The Boston Imbiber

"The give and take
Of sugar and starch
Will set the stage
For launching in March."

During these cold months, our hops are performing yet another chore in addition to the vernalization process that we covered last time. Similar to the mashing process in all-grain brewing, our industrious hops are busy converting much of the starch which is stored in their root system into soluble sugars. These soluble sugars then provide the ready fuel reserves which enable the awesome growth rate that our hops shoots display in the springtime. Most of this vegetative growth surge consists of the primary bines extending rapidly with relatively little accompanying leaf-out. Since there is relatively little leaf area at this stage, there is also not much food being produced by photosynthesis in the leaves yet. Thus, the hop plant is very dependent on its fuel supply stored in its roots during its primary growth phase.

We are indebted to Williams, Thomas and Weston, who studied photosynthesis and changes in the carbohydrate balance of hops back in the 1950's and 1960's. They found that the carbohydrate reserves (mostly soluble sugars) were nearly depleted during the early spring primary growth phase from February until June. During the secondary growth phase in July, nearly all the plant's vegatative growth takes place in the laterals and their leaves as they branch out from the primary bines. Photosynthesis is well underway now and more carbohydrates are being produced than the plant needs to sustain its growth. These excess carbohydrates are thus sent to the plant's rootstock and so its reserve of carbohydrates is being replenished during this phase. In late June and early July, hop burrs form and blossom into cones. As the cones mature, they also begin contributing photosynthetically-produced carbohydrates, and the rootstock reserve replenishment accelerates. In this phase of the hop plant's growth cycle, there is not much more shoot extension or leaf production, so the additional carbohydrates produced by the cones goes largely into the plant's rootstock.

Let's recap the annual carbohydrate cycle that takes place in the hop's rootstock. The carbohydrate reserves in the rootstock reaches a peak in the late fall and gradually gets converted from starch to soluble sugar in the winter. (Some of the reserves are actually used to provide for the hop's metabolic needs during this time.) During the spring "blast-off" primary growth phase, these reserves, largely in the form of soluble sugars, are rapidly depleted. By late June, as the primary growth phase subsides and the plant leafs out, reserve consumption-rate decreases as some photosynthetic activity augments the rootstock's fuel supply. As secondary growth of the laterals and leaves gets underway in July, rootstock replenishment gets seriously underway too. As the cones form in late July/early August and start photosynthesis in their bracts and bracteoles, reserve replenishment in the rootstock accelerates. Finally, as the plant matures and growth essentially stops by late September, the carbohydrate reserve in the rootstock reaches its peak. The conservative tendency of Mother Nature is again demonstrated at this point. As the weather cools and the hop plant begins to enter dormancy, any available carbohydrates still in the leaves and stems flows down into the roots. Then the leaves turn brown and drop off, and the bines whither and dry out.

Understanding these changes in carbohydrate storage can help us in our quest to be good stewards of our hop plants and help them grow stronger every year. First, when we are looking for rhizomes to plant, we should try to obtain the biggest, thickest rhizomes. (We should also make sure they are vernalized.) These will contain the most carbohydrates and enable the plants to attain their best primary growth. Secondly, we need to be diligent in providing sufficient fertilization to support the plant's growth efforts in order to produce an optimum leaf-out. These leaves are an important source of carbohydrate-fuel for the plant. Next, we need to strive to supply the best conditions for cone formation. Not only do they supply us with lupulin for use in brewing, but they supply the plant with additional carbohydrate reserves. Finally, at harvest time, we should try to pick the hops without first cutting down the bine. In this way, additional carbohydrates can still be produced after harvest and placed into storage in the hop's rootstock.

So even though a casual observer would say that our hops appear to be doing nothing during Jan/Feb, we know they are actually busy with their sub-terranean preparations for a successful spring blast-off. One other thing that we can do during this time of year is keep the hop rootstock moist. Hops will die if they are allowed to dry out (they will also rot if left in standing water, so provide good drainage). So, if there is not a snow cover with an occasional thaw or the occasional rainstorm in your part of the world, go out and sprinkle the ground over your hop plants with some water. Your efforts will be rewarded this spring with a spectacular display of hops shoots racing skyward.

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