dead roots and detangling any circling roots so that growth into the new pot will not be impeded. If planting a bare-rooted mail order tree, gently shake the shavings loose from the roots and mix them with the planting mix. Place the loosened root mass into the new container and gently fill with your fresh planting mix, packing down lightly to remove large air spaces from the root zone. The top of the roots should be just beneath the soil surface, and crown roots (root collar area) should show above the soil line. Water deeply. Stake loosely with green tie if needed. It’s a good idea to repot every year or so, or when you see roots peeking through drainage holes.
Selecting a Location for Outdoor Containers
Sunny, wind free locations with southern exposure are the best. If in doubt, leave the tree in its plastic container and place it in the spot you have in mind. After a week or two, you should be able to tell whether or not it is thriving. Reflected heat from sidewalks or houses can also help to create a warmer microclimate. Avoid placing containerized citrus trees on or near lawns that get frequent, shallow watering. To reduce excessive heat on the roots, try nesting plain plastic nursery pots into slightly larger decorative pots. This can help roots stay cooler. Be sure the pot never sits in standing drainage water.
Consistency is the key with citrus watering. Citrus trees require soil that is moist but never soggy. Watering frequency will vary with soil porosity, tree size, and environmental factors. DO NOT WATER IF THE TOP OF THE SOIL IS DRY WITHOUT CHECKING THE SOIL AT ROOT LEVEL! A simple moisture meter, available at garden supply stores, will read moisture at the root level. This inexpensive tool will allow you to never have to guess about whether or not a plant needs water. See also: the dowel method, item 7 above.
A wilted tree that perks up within 24 hours after watering indicates the roots got too dry. Adjust the watering schedule accordingly. A tree with yellow or cupped leaves, or leaves that don't look perky AFTER watering can indicate excessive watering and soggy roots. Give your tree water less often.
Citrus prefer infrequent, deep watering to frequent, shallow sprinklings. Deeper watering promotes deeper root growth and strengthens your tree. Generally, once or twice a week deep watering works well for container specimens. Be sure to adjust based on weather conditions! In general, it is probably best to water in the morning, but if plants are dry or wilted it is better to water them right away than wait until morning. See our watering page.
Citrus trees feed heavily on nitrogen. Your fertilizer should have more nitrogen (N) than phosphorous (P) or potassium (K). Use at least a 2-1-1 ratio. Miracid Soil Acidifier is a water-soluble product that works well and is a 3-1-1 ratio. In some regions, you may be able to find specialized citrus/avocado fertilizers. Buy a good brand and apply according to package directions.
Any good citrus formula will contain trace minerals like iron, zinc, and manganese. Many all-purpose products will work. Just add trace mineral supplements if your fertilizer is deficient. We prefer slow release fertilizers in the granular form rather than fertilizer stakes. Follow rates on the package carefully as fertilizers come in different strengths, release rates, and application schedules. We recommend that you fertilize more often than recommended with most slow release fertilizers. Foliar applications of trace minerals in the form of kelp or other soluble fertilizers can be effective. Yellowing leaves indicate lack of fertilizer or poor drainage.
Commercial organic fertilizers can work well for citrus trees. Lily Miller, Dr. Earth and a number of other companies now sell Organic tree fertilizer formulations. Supplement granular applications with foliar sprays of fish emulsion and kelp. Some people brew compost ‘teas’ which can be helpful when applied to plant roots.
Know where the graft union is on your tree. It can usually be seen as a diagonal scar between 4 and 8 inches from the soil. Remove all shoot growth below the graft. These so-called "suckers" take vitality from the top of the tree (the fruiting wood). Especially on young trees, they are very vigorous. Remove suckers as soon as they are observed. See photos.
Thorns are removed from rootstocks when they are grafted. Juvenile fruiting wood will sometimes have thorns; this is a young plant's way of defending against grazing animals. As the tree matures, thorns will not appear as often. Prune off thorns if desired. Double-check thorny branches to be sure they are fruiting wood branches and not from the rootstock below the graft.
Citrus will look fuller with occasional pruning to shape leggy branches, and can be shaped as desired. Pruning is fine any time of year, except in the winter for outdoor trees. Some trees may develop erratic juvenile growth above the graft. If so, prune for shape and balance. Don’t be afraid to completely prune off an erratic branch if it is too irregular or crossing another branch. Other fruitful branches will replace it. Any growth above the graft can eventually bear fruit. Well-pruned trees have higher fruit yields and are less prone to branch breakage.
Citrus are self-fruitful indoors, and don’t generally require pollination to be productive. There is some evidence that pollination increases fruit size however pollination is generally considered optional for fruitfulness. Some people enjoy pollinating their trees, using a small soft brush or cotton swab to transfer pollen among the flowers. A technical article about pollination of citrus by honeybees from the University of Florida is here.
Most insects do no harm to citrus trees! Spiders, syrphid flies, lady beetles, lacewings, and preying mantids are among the beneficial insects you may see around citrus trees outdoors. You can even buy some predators and parasitic insects for release in your garden. One reputable source for beneficial organisms is ARBICO.
It is important to keep your tree free of ants, because they will “farm” scales and other honeydew-producing pests, moving them from place to place, milking their secretions, and protecting them from their natural enemies. Ant baits that contain boric acid may be helpful. A recipe for a homemade ant spray can be viewed here. Homemade pest spray
If you find harmful insects like scales, aphids, or mites, a household spray bottle of water with some mild dish soap could be all you need. Orange TKO, an organic cleaner, works very well at a dilute rate. You can also find specially formulated Horticultural Soap products at local garden centers. Use a soft toothbrush to scrub away adherent scale insects and recheck in a week to see if another treatment is needed. If scale insects persist, the usual nursery treatment is a 1% solution of light horticultural oil. Learn more.
Many citrus varieties can tolerate temperatures as low as 32 degrees for 2-3 hours. See this chart for the lower temperature tolerance thresholds of different citrus varieties.
Even temperate locations can drop below freezing so it's good to have a plan of action ready. Old fashioned Christmas lights (that produce some heat) can be effective, either alone or in combination with frost covers. Anti-transpirant sprays such as ‘Cloud Cover’ can also be effective when used according to directions. Straw mulches, cloth covers and even plastic sheeting can be combined as needed to provide the necessary level of protection. See this link for more on frost protection options: http://davesgarden.com/guides/articles/view/319/
Overwintering your citrus trees indoors may be another option.