How to get Clerodendrum to bloom?

Q: My Clerodendrum thomsoniae is not blooming. Actually it is not doing much of anything except putting out weak growth and small leaves. I purchased this plant May 26. 2015. Over the winter it was in a heated sunroom, at night 60 degrees, where it received some direct sun from the skylights. I reduced the water to prevent excessive leggy growth. I don't see how this plant can take full sun or even part sun. Temps here in Raleigh NC are 80-85 degrees and 65-70 at night, at the moment. I figured I would gradually expose it to more direct sun after being in a sunroom but the leaves burn. I had this plant in San Jose many years ago where it did quite well, blooming with no special treatment. So thought I'd give it a try again. Any advice?

A: Clerodendrums are all time favorites, appreciated by both gardeners and house plant collectors, for their showy, fragrant flowers and very easy culture. When growing Bleeding Heart (Clerodendrum thomsoniae), a few things should be taken in consideration:

1) Temperature.Like most clerodendrums, this plant is semi-decidious outside of tropics and goes dormant in winter. It may lose some or all leaves if temperatures drop below 60-65F. It is not too cold sensitive, the plant can even take some light freeze. However when it is not hot and humid, it slows down metabolism. This means, water should be reduced during cooler months.

2) Light. This plant can grow in both sun and shade like most clerodendrums - this is the beauty of this genus. However like with all flowering plants, more sun promotes more bloom. In shade, it will grow beautiful dark green foliage (leaves will be bigger than in the sun) on the account of flowering; in full sun leaves turn lighter color and sometimes may even get unattractive "faded" look, but flowering will be profuse. Also remember that Arizona full sun is different than New York full sun. Here in Florida, Bleeding Heart can take some full sun, but if exposed to sun all day long, leaves often get sun burn.

3) Acclimation. Also called acclimatization - this is a process when a living organism adjusts to environment changes. Acclimation is always the case when growing plants indoors, even in a sun room. When Spring comes, and especially when we start taking outdoors those plants that have spent a few months indoors, light level increases dramatically, and this may cause leaf loss, and leaf burn. It is not necessarily a bad thing, it is just a mechanism of acclimation. Example: imagine yourself after living in a warm tropical climate, moving to a cold country. For a while your body will feel discomfort from "too much cold", while native residents may feel comfortable. We call it "My blood has thinned after living in Florida" - and this is a physiological fact. And vice versa, if you are a Northerner, moving to hot climate may be a challenge; it will take a while until you get used to hot and humid tropical summers. Same thing with plants: during cooler and darker period, their body (leaves and stems) becomes "winter type", with some serious chemical restructuring. Immediate environment change, like bright light and high temperature, causes a shock to those "winter cells", and as a defense mechanism, the plant gets rid of those useless "winter" leaves, replacing them with new "summer" leaves with completely new chemistry and metabolism.

From what you described, you know your plants, and you know what you are doing. You did everything right by reducing watering in winter and gradually moving the plant into brighter light. You still may see some stress, and this is normal. If you patiently keep changing environment slowly, eventually your plant will generate new healthy "summer" growth, it will also improve more vigorous root grown which will help the plant to establish better and to be stronger. You will see larger, thicker leaves, and definitely some flowers.

Taking care of Soursop after shipping

Q: Since I have never grown a soursop tree before I need some pro help. My tree was delivered absolutely beautiful, leaves were a pretty green. I potted it and gave it a good drink of water and put it in a shaded area outside. Then the weather here became cool so I brought it in for a few days until the weather warmed, and it lost all the leaves. Is it in shock and will come around eventually? Will I be able to grow this tree indoors during winter?

A: Soursop - Annona muricata trees are very sensitive to temperature drops. This always causes leaf loss. You seem to be doing everything right. Do not water until soil gets slightly dry; keep it in bright shade. The weather should be good now with high temperatures and humidity rising. No fertilizer until the plant shows active new growth. Be patient with your plant, it should recover soon.

Soursop is an ultra-tropical tree and doesn't take any freeze. If you live in cooler climate, keep the plant in a pot (the good news is, Annonas in general have compact nature and are perfect for container culture). Bring the tree indoors during cold period, providing bright light.

We have very interesting article about growing and fruiting Soursop in apartment. Check out 4534 Tropical Treasures Magazine # 7.

Seeds germination in summer

Q: What is the best way to germinate seeds in summer? Should I keep trays indoors or put them outside?

A: Summer is the best growing season for plants, and for their propagation. Seed germination process of tropical plants usually benefits from warm, and even hot temperatures, so keeping pots with seeds outside in full or partial sun can be the best way. However some seeds may be more sensitive than others, or require slightly cooler or higher temperature for germination. These are a few tips that may help:

- For seed germination, use only well drained mixes, containing either peat moss or coconut fiber to retain moisture. Some succulents may require adding sand to the germination mix. You may also try our Professional Formula Seed Germination Mix.

- Large tropical seeds, like palms, or seeds of Fabaceae (Bean) family, can be grown in full sun. Their germination will benefit from higher temperatures (up to 90-95F). Make sure to keep soil moist. Cover them well, with 3/4 to 1 inch of soil.

- Fruit seeds (large size) should be germinated either in individual cells or small pots (3-4"diameter).

- Small to medium size seeds can be grown in so-called community pots. Seedlings can be separated after they establish their first roots.

- Tiny seeds should be planted closer to the surface, covered with only 1/4-1/8 inch of soil; some seeds require bright light for germination, so full sun will be a plus. Some small seeds like Ficus for example, prefer to be broadcasted on the surface, uncovered. Put containers with such seeds in bright shade, as you don't want the surface of the soil to dry out.

- Once your seeds sprouted, move them in filtered light - bright to medium shade depending on tenderness of the species. (Gingers prefer shade, while succulent sprouts can stay in brighter light). Regardless of water/sun needs of the species, all young sprouts and first leaves are sensitive to hot sun and may get burned or even killed. Once a baby plant has a few leaves and well-branched root system, you may start moving trays into a brighter light.

- Do not overwater young seedlings, keep soil slightly moist but not soggy.

See full list of available seeds.