Growing Citrus

Growing Citrus

When you think of Citrus, you might think of the pitchers of lemonade you downed on hot summer afternoons as a kid — or perhaps the enticing scent of orange blossoms perfuming the air of some far-off grove in your mind’s eye — but we simply envision our back patios loaded up with potted Lemons, Limes, Oranges, and more! With just a little bit of planning and effort, home gardeners across the Pacific Northwest can enjoy these beautiful trees for many years, offering not only glossy, evergreen leaves and starry, fragrant flowers, but also those classically tart fruits that — yes — can be used to make some pretty awesome homemade lemonade, or a grown up Lemon Drop!

The Basics of Citrus Care in Portland

In our corner of the Pacific Northwest, we are privileged to be able to grow a wide variety of plants in our gardens year-round — and indeed, we can grow Citrus outdoors here for most of the year — but our wet weather from fall through spring and frequent dips in winter temperatures make it impractical to plant most Citrus plants in the ground. Our winters have been warming, but Portland will still dip into the 20s from time to time. For that reason, we recommend growing Citrus trees in pots that can be enjoyed outdoors for most of the year, then temporarily relocated to a protected site when it gets truly cold. If you have a bright sun room or are willing to offer robust supplemental lighting, Citrus trees can be grown indoors, but your plant will be happiest spending as much time outdoors as possible. The key is not to stress your tree by changing its growing conditions too rapidly.

Start with a healthy, nursery-grown plant like the ones we offer at Cornell Farm. There’s nothing wrong with leaving a newly-acquired plant in the nursery pot it’s already growing in for a time, but you’ll likely want to pot it up into a prettier container right off the bat — just make sure it has drainage holes! In general, containerized Citrus should be repotted every third year or so in the early spring. (If you don’t want to up-pot your plant, you can always root-prune it as you would a bonsai specimen.) Because Citrus like to dry out somewhat between waterings, it’s important to use a well-draining growing medium such as a Citrus and Cactus mix whenever you repot or root-prune your plant.

Before watering, test the soil in your Citrus tree’s pot; if it is dry to roughly three inches down, you are okay to proceed. If you notice your plant’s leaves are turning yellow or beginning to drop off, you are overwatering it. But don’t let that warning scare you into under-watering your plant, either! Both conditions will stress your plant and potentially kill it, but there’s no need to panic. If you notice these symptoms and course-correct with a proper watering schedule quickly, your plant will recover.

You should fertilize your plant using a specially-formulated Citrus fertilizer such as EB Stone Organic Citrus Fertilizer once a month from January to August. Our regimen at Cornell Farm includes Growmore Seaweed Extract, a micro-nutrient foliar spray to promote dark green foliage, encourage vigorous root development, and prevent transplant shock.

Winter Care

Healthy, mature specimens of some Citrus can withstand winter temperatures into the 30s for short periods of time, while other varieties may need to be protected at temperatures as warm as 45°F — especially if the temperature change is abrupt and they have not had a chance to “harden off.” Regardless of what variety of Citrus you are trying to grow, you will want to protect your plant from cold temperatures during the winter. Again, it is important to make these transitions gradually, rather than throwing your plant directly from the cold, wet conditions outside into the dry heat of your home — and vice-versa. In general, Lemons and Limes are some of the least cold hardy Citrus and should be protected below 37°F. Oranges, Grapefruits, Tangerines, Mandarins, and Kumquats, on the other hand, may fare alright to as low as 28°F.

As a general guideline, most Citrus can be kept outdoors while temperatures are consistently above 40°F. When nighttime temperatures are predicted lower than this, your plants can be covered with frost cloth and relocated to covered location up against a house, such as front porch, for a transitionary period of a few days. (Plant caddies that hold up to 500 lbs. are ideal for moving larger potted Citrus, but Potlifters are another option.) When nighttime temperatures are predicted to fall lower than 30°F, your Citrus should be further relocated to an unheated garage or basement under artificial lights. The goal is to minimize your plant’s time indoors as much as possible, so as soon as temperatures regulate again, you can slowly transition your Citrus back outside, being sure to place it under cover for a few days before returning it to its spot out in the open on your patio.

If you do not have a protected location like a garage or basement that can serve as temporary protection for your potted Citrus, you can also try bringing your plant fully indoors as a houseplant in the fall and returning it in the spring. If you opt for this route, rather than wait for freezing temperatures, you should make these same sort of gradual transitions outlined above when outdoor temperatures consistently reach 50°F — enough to trigger partial dormancy in your plant, but not so far from indoor temperatures as to make the transition a total shock. You will also need to provide supplemental light.

Frequently Asked Questions

How big do Citrus trees get?

In Southern California gardens, the dwarf to semi-dwarf Citrus varieties we sell could reach 8 to 12 feet high or more at maturity, but here in Portland, your plants are unlikely to grow to these kinds of sizes. When gown in pots, these same Citrus are easily kept at much more manageable sizes through a combination of light pruning — which can be performed virtually any time of year — and the natural dwarfing effects of pot culture.

Is my new Citrus tree going to give me fruit this year?

That depends upon how mature the plant is. Even young Citrus plants will put on a lot of flowers, followed by tiny fruits; however, it is a good idea to remove this fruit from young trees to allow your plant to allocate more energy towards growing roots. Healthy roots make for long-lived trees that will provide you with fruit and pleasure over many years.

If your heart is set on harvesting Citrus fruit sooner rather than later, start with an older tree. In its second year, you can let a few fruits ripen, and over the years you can allow your tree to set more and more fruit.

What if I want to grow a Citrus tree in the ground?

If you are undaunted by the prospect of a failed “zone busting” experiment, we would recommend opting for a Citrus variety with the highest baseline cold hardiness — like a Kumquat. We’ve known a few clever gardeners who’ve successfully grown Citrus in their gardens year-round by planting them in a sunny-but-sheltered micro-climate that offers protection from freezing, whipping winds in addition to well-draining soil. In the winter, you will need to water your in-ground hardy Citrus tree deeply and mulch around the base of the tree to protect its roots from freezing. On particularly cold nights, you should also cover its foliage with frost cloth and wrap the trunk with insulated material, but if you have the right growing conditions and are up to the challenge, this is a great way to earn bragging rights with your gardener friends!

Cornell Farm offers a wide selection of Citrus trees in our Kitchen Garden throughout the year, including during the holiday season when they are often given as gifts! Look for different varieties of Lemons, Limes, Mandarins, Calamondins, Tangerines, Oranges, and more. We also sell all the pots, soils, and fertilizers you’ll need for your Citrus thrive in our climate. If you would like any help selecting the right Citrus for you or have any questions about its care, come visit us in person, and we’ll be happy to assist you so that you can reap the rewards of growing Citrus trees in our climate.