How to Grow and Care for Rue

Rue is a short-lived perennial herb with a small, shrub-like growth habit. It features aromatic, blue-green foliage with a fern-like appearance. And in the summertime, it sports clusters of small yellow flowers that attract butterflies and other pollinators to the garden, as well as parasitic wasps. The ornamental herb has a moderate growth rate and should be planted in the spring after danger of frost has passed. Be aware that despite their past as a traditional use as a medicinal herb, rue leaves are toxic both to people and pets.

How to Plant Rue

When to Plant

Rue is normally planted from potted nursery starts or from seeds in the garden once spring soil temperatures reach around 70 degrees Fahrenheit. Seeds will germinate in one to four weeks.

Selecting a Planting Site

If you choose a sunny site with good drainage for your rue plants, they almost certainly will thrive with virtually no care. Rue flowers are good candidates for tough sites and will even grow in gravel. If your garden has heavy or wet soil, consider container culture. Avoid putting the plants near walkways or other areas where you might come in contact with them, as the sap can cause skin irritation.

Spacing, Depth, and Support

Smooth the soil of your garden site prior to planting, and break up any soil clumps. Then, simply scatter the seeds over the moist soil surface and slightly press them in, as they need light to germinate. Space plants around 1 to 2 feet apart. Do not allow seedlings to dry out. A support structure typically won’t be necessary, as rue naturally has an upright growth habit.

Rue Plant Care

Light

Rue grows best in full sun, meaning at least six hours of direct sunlight on most days. But partial shade is also tolerated. However, plants will produce fewer flowers in the shade.

Soil

Sharp drainage is important for healthy rue plants. Add sand, perlite, or vermiculite to the soil to help drainage. Or use raised beds with prepared soil in gardens where heavy clay dominates. Rue likes a moderately rich soil but can tolerate poor soils. And it can grow in a slightly acidic to slightly alkaline soil pH.

Water

Once established, common rue is very drought tolerant and is a good candidate for a xeriscape or rock garden. You won't need to water except for periods of extensive dry weather. Avoid overwatering, which can cause root rot.

Temperature and Humidity

Rue plants thrive in hot weather and low humidity, similar to their native habitat of Greece, Turkey, and Italy. However, the plants are tolerant of humidity as long as they have good soil drainage and air circulation around them.

Fertilizer

Do not fertilize rue plants. Excess nutrients will cause the plants to produce more foliage at the expense of the flowers.

Pollination

Garden pollinators, including bees and butterflies, are highly attracted to rue and assist it in its pollination.

Types of Rue

There are several varieties of rue, including:

• ‘Blue Beauty’: This plant has especially vivid blue-green leaves. 
• ‘Jackman’s Blue’: This variety features a strong blue color and a potent aroma.
• ‘Variegata’: The leaves on this variety have some white in them.

Rue vs. Fenugreek

As another bitter herb that bears small yellow flowers, it's easy to confuse fenugreek (Trigonella foenum-graecum) with rue. Fenugreek, however, is an annual legume and does not have some of the toxic properties that rue flowers do. You can grow fenugreek in the sunny garden after all danger of frost has passed and use the ground seeds in curries or the leaves in salads.

Harvesting Rue

Rue is often harvested to use as dried flowers. And some people make sachets out of rue and use them to deter pests, including fleas and ants. Wear gloves and long sleeves when working with rue to protect your skin. Cut a mature plant at ground level with pruners. Then, hang it in a dark, dry place to dry until the leaves become brittle. Keep the fully dried rue in an airtight container until you’re ready to use it for sachets or other purposes. 

How to Grow Rue in Pots

If you don’t have garden space or have heavy soil, container growth is a good option for rue. Choose a pot that’s around 12 to 16 inches wide and deep, and make sure it has drainage holes. An unglazed clay container is ideal because it will allow excess soil moisture to escape through its walls.

Pruning

Rue is a semi-woody perennial that flowers on new growth. To keep the plant vigorous and looking its best, cut stems back to around 6 inches in the early spring. Don’t wait too long, or you’ll end up pruning off some flower buds. You also can prune in the fall after flowering is finished.

Propagating Rue

It's easy to make new rue plants via stem cuttings. This is a quick and inexpensive way to replace mature plants that are nearing the end of their life cycle, as rue plants only live around five years. The best time to take cuttings is in the late summer from new growth, but be sure to wear protective clothing during the process. Here's how:

1. Cut roughly a 6-inch piece of stem from new growth.
2. Remove any foliage on the lower half of the cutting.
3. Plant the cutting in a container of moistened soilless potting mix.
4. Place in a clear bag to maintain moisture.
5. Keep the mix moist but not soggy. Once you feel resistance when you gently tug on the stem, you'll know roots have developed.

How to Grow Rue From Seed

Rue is easy to start from seeds in the garden or in trays. The soil must be at least 68 degrees Fahrenheit for germination, and some light must reach the seeds. When the seedlings develop at least two sets of true leaves, they can be transplanted into larger pots. Harden off seedlings before planting in the garden.

Rue plants will self-seed, sometimes aggressively, in warm regions. You can collect the brown seed capsules in late summer after flowering to plant elsewhere.

Potting and Repotting Rue

You can use any well-draining potting mix for rue in containers. Repotting is necessary when you see roots coming out of the drainage holes of the pot. Remember to wear protective clothing when repotting.

The bluish foliage of rue plants marries well with plants that have golden foliage, such as the gold cultivars of oregano, sage, or thyme. These herbs all like the same sunny, dry conditions and well-drained soil that rue thrives in, so they blend well in mixed containers.

Overwintering

In the northern portion of rue’s growing zones, add a layer of mulch around the plants to protect them over the winter. Aim to do this before frost hits in the fall.

Common Pests and Plant Diseases

Rue doesn’t have any major pest or disease issues. In fact, if you see caterpillars feeding on your rue plants, don't spray them. It's likely they are swallowtail butterfly caterpillars, which use rue as a host plant and benefit your entire garden. The primary disease issue that can affect rue is root rot from wet soils. So ensure that your plants are never waterlogged.