I just received some vey nice plants from Logee's. They are in 2.5 inch containers. The instructions say to repot into the next larger container, 4 inches. Some of these plants will be large container plants (Bouganvillea, Aglaia odorato, Pelargonium, etc). Why would I not pot them into their final containers? It seems logical to me to repot into the final pot.
repotting plants
Most plants will perform better when they're a little root bound. Also a bigger pot will hold more water and that can encourage root rot.
I'm not picking on you, Rogmee - I just want to use your post to explain something. ;o)
Where plants occur naturally, if being root-bound was a survival advantage, they would concentrate rootage in the soil where the stem emerges from the ground. We do not see this in nature, where roots spread over large areas in search of water, air, and nutrients. That a plant flowers better or tries to reproduce itself, due in part to the added stress of tight roots in pots, is not a sign that the plant prefers it. It may be better for us, because we get the advantage of seeing the plant try to reproduce itself, but is it better for the plant?
There is a direct relationship between the size of the plant, the size of the pot, and the ability of the soil to drain. You can grow very small plants in large pots if the soil drains well (and continues to drain well), but you cannot grow small plants in large pots (and expect good vitality) with soil that drains poorly. The best soil for most plants that are not drought-tolerant is one that requires very frequent watering - even daily.
Each time you water, you force old gasses from the soil. As the water remaining in soil is used, additional air takes its place. This creates a very healthy rhizosphere (soil surrounding roots). In soils that retain too much water, the roots do not get enough air. The all important fine, hair-like roots, when deprived of air, begin to die very quickly - certainly within 24 hours. The size of rootage killed is progressive - the longer the roots are deprived of air, the larger the roots are that are killed. When this occurs one of two things occur - root rot sets in, or, if we are more fortunate, we wait until enough water is removed from the soil through evaporation or by the plant for air to return to the soil and for root regeneration to begin. This cycle of root death and regeneration in poor soils is extremely taxing to the plant, and uses energy that could have been directed toward the production of flower/fruiting parts, disease suppression, fighting off insects, or simply increasing the plants biomass (size).
Al
Thank you for the advice and explanation. I have pottted my new plants in 5" containers.
Now, how will I know when to pot them into larger containers?
When I do repot again, can I go from 5" containers to 12" containers/hanging baskets? Or do I have to find another intermediate sized pot?
I am using Miracle Grow potting soil and the drainage seems good. I plan to wait until the surface is dry before watering again.
On a related subject, some of the new Bougainvillea plants had roots encircling the small pot. I wanted to cut the roots to prevent a girdling root system but I've read that Bougainvillea roots should not be disturbed. I ended up repotting without disturbing the roots. What should I have done?
John
A fast draining soil is one that you can water from the top and water appears at the drain hole within a few seconds. I grow in exceptionally fast soils, but don't recommend them for everyone because they require lots of time devoted to watering and fertilizing, but the plants in them are exceptionally healthy. For most containers, I can apply water from a 3/4 inch hose & if the drain hole is large enough, water drains as fast as it comes out of hose. Miracle grow, even when fresh drains moderately. As it ages, drainage slows. We hope that roots become a part of the soil structure with these soils and that they (roots) prevent soil collapse. A jump to a 12" container from a 5" container is a big jump. You can do it if you're careful about watering. Checking soil moisture at the drain hole instead at the top is helpful.
It's true that bougies don't tolerate major root work well. In bonsai, root pruning is usually limited to 25% of roots or less. At the time you repotted, you could have taken a razor knife & made vertical slits through the encircling roots. The roots were growing there because they lacked sufficient air in the soil. If you think about it, what does the space at the outside of the soil offer? Not water, nutrients, or sun - it was air the roots were looking for.
Al
Jrhodes - you can definitely repot your 5" potted plants into their final containers when they're ready. Just give them some time to adapt to the 5" pots first before uprooting them again - at least a couple of months. I've done this with both Pelargoniums & Bouganvillea & they've done fine.