Streptocarpus: Feed with a general-purpose houseplant feed in spring, then change to a high potash feed in summer to promote flowering. Use a specialist Streptocarpus food, or use tomato feed diluted to at least half-strength. These are calcium (Ca), magnesium (Mg), and sulfur (S). Without all 6 nutrients, plants have a hard time completing their life cycle.Most residential soil usually contains the latter three but often fluctuates in N, P, and K depending on what else has been grown in it and other factors. Citrus trees love their sunlight and as the sun is now setting earlier and rising later it’s important to get your tree in a bright location where it can still get a good few hours of direct light a day.

Citrus plants need to be periodically repotted to maintain a healthy plant - once a year or once every 2 years for trees up to 6ft in height. For trees over 6ft you can usually just top up the compost once a year and repot every 3 or 4 years.

Where to grow a citrus tree 

Feed citrus with a proprietary citrus fertiliser. Use a high-nitrogen liquid feed from early spring to mid-summer Outside the growing period, you will find that you are watering less often so every other watering might be once ever 3 weeks which is fine. The fruits will develop using the energy that has been stored up in the leaves and stems of the plants throughout the growing period.

A citrus tree needs a sunny, sheltered outdoor spot in summer, and a greenhouse or other bright, frost-free location for winter. Lemon and lime trees need a minimum winter night temperature of 10°C (50°F), while kumquats can cope with a slightly lower 7°C (44°F). They usually flower in late winter, and fruits take a year to develop, so you’ll often see fruit and flowers on the tree at the same time. The creamy white flowers are very fragrant. Central heating can be a problem for citrus trees in winter, as they don’t like a dry atmosphere. To increase the humidity level around your tree, stand it on a tray filled with gravel, and top up with water to just below the surface of the gravel. Open greenhouse vents on sunny spring days when temperatures inside can soar. Most citrus growers fertilize with powdered organic fertilizer. Here, feed your orange, lime, or lemon tree in dormancy. Thoroughly water the area, then evenly spread the powder. For established plants and shrubs, apply the powder at the drip line at 1 cup per 1.5 feet of spread, or 2 cups per 3 feet of spread. For a fully-grown tree, use 3 cups per inch for trunks that are 3 inches in diameter or less. Use 9 cups for a larger tree. Two brands that use natural sources for their powders are Espoma and Bumper Crop. Fruit fall: Fruits should ripen in a period of warm sunny weather, taking almost a year to develop to full size. Most cultivars set too much fruit for the size of the plant. Some of these will be shed, or clusters should be thinned to one fruit each on young plants. If your chosen fertilizer is in spike form, put these in the ground during the dormant season, shortly before spring. Find the drip line of your tree (or the area 2 to 3 feet outside the circumference of the canopy), and water the area thoroughly. Place the protective cap on the spike, and hammer it in so it’s flush with the ground. You can use multiple spikes for one tree, and up to 4 at one time. Younger trees should have spikes closer to the 2-foot range outside the trunk diameter, and older trees should have fertilizer spikes in the 3-foot range. In containers, place one as far from the trunk as possible. Sprays Container-grown trees like this mandarin may need more regular fertilization. Source: crouz1Just as watering is important for lemon trees, so is feeding it. There are certain nutrients that lemon trees need that are essential for them to thrive, without these nutrients, the leaves will change to various different colours—telltale signs that your plant is starved for iron, magnesium or nitrogen. Mandarin oranges and satsuma trees are one of the most cold hardy citrus varieties as well as the beautiful limequat , but should still be brought in during the winter for protection. The size of the new pot should be large enough to allow a few centimeters of new soil around the edge of the old rootball. It can be repotted in any well drained mixture that is slightly acid. Probably the easiest solution is to buy a good quality container or ericaceous compost in a garden centre but you can also use top soil from the garden or 50:50 a mixture of top soil and ericaceous compost with a handful of sharp sand/grit/stones for extra drainage. The ideal pH is 5 to 5.5. Guidance on Repotting A slow-release fertilizer for orange tree growers is an excellent way to reduce the number of times you have to fertilize. This lessens the workload and simplifies your citrus fertilization schedule. So if you’re wondering when to fertilize lemon trees with slow-release plant food or granular fertilizer, know it will only have to be a few times per year. The best citrus tree fertilizer of this kind is adaptable to an indoor or outdoor tree. In the case of slow-release organic fertilizer for indoor trees, you can fertilize all year round for active growth. An outdoor tree should receive fertilizer in dormancy. Just sprinkle the granules around the area to be fertilized at a rate of 3 tablespoons for every 2 by 2-foot area. Then work them lightly into the soil, and water them in. Frequently Asked Questions Yellowed leaf edges can be a sign of nutrient deficiency. Source: Keith Williamson If your lemon tree is currently being kept directly inside the house, then stop! Despite citrus trees being classed as 'indoor trees', they don’t like direct heat and central heating can dry out the air where humidity is needed. Citrus trees flourish in places with good air circulation and where they can receive plenty of light, so a porch area for example would be perfect.